STUDIES IN THE USE OF HAIR AS A BIOPSY MATERIAL 
FOR ESTIMATING LEAD EXPOSURE. 
A Thesis 
Submitted in Fulfilment of the Requirement for the Degree of 
Master of Philosophy in Chemistry 
of 
The University of The West Indies 
by 
GARVIN WILLIAMS 
1993 
Department of Chemistry 
Faculty of Natural Sciences 
St. Augustine. 
i 
ABSTRACT 
Studies In The Use of Hair As A Biopsy Material 
For Estimating Lead Exposure. 
Garvin Williams 
This dissertation deals with the investigation of the use of hair as a biopsy material 
for estimating lead exposure. The Trinidadian population was thought to be suitable for this 
study because: (1) being a multiracial society, comparative studies of lead levels among the 
various racial groups could be assessed. Many of the studies reported in the literature were 
done on populations comprising a single race. (2) Trinidad uses leaded gasoline with a lead 
concentration of approximately 0.79g/L. Studies have shown that lead in gasoline causes 
enhanced lead levels in the environment which often result in increased blood and hair lead 
levels in individuals residing in areas close to highways and busy intersections. 
The sample population consisted of one hundred and eighty nine volunteers belonging 
to four races: East Indian (N=91), African (N=49), Chinese (N=ll), and Mixed (N=41). 
Also sampled were traffic police personnel (N=29) and battery workers (N=22). The hair 
samples were taken from the nape of the neck by cutting 2-3cm closest to the scalp and were 
washed using a washing procedure developed in our laboratory. The effectiveness ot the 
ii 
washing procedure was partly determined using scanning electron microscope analysis of 
the hair samples. Both hair and blood samples were acid digested using nitric/perchloric acid 
mixture and nitric/trichloroacetic acid mixture respectively and analyzed for lead using flame 
atomic absorption spectroscopy. The sulphur and carbon:sulphur ratios of the scalp hair 
sample were determined by elemental analysis. 
The results of the investigation into scalp hair lead levels among the African, East 
Indian and Chinese racial groups indicated significant differences among the three races. As 
a result separate upper limits have to be set for each race. No significant differences were 
found for either pubic hair lead levels or blood lead levels among the three races. In each 
of the East Indian and Mixed racial groups, scalp hair, pubic hair and blood lead values 
between males and females were significantly different. However, no significant difference 
was found in the African group. No significant correlation was found between scalp hair lead 
and blood lead values of the general population but a difference was found between the scalp 
hair lead levels and the pubic hair lead levels. No significant correlation was found between 
the time spent in "traffic jams" or the time spent on the road in motor vehicles and scalp hair 
lead levels. Traffic police and battery plant operators sampled had a much higher average 
scalp hair and pubic hair lead levels than the non-occupationally exposed general population. 
No significant difference was found between the blood lead values of these workers and the 
general population. The percentage sulphur or the carbon:sulphur ratios in scalp hair did not 
iii 
influence the scalp hair lead levels among the general population. A significant difference 
in the carbon: sulphur ratios was observed between African and East Indian racial groups. 
Many problems associated with the use of hair as a bioindictor for detecting lead 
exposure still exist. Once these problems have been resolved, hair analysis is likely to gain 
more international recognition as a bioindicator for determining lead levels. 
iv 
ACKNOWLEDGEMENTS 
The author wishes to express his utmost appreciation to Dr. 
L. Hall and Dr. J. Addae, both of whom had made this work 
possible through their close and careful supervision, and their 
expert suggestions. He also extends his appreciation to Ms. Rachel 
Williams for her vital assistance in the statistical treatment of the 
data in this project. 
V 
DEDICATION 
TO RHONDA 
vi 
TABLE OF CONTENTS 
Page: 
ABSTRACT (i) 
ACKNOWLEDGMENTS (iv) 
DEDICATION (v) 
LIST OF FIGURES (x) 
LIST OF TABLES (xii) 
CHAPTER ONE: LITERATURE REVIEW 1 
1:1 HISTORY OF LEAD POISONING 2 
1:2 LEAD IN THE LOCAL ENVIRONMENT 7 
1:3 MAJOR PROJECT OBJECTIVES 8 
1:4 ASSESSMENT OF INDICATORS OF LEAD 
EXPOSURES 11 
1:5 FACTORS AFFECTING TRACE ELEMENT 19 
CONCENTRATIONS IN HAIR 
1:5.a Length of Hair 19 
1:5.b Anatomical Location 20 
l:5.c Hair Colour 21 
l:5.d Geographical Habitat 22 
1:5.e Dietary Suppliments and Medicines 23 
l:5.f Age, Race and Sex 23 
1:6 LEAD IN THE ENVIRONMENT:-
NATURAL OCCURRENCES 26 
1:6.a Rocks 26 
1:6.b Soils 26 
l:6.c Water 27 
1:6.d Air 29 
l:6.e Plants 20 
1:7 GENERAL CONSUMPTION AND USE OF LEAD 
AND ITS COMPOUNDS AND THE RESULTING 
POTENTIAL FOR POLLUTION 
7.a Storage Battery Industry 
7.b Alkyllead Fuel Additives 
7.c Chemical Industry 
7.d Miscellaneous 
7.e Pollution by use and Consumption 
of Lead 
1:8 ENVIRONMENTAL TRANSPORT AND 
DISTRIBUTION OF LEAD 
1:9 EFFECT OF LEAD ON HUMAN BEINGS 
1:9.a Hyperactivity and Physiological Effects 
in Children 
1:9.b Social Deviance in Children 
1:9.c Brain Structure and Biochemical 
Effects 
1:9.d Other Effects of Lead 
ANALYTICAL METHODS 
l:10:a Colorimetric Analysis 
1:10.b Polarography 
1:10.c Atomic Absorption Spectrometry 
1:10.d Elemental Analysis 
1:11 DIGESTION PROCEDURES 
CHAPTER TWO: EXPERIMENTAL 
2:1 INSTRUMENTS AND REAGENTS 
2:2 SAMPLING 
2:3 HAIR WASHING PROCEDURES 
viii 
Page: 
2:4 SCANNING ELECTRON MICROSCOPE ANALYSIS 63 
2:5 LEAD DETERMINATION IN HAIR AND BLOOD 64 
2:6 CARBON AND SULPHUR ANALYSIS 66 
CHAPTER THREE: RESULTS AND DISCUSSION 67 
3:1 SELECTION OF HAIR WASHING PROCEDURE 68 
3:2 GENERAL DISCUSSION 76 
3:3 LEAD LEVELS: GENERAL POPULATION 82 
3:3.a. Scalp Hair Lead Levels 82 
3:3.b. Pubic Hair Lead Levels 91 
3:3.c. Blood Lead Levels 94 
3:3.d. Analysis of Lead Levels With Respect 
to Sex 97 
3:3.e. Blood Lead-Hair Lead Correlation 100 
3:4 COMPARISON OF BATTERY WORKERS AND 
TRAFFIC POLICE PERSONNEL WITH THE CONTROL 
GROUP 104 
3:4. a Introduction 104 
3:4.b Scalp Hair Lead Levels 104 
3:4.c Pubic Hair Lead Levels 105 
3:4.d Blood Lead Levels 107 
3:5 COMPARISON OF THE TWO OCCUPATIONALLY EXPOSED 
GROUPS HO 
3:5. a Introduction HO 
3:5.b Scalp Hair Lead Levels 11 • 
3:5.c Pubic Hair Lead Levels 112 
3:5.d Blood Lead Levels 112 
3:6 MEDICAL SYMPTOMS 115 
3:7 SULPHUR AND CARBON:SULPHUR HAIR ANALYSIS 118 
ix 
Page: 
CHAPTER FOUR: 122 
4:1 CONCLUSION 123 
4:2 RECOMMENDATIONS 127 
REFERENCES 129 
LIST OF FIGURES 
FIGURE 1. SCHEMATIC FOR EDTA WASHING PROCEDURE 
FIGURE 2. SCHEMATIC FOR DETERGENT WASHING PROCEDURE 
FIGURE 3.a. UNWASHED HAIR SAMPLE 
FIGURE 3.b. ETHER WASH 
FIGURE 3.c. EDTA WASH 
FIGURE 3.d. DETERGENT WASH 
FIGURE 3.e. SODIUM LAURYL SULPHATE 
FIGURE 3.f. ULTRASONIC WASH 
FIGURE 3.g. ACETONE WASH 
FIGURE 3.h. KLEENOL® WASH 
FIGURE 3.i. KLEENOL® WASH OF A BATTERY WORKER HAIR 
STRAND 
FIGURE 3.j. KLEENOL® WASH OF A TRAFFIC POLICE HAIR STRAND 
FIGURE 4. SCALP HAIR LEAD LEVELS: GENERAL POPULATION 
FIGURE 5. SCALP HAIR LEAD LEVELS: TRAFFIC POLICE 
FIGURE 6. SCALP HAIR LEAD LEVELS: BATTERY WORKERS 
FIGURE 7. PUBIC HAIR LEAD LEVELS: GENERAL POPULATION 
FIGURE 8. PUBIC HAIR LEAD LEVELS: TRAFFIC POLICE 
FIGURE 9. PUBIC HAIR LEAD LEVELS: BATTERY WORKERS 
FIGURE 10. BLOOD LEAD LEVELS: GENERAL POPULATION 
FIGURE 11. BLOOD LEAD LEVELS: TRAFFIC POLICE 
FIGURE 12. BLOOD LEAD LEVELS: BATTERY WORKERS 
XI 
FIGURE 13. SCALP HAIR LEAD: GENERAL POPULATION 
FIGURE 14. SCALP HAIR LEAD: TRAFFIC POLICE 
FIGURE 15. SCALP HAIR LEAD: BATTERY WORKERS 
FIGURE 16. PUBIC HAIR LEAD: GENERAL POPULATION 
FIGURE 17. PUBIC HAIR LEAD: TRAFFIC POLICE 
FIGURE 18. PUBIC HAIR LEAD: BATTERY WORKERS 
FIGURE 19. BLOOD LEAD: GENERAL POPULATION 
FIGURE 20. BLOOD LEAD: TRAFFIC POLICE 
FIGURE 21. BLOOD LEAD: BATTERY WORKERS 
FIGURE 22. SCATTER DIAGRAM OF BLOOD-LEAD CONCENTRATION 
VERSUS SCALP HAIR-LEAD CONCENTRATION 
FIGURE 23. PERCENTAGE SULPHUR IN SCALP HAIR 
xii 
LIST OF TABLES 
TABLE 1 COMPARISON OF WASHING PROCEDURES FOR HAIR 
CONCENTRATION OF PB UG/G (MEAN ± SD) IN 4 SAMPLES 
TABLE 2 SCALP HAIR LEAD LEVELS FOR THE FOUR GROUPS 
TABLE 3 ANALYSIS OF VARIANCE OF LEAD LEVELS IN THE SCALP HAIR 
AMONG THE EAST INDIAN, AFRICAN AND CHINESE RACIAL 
GROUPS 
TABLE 4 STEPWISE REGRESSION ANALYSIS OF SCALP HAIR LEAD FOR 
ETHNIC GROUPS IN RELATION TO GIVEN VARIABLES SETS 
TABLE 5 PUBIC HAIR LEAD LEVELS FOR THE FOUR GROUPS 
TABLE 6 ANALYSIS OF VARIANCE OF LEAD LEVELS IN THE PUBIC HAIR 
AMONG THE EAST INDIAN, AFRICAN AND CHINESE RACIAL 
GROUPS 
TABLE 7 BLOOD LEAD LEVELS FOR THE FOUR GROUPS 
TABLE 8 ANALYSIS OF VARIANCE OF LEAD LEVELS IN THE BLOOD 
BETWEEN THE EAST INDIAN, AFRICAN AND CHINESE RACIAL 
GROUPS 
TABLE 9 SCALP HAIR LEAD LEVELS BETWEEN SEXES 
TABLE 10 ANALYSIS OF SCALP HAIR LEAD WITH RESPECT TO SEX 
TABLE 11 ANALYSIS OF PUBIC HAIR LEAD WITH RESPECT TO SEX 
TABLE 12 ANALYSIS OF BLOOD LEAD WITH RESPECT TO SEX 
TABLE 13 SCALP HAIR LEAD LEVELS 
TABLE 14 PUBIC HAIR LEAD LEVELS 
TABLE 15 BLOOD LEAD LEVELS 
xiii 
TABLE 16 NUMBER OF INDIVIDUALS WITH SYMPTOMS OF LEAD TOXICITY 
OVER THE PRECEDING MONTH (EXPOSED VS NON-EXPOSED 
GROUPS) 
TABLE 17 THE %SULPHUR IN SCALP HAIR AMONG THE FOUR GROUPS 
TABLE 18 THE CARBON:SULPHUR RATIO IN SCALP HAIR AMONG THE FOUR 
GROUPSLIST OF TABLES 
1 
CHAPTER ONE: 
LITERATURE REVIEW 
2 
1:1 HISTORY OF LEAD POISONING 
Historically, the use of lead by human beings began about 9000 years ago1. A number 
of biblical references to lead have been made, some of which dealt with the refining of 
precious metals from lead containing ores. In addition, ancient ruins containing metallic lead 
artifacts dating back to the fifth and sixth millenia B.C., have been discovered in Turkey, 
Iraq and Egypt1. 
Despite the fact that lead was used in ancient times for making a variety of objects 
and utensils, its use did not attain industrial proportions until Roman times. The Romans 
developed an impressive lead technology after they began utilizing lead pipes for the 
transport of water. This resulted in an increase in the risk of lead poisoning associated with 
the use of lead and lead plumbing1. It was during this period that the first case of lead poi­
soning was reported. Also, at that time, a concentrated grape syrup, supa, was used for 
making wine and as a sweetening agent. This additive used in wine preparation contained 
significant amounts of lead which originated from the utensils used in its production and 
added to the problem of lead contamination. According to authentic Roman recipes, the lead 
used as a flavouring agent in wine was present at a level between 15 to 30 mg Pb/L1. Due 
to their consumption of large quantities of wine, the Roman aristocracy on average ingested 
between 160 to 1520 ug Pb/day compared to only 35 to 320 ug Pb/day for an average 
Roman citizen1. 
3 
A significant number of cases of lead poisoning were reported during the Middle 
Ages as well, mostly due to the contamination of beverages with lead. Even as late as the 
eighteenth century alcoholic beverages were still being distilled using lead containers1. 
Many lead workers were known to be exposed to lead in the period of history known 
as the Industrial Revolution. Lead production rose during this period, increasing from about 
100,000 tonnes per year, 300 years before, to one million tonnes per year. Lead production 
prior to the Industrial Revolution, had peaked at approximately 80,000 tonnes per year at the 
height of the Roman Empire and then declined1. During the Industrial Revolution era, a 
higher than normal incidence of sterility, abortion, stillbirth and premature delivery occurred 
in female lead workers and wives of male lead workers. Mental retardation, failure to thrive, 
convulsion and congenital lead poisoning were experienced by their offspring1. 
The first documented case of lead poisoning from contaminated paint occurred in 
Australia in 1890 while the first case in the United States was reported in 1914'. However, 
the severity of the poisoning problem from lead-contaminated paint was not recognized until 
the middle 1950's. For example, a report from a study done in Baltimore, USA, in 1956 
revealed that 90% of the infants studied had blood lead concentrations in excess of 30 ug/dL 
which was higher than the presently accepted critical limit in children of 10 ug/dL proposed 
by the Centres for Disease Control (CDC) in the U.S.A.2 This was attributed to lead found 
4 
in wall paint in the low-income area studied. Blood lead concentrations in excess of 60 ug/dL 
were found in 26% of these infants. 
There was also great concern in the United States that a number of inner-city children 
had abnormally elevated blood lead levels (greater than 40ug/dL) during the period 1965-
1970. Many researchers studying the blood-lead levels in children during this period found 
that a significant percentage of children had levels greater than this value. For example in 
1965, Bradley3 reported that 40% of the 333 children screened in a low income area of 
Baltimore had blood lead levels greater than 50ug/dL. Also in a New York city study, done 
in 1969, 45% of the children had blood lead levels greater than 40ug/dL. The number of 
children studied (2468) was considered to be a fair representation of the entire population. 
In all three studies, elevated blood lead levels in children were attributed to ingestion of lead-
containing paints. 
However, in 1976, Billick4 studied blood lead levels in a sample of New York city 
children and found that there had been a consistent decline in blood lead levels from 
36ug/100mL in 1970 to 22ug/100mL at the time the study was done. Also, a research project 
done in the United States by The Second National Health and Nutrition Survey (NHANES II) 
revealed that the mean blood lead values of 675,000 children (between 6 months- 5 years) 
sampled for the period 1976-1980 was 30ug/dL which represented a decrease from 19705. 
Billick4 had shown in his study that the blood lead levels in children correlated with gasoline 
lead levels. It should be noted that gasoline consumption started to decrease in 1970. 
5 
Therefore, the decreased lead levels in blood was most likely due to the decrease in gasoline 
consumption. Other factors responsible for the decrease in lead in the American environment 
and the associated decrease in blood lead levels were: 
(1) The change in buying habits of the American automobile consumers. They 
started buying cars with low compression engines which used regular gasoline 
with a lower lead content. 
(2) The phase-down in the allowable lead in gasoline called for by The 
Environmental Protection Agency (EPA) regulations. 
(3) The increased activities related to lead pollution by other Federal Agencies. 
New regulations governing lead exposure of the population in general had 
been implemented. 
Today, approximately three million tonnes of lead are produced worldwide each 
year. Due to poor antipollution practices, a significant amount of lead pollution seems to 
occur in third world countries. For example, it is reported that Nigeria is significantly af­
fected by lead pollution. There are many lead smelters and mines in Nigeria and environ 
6 
mental safety precautions are virtually nonexistent. In addition, in 1991 gasoline sold in 
Nigeria contained 7ug/L of lead (The European Communities' upper limit is 1.5ug/L)6. 
The results of all these practices are: 
1. street dust lead concentrations of 7000ug/g; one of the highest reported in the 
world and 
2. a water lead concentration of 2ug/L. Countries like Glasgow in England and 
Boston, Massachusetts, U.S.A consider a water lead level of 0.5ug/L critical. 
The high lead levels in soil, street dust and water is reflected in the ingested lead and 
blood lead concentrations of people living in Nigeria. Children in Lagos, Nigeria ingest 
between 150-1200ug/day of lead and have blood lead levels higher than that defined 
(25ug/dL) as critical by The Centers for Disease Control in the United States of America6. 
As in biblical times, the problem of lead pollution still exists in the present day 
environment. However, there is now a greater awareness of the problem coined by many as 
the 'silent epidemic'. As such, a number of countries have reduced the concentration of lead 
used in gasoline or have altogether started using unleaded gasoline. Also, industries are 
implementing preventative measures in factories in order to reduce the environmental levels 
of lead contamination. 
7 
1:2 LEAD IN THE LOCAL ENVIRONMENT 
A major source of lead in Trinidad is from automobile exhaust emissions. It is 
estimated that approximately 6.84 tonnes of lead per month are emitted into the Trinidad 
environment by this means7. Further, it has been suggested that about 80% of the particulate 
lead emitted from gasoline combustion is less than 0.9 urn in mean diameter, and fifty 
percent of these particulates can be absorbed by inhalation. The local population is therefore 
exposed to approximately 2.7 tonnes per month of these lead particles that can be absorbed 
via respiration7. 
There are also other major sources of lead contamination in Trinidad. These include 
(1) three battery manufacturing plants; (2) paint manufacturers; (3) printing enterprises; 
(4) ceramic industries and (5) many battery repair operations. These sources of lead may 
together represent greater health hazards than automobile exhaust emissions7. This is because 
lead emitted by these sources tend to be localized, resulting in high concentrations whereas 
lead from automobile exhaust emissions becomes delocalized due to diffusion along the roads 
and highways. 
8 
1:3 MAJOR PROJECT OBJECTIVE 
Although the use of hair as a biopsy material is increasing, blood is still the most 
widely used indicator of human exposure to inhaled and ingested lead. The major objective 
behind this project was to further investigate the viability of replacing blood by hair as an 
indicator of lead exposure. The rationale for testing this alternative is now presented: 
(1) Hair samples are more easily obtained and easier to manipulate than blood 
samples. Hair is also a stable material and can be stored for longer periods 
and at lower cost than blood. For third world countries like Trinidad and 
Tobago, the cost of analytical procedures used in assessing any environmental 
problem in general, and exposure to lead in particular, is of paramount 
importance due to existing economic problems. 
(2) In spite of the fact that attempts have already been made to use hair as a 
biopsy material, convincing proof has to be forthcoming in order that 
acceptance by the recognized World Health Organizations is to be achieved. 
Therefore, this project attempted to gain additional evidence which might have 
been useful in fulfilling this goal. 
9 
Other related objectives were as follows: 
(1) To investigate any significant differences between scalp hair and pubic hair 
lead levels, in order to determine the effects of contamination of scalp hair by 
exogenous lead. Pubic hair is not normally exposed to exogenous lead and it 
was assumed that comparisons of lead levels would help to shed further light 
on this problem. 
(2) To determine whether there are any significant differences in scalp lead levels 
among the racial groups since. If differences were shown to exist, separate 
upper limits for normal lead exposure would then have to be established for 
each race in multiracial societies. 
(3) To determine any correlation between hair texture and lead levels in scalp 
hair. Different races tend to have different hair textures which might be 
related to the carbon/sulphur ratios. Since absorption of lead by hair is 
apparently affected by the sulphur content it was decided to investigate 
whether any correlation existed. 
10 
(4) To study special groups such as industrially exposed persons and police 
personnel involved in traffic control, in order to investigate the relationships 
between hair and blood lead levels and occupational exposure. 
(5) To compare our findings with respect to well-researched factors like sex and 
hair colour with findings in the literature. 
(6) To investigate any relationship between blood and hair lead levels and any 
medical symptoms associated with enhanced lead levels in the human body. 
11 
1:4 ASSESSMENT OF INDICATORS OF LEAD EXPOSURE 
There are many types of tissues in the human body that can be used for lead analysis. 
However some of them such as bone, kidney, brain and liver are not accessible from living 
individuals. Specimens readily available for analysis include blood, hair, teeth, urine and 
nails8. There are disadvantages associated with the use of urine, teeth and nails that make 
them unpopular, especially for routine testing. Lead levels from urine samples reflect the 
amount of lead that is being excreted from the body but not the amount of lead the body 
actually contains8. Healthy teeth are difficult to obtain and little information about nails is 
available. 
Thus, hair and blood remain the most appropriate specimens for lead analysis. Their 
worth as bioindicators is dependent on their capacity to store trace elements. In the case of 
blood, trace elements spend a maximum of a few days after which they are deposited in 
other parts of the body. Hair, however, is a storage organ and retains trace elements over 
an extended period of time8. Hence, hair can provide information on the lead intake of the 
body over several months while blood lead levels only indicate the extent of recent exposure. 
It must be emphasized that these two indicators do not represent different means of assessing 
the same information but reflect the body's trace element status for different time periods. 
12 
In spite of the fact that researchers and medical practitioners traditionally use blood 
as a diagnostic tool there are instances where it has been proven to be an inadequate 
medium. Although lead in blood is still the most commonly used index for measuring 
exposure to lead it does not appear to be the ideal indicator for the following reasons8: -
(1) Lead in blood has a half-life of about one month after which the lead is 
deposited in the bones and hair. Hence, blood lead levels may not give a true 
indication of exposure when such exposure is on an intermittent basis. 
(2) Lead can be quite suddenly released from bones. This results in a person's 
blood lead concentration increasing significantly when such conditions exist 
compared to concentrations prior to the release. 
(3) The sensitivity of blood to numerous influences results in many constraints as 
to its use as a bioindicator. Blood is a complex and heterogenous medium 
where all the parts exhibit different concentrations of trace elements. It is not 
certain which of the following - whole blood or its components plasma, 
serum, leucocytes, or erythrocytes - offer a reliable reflection of the body 
status of trace elements. Trace elements in the blood are not fixed to any of 
these components but are constantly transferred from one component to anoth­
er. The parts are in equilibrium with each other8. In addition, there appears 
13 
to be a wide range of factors involved in the binding of lead to the haemoglo­
bin which is a component of the erythrocytes. The protein in blood provides 
a matrix onto which metals are strongly bound, resulting in difficulty in deter­
mining these protein-bound metals directly9. Many metals are present as 
complexes in blood but there is still much uncertainty about the mechanism 
of interaction between blood and metals. In order to remove trace elements 
from such complexes, two methods are generally employed. Chelating agents 
can be used to form a complex with the lead, or acid digestion of the blood 
can be used to decompose the blood-lead complex. Many of these procedures, 
however, have either a significant risk of contamination or a considerable 
decomposition time. 
Given the difficulties with the use of blood as a specimen, hair deserves special 
consideration as an alternative since hair offers a number of advantages8:-
(1) Short term variations are averaged out in hair, when hair representing a few 
weeks of growth is sampled and its trace element concentration measured. 
From this, one can obtain an average value for a certain period of time. This 
can be done by cutting the hair into similar sections (each section representing 
a particular time period) and analyzing each separately or by taking samples 
NOT TO BE REMOVED 
CDflM i u C  I I DOADV 
14 
periodically eg. monthly. This allows for a better assessment of the normal 
trace element concentrations in the body. 
(2) Hair is inert, chemically homogeneous and forms a permanent structure. Once 
trace element atoms are incorporated into it, they become fixed. In addition, 
there are no problems caused by deterioration during storage prior to analysis. 
(3) Hair-lead concentrations are comparatively higher than the values obtained 
from other tissue specimens and therefore measurements are less subject to 
error. 
(4) Compared to blood, urine and other tissue specimens, hair can be collected 
quickly, easily and without pain or embarrassment to the donors. In addition, 
collection requires no special training or equipment. 
(5) Samples may be taken retrospectively, since hair provides a record of past as 
well as present trace element levels. For example, if a pregnant woman has 
been diagnosed for lead poisoning, a sample can be taken to discover her 
condition prior to conception. 
15 
Although these advantages clearly make hair an attractive alternative for trace element 
testing, a number of criticisms have been made which require consideration. 
Firstly, there exists some variation in the trace element concentrations of the hair 
across the scalp. However, these variations tend to be small when compared to the variations 
found between individuals. These small diversities in the hair-lead values obtained from one 
patient may be due to hair samples of differing lengths being taken from different locations 
on the head. This problem can be resolved, by sampling from only one specific region of 
the head. The nape of the neck is usually regarded as the most appropriate place since it is 
least exposed to exogenous contaminants10. 
Secondly, there is the problem of exogenous contamination of the hair with trace 
elements. For example, hair treatment effects must be considered. Mild hair preparations, 
such as conditioners and hair sprays do not leach out trace elements but bleaching and dyeing 
do11. In order to avoid incorrect results, account must be taken, where necessary, of the use 
of hair treatments. As a result of exogenous contamination it is difficult to always differen­
tiate between systemic trace elements and non-systemic trace elements in hair. However, 
research has shown that the least amount of diffusion occurs in hair closest to the root10. 
Thus this segment gives a better exposure index than other segments and provides, at least, 
a partial solution to the problem. 
16 
Another alternative for reducing the problem of exogenous contamination associated 
with scalp hair is to use pubic hair since it is not usually subjected to the application of 
cosmetics and shampoos that may contain heavy metals. However, it grows more slowly than 
scalp hair and therefore when comparing pubic hair with scalp hair the growth rate of each 
would have to be taken into consideration10. 
Thirdly, choosing an effective washing procedure poses problems. In the literature 
there is a variety of washing procedures, ranging from methods involving distilled water to 
complicated procedures involving organic solvents. The acetone washing procedure is 
accepted by The International Atomic Energy Agency12. However, this washing procedure 
has been criticized because acetone removes less exogenous trace elements than ether, EDTA 
or detergent washing procedures and thus acetone-washed samples do not give as good an 
indication of systemic lead as samples washed using the ether, EDTA or detergent washing 
procedures13. 
At the present time it is not possible to deduce whether some trace elements are 
extracted from the hair by the washing methods employed. As a result, it is difficult to deter­
mine which is the most suitable washing procedure. However, comparisons can be made 
between washing procedures where the effects are shown to be similar and such comparisons 
should then be reasonably valid14. 
17 
Finally, it must be remembered that the time scale for blood and hair is different and 
therefore one should not expect any clear-cut correlation between the concentrations in the 
hair and blood11. 
Since lead must enter the blood in order to produce detrimental changes to the body, 
it is important to know how much lead is in the blood. But, in terms of assessing exposure 
and health problems, lead in the hair seems to be a better indicator. Thus, a number of 
studies have shifted to using lead levels found in hair1213,14. 
Nowadays, some international recognition is being given to scalp hair for the 
monitoring of heavy metal toxicity. For example, in Japan, Iraq and the United States, hair 
has been used to estimate the body burden of mercury15. More recently, similar reports on 
the use of hair as a bioindicator have been published. One study has used hair zinc analysis 
as one of the criteria for identifying children with increased body burdens16. Another has 
reported the scalp hair lead levels from children suffering from chronic plumbism, mostly 
from pica17, while yet another study has compared the lead levels in antique and contempo­
rary hair samples from both children and adults18. 
As cited in the literature, hair is of significant importance as a bioindicator for trace 
metal analysis. Hair therefore offers a possible alternative to blood as a bioindicator. In 
18 
many instances when trace element concentrations in the body are to be determined, hair can 
be the more appropriate bioindicator. 
19 
1:5 FACTORS AFFECTING TRACE ELEMENT CONCENTRATIONS IN HAIR 
The major factors that affect the trace element concentrations in hair are19: 
(1) the distance from the scalp from which the hair sample was taken; 
(2) the anatomical location of the hair sample; 
(3) the colour of the hair sample; 
(4) the geographical location of the donor; 
(5) dietary supplements and medications consumed by the donor and 
(6) age, race and sex 
l:5.a Length of Hair 
A study done by Hambidge revealed that the length of the hair influenced trace metal 
concentrations. Hair samples used were from subjects who did not use treatments such as 
dyes or bleaches and each sample was separated into a proximal and a distal section. 
Analysis of these samples for copper showed that there was an increasing concentration 
gradient in progressing from the proximal to the distal end of the hair19. It was concluded 
20 
that since the distal region of the hair was exposed to the environment for a longer period 
of time, the contamination of this region was greater and hence the reason for the higher 
copper concentration.Other independent studies which showed similar trends were done by 
Grandjean20, Fergusson et al21, and by Renshaw et al22. Exogenous contaminants such as, 
dirt, sweat, and sebum were shown to be the cause of these differences. 
l:5.b Anatomical Location 
In humans, hair is distributed unevenly over the body and can be categorized into the 
following four groups-: pubic, scalp, facial and axillary hair. Many researchers have 
compared the effectiveness of hair obtained from these anatomical sites for the purpose of 
determining extent of exposure to lead. 
Pubic and pectoral hair are not normally exposed to the environment and should be 
less affected by exogenous contaminants compared to hair obtained from other regions of the 
body. The uncertainty associated with exogenous contamination could be removed by using 
pubic or pectoral hair as a bio-indicator instead of scalp hair. However, it must be noted that 
pubic and pectoral hair grow more slowly than scalp hair and are more liable to be 
contaminated by sweat and sebum19. 
21 
In addition to environmental contaminants, hair from different parts of the body are 
also exposed to different external conditions with respect to toiletries and medications. 
However, there is at present no experimental evidence to support the possibility that these 
factors contribute to the lead body burden. 
One investigation compared the concentrations of zinc, cadmium, lead and copper in 
facial and scalp hair samples taken from the same individuals19. It was found that the scalp 
hair concentrations were from 2 to 20 times greater than those for the facial hair. Similar 
investigations showed mean scalp hair values to be significantly higher than those for pubic 
hair19. However, in a more recent study, the scalp and pubic hair from 15 healthy non­
pregnant women showed no significant difference between their copper, zinc and manganese 
concentrations19. 
Since at present there is no means of differentiating between trace elements of 
exogenous and endogenous origin, one must be careful when lumping together data acquired 
from hair belonging to different anatomical sites. 
l:5.c Hair Colour 
Hair colour is another variable which can affect the concentration of trace elements 
in hair. The colour of one's hair is influenced by the concentration of melanin pigment in 
the cortex. Blonde or white hair has less melanin than dark hair. Red hair contains an 
additional pigment called siderin. It was suggested that since the siderin pigments contain 
iron and since copper is used as a cofactor for the enzyme tyrosinase in the biosynthesis of 
22 
the melanin pigment, there may be a relationship between iron and copper concentrations and 
colour. Black or blonde hair was reported to have a lower iron content compared to red 
hair19. 
Although dark hair tends to have a higher level of lead than white hair, a study done 
by Grandjean20 showed no significant difference between dark hair and white hair among 
occupationally exposed workers. However work done by Shroeder and Nason23 showed that 
hair lead levels decrease in the order, brown, blonde, black, and red. 
1:5.(1 Geographical Habitat 
Geographical location appears to contribute to the concentration of trace elements in 
scalp hair. In some cases, these differences are due to variations in environmental pollution 
from one location to another. For example residents of Port Arthur19, Texas, U.S.A., were 
found to have scalp hair lead levels 36% greater than the residents of Hanover, New Hamp­
shire, U.S.A. It was proposed that the higher hair lead concentrations were as a result of 
exposure to airborne lead from the gasoline production center at Port Arthur. Differences 
23 
may also be due to genetic and/or dietary factors for races who often tend to inhabit specific 
geographical locations across the globe. 
l:5.e Dietary Supplements and Medicines 
Distinct differences in trace element concentrations in scalp hair have been found 
between vegetarians and non-vegetarians by some investigators19. In addition, it has been 
reported that scalp hair zinc concentrations for the subjects studied increased after a period 
of zinc supplementation19. The consumption of a highly refined diet can also result in an 
increase in scalp hair zinc level19. 
l:5.f Age. Race and Sex 
Many examples have appeared in the literature which suggest that age, race and sex 
do influence trace element concentrations. A number of researchers have found an associa­
tion between trace element concentration and age. In one study the scalp hair concentrations 
of copper, lead and cadmium of donors under the age of 30 were found to be significantly 
different from donors over the age of 4023. In another study done by Petering and Yeager, 
lead and cadmium concentrations were also found to be dependent on age24. 
Among age dependent subgroups, variations in trace element concentrations exist19. 
This could be attributed to differences in dietary habits and nutritional consumption. 
24 
Racial/ethnic groups often have unique and characteristic dietary habits associated with their 
culture. This may give rise to the variations in trace element concentrations seen among these 
groups. 
Race was also thought to influence trace element concentrations in the body. Hung 
et al25 studied 20 Vietnamese students and their Polish counterparts, all of whom lived under 
identical conditions in a hostel in Krakow, Poland. The study involved comparing the iron:zi­
nc, coppenzinc and calciumrzinc ratios in both groups of students. Both the ironrzinc and 
the calcium:zinc ratios of the Vietnamese were approximately half that of the Polish, while 
the copper:zinc ratio was the same for both groups. A study done by Hall et al26 on a sample 
of 115 Trinidadians showed that there was a significant difference in the lead concentration 
among the East Indian, African, Chinese and Mixed race groups studied. This was attributed 
to differences in hair texture. In another study done in Santo Amaro, Brazil the ethnic group 
'Dark', had a higher lead concentration compared to the ethnic groups 'Medium' and 
'Light'27. The classification was based on the degree of the negroid phenotype. Hair colour, 
type and conformation of nose and lip, and skin colour were the criteria used in phenotyping. 
It must be noted that differences found among ethnic/racial groups may also be affected by 
environmental and geographical factors. 
Whether or not a significant difference exists in trace element concentrations of scalp 
hair between males and females, is still a subject of controversy. One investigator found that 
25 
at the 90% confidence level there is no significant difference in the mean lead in the scalp 
hair between sexes28. Another reported that the lead content of hair from females was 
significantly higher than that from males29. In yet another study it was found that, in females, 
the calcium and magnesium levels were twice that of males while the nickel levels were four 
times that of males. Petering and Yeager24 also found that lead and cadmium concentrations 
in hair are dependent on sex. It has been postulated that differences in hormonal activity may 
be responsible for variations in trace element concentrations found between sexes. 
As mentioned before in this section, many factors affect the trace element 
concentrations in hair. As such researchers would have to pay attention to these factors when 
pooling data of trace elements in hair and when comparing their research results with those 
present in the literature. 
26 
1:6 LEAD IN THE ENVIRONMENT:-NATURAL OCCURRENCES 
l:6.a Rocks 
Rocks that make up the earth's crust have lead concentrations that range between 10-
20ug/g30. There are areas, such as lead ore deposits for example, where the concentrations 
are higher. Igneous and metamorphic rocks characteristically contain lead, having concentra­
tions ranging between 10-20mg/kg30. Sedimentary rocks also tend to have concentrations of 
lead between 10-20mg/kg. Sandstone and the carbonaceous shales from both the United 
States and Europe have lead concentrations ranging between 10-70mg/kg30. Phosphate rocks 
tend to have even higher concentrations that exceed lOOmg/kg in certain instances31. 
l:6.b Soils 
Surface soils are in contact with the external environment and hence are most likely 
to be polluted by man's activities. Therefore, one has to distinguish between soils that 
contain naturally occurring lead and those that are polluted by man. Levels of naturally 
occurring lead in soils have a range between 2-200mg/kg and a mean concentration of 16mg-
/kg32. These values are extremely low compared to industrially polluted soil. One investigator 
27 
found the lead concentration in soil near a lead mining area to have a value of 20,000mg/K-
g32. 
With respect to naturally occurring lead, alkaline soils tend to have a higher content 
than acidic soils. The lead content in alkaline soil is influenced by the nature of the organic 
matter present. Those rich in chelating agents tend to have high levels of bound lead . This 
results in either movement of lead out of the soil or fixing of the metal in the soil, depending 
on the solubility properties of the lead complexes33. 
Lead analyses done on surficial soil along a major highway in Trinidad (The 
Churchill Roosevelt Highway), showed that the lead levels increased over a one year period. 
In July of 1977 the lead levels in soil found close to this highway was recorded as being 
90ug/g. Soil samples taken at the same location in February, 1978 contained 172ug/g of lead 
and in August in the same year, 238ug/g of lead34. 
l:6.c Water 
Many investigators have carried out studies of the lead concentrations in natural 
surface water. Friberg et al. have found the lead concentrations in water to be in the range 
of 7-10ug/L in rivers of the Midi-Pyrenees of France32. Livingstone et al.35 have estimated 
that a range of l-10ug/L of lead is considered to be the global range for rivers and lakes. 
28 
This is considered to be a reasonable estimate although it includes man-made pollution. The 
self-cleaning mechanism of water flowing through the ecological system allows for this 
accommodation. 
Research has shown that freshwater has a higher lead concentration than seawater. 
With respect to seawater, surface seawater tends to have higher lead concentrations than deep 
seawater. For example surface seawater around the coast of California was reported to have 
lead concentrations in the range of 0.08-0.40 ug/L while deep waters around the coast of 
Bermuda contained an average of 0.07ug/L of lead36. It has been estimated that surface ocean 
waters have a lead concentration range of approximately 0.30ug/L while deep ocean waters 
have a concentration of about 0.10-0.22ug/L37. 
A survey done in 1980 by the Water and Sewerage Authority in Trinidad showed that 
the concentration of lead in freshwater lay between 4.1-8.1 ug/L34. At that time these values 
were considered too low to be of any significance. They were actually lower than the present 
standard for potable water in the USA which is set at 50ug/L. More recent figures are 
unavailable. 
29 
l:6.d Air 
In the most remote areas of the world, for example Greenland, the concentration of 
lead in air ranges between 0.0001-0.00lug/m3 38. The concentration of naturally occurring 
lead in air using geochemical data was estimated to be approximately 0.0006ug/m3 39. 
However, in a study done in 1972 in the remote Southern California mountains, in the 
U.S.A., the concentration of lead in air was found to be 0.008ug/m340. It seems therefore 
that the air lead concentrations even in remote uninhabited areas have been affected by man-
made pollution. Other examples are the North-Central Pacific Ocean and Southern Indian 
Ocean, where the mean air lead concentration is 0.001ug/m3. On the contrary, a typical 
urban environment has ambient air lead concentrations in the range of 280ug/m3 - 3000ug/m3 
in the vicinity of heavy traffic41. 
The eight-hour daily average lead levels in air along the single lane section of a busy 
highway in Trinidad (The Solomon Hochoy Highway) measured over a three month period 
in 1988 ranged between 0.83-12.65ug/m3. The United States Environmental Protection 
Agency has set an ambient air quality standard of 1500ug Pb/m3 for eight-hour averages. It 
is clear that the study done in Trinidad showed lead in air values below this limit42. 
30 
l:6.e Plants 
Plants also accumulate lead naturally from the environment. Leaves and twigs of 
woody plants have normal lead concentrations of 2.5ug/kg (dry weight) while vegetables and 
cereals have concentrations ranging between 0.1-1.0mg/kg43. 
Grasses that grow in the vicinity of roads prone to heavy traffic, may have very high 
lead concentrations. One such study showed a lead value of 250mg/kg in grasses at 
roadsides32, this being attributed to environmental exposure. In a study conducted in 197934, 
it was shown that vegetables grown close to the Churchill Rosevelt Highway in Trinidad con­
tained about l-5ug/g of lead by dry weight for parts usually consumed. It was also 
demonstrated that much of the lead deposited on vegetables was removed during rainfall or 
by washing. 
Lead occurs naturally in all areas of the environment. It is present in air, water, soil, 
rock and even in plants. The lead concentrations that occur naturally in components of the 
global environment are way below the levels which pose a threat to man and his 
environment. However, due to man's activities lead levels have increased significantly 
throughout the ages. Therefore, the severe environmental problems which face man today 
with respect to lead pollution, is as a result of his disregard for the well-being of the 
environment. 
31 
1:7 GENERAL CONSUMPTION AND USES OF LEAD AND ITS COMPOUNDS 
AND THE RESULTING POTENTIAL FOR POLLUTION. 
l:7.a Storage Battery Industry 
The largest consumption of industrial lead normally results from the manufacture of 
electric storage batteries. Lead, both in the form of lead-antimony alloys and lead oxide is 
used by this industry in almost equal proportions. While the oxides litharge (PbO), red lead 
(Pb304) and grey oxide (Pb02) are used in the active material that is pasted on the plates, the 
metallic lead is used in grids and lugs. Much of the lead used in the battery industry comes 
from secondary lead production. It has been established that about 80% of the lead in storage 
batteries is recovered lead, produced at secondary smelters44. 
l:7.b Alkvllead Fuel Additives 
Using alky Head compounds as additives has been the most economical way of 
achieving required octane levels in commercial gasolines. By far, the most commonly used 
lead alkyls are tetraethyllead (TEL) and tetramethyllead (TML) which were discovered in 
the early 1920's45. The use of alkyllead additives is now the major contributor to lead 
pollution worldwide as it is in Trinidad and Tobago. 
32 
l:7.c Chemical Industry 
About 40% of the lead produced worldwide is incorporated into chemical compounds. 
Lead salts form the principal ingredient in the manufacture of some paints and pigments. 
White pigments are produced from lead carbonate and lead sulphate. Lead chromate paints 
(chrome yellow and chrome red) are used for painting steel structures. Other chemicals 
containing lead are lead arsenate (insecticide), lead sulphate (rubber compounding) and lead 
naphthenate (dryer in oil paints)46. 
The paint industry in Trinidad and Tobago uses lead compounds in the manufacture 
of some paint. The lead compounds are used as: 
(1) dryers in oil paint; 
(2) anti-corrosive agents in primer for steel work; 
(3) components in certain car paints and 
(4) antifouling agents in boat-bottom paint to prevent barnacle formation7. 
33 
l:7.d Miscellaneous 
The surface of lead oxidizes readily to form a layer that is very resistant to corrosion. 
As a result of this property, the motor vehicle industries coat motor vehicles and 
motor vehicles spare parts which can become carroded with a layer of lead. Such industries 
account for a substantial proportion of the total lead consumption. Lead sheet is used for 
roofing and other flashings, wall cladding and sound insulation in the building and construc­
tion industries. Solder, bearing metals, brasses, type metal and collapsible tubes are all made 
from alloys of which lead is a component46. 
l:7.e Pollution bv the Use and Consumption of Lead 
Automotive exhaust is the major contributor to lead emissions in most cities. Other 
minor sources include paint and factory emissions. In Trinidad and Tobago, the gasoline sold 
contains approximately 2.75mL of tetraethyllead (TEL) per US gallon (4.5L) and together 
with other additives the total concentration of lead is about 0.5g/L. The average annual 
consumption of gasoline in Trinidad and Tobago is 517,972 kilolitres. Therefore, gasoline 
containing at least 259 metric tonnes of lead is utilised by automobiles in Trinidad and 
Tobago every year7. In Australia it has been estimated that about ninety eight percent of lead 
emissions come from lead in petrol, though the lead added to petrol only represents fourteen 
percent of the total usage47. 
34 
There are also other sources of lead that contribute to environmental pollution. Eye 
cosmetics used by women and children in India, Bangladesh, the Middle East, Pakistan and 
North Africa contain lead. It is called kohl or surma and contains lead sulphide48. Many 
earthenware containers used at present contain lead in the form of lead oxide, lead carbonate 
and lead monosilicate. These lead compounds are leached out of the containers during use49. 
Mexican children and adults use a folk medicine called azarcon, which contains 86 to 90 
percent lead tetraoxide, to relieve abdominal symptoms50. Toys, furniture, lead plumbing and 
leaded glass artwork also contribute to environmental pollution51. 
35 
1:8 ENVIRONMENTAL TRANSPORT AND DISTRIBUTION OF LEAD 
The mechanism by which lead is transported and distributed in the environment, 
whether it is from a stationary or mobile source, is mainly through the atmosphere. Large 
discharges may also occur directly into natural waters and onto the land. But in such cases, 
lead tends to be localized near points of discharge owing to very low solubilities of the com­
pounds that are formed upon contact with soil and water52. The mechanism by which lead 
is removed from air and transferred to other media is not fully understood. The most 
efficient cleaning method is probably rain. There are however data which suggest that 
sedimentation contributes significantly to the proportion of lead that is removed from air53. 
The high affinity of organic matter for lead results in lead being rapidly removed from water 
as it passes through soil and bottom sediment. Thus, lead concentrations in both natural 
water and water supplies are generally low54. 
Motor vehicle exhaust systems emit lead compounds into the atmosphere in a number 
of forms. Lead can be emitted as volatile lead compounds such as lead halides, unburnt tetr-
aethyllead and as particulates such as lead oxides. Approximately 70% of these particulates 
have a size of less than 0.1 micron which make them easily dispersed over large distances, 
and extremely hazardous to humans, since they are small enough to pass into the lower part 
of the lungs47. 
36 
In Trinidad and Tobago a great proportion of the lead in the atmosphere comes from 
automobile exhaust emissions. Most of this lead emitted is deposited in the region of roads 
and highways7. Thus the roadside vegetable vendors and the vegetables sold by them become 
contaminated by this lead deposit. However, most of these vegetables are washed prior to 
human consumption and as such pose little threat with respect to the ingestion of lead by 
humans. 
37 
1:9 EFFECTS OF LEAD ON HUMAN BEINGS 
As expected from a poison which damages the nervous system, with acute lead 
poisoning there are physiological and behavioural effects. Since most neurotoxins show 
disturbance of behaviour and/or intelligence it is no surprise that behavioural effects result 
from lead intake at even low concentrations. 
l:9.a Hyperactivity and psychological effects in Children 
Chronic lead exposure has been linked to hyperactivity in children. One definition of 
hyperactivity is "a sustained and excessive level of motor activity which gives rise to signifi­
cant complaints at home and at school" 55. The symptoms of hyperactivity include restless­
ness, difficulty in concentrating, excessive talking, poor tolerance to frustration, rejection 
of authority and poor control of impulses. 
The most comprehensive study so far done on the effects of subclinical lead 
intoxication in children has come from the Harvard Medical Center in Boston, Massachu­
setts, U.S.A.56 In this study, social and environmental factors were eliminated through the 
statistical technique of analysis of variance. This technique compensates for the effects of 
aggregate socioeconomic background factors. In this study done by Needleman56, the sample 
population consisted of 2000 children. A Teacher's Behavioural Rating Scale assessment of 
38 
each child was done by his/her teacher and each child was also given a standard psychologi­
cal performance test. A shed milk tooth was the indicator used to determine the concentration 
of lead in each subject. 
The main conclusions from the study were: 
1. Higher-lead groups had an Intelligence Quotient (I.Q.) of about five points 
lower than lower lead groups. 
2. Higher-lead groups had an attention span test performance of about 14% 
below that of the control group. 
3. Reaction times for picture completion and some verbal processing were 
delayed by about 16%. 
4. Teacher assessment showed a number of characteristics associated with high 
lead level groups, such as: 
(a) lack of independence 
(b) lack of organization 
(c) hyperactivity 
39 
(d) lack of persistence 
(e) distractibility 
The Needleman study showed that there is no clear-cut "no effect" threshold at which 
the problem could be considered safe. The number of behavioural problems increased in a 
dose-related fashion with dentine lead levels. 
l:9.b Social Deviance in Children 
According to researchers there have been suggestions of direct links between the 
concentration of lead in the blood and a range of socially deviant behaviour57. Skepticism 
initially greeted this idea. However, there have now been studies showing possible relation­
ships. A link between aggressive to violent behaviour and high blood lead levels has been 
suggested by one study58. In Sydney, Australia the lead content of the blood and hair of 
school children was studied as well as the lead content of the surrounding air. This study 
investigated the effecs of lead on the behavioural characteristics in children. A strong 
association was found between lead levels in blood and behavioural characteristics47. 
l:9.c Brain Structure and Biochemical Effects 
The level of uncertainty in the behavioral studies, due to the possibility of other social 
causes, was reduced considerably when it was found that complementary studies55 showed 
40 
that lead alters the brain structure and the biochemistry of the nervous system in the 
following ways: 
(i) Biochemical changes 
Lead inhibits many enzymes in the brain and thus affects several biosynthetic 
pathways. Lead also competes with calcium in a range of other biochemical processes. A 
study59 showed that interference with calcium by lead results in changes to: 
(a) brain maturation processes; 
(b) the conduction of nervous impulses resulting in alteration of anxiety levels; 
(c) the regulation of energy supplies to the brain and 
(d) the ability of the brain to mediate sensory inputs and behaviour outputs. 
(ii) Brain Structure Changes 
Lead exposure also produces physiological changes in addition to biochemical 
changes. A 23% reduction in the number of synapses in rats60 with significant alteration in 
brain tissue50 and a 13% reduction in brain weight have been found at high lead levels. It 
41 
was also found that at lower levels - equivalent to normal urban exposure - lead concentrated 
in regions of the brain believed to control behaviour resulted in these regions exhibiting 
changes, particularly in cell thickness60. Needleman56 demonstrated that children with high 
dentine lead levels also showed significantly different electrical activity in the brain. This 
study showing how behavioural changes can be induced by low lead level exposure is consid­
ered one of the most significant pieces of work done in this area. 
l:9.d Other Effects of Lead 
(i) Development of the Foetus 
Studies have shown that the foetus can concentrate lead in the brain which can cross 
the placental membrane from the mother to the developing foetus61. For about fifty years it 
has been known that the foetus can be exposed to lead via the mother's blood. Also known 
was the fact that women exposed to lead had a higher risk of spontaneous abortions and still­
born babies. 
Males can also contribute to deformities and behavioural problems in the developing 
foetus of the children, if they were exposed to lead. This is because lead which accumulates 
in the sperms causes the sperms to change their normal shape resulting in unfavourable 
mutations62. 
42 
(ii) Cancer 
Strong correlations have been found between exposure to lead and cancer mortality 
among lead workers and those exposed to vehicle exhaust fumes47. Well below the human 
exposure limit (4ug/100mL for blood) lead has been found to cause chromosomal damage. 
Lead binds to organic chemicals such as benzpyrene very easily. This could therefore be the 
means by which benzpyrene can be transported into the body and could help to explain the 
increased levels of cancer found near busy roads. 
(iii) Decreased Resistance 
Research has revealed that at doses below clinical lead toxicity levels, lead interferes 
with the body's immune system resulting in viral infections47. 
(iv) Interference With Drugs 
Lead reacts with a variety of organic compounds and since most drugs are organic 
by nature it can possibly alter the pharmocological effects of these drugs. This is particularly 
important in cases where the drugs are chelating agents which could cause the release of lead 
stored in bones or organs and its subsequent redeposition into more susceptable areas such 
as the brain47. 
43 
1:10 ANALYTICAL METHODS 
Introduction: 
The choice of a method for the determination of lead in a particular laboratory 
depends on factors such as: 
(1) the purpose of the analysis; 
(2) the availability of equipment; and 
(3) the number of samples to be analyzed per day. 
The analysis of samples for low levels of lead is carried out by three main methods: 
(1) colorimetric analysis; 
(2) polarographic analysis; and 
(3) atomic absorption spectroscopy (AAS). 
There are also several non-routine methods for the analysis of lead in a variety of 
matrices. These methods include electron microprobe analysis, X-ray fluorescence 
44 
spectroscopy, neutron activation analysis and mass spectroscopy. All require the use of 
expensive facilities and a high degree of analyst expertise. 
l:10:a Colorimetric Analysis63 
Of all the reagents which form coloured complexes with lead, dithizone is considered 
the best reagent for the determination of trace quantities of that metal. The results obtained 
are comparable to those obtained by Atomic Absorption Spectroscopy. However dithizone 
forms coloured complexes with seventeen metals including mercury, bismuth, copper, gold, 
thallium and cadmium. The latter two, not masked by cyanide, are co-extracted with lead. 
Since a colorimeter cannot differentiate between the dithizonates of lead, thallium and 
cadmium the accuracy of lead determination can be seriously affected in the presence of 
thallium and cadmium. Many modifications of the dithizone method for lead analysis can be 
found in the literature, but sources of error in the dithizone method still exsist, especially 
when analyzing clinical samples. 
Other complexing agents can also be utilised in the colorimetric determination of lead. 
For example, lead can be quantitatively extracted as a benzoyl acetonate over a pH range of 
7-10 while hydroxyquinoline forms a complex extractable over the pH range of 6-10. At pH 
5, lead can be extracted as a thenoyltrifluoroacetonate complex. Cupferron extracts lead 
completely over pH range 3-9. Beta-naphthylthiocarbazone is employed in the analysis of 
45 
lead in biological material. The beta-naphthylthiocarbazone complex formed is completely 
extractable at pH 9.8. Ammonium pyrollidine dithiocarbamate (APDC) is a fairly effective 
lead chelate over a narrow pH range of 2.2-2.863. Once extracted with the specific 
complexing agent, the lead concentration is then determined colorimetrically at wavelengths 
appropriate to the respective complex. 
l:10.b Polarographv64 
Isolation of lead by its electro-deposition from a solution of decomposed biological 
material was recommended as early as 1941. Microgram quantities of lead could be detected 
by this method. Iron and copper were found to interfere but their effects could apparently 
be minimized by the addition of potassium cyanide. 
The technique, using anodic stripping voltametry (ASV), has become a widely 
accepted method for lead analysis. In this method ionic lead in samples is first reduced to 
elemental lead by a negative potential applied to a working mercury electrode. After a pre­
selected time the working electrode potential is moved towards more positive values, thereby 
causing re-oxidation of the lead. The resulting anodic current from this oxidation, which is 
proportional to the concentration of lead in the sample, is measured64. 
46 
l:10.c Atomic Absorption Spectrometry65 
Atomic absorption spectrometry appears to have a number of advantages over 
methods such as polarography and atomic emission spectroscopy for trace metal 
determination. It is still one of the cheapest methods of metal analysis. In addition, a large 
number of samples can be rapidly analyzed using autosamplers. Another distinct advantage 
is that interference problems are either minor or non-existent, and where such problems 
exist, simple solutions are readily available. 
The most widely used technique for analysis of heavy metals in recent times is atomic 
absorption spectrometry. It is based on the absorption of radiation by free ground state 
atoms. Basically it is a method which interposes metal atoms in the pathway of a beam of 
radiation emitted by the same atomic species and measures the amount of radiation which 
is absorbed. This is compared with standard solutions of the same metal for the determina­
tion of the concentration of the metal in the solution being studied. Since radiation is emitted 
and absorbed at a characteristic line peculiar to that element, the presence of large excesses 
of the other atoms is not normally a serious problem, although matrix affects can lead to 
errors of analysis. 
The sample, liquid in the case of flame atomic absorption, is aspirated into a flame 
in which the solvent is evaporated and the molecules are decomposed into atoms. The 
radiation from the hollow cathode lamp (HCL) or electrodeless discharge lamp (EDL), made 
47 
of the element to be determined, is directed through the flame and is received on a detector 
(a photo cell or photomultiplier). The radiation is decreased when solutions of the species 
are aspirated, and the reduction in intensity of the radiation received is recorded or displayed 
as the signal. The recent development of the carbon tube atomizer, which is electrically 
heated, has enabled the use of smaller volumes of liquid samples and allowed the direct 
analysis of solid samples. 
There are few spectral interferences in atomic absorption spectroscopy, since the 
resonance line in the spectrum of the element being determined is used. In the determination 
of trace metals by atomic absorption spectroscopy the main interference problems are due 
to: 
(1) scattering of radiation by particles in the flame, 
(2) matrix effects due to large excess of other ions, 
(3) flame instability, and 
(4) background absorption by other molecules in the flame. 
Most of these interferences can be adequately corrected for, through the use of 
deuterium background correction. At very low levels, flame noise becomes predominant and 
48 
limits the sensitivity. One other source of error which cannot easily be corrected is the effect 
on the flame of the constituents of the sample solution, since this is unknown. 
The advantages of atomic absorption spectrometry: 
(1) high specificity, 
(2) high sensitivity, 
(3) many elements can be determined in one solution, 
(4) relatively low sample preparaton and analysis time, and 
(5) versatility with regards to sample types and concentration 
ranges. 
lilO.d Carbon/Sulphur Analvsis-The Elemental Analyzer 
The modern analytical techniques for carbon and sulphur determination are still based 
on The Dumas-Pregl method66. The Perkin elmer 240B Elemental Analyzer is based on this 
method. 
49 
The 240B Elemental Analyzer 
In the 240B model, the weighed sample is combusted in a pure static oxygen 
atmosphere. This has been shown to be the most efficient means of combusting even the 
most volatile sample material. The process is finished with a dynamic combustion (rapid 
flow) to ensure complete combustion of even the most stable materials. The products of 
combustion are passed over suitable selective materials to ensure complete oxidation and 
removal of undesirable by-products such as phosphorus and halogen gases. The combustion 
products are then passed through the reduction tube, where oxides of nitrogen are converted 
to molecular nitrogen. 
The carbon dioxide, sulphur dioxide and nitrogen are then flushed by helium into a 
mixing chamber where they are thoroughly homogenized at a precise temperature of 1000°C 
and pressure of 30 atm. This homogenous mixture is then analyzed by passage through a 
series of three high precision thermal conductivity detectors (glass coated platinum thermal 
filaments), each detector consisting of two sensing cells. 
For sulphur determination, between the first pair of T-cells, there is a tube 
containing a tungstic oxide packing plus a dehydrating agent in the cool zone of this same 
tube. The T-cells are the combustion units in the elemental analyser. There is a bridge area 
packed with silver oxide to absorb sulphur dioxide, the product of combustion. The sulphur 
from the sample is oxidized to form sulphur dioxide and the water formed is removed in the 
combustion tube. Between the first pair of T-cells is an absorption trap containing a 
50 
dehydrating material, magnesium perchlorate. As the gas passes through, water is removed 
from the stream. The differential signal obtained before and after the trap, as read on the 
potentiometric recorder, reflects the sulphur dioxide concentration and therefore the amount 
of sulphur in the original sample. A similar measurement is made with a second pair of 
conductivity cells between which there is a trap that removes carbon dioxide. The remaining 
gas now consists of only helium and nitrogen. This gas passes through a conductivity cell, 
the output of which is compared to that of the reference cell, through which pure helium 
flows, to give the nitrogen concentration. The main detection systems used in modern instru­
ments utilise thermal conductivity and infra-red detectors. 
51 
1:11 DIGESTION PROCEDURES 
Quantitative extraction procedures are dependent on the effectiveness of the 
decomposition steps. Thus the decomposition procedure is one of the most important steps 
in the analysis of a sample. Several different acid mixtures can be used for the extraction of 
heavy metals from biological samples of which nitric-sulphuric-perchloric, nitric-perchloric 
and nitric-sulphuric acid mixtures are the most popular combinations. However, it is 
important to avoid utilising troublesome and possibly dangerous reagents for such proce­
dures. Simple and safe methods are desirable67. 
The explosive nature of perchloric acid makes it unattractive for routine digestion 
methods. However, although perchloric acid is a very potent oxidant, only relatively small 
volumes are required for the digestion of hair samples and therefore its use could not have 
been ignored in this project. The decomposition procedure involving perchloric acid is 
simple, economical, relatively safe and provides an effective means of lead determination in 
routine monitoring of a large number of samples. In addition, since it involves the use of 
only small amounts of reagents the blank value is normally kept low. 
52 
CHAPTER TWO: 
EXPERIMENTAL 
53 
2:1 INSTRUMENTS AND REAGENTS 
Instruments Used 
Atomic Absorption Spectrophotometer (Pye Unicam SP-9, England) 
Elemental Analyzer (Perkin Elmer 240 B, United States) 
Scanning Electron Microscope (JEOL JSM-35CF, England) 
zu Centrifuge (DAMON/IEC Division CU-5000, France) 
ZD 
«c 
/O Ultrasonic Cleaner (CHIMICA OMNIA, Italy) 
=C 
£ 
Microbalance (Perkin Elmer Ultra-Microbalance Model AD-6, England) 
Reagents 
The major reagents nitric acid, methanol, perchloric acid, trichloroacetic acid and all 
other chemicals were of AnalaR grade and were used as obtained from the British Drug 
Houses (BDH), Poole, England. The liquid detergent Kleenof is a product of Superchem, 
Trinidad and Tobago Limited. 
54 
2:2 SAMPLING 
The sample population consisted of one hundred and eighty nine volunteers from four 
different races-: African, East Indian, Chinese and persons of Mixed parentage. Classi­
fication was based on phenotype and as claimed by the participants. The sample population 
consisted of 46 Africans, 91 East Indians, 11 Chinese and 41 Mixed (ie. persons of mixed 
parentage). Also included were occupationally exposed groups which would normally have 
a greater risk of being exposed to lead contamination compared to the general population. 
These consisted of 22 battery plant workers and 29 traffic police personnel. All participants 
were given a questionnaire designed to obtain information on social and environmental 
factors that are known to have an impact on lead contamination as well as their health status. 
As recommended17, hair growing 2-3 cm closest to the scalp was cut from the nape 
of the neck, using a pair of stainless steel scissors washed with ethanol. The hair samples 
were kept sealed in plastic bags prior to analysis. Venous samples of blood were taken from 
each subject's arm and stored in heparinized lead-free containers prior to analysis. All blood 
lead analyses were done within twelve hours of obtaining the samples. 
55 
2:3 HAIR WASHING PROCEDURE 
No washing procedure has yet been developed which removes all the exogenous 
particulates from the surface of the hair. Therefore, several washing procedures were 
compared in order to select the one which removes most of the exogenous particulates. All 
washing procedures except the Kleenol/methanol wash were recommended literature 
procedures used in other studies. 
(i) Ether Wash68 
The hair samples (— 0.30g) were placed, without prerinsing, into the thimble of a soxhlet 
apparatus. Both the thimble and the reflux condenser were washed with dilute nitric acid 
prior to the insertion of the hair samples. The hair samples were refluxed for six hours at 
an average rate of five minutes per cycle, using diethyl ether. The samples of hair were then 
removed and allowed to stand overnight at room temperature. The dry samples were then 
stored in a sealed plastic bag. 
(ii) EDTA Wash68 
All glassware used in this washing procedure was rinsed with dilute nitric acid and 
then thoroughly washed with deionized water. The average sample weights used were 0.5g. 
The washing procedure was carried out as follows: 
(1) The hair samples were each placed in 1L of deionized water in a 
glass beaker and then stirred with a glass rod to effect wetting and 
56 
help separate heavier particulate matter adhering to the hair 
strands. The deionized water was drained and the procedure 
repeated. Each of the drained hair samples was then placed in 1L 
of 10% Kleenol* detergent solution. 
The detergent solution containing hair was then heated, with 
frequent stirring, to incipient boiling. The hair was again drained 
and rinsed with 1L of deionized water. The deionized water was 
then drained from the hair sample. The entire process was repeat­
ed, with the exception that two deionized water rinses were used. 
The drained hair from (2) was soaked in 200mL of AR acetone, 
drained again and this process repeated. 
The drained hair from (3) was soaked in 1L of a saturated solution 
of EDTA and heated to incipient boiling. The EDTA solution 
containing the hair was stirred frequently and allowed to stand for 
5 minutes (when permitted to stand for longer than five minutes, 
the saturated solution, upon cooling, precipitated fine EDTA crys­
tals unto the hair. 
57 
Fig.l: Schematic for EDTA Washing Procedure. 
58 
These proved difficult to remove in the remaining steps.) The hair 
was then drained and rinsed in 1L of deionized water and drained 
again. A second deiomsed water rinse was then carried out. 
(5) The drained hair was covered and dried at room temperature 
overnight. It was then stored in a sealed plastic bag. The 
schematic diagram for this washing procedure is seen in Fig. 1. 
(iii) Detergent Washes 
(a) Method used by Clark et al68: All glassware used in 
this washing procedure was rinsed with dilute nitric 
acid and then thoroughly washed with deionized water. 
The average sample weights used were 0.5g. 
The washing procedure was carried out as follows: 
(1) The hair samples were each placed in 1L of deionized water in a 
beaker and then stirred with a glass rod to effect wetting and help 
separate heavier particulate matter suspended in the hair strands. 
The deionized water was drained and the procedure repeated. 
Each of the drained hair samples was then placed in 1L of 10% 
Kleenof detergent solution. 
59 
(2) The detergent solution containing the hair was then heated, with 
frequent stirring, to incipient boiling. The hair was again drained 
and rinsed in 1L of deionized water. The deionized water was 
then drained from the hair sample. The entire process was then 
repeated, with the exception that 2 deionized water rinses were 
used. 
(3) The drained hair from (2) was soaked in 200mL of AR acetone, 
drained again and this process repeated. 
(4) The drained hair from (3) was then soaked in 1L of deionized 
water, drained and this process repeated. 
(5) The drained hair was covered and dried at room temperature 
overnight. It was then stored in a sealed plastic bag. The 
schematic diagram for this washing procedure is given in Fig. 2. 
60 
Fig.2: Schematic of Detergent Washing Procedure 
61 
Method used by Creason et al69: The hair samples 
(~0.30g) were placed in a beaker containing approxi­
mately 200 mL of diethyl ether for 10 minutes with 
frequent stirring. The ether was then decanted and the 
hair samples placed in an aqueous solution of 50% 
sodium lauryl sulphate at 35°C for 20 minutes. The 
aqueous solution of lauryl sulphate was then decanted 
and the hair rinsed with deionized water until all the 
detergent was removed. Each hair sample was then 
rinsed with acetone followed by diethyl ether, dried 
between filter papers and stored in a sealed plastic bag. 
Method used by Salmela et al:13 Each hair sample 
(~0.30g) was washed with acetone for twenty minutes 
in an ultrasonic bath. The acetone was decanted and a 
2mL aliquot of a 1% Triton X-100 solution added to 
each hair sample. Each sample was placed again in the 
ultrasonic bath for two minutes. This was followed by 
the decanting of the detergent solution and the rinsing 
of the hair with deionized water and acetone 
sequentially. The hair samples were then placed in an 
oven to dry at approximately 100°C for 30 minutes. 
62 
Each hair sample was then stored in a sealed plastic 
bag. 
(iv) Acetone Wash (used by Hamhidge et al):14 
Each hair sample (approx. 0. lg) was placed in a beaker containing 125mL of acetone 
and stirred using a magnetic stirrer for 10 minutes. The acetone was decanted and the hair 
sample washed twice with 125mL aliquots of deionized water. Upon decanting of the 
deionized water, the hair was again washed with 125mL of acetone, then placed between 
filter papers to remove excess acetone and air dried at room temperature for 24hours. The 
hair was then stored in a sealed plastic bag. 
(v) (Kleenol7Methanol Wash (used in this project) 
Hair samples were washed sequentially with 50mL of aqueous Kleenol* solution (10% 
V/V) and 50mL of methanol for approximately ten minutes. These washings were 
accompanied by frequent stirring to remove grease and superficial particulates. The hair 
samples were dried in an oven (approx. 100°C) for 10 minutes. Each hair sample was then 
stored in a sealed plastic bag prior to analysis. 
63 
2:4 SCANNING ELECTRON MICROSCOPE ANALYSIS 
The efficiencies of the washing procedures carried out were determined by comparing 
the scanning electron microscope (SEM) photographs of hair samples washed by the different 
procedures. These photographs were taken at x 1500 magnification. The scanning electron 
microscope analyses were done by the Caribbean Industrial Research Institute, Mocoya, 
Trinidad, West Indies. 
64 
2:5 LEAD DETERMINATION IN HAIR AND BLOOD 
(i) Hair-Lead Determination 
Hair samples between 0.2 - 0.3g were wet digested with 12mL of a 5:1 mixture of 
concentrated nitric acid and concentrated perchloric acid for approximately twenty minutes26. 
The digested samples were then filtered into lOmL volumetric flasks and made up to lOmL. 
The lead concentrations were determined directly on the digests using flame atomic absorp­
tion spectrophotometry. Suitable blanks were determined along with the samples. Estimations 
were carried out at least twice. If the range of duplicates exceeded 10% of the mean, further 
aliquots were analyzed. 
In all analyses, a hollow cathode lamp was used as the source of radiation and 
acetylene as the fuel. Lamp current and position, slit width, wavelength and air/fuel ratio of 
the spectrophotometer were optimized prior to each determination. The principal line of 
217nm with automatic deuterium continuium background correction was used. 
Standards were made by serial dilution of a stock solution (1000 ug mL"1) of lead 
nitrate. Concentrations of the standard solutions were chosen such that the linear range for 
the element was not exceeded. Appropriate sample dilutions were made in instances where 
this condition was not fulfilled. All stock solutions were prepared according to the 
procedures recommended by the Pye Unicam handbook68. 
65 
(ii) Blood-Lead Determination 
Blood lead was estimated following acid digestion. Ten mL. of whole blood was 
digested using 4mL of 20% V/V concentrated nitric acid and 4mL of 7% m/v trichloroacetic 
acid. Samples were homogenized using a vortex mixer and centrifuged at 2500g for 20 
minutes70. A known volume of the supernatant was then analyzed by flame atomic absorption 
spectrophotometry. 
The Pye Unicam atomic absorption spectrophotometer was used, and determinations 
done at a wavelength of 217 nm with automatic deuterium continuium background 
correction. Suitable blanks were analyzed along with the samples. Estimations were carried 
out at least twice. If the range of duplicates exceeded 10% of the mean, further aliquots were 
analyzed. 
Standard material was prepared by adding known amounts of lead to a human blood 
pool which had a known low lead concentration. This was done in order to compensate for 
the matrix effect of blood. 
66 
2:6 CARBON AND SULPHUR ANALYSIS 
(i) Carbon and Sulphur Determination 
Hair samples were chipped into very fine segments using a pair of stainless steel 
scissors. Roughly 2-3 mg of each sample was placed in a platinum boat and weighed on a 
microbalance. 
All elemental analyses were done by a Perkin-Elmer 240B elemental analyzer. For 
carbon and sulphur analysis, an auxiliary temperature of 820°C, combustion temperature of 
1000°C, oxygen pressure of 35 psi and helium pressure of 30 psi, were used as 
recommended by the Perkin-Elmer 240B elemental analyzer handbook. The elemental 
analyzer was standardized using high purity thiourea. 
67 
CHAPTER THREE 
RESULTS AND DISCUSSION 
68 
3:1 SELECTION OF HAIR WASHING PROCEDURE 
The scanning electron micrographs (SEMS) of the unwashed hair samples showed that 
the hair shafts were contaminated with particulate material which possibly included lead. 
Therefore the samples needed to be washed before analysis in order to attempt to eliminate 
these exogenous contaminants (Fig. 3a). 
The washing method that removes the most exogenous particulate material from hair, 
as evidenced by SEM analysis, has traditionally been selected by researchers as the method 
of choice. For example, Clarke et al68 chose an EDTA washing procedure over a detergent 
wash or an ether wash because the SEMS of the hair samples subjected to the detergent 
washing procedure or the ether washing procedure showed a greater concentration of par­
ticulates on the hair surfaces than the SEMS of the hair from the EDTA wash. In addition, 
the lead levels in hair samples subjected to the EDTA wash were lower than those hair 
samples subjected to the detergent wash or the ether wash. Grandjean20 found that the lowest 
concentration of lead in a scalp hair sample was obtained after washing the hair using an 
ultrasonic method compared to washing procedures involving Freon, diethyl ether and 
sodium lauryl sulphate respectively. 
69 
TABLE 1 COMPARISON OF WASHING PROCEDURES FOR HAIR 
CONCENTRATION OF PB UG/G (MEAN ± SD) 
IN 4 SAMPLES 
Samples 
Washing 
Procedures A B C D 
Ether 32.39 21.21 11.64 10.64 
± 0.52 ± 0.72 ± 0.14 ± 0.54 
EDTA 23. 5 5 19.61 10.6 0 10.35 
± 0.38 ± 2.06 ± 0.43 ± 0.59 
Detergent 28.94 25.6 4 26.22 15.5 9 
± 0.06 ± 1.08 ± 1.99 ± 0.03 
Ultrasonic 33. 6 6 21.96 11.55 12. 5 2 
± 1.16 ± 0.94 ± 0.15 ± 0.72 
Acetone 37.69 31.10 21.44 20.6 2 
± 0.25 ± 0.14 ± 0.09 ± 0.16 
Sodium 34.84 37.40 11.60 15.52 
Lauryl ± 1.25 ± 0.36 ± 0.16 ± 0.32 
Sulphate 
15.0 3 18.64 8. 6 4 9.9 2 
Kleenol@ ± 0.50 ± 0.35 ±1.45 ±1.1 5 
70 
The results in Table 1 show that the lowest concentration of lead found in the acid 
digests from the four different hair samples occurred in the digests from the samples subject­
ed to the Kleenol" washing procedure. In addition, the Scanning Electron micrographs 
(SEMS) suggested that the Kleenol" wash removed more particulates from the surface of the 
hair than other methods (Fig. 3b-3h). This method was therefore selected as the washing 
procedure for this investigation since the results indicated that it gives the cleanest wash. 
The higher lead level values found in the digests by the other washing procedures 
were probably due to the failure of these procedures to remove as much exogenous lead con­
tamination as the Kleenol* procedure resulting in elevated lead levels in these digests. 
Fig. 3:b. ETHER WASH 
Fig. 3:d. DETERGENT WASH 
Fig. 3:f. ULTRASONIC WASH 
Fig. 3:g. ACETONE WASH 
Fig. 3:h. KLEENOL WASH 
Fig. 3:j. KLEENOL WASH OF A TRAFFIC POLICE HAIR STRAND 
76 
3:2 GENERAL DISCUSSION 
The data were acquired on one hundred and eighty nine (189) non-occupationally-
exposed persons and are presented in terms of, (1) race, (2) sex, (3) total time spent in 
traffic, (4) time spent in traffic jams, and (5) the %C, %S and C:S ratio in scalp hair 
samples. Age was not considered because most of the sample population belonged to the 
adult age group (20-35 years). The four racial groups studied were African, East Indian, 
Chinese and Mixed (that is, of mixed parentage). The non-occupationally exposed group was 
made up of volunteers, and phenotyping was used to categorize the individuals into racial 
groups. The sample population consisted of 46 Africans, 91 East Indians, 11 Chinese and 
41 persons of Mixed parentage. The individuals selected all had non-processed hair (that is, 
not chemically treated except for washing with soap and/ or shampoos and conditioners). 
Two occupationally exposed groups, which consisted of 27 traffic police personnel and 22 
battery workers were also sampled.These occupationally exposed groups were also made up 
of volunteers. Sampling was done between 10.00am and 12.00 noon, that is, a few hours 
after the volunteers completed their morning commute to their places of work. 
Statistical analysis suggested that the distribution of the data obtained in this project 
was skewed (Figs.4-12). In order to normalise the distribution the data were log transformed 
such that parametric analysis could be used (Figs. 13-21). 
SCALP HAIR LEAD LEVELS 
GENERAL POPULATION 
N 
U 
M 
B 
ER  
O 
F 
P 
EO  
P 
L 
E 
0 
5 .15 25 35 45 55 65 75 85 
LEAD CONCENTRATION (ug/g) 
Fig.4 
SCALP HAIR LEAD LEVELS 
TRAFFIC POLICE 
LEAD CONCENTRATION (ug\g) 
Fig.5 
SCALP HAIR LEAD LEVELS 
BATTERY WORKERS 
0 xaw/mm/wssm 
50 100150 . 350 . 350 . 450 . 550 . 650 . 750 . 850 . 950 1000 
LEAD CONCENTRATION (ug\g) 
Fig.6 
PUBIC HAIR LEAD LEVELS 
GENERAL POPULATION 78 
13 17 22 27 32 37 42 47 62 57 62 67 72 77 82 
LEAD CONCENTRATION (ug\g) 
Fig.7 
PUBIC HAIR LEAD LEVELS 
TRAFFIC POLICE 
LEAD CONCENTRATION (ug\g) 
Fig.8 
PUBIC HAIR LEAD LEVELS 
BATTERY WORKERS 
LEAD CONCENTRATION (ug\g) 
Fig.9 
BLOOD LEAD LEVELS 
GENERAL POPULATION 79 
N 
U 
M 
B 
RE  
O 
F 
P 
OE  
P 
L 
E 
0 mv/J 
2 .7 .12 .17 22 27 32 37 42 47 52 57 62 67 72 77 
LEAD CONCENTRATION (ug\100mL) 
Fig.io 
BLOOD LEAD LEVELS 
TRAFFIC POLICE 
12 17 22 27 32 
LEAD CONCENTRATION (ug\100mL) 
Fig.11 
BLOOD LEAD LEVELS 
BATTERY WORKERS 
12. 17. 22 27. 32 37. 42 
LEAD CONCENTRATION (ug\100mL) 
Fig.12 
SCALP HAIR LEAD 
GENERAL POPULATION 80 
35 
N 30 
U 
M 
B 25 
E 
R 
20 
O 
F 
15 
P 
E 
0 10 
P 
L 
E 5 
0 
0.4 .0.6 .0.8 .1 .1.2 .1.4 .1.6 .1.8 2 
LOG. CONCENTRATION (ug/g) 
Fig.13 
SCALP HAIR LEAD 
TRAFFIC POLICE 
N 
UM  
B 
E 
R 
O 
F 
P 
EO  
PL  
E 
LOG. LEAD CONCENTRATION (ug/g) 
Fig.14 
SCALP HAIR LEAD 
BATTERY WORKERS 
N 
U 
M 
B 
E 
R 
O 
F 
P 
OE  
P 
L 
E 
1.8 .2.0 .2.2 .2.4 .2.6 
LOG. LEAD CONCENTRATION (ug/g) 
Fig.15 
81 
PUBIC HAIR LEAD BLOOD LEAD 
GENERAL POPULATION GFNFRAL POPULA 
.0.6 0.8 1 .12 .1.4 .16 .1.8 2 0.2 0.4 0.6 0.8 10 1.2 
LOG. CONCENTRATION (ug/g) LOG. LEAD CONCENTRATION (ug/100mL) 
Fig.16 
PUBIC HAIR L EAD BLOOD LEAD 
TRAFFIC POLICE TRAFFIC POLICE 
o 4= 
•1.2 .14 .1.6 .18 .2.0 .2.2 2.4 2.6 -0.1 ^0.2 -0.3 -0.4 -0.5 -0.6 -0.7 -0.8 -1.0 
LOG. LEAD C ONCENTRATION (ug/g) LOG. LEAD CONCENTRATION (ug/100mL) 
Fig.17 Fig.20 
PUBIC HAIR L EAD BLOOD LEAD 
BATTERY WORKERS BATTERY WORKERS 
0 
• 00 -0.2 -0.4 -0.6 -0.8 -1.0 
LOG. LEAD CONCENTRATION (ug/g) LOG. LEAD CONCENTRATION (ug/100mL) 
Fig.18 Fig.21 
82 
3:3 LEAD LEVELS: GENERAL POPULATION 
3:3.a Scalp Hair Lead Levels 
Trinidad is a country with a multi-racial population. The population has a percentage 
composition as follows: African 40.58%; East Indian 40.80%; Mixed 16.42%; Chinese 
0.50%; and Others 1.70% (figures from 1980 census)71. 
Of the four racial categories studied the mean scalp hair lead level for the Chinese 
was the lowest (18.28 ug/g) while the mean scalp hair lead value for the African category 
(41.85 ug/g) was the highest (Table 2). The mean for the East Indians (27.02 ug/g) was 
close to the Mixed category (27.83ug/g) while the mean for the African category (41.85 
ug/g) was about 23ug/g higher than the Chinese and about 14ug/g higher than the East 
Indians (Table 2). It must be noted that only eleven Chinese were sampled because of the 
difficulty in obtaining Chinese volunteers in a population of 0.5% Chinese17. 
Klevay72 obtained a mean value of 30.23 ug/g (N=426) and a range between 30-40 
ug/g of lead in scalp hair in a study done in Panama on non-occupationally exposed Panama­
nians from both urban and rural areas. Panamanians generally have similar hair to that of 
the East Indians studied in this research project. The mean scalp hair lead values for the East 
Indian and Mixed categories were similar to the mean found in Klevay's study. The mean 
scalp hair lead values for the Chinese category was lower, while the value for the African 
category was higher than that obtained by Klevay72. Grandjean20 obtained median values 
between 3.70 ug/g and 7.00 ug/g for dark hair, blond hair and grey hair individuals respec­
83 
tively (N=79) (no arithmetic mean was given) for a population of Caucasians. The median 
values obtained in the Trinidad study ranged from 15-34 ug/g, with the highest value being 
that for the African group and the lowest being that of the Chinese group. The difference in 
the scalp hair lead levels of the African category compared to Klevay's or Grandjean's 
studies could be that the scalp hair lead levels of the African sample population represented 
a different position on the normal distribution curve of the total (international) population 
when compared to the other studies mentioned. No test of significance could be done because 
neither Klevay nor Grandjean reported standard deviations for their samples. 
One obvious physical difference between the racial groups studied is the hair texture. 
Since one of the major problems with scalp hair as an indicator of lead exposure is 
exogenous contamination, it is possible that the difference in scalp hair lead values between 
the Panamanians studied by Klevay72 and the African and Chinese categories in the Trinidad 
study may be due to the differences in the extent of adsorption of exogenous lead particles. 
The East Indian category has similar scalp hair lead values to the subjects of Klevay's study 
possibly because of similar hair characteristics (straight and thick) of both groups. The 
Chinese have fine straight hair which should not be as susceptible to exogenous 
contamination as persons of East Indian descent and hence the lower scalp hair lead values 
than those obtained in Klevay's study. On the other hand, persons of African descent have 
coarse-grained, curly hair which should retain larger amounts of exogenous particles for 
longer periods resulting in a greater chance of being chemisorbed and eventually becoming 
endogenous lead. This may be a possible reason why African lead levels are higher than that 
of the Chinese and East Indians. Also, it may be that the difference between the levels 
84 
obtained in Klevay's study and those obtained for the African and Chinese categories in the 
Trinidad may be due to differences in environmental factors. 
The average scalp hair lead values found in this study were comparable to those found 
in a previous study done by Hall et al.26 in which average scalp hair lead values obtained for 
the different racial group were as follows: African (40.10ug/g, N=35), East Indian 
(26.82ug/g, N=38), Chinese (18.83ug/g, N=6) and Mixed (47.87ug/g, N=36). However, 
the values for the Mixed category in both studies differed markedly. It is possible that the 
variation in racial combinations of the mixed category in these two studies were sufficiently 
different to cause the observed disparity between the average scalp hair lead values. The 
sample population used by Hall et al26 was similar to the one used in this project with respect 
to age, gender and geographical location. 
85 
TABLE 2 SCALP HAIR LEAD LEVELS FOR THE FOUR GROUPS 
GROUPS NUMBER MEAN1SD MEDIAN RANGE 
SAMPLED (ug/g) (ug/g) (ug/g) 
EAST 
INDIAN 91 27.02 17.23 2.80-107.05 
±0.52 
AFRICAN 46 41.85 33.86 5.76-155.36 
±0.38 
CHINESE 11 18.28 15.70 1.00- 45.62 
±0.25 
MIXED 41 27.83 20.70 3.41-126.93 
±0.50 
86 
The ranges for the different racial groups studied in the general population in this 
project (Table 2) were much wider than those obtained in the other investigations mentioned. 
The scalp hair lead values obtained in Grandjean's study ranged between 37.00 - 48.00ug/g 
while the ranges in this study were 2.80 - 107.05ug/g for the East Indian group and 5.76 -
155.36ug/g for the Africian group. A probable reason for this observation is that persons 
chosen in our study came from diverse geographical locations where the level of lead 
contamination they were exposed to varied to a greater extent than those persons studied by 
Grandjean20. The difference found between the mean and median scalp hair lead values in 
the Trinidad study (Table 2) was due to some individuals having significantly different values 
from the rest of the sample population. 
In order to establish whether there was a significant difference in scalp hair lead 
among the East Indian, African and Chinese racial groups in the Trinidad study an 
unweighted one-way analysis of variance (ANOVA) was carried out. The data indicated that 
the interracial differences observed were real (Table 3). The Mixed category was not used 
in this statistical analysis because of the differences in the type and extent of mixing in this 
category. Therefore, if lead in hair is accepted as a suitable bioindicator it is likely that 
separate upper limits for different racial groups would have to be set for non-occupational 
exposure to lead, since each racial group appears to be affected differently even when they 
inhabit similar environments. Already upper limits have been proposed by 
8 7  
TABLE 3 ANALYSIS OF VARIANCE OF LEAD LEVELS IN THE 
SCALP HAIR AMONG THE EAST INDIAN, AFRICAN 
AND CHINESE RACIAL GROUPS 
SOURCE DEGREE OF SUMS OF MEAN F-RATIO P 
FREEDOM SQUARES SQUARES VALUE 
TOTAL 191 28.89 
TREATMENTS 2 1.81 0.60 4.21 <0.05 
ERROR 189 27.08 0.14 
88 
other workers. In one study done by Grandjean20 on Caucasians, an upper limit of 70ug/g was 
set while an upper limit of 1 lOug/g was set for Japanese in a study done by Suzuki73. In the 
Trinidad study the upper limits for each racial group were established by using the mean 
scalp hair lead values plus two standard deviations. This method of selecting the upper limits 
was found to give a reliable minimum value which is considered to be critical with respect 
to lead toxicity74. The upper limit for the East Indians was 28.06ug/g, for the Africans was 
42.62ug/g, for the Chinese was 18.75ug/g and the Mixed was 27.83ug/g. The methods for 
selecting the upper limits in Grandjean20 and Suzuki73 studies were not known and therefore 
cannot be compared with the Trinidad study. Having established that there was also a 
significant difference in scalp hair lead among the three racial groups in this present study, 
a forward multiple regression analysis was carried out on East Indian, African and Mixed 
racial groups in order to determine what possible factors could have influenced such a result. 
Scalp hair lead was used as the dependant variable and the four independent variables used 
were time spent in vehicular traffic on the road, time spent in "traffic jams" (as defined in 
the following section), sex and blood. None of the variables had statistically significant 
association with scalp hair lead concentration for any racial group (Table 4). There was 
insufficient data to do a forward multiple regression analysis for the Chinese group. 
8 9  
TABLE 4 STEPWISE REGRESSION ANALYSIS OF SCALP HAIR 
LEAD FOR ETHNIC GROUPS IN RELATION TO GIVEN 
VARIABLES SETS 
ETHNIC R2 C/S 
GROUPS RATIO 
TIME SPENT TIME SPENT SEX BLOOD 
ON ROAD IN TRAFFIC 
EAST 
INDIAN 0.02 0.003 0.09 0.11 0.0 2 
AFRICAN 0.05 0.03 0.01 0.39 0.25 
MIXED 0.05 0.03 0.01 0.01 0.26 
n.s . 
90 
A study done on a sample of the Trinidad population by Hall et al26 in 1990 also 
found a significant difference in scalp hair lead levels among the four racial groups studied. 
In order to account for the differences among racial groups in Hall's study a multiple 
regression model was used, with scalp hair lead as the dependant variable and total time 
spent in traffic, time spent in "traffic jams" and sex as independent variables. A "traffic jam" 
was defined as a condition in which, because of traffic congestion, vehicular movement was 
slow (0-24 kph) and sporadic. The Chinese population in this study was too small to allow 
multiple regression to be done. However, the highest coefficient of determination (R2 = 
0.51) was obtained for Africans, and for this category, the regression coefficients for all 
variables were significant, thus total traffic exposure time, "traffic jam" exposure and sex 
all appeared to have contributed to the level of lead in the hair of people of African descent. 
In the case of the East Indian category, however, it was found that none of the regressors 
in the model used was significant. 
It is generally expected that total time spent in vehicular traffic on the road and time 
spent in traffic jams should have some impact on scalp hair lead levels, since lead emitted 
from gasoline can be inhaled and then transported in the blood to binding sites in the hair 
or deposited on the surface of hair and become chemisorbed into the hair. However, the 
results did not show any correlation between scalp hair lead levels and any of the parameters 
mentioned. This is possibly due, at least partly, to two factors namely: (1) the times given 
by persons studied may have been inaccurate since they were estimates made by the partici­
pants and were not measured accurately with a timing device, (2) maybe the lead particles 
91 
emitted from the motor vehicles did not circulate in the atmosphere at heights where they 
could have been inhaled or entrapped in the hair of the individuals sampled. 
It must be emphasized too, that the non-significance of a particular regression 
coefficient in general does not imply that the independent variable concerned does not affect 
the dependant variable. It implies that at the 5 % level of significance adopted, given the 
variability of the results, the confidence interval for the estimate of the regression includes 
zero as a possible value. Thus it cannot be discounted that the time spent on the road and 
time spent in "traffic jams", actually contributed to scalp hair lead levels. It may be 
concluded then, that further work is required to define the relationship more precisely. 
3:3.b Pubic Hair Lead Levels 
Of the four racial groups, the mean pubic hair lead value for the Chinese group was 
the lowest (14.89ug/g) while the mean values for the African group (20.45ug/g), East Indian 
group (20.45ug/g) and Mixed group (18.12ug/g) were all close to each other (Table 5). 
TABLE 5 PUBIC HAIR LEAD LEVELS FOR THE FOUR GROUPS 
GROUPS NUMBER MEAN±SD MEDIAN RANGE 
SAMPLED (ug/g) (ug/g) (ug/g) 
EAST 
INDIAN 91 20.50 10.77 5.62-167.42 
±0.42 
AFRICAN 46 20.45 16.57 2.85-73.59 
±0.37 
CHINESE 11 14.84 8.76 2.06-57.78 
±0.8 4 
MIXED 41 14.89 8.76 2.06-57.78 
±0.57 
TABLE 6 ANALYSIS OF VARIANCE OF LEAD LEVELS IN THE 
PUBIC HAIR AMONG THE EAST INDIAN, AFRICAN 
AND CHINESE RACIAL GROUPS 
SOURCE DEGREE OF SUMS OF MEAN F-RATIO P 
FREEDOM SQUARES SQUARES VALUE 
TOTAL 188 41.10 
TREATMENTS 2 0.60 0.20 0.92 >0.05 
ERROR 186 40.51 0.22 
93 
Pubic hair lead levels showed no significant difference among the East Indian, 
African and Chinese racial groups studied. This was revealed by the statistical test of 
unweighted one-way analysis of variance (ANOVA) at the 95% confidence level (Table 6). 
As mentioned previously, pubic hair is not normally exposed to the environment and 
therefore the problem of exogenous lead contamination may not be as great as in the case 
of scalp hair. As a result the effect of hair texture for different racial groups may not be an 
important factor when pubic hair is involved. 
The median values for the four racial groups studied were East Indian (16.57ug/g); 
African (10.77ug/g); Chinese (8.76ug/g) and Mixed (9.63ug/g). The difference found 
between the mean and median pubic hair lead values for the different racial groups in the 
Trinidad study (Table 5) was due to some individuals having significantly different values 
from the rest of the sample population. The mean and median values for pubic hair lead were 
significantly lower than those of scalp hair lead for any given racial group. One explanation 
for this is that exogenous contamination is greater in scalp hair than pubic hair since the 
latter is not normally exposed to the environment. Although all hair samples were washed 
before hair analysis was carried out, no washing procedure has been shown to completely 
remove exogenous material. The scanning electron micrographs showed that none of the 
washing procedures employed completely removed all external contaminants. Thus it is 
possible that the greater quantity of exogenous lead on scalp hair accounts for the higher lead 
concentration in scalp hair compared to pubic hair. This difference in lead levels between 
the two bioindicators can also be explained in terms of the growth rate of both types of hair. 
Pubic hair grows more slowly than scalp hair and therefore lead accumulation in pubic hair 
94 
would be less than that of scalp hair75. As pubic hair grows more slowly than scalp hair, it 
may be that less binding sites (disulphide groups) of the hair proteins are available for the 
deposition of lead from the blood at any particular time period, compared to scalp hair. This 
could have resulted in the lead concentration in scalp hair being significantly higher than in 
pubic hair75. It is proposed that pubic hair is more suitable than scalp hair because it is not 
usually subjected to the application of cosmetic preparations or shampoos that may contain 
lead75. 
3:3.c Blood Lead Levels 
The four racial groups mentioned in this study have blood lead values of the same 
order of magnitude (Table 7). The mean values for the four groups studied were East Indian 
(0.26ug/mL); African (0.34ug/mL); Chinese (0.27ug/mL) and Mixed (0.21ug/mL). In order 
to establish whether there was a significant difference in blood lead levels among the East 
Indian, African and Chinese racial groups an unweighted one-way analysis of variance 
(ANOVA) was carried out. The statistical test indicated no significant difference in blood 
lead levels among these groups (Table 8). A study done by Singal76 in the United Kingdom 
among Caucasian and ethnic minorities also showed that race is not a factor affecting lead 
deposition in other organs8. It may be that only when lead is deposited in other tissues (for 
example scalp hair) that the effect of race becomes pronounced. 
In a study done on a group of Caucasians by Hunt et al77, the mean and range of 
blood lead values found were 0.30ug/mL and 0.18-0.44ug/mL respectively, while Mahaffey 
95 
et al78 obtained mean and median values of 0.14ug/mL and 0.13ug/mL (N =1 041) 
respectively in a study done to estimate the national blood lead levels in the United States. 
The sample population contained both Caucasians and African-Americans which belonged 
to the age group 25-34. The median values in the Trinidad study were East Indian (0.24ug/-
mL); African (0.30ug/mL); Chinese (0.21ug/mL) and Mixed (0.20ug/mL). The similarity 
found between the mean and median blood lead values for the different racial groups in the 
Trinidad study (Table 7) was due to the fact that all the individuals in the sample population 
had values which fell within a narrow range. 
All the mean and median values in this study were similar to those found by Hunt et 
al77 but different to those obtained in the Mahaffey et al78 study. The similarity in blood lead 
values in the former case with that found in this study could have been due to the fact that 
both sample populations were from urban and suburban districts, while Mahaffey et al78 also 
included subjects from rural districts in his study. Urban and suburban areas normally have 
more motor vehicles and greater vehicular congestion compared to rural 
96 
TABLE 7 BLOOD LEAD LEVELS FOR THE FOUR GROUPS 
GROUPS NUMBER MEAN±SD MEDIAN RANGE 
SAMPLED ( u g / g )  ( u g / g )  ( u g / g )  
EAST 
INDIAN 9 1  0 . 2 6  0 . 2 4  0 . 0 5 - 0 . 8 2  
± 0 . 0 2  
AFRICAN 4 6  0 . 3 4  0 . 3 0  0 . 2 3 - 0 . 6 6  
± 0 . 0 4  
CHINESE 1 1  0 . 2 7  0 . 2 1  0 . 0 7 - 0 . 9 1  
± 0 . 0 5  
MIXED 4 1  0 . 2 1  0 . 2 0  0 . 0 8 - 0 . 4 1  
± 0 . 0 3  
TABLE 8 ANALYSIS OF VARIANCE OF LEAD LEVELS IN THE 
BLOOD BETWEEN THE EAST INDIAN, AFRICAN 
AND CHINESE RACIAL GROUPS 
SOURCE DEGREE OF SUM OF MEAN F-RATIO P 
FREEDOM SQUARES SQUARES VALUE • 
TOTAL 188 15.12 
TREATMENTS 2 0.77 0.26 3.33 >0.05 
ERROR 186 14.35 7.75X10"2 
n.s  
97 
areas. As a result it is expected that there would be a greater amount of lead emissions from 
gasoline in these areas than in rural areas. The lead particles emitted from gasoline can be 
deposited on food and in water which can enter the body by ingestion. This is conceivable, 
since ingestion of lead is thought to account for most of the lead that enters the human 
body26. The sample population in Mahaffey's et al78 study consisted mainly of Caucasians. 
His study showed that Caucasians had lower blood lead values than the African-Americans. 
No Caucasians were sampled in the Trinidad study because of the difficulty in obtaining 
volunteers. Caucasians make up a very small fraction of the total population in Trinidad. 
3:3.d Analysis of Lead Levels with Respect to Sex 
In order to establish whether there was a significant difference in scalp hair lead 
levels, pubic hair lead levels and blood lead levels between sexes in the general population, 
unpaired t-tests were carried out. No significant difference in scalp hair lead levels was 
found between males and females belonging to the general population (Table 9). In addition 
no significant differences were found in pubic hair lead levels and blood lead levels between 
males and females belonging to the general population. The data were then categorized on 
the basis of racial groups to see if there was any difference in lead levels between males and 
females belonging to a particular racial group (Tables 10-12). The data showed that scalp 
98 
TABLE 9 SCALP HAIR LEAD LEVELS BETWEEN SEXES 
SEX MEAN MEDIAN RANGE 
(ug/g) (ug/g) (ug/g) 
MALE 30.40 20.01 1.00-38.10 
FEMALE 28.49 26.31 2.80-86.43 
TABLE 10 ANALYSIS OF SCALP HAIR LEAD WITH 
RESPECT TO SEX 
RACIAL MEAN LEAD MEAN LEAD UNPAIRED P 
GROUPS LEVELS(ug/g) LEVELS(ug/g) t-TEST VALUE 
(MALES ) (FEMALES ) VALUES  
EAST 25.60 19.80 t=2.33 <0.05 
INDIAN (N=91) 
AFRICAN 34.28 23.82 t=1.17 >0.05 
(N=29) 
MIXED 22.29 15.52 t=1.84 <0.05 
(N=30) 
99 
TABLE 11 ANALYSIS OF PUBIC HAIR LEAD WITH 
RESPECT TO SEX 
RACIAL MEAN LEAD MEAN LEAD UNPAIRED P 
GROUPS LEVELS(ug/g) LEVELS(ug/g) t-TEST VALUE 
(MALES) (FEMALES) VALUES 
EAST 20.45 11.23 t=2.40 <0.05 
INDIAN (N=91) 
AFRICAN 20.63 14.44 t=l.51 >0.05 
(N=32) 
MIXED 9.43 18.71 t=2.01 <0.05 
(N=31) 
TABLE 12 ANALYSIS OF BLOOD LEAD WITH 
RESPECT TO SEX 
RACIAL MEAN LEAD MEAN LEAD UNPAIRED P 
GROUPS LEVELS(ug/mL) LEVELS(ug/mL) t-TEST VALUE 
(MALES ) (FEMALES ) VALUES  
EAST 0.26 0.40 t=2.34 <0.05 
INDIAN (N=91) 
AFRICAN 0.31 0.37 t=0.95 >0.05 
(N=33) 
MIXED 0.19 0.23 t=2.86 <0.05 
(N=35) 
100 
hair, pubic hair and blood lead values between males and females belonging to the Mixed 
category were significantly different. Significant differences in scalp hair, pubic hair and 
blood lead values, between male and females were also found in the East Indian category. 
It may be that differences in hormonal activity between males and females in these two 
groups influence blood , scalp and pubic lead levels to different extents resulting in 
significant differences. It is also possible that the difference in hair growth rate between 
males and females can influence the scalp and pubic hair values to different extents. In 
addition, the discharge of blood during the menstruation in females may lower blood lead 
levels, resulting in a significant difference when compared to male blood lead values. 
The African category however showed no significant differences in scalp hair lead 
values blood lead values and pubic hair lead values between males and females. The lack 
of any significant differences in the lead levels between males and females for the African 
category could be probably due to some other factor which influences both sexes to the same 
extent and which is also more influential to lead accumulation than hormonal activity. The 
data for the Chinese group was to few to carry out any meaningful statistical analysis. 
3:3.e Blood Lead-Hair Lead Correlation 
The scalp hair lead and blood lead data for the general population were subjected to 
a correlation analysis. The association of lead in blood and scalp hair of the general 
population studied indicated an exponential distribution with values ranging from 1-1 lOug/g 
in hair and from 0.05-0.8lug/mL in blood. The correlation coefficient obtained (R=0.31) 
101 
was found to be statistically insignificant, indicating that scalp hair lead did not correlate well 
with the blood lead levels in the present study (Fig. 22). The data were best fitted by the 
regression equation log Y=0.1X+0.38 where Y and X are scalp hair and blood lead 
concentrations, respectively. 
There was no statistically significant correlation between scalp hair lead concentra­
tions and blood lead concentrations by race for the four racial groups studied (Chinese, 
r=0.04; East Indian, r=-0.32; African, r=-0.63; and Mixed, r=-0.10.) In addition, no 
significant correlations were found between pubic hair lead concentrations and blood lead 
concentrations with respect to race for the racial groups studied except for Chinese (Chinese, 
r=0.63; East Indian, r=0.10; African, r=-0.07; and Mixed, r=-0.10). 
This was similar to the observation made by Laker8, and also by Ahmed et al79 that 
one should not expect a correlation between lead contents of these two body tissues. Lead 
in blood is constantly being transferred from one components to another. Lead binds to the 
sulphur atom of the amino-acid cysteine, which is incorporated in proteins found in blood80. 
Lead concentrations in blood are time-dependent, reflecting their intake in the previous hours 
or days. In contrast, hair, being metabolically inert, fixes trace elements, and there provides 
a lasting record of intake over the previous several months. The disulphides of the hair 
protein have been proposed as the binding sites for lead. The amino groups may also be 
involved80. The binding of endogenous lead in the hair is assumed to be irreversible80. Thus, 
hair shows a cumulative concentration which cannot be compared with the transient 
concentrations in blood80. 
102 
However, the lack of correlation between hair lead levels and blood lead levels should 
not detract from the importance of hair as a useful biopsy material for epidemiological 
studies of environmental pollutants. The use of hair depends on the scope and objectives of 
the particular research or monitoring programme, and the expertise and facilities available. 
Blood Lead (ug/g) 
120 
100 4-
80 
60 4- 4- + 4-
4- * 
40 + 4-+ + + t + 
4-
4- 4- + 4- + 
20 4- + 
X4 + ±-  ,4-4X_4 -J4  +  X•+4 i  +X  
4-
4-
4-
0 4-
0 0.2 0.4 0.6 0.8 
Scalp Hair Lead (ug/g) 
Fig.22 Scatter Diagram Of Blood-Lead 
Cone, vs Scalp Hair-Lead Cone..Note 
that no correlation was observed. 
104 
3:4. COMPARISON OF BATTERY WORKERS AND TRAFFIC POLICE PERSON­
NEL WITH THE CONTROL GROUP 
3:4.a Introduction 
The extent of lead accumulation in occupationally exposed persons was seen when 
their lead levels were compared with those of the non-occupationally exposed group which 
was used as a control. This control group consisted of members of the general population 
who were not exposed to any occupational lead contaminants. It comprised 189 persons while 
the occupationally exposed groups consisted of 27 traffic police personnel and 22 battery 
plant operators. 
3:4.b Scalp Hair Lead Levels 
An unpaired t-test between the scalp hair lead levels of the control group and that of 
the battery workers indicated that there was a significant difference between the two groups 
(t=2.43 P<0.05) (Table 13). Similar results were found for scalp hair lead levels between 
the control group and that of the traffic personnel group (t=2.30 P<0.05) (Table 13). 
These results indicate that the significantly high scalp hair lead values observed by the 
battery workers and the traffic personnel are occupationally related. The traffic personnel 
sampled worked among vehicles which utilised gasoline containing an average 
concentration of about 0.78g/L26 of lead during the hair sampling period. The battery plant 
employees worked in areas that contained high lead particulate loadings. Both categories of 
105 
workers were therefore exposed to atmospheric lead for longer periods during their normal 
working hours compared to the average person sampled from the control group. The 
scanning electron micrographs (Fig. 3.i and 3.j) of washed hairs (Kleenol® washing 
procedure) of battery workers and traffic personnel showed a much smaller number of 
absorbed particles when compared to the unwashed hair samples. It is therefore reasonable 
to assume that the lead levels obtained from these special groups of workers provided a 
reasonable estimate of endogenous lead levels. The mean scalp hair lead value for battery 
workers (418.22ug/g) was much higher than that of the traffic personnel (66.19ug/g). This 
may be due to the fact that most of the lead contamination of traffic police personnel was 
from lead particulates from automobile exhausts which has relatively low atmospheric 
concentrations. On the other hand, in the battery plants, atmospheric lead concentrations are 
more likely to be much higher. 
3:4.c Pubic Hair Lead Levels 
Significant differences in pubic hair lead levels were found between the control group 
and the battery workers group (t = 1.92, P=0.05) and between the former and the traffic 
personnel group (t = 1.74, P=0.05). The mean pubic hair lead level for battery workers 
(306.17ug/g) was also much higher than that for the traffic police personnel (72.43ug/g, 
Table 14). 
106 
TABLE 13 SCALP HAIR LEAD LEVELS: 
CATEGORY NUMBER MEAN±SD MEDIAN RANGE 
SAMPLED (ug/g) (ug/g) (ug/g) 
TRAFFIC 27 94. 11 66.19 27.52- 603.17 
POLICE ±0.81 
BATTERY PLANT 22 589.41 418.22 50.93-1513.00 
OPERATORS ±1.42 
GENERAL 189 29.7 2 20.7 0 1.00- 110.36 
POPULATION ±0.41 
107 
Explanations given for these results are similar to those given for the distribution of scalp 
hair lead among the three categories studied. In addition, pubic hair is not normally exposed 
to the environment and as a result the problem of exogenous lead contamination should be 
reduced. However the possibility of exogenous contamination still exists. Exogenous lead 
may be deposited on pubic hair from any lead particles being carried by air currents through 
the relatively loose clothing used by the traffic police and the battery plant workers. 
3:4.d Blood Lead Levels 
According to the Occupational Safety and Health Administration (OSHA,1991), 
elevated blood lead levels of 0.4ug/mL or more in persons, is cause for concern of possible 
lead toxicity. The frequency distribution of lead concentrations in blood lead levels for the 
three different categories are given in (Figs. 10-12). The results show that 65% of the 
control group had blood lead levels less than 0.4ug/mL, whereas 100% of the battery 
workers and traffic police had blood lead levels of less than 0.4ug/mL. Unpaired t-tests 
indicated that no significant differences were observed between the control group and the 
battery workers (t=0.95, P<0.05); and the control group and the traffic personnel (t=0.64, 
P<0.05). It seems therefore with respect to blood lead levels, the occupationally exposed 
workers are below the currently acceptable upper limit (0.4ug/mL) (Table 15). 
108 
TABLE 14 PUBIC HAIR LEAD LEVELS: 
CATEGORY NUMBER MEAN MEDIAN RANGE 
SAMPLED (ug/g) (ug/g) (ug/g) 
TRAFFIC 27 72.43 319.09 13.74-4043.17 
POLICE ±1.27 
BATTERY PLANT 22 306.17 419.03 98.13-1671.69 
OPERATORS ±10.47 
GENERAL 189 19.7 7 10.43 0.14- 167.72 
POPULATION ±1.36 
TABLE 15 BLOOD LEAD LEVELS • • 
CATEGORY NUMBER MEAN±SD MEDIAN RANGE 
SAMPLED (ug/g) (ug/g) (ug/g) 
TRAFFIC 27 0.26 0.11 0.14-0.48 
POLICE ±0.02 
BATTERY PLANT 22 0.23 0.22 0.12-0.62 
OPERATORS ±0.09 
GENERAL 189 0.27 0.24 0.05-0.91 
POPULATION ±0.06 
109 
The results (Tables 10-12) indicate that in the case of occupational exposure, blood lead 
reveals little information about the state of lead accumulation in the body. The disadvantages 
of blood as an indicator relative to hair have already been discussed. 
110 
3:5 COMPARISON OF THE TWO OCCUPATIONALLY EXPOSED GROUPS 
3:5.a Introduction 
Two occupationally exposed groups were studied in this project. They were workers 
of a battery manufacturing company and traffic police personnel. The battery plant 
employees were considered to be occupationally exposed since they constantly worked in an 
environment with a large particulate loading of lead generated from the lead and various lead 
compounds used in the manufacture of battery components. 
The traffic police personnel were considered to be occupationally exposed since motor 
vehicle exhaust emissions contained lead particles which were constantly inhaled during their 
patrols along the busy highways. About six hours a day, five days a week, were spent on 
the highways and at traffic intersections. These traffic police worked two three-hour sessions 
(6am-9am and 3pm-6pm) separated by a six hour period per day. On the other hand, persons 
belonging to the normal population, generally spent about one hour in the morning and one 
hour in the afternoon on the roads in their journeys to and from their places of work. 
I l l  
3:5.b Scalp Hair Lead Levels 
For the occupationally exposed groups studied, the mean value of scalp hair lead for 
Battery Workers was 589.4lug/g (N=22) while that for traffic police was 94.41ug/g (N=27) 
(Table 13). The much higher mean scalp hair lead value of the battery workers compared 
to the traffic police personnel is due to reasons already mentioned in section 3:4.b. 
In a study done by Fergusson21 in Christchurch, New Zealand on Caucasian battery 
workers, a mean scalp hair lead of 363ug/g (N=16) was obtained while Nishiyama81 
obtained a mean value of 217ug/g for his Japanese sample population. The median values 
for the battery workers and the traffic police studied were 418ug/g and 66.19ug/g respective­
ly. The mean and median values in the Trinidad study were much higher than those found 
by Fergusson21, and Nichiyama78. The median and ranges in this study were also higher than 
those found by Chattopadhay in Toronto,Canada15. The higher lead levels obtained in this 
project for two occupationally exposed groups were assumed to be at least partly explicable 
in terms of race. The sample population of workers studied by Fergusson21 and Nishiyama81 
were basically Caucasian and Japanese respectively whereas those studied in this project were 
of African descent. Possibly the inherent variations in race could result in Africans having 
a greater susceptibility to lead accumulation in the body than the two other races mentioned. 
Hair texture is another possible reason for this observation. This is fully explained in 
section 3:3.a. 
112 
3:4.c Pubic Hair Lead Levels 
Of the two occupationally exposed groups, the average pubic hair lead value for the 
battery workers (419.03ug/g) was higher than that for traffic police (319.09ug/g). The 
median value for the battery workers was also higher (306.17ug/g) than that for the traffic 
police (72.43ug/g). The large disparity between the mean and median values in the two 
occupationally exposed groups studied indicated that the pubic hair lead values in their 
sample populations were not normally distributed but skewed (Table 14). Reasons which 
could have attributed to the higher mean and median pubic hair lead values found for battery 
workers compared to traffic police personnel are mentioned in section 3:4.b Reasons for the 
lower values found in pubic hair compared to scalp hair of the occupationally exposed groups 
are mentiond in section 3:4.c. Some individual values were much higher than the rest of the 
sample population in both occupationally exposed groups. Two battery workers had individ­
ual pubic hair lead levels of lOOO.OOug/g and 1094.94ug\g respectively. They were both 
furnace operators and as such were possibly exposed to larger amounts of lead dust and 
fumes which was intermittently emitted from the furnace. One traffic police officer studied 
had a pubic hair lead level of 4043.17ug/g indicating high and prolonged exposure to a 
source of lead, which is as yet unknown. 
113 
3:4.d Blood Lead Levels 
The mean blood lead levels for battery workers and traffic police found in this study 
were 0.23ug/mL and 0.26ug/mL respectively (Table 15). The median values for the battery 
workers and the traffic police were 0.22ug/mL and 0.21ug/mL respectively while the ranges 
for the battery workers and traffic personnel were 0.12 - 0.62ug/mL and 0.14 - 0.48ug/mL 
respectively. The blood lead values for both occupationally exposed groups were of the same 
order of magnitude. 
The mean blood lead value for occupationally exposed groups obtained by Dahlgrem82 
was 0.70ug/mL whereas Chattopadhay15 obtained a range of 0.08 - 0.67ug/mL (no mean 
value was given). In all three studies the participants were Caucasians working in battery 
plants. A median value of 0.66ug/mL was obtained by Grandjean20. The mean, median and 
range obtained in this study for the two occupationally-exposed groups were lower than those 
obtained by Dahlgram82, Grandjean20 and Chattopadhay15 respectively. In fact the means, 
medians and range in this study for the occupationally exposed groups were similar to those 
found in the general population study (Table 15). Similar results were found by Chattopadh­
ay15. This is possibly due to the fact that since blood is a circulatory system, it deposits lead 
in tissues (eg. hair) as it circulates through the body. Thus, blood lead levels would tend to 
be lower than the concentration found in the hair, brain, kidney or liver of persons, except 
if the samples are taken immediately after exposure. These observations emphasize the 
114 
These observations emphasize the disadvantage of using blood as a bioindicator when the 
accumulation of lead in the body over extended periods is being studied. 
115 
3:6 MEDICAL SYMPTOMS 
A section of the study dealt with the symptoms associated with lead poisoning. A 
majority of the exposed workers indicated a combination of these symptoms. The most common 
symptoms indicated by the exposed workers were leg cramps, metallic taste, headaches, 
diarrhoea, sluggishness, constipation, vomiting and irritability. 
A chi-square statistical test was carried out in order to establish if there was any 
association between the occupationally exposed groups and the symptoms of lead toxicity. The 
control group used in this statistical test consisted of persons from the general population. The 
results (Table 16) of the statistical test indicated that there was a significant difference at the 
95% confidence level between the occupationally exposed group and the control in relation to 
the lead toxicity symptoms (chi-square = 33.39). Occupation may therefore be a factor which 
affects the health of persons with respect to lead toxicity in this instance. 
The results in Table 16 show that for most of the symptoms of lead poisoning both 
occupationally exposed groups had a higher percentage of persons having these symptoms 
compared to that of the normal population (Table 16). The large number of persons showing 
these symptoms in the occupationally exposed groups may be due to exposure to 
TABLE 16 NUMBER OF INDIVIDUALS WITH SYMPTOMS OF 
LEAD TOXICITY OVER THE PRECEDING MONTH 
(EXPOSED VS NON-EXPOSED GROUPS) 
SYMPTOMS EXPOSED NON- X2 P SIG. 
GROUP EXPOSED VALUE VALUE DIFF. 
(N=49) (N=189) 
abdominal 19 15 16.11 <0.05 YES 
pain 
headaches 19 17 15.75 <0.05 YES 
leg cramps 18 13 13.35 <0.0 5 YES 
metallic taste 27 2 47.27 <0.05 YES 
irritability 12 8 10.20 <0.05 YES 
constipation 13 2 20.08 <0.05 YES 
vomiting 15 2 25.84 <0.05 YES 
diarrhea 10 11 5.0 1 >0.0 5 NO 
apathy 8 27 0.05 >0.05 NO 
117 
enhanced levels of lead since persons belonging to these groups are exposed to lead to a greater 
extent than those belonging to the normal population. This is supported by the high mean scalp 
and pubic hair lead levels for the occupationally exposed groups. 
It must be noted however that these were the reported symptoms over the month 
preceeding sampling and that no subject had a combination of these symptoms in such severe 
forms as to warrant a suspicion of acute lead poisoning. 
Furthermore since the mean scalp hair and pubic hair lead values of occupationally 
exposed workers were significantly higher than persons belonging to the normal population, 
whereas the mean blood lead levels for both the occupationally exposed groups and the normal 
population were similar, these results suggest that lead in hair provides a more realistic estimate 
of long term exposure to lead contamination compared to lead in blood. 
118 
3:7 SULPHUR AND CARBON:SULPHUR HAIR ANALYSIS 
The percentage sulphur and the carbon:sulphur ratio in hair influences hair texture80. It 
has been suggested therefore that the difference in scalp hair texture between the East Indian, 
African and Chinese racial groups was due to the different sulphur percentages and car­
bon: sulphur ratios in the scalp hair. Furthermore, the disulphide groups of the hair protein have 
been proposed as the binding sites for lead80. 
The carbon:sulphur ratios of scalp hair of the general population show a normal 
distribution (Fig. 23). In order to check for any possible relationship between the percentage 
sulphur (Table 17) and the carbon:sulphur ratio (Table 18) with that of scalp hair lead, 
correlation analyses were carried out between:- (1) the sulphur percentages and the scalp hair 
lead levels and (2) the carbon:sulphur ratios and the scalp hair lead levels. The results indicate 
no correlation between the scalp hair lead levels with both the sulphur percentages (r=0.02) and 
the carbon: sulphur ratios (r=0.25). The lack of correlation may be due to the presence of other 
binding sites (other than disulphide groups) in hair which bonds to systemic lead or that the hair 
lead levels are only influenced by environmental lead exposure and not the sulphur percentages 
or the carbon:sulphur ratios. 
The carbon:sulphur ratios of the East Indian and African racial groups were compared 
since members of these groups generally have different hair textures. Africans have coarse curly 
scalp hair whereas East Indians have thin straight scalp hair. An unpaired t-test was used to 
119 
compare the carbon:sulphur ratios of these two racial groups and the results showed a significant 
difference in carbon:sulphur ratios (t=2.12, P=0.05) between them. Since a significant 
difference was also observed in scalp hair lead levels between the East Indian and African racial 
groups (t=2.47, P=0.05) it may be that the carbon:sulphur ratios between these two groups is 
a factor contributing to the differences in the scalp hair lead levels observed. The curly scalp 
hair texture of the African racial group compared to the East Indian racial group is due to the 
higher percent of sulphur in the hair. It is possible that exogenous lead can be chemisorbed into 
African hair to a greater extent compared to East Indian hair since it spends a longer time 
trapped on the hair surface of the African hair due to its curly texture. 
© PERCENTAGE SULPHUR IN (N SCALP HAIR 
0  
0.0 1-0 2.0 3.0 4.0 5-0 6.0 7.0 8.0 9.0 10.0 11.0 
PERCENTAGE SULPHUR 
Fig.23 
TABLE 17 THE %SULPHUR IN SCALP HAIR AMONG THE 
FOUR GROUPS 
GROUPS MEAN MEDIAN RANGE 
% % % 
EAST (N=35) 9.78 11. 15 2.11-17.96 
INDIAN 
AFRICAN 12.17 13.23 2.53-19.02 
(N=17) 
CHINESE 12.34 12.41 2.32-20.85 
(N=14) 
MIXED 14.09 14.73 7.29-19.61 
(N=8) 
TABLE 18 THE CARBON :SULPHUR RATIO IN SCALP HAIR 
AMONG THE FOUR GROUPS 
GROUPS MEAN MEDIAN RANGE 
EAST 8.32 4.41 2.32- 6.69 
INDIAN 
(N-3) 
AFRICAN 5. 14 3.66 2.56-17.74 
(N=17) 
CHINESE 5.30 3.62 1.66-19.58 
(N=14) 
MIXED 3.82 2.95 2.49- 6.88 
(N=8) 
122 
CHAPTER FOUR 
CONCLUSION 
123 
4:1 CONCLUSION 
As a result of the previously mentioned problems associated with the use of blood as a 
bioindicator, a project designed to investigate further the possibility of using hair as an 
alternative was undertaken. 
In any study on the use of hair as a biopsy material, finding a suitable washing procedure 
is of paramount importance. In this project, although the washing procedure used seems to give 
the best results when compared to others, there are still problems to be addressed. The scanning 
5 
? electron microscope (SEM) photographs taken after hair samples were washed using the Kleenol" 
• 
method, still indicated the presence of some particulates. Therefore there is the possibility of 
2 exogenous lead contamination of the hair samples. In addition, no method was employed to test 
2 
whether endogenous lead particulates were removed during washing. The problem of identifying 
a totally acceptable washing procedure therefore remains unresolved based on the results of this 
study. 
A significant difference was found in scalp hair lead levels among the racial groups 
studied. Since no correlation between scalp hair lead levels and sulphur and carbon:sulphur 
content was found, this suggested that these factors were not responsible for the significant 
differences in scalp hair lead levels among racial groups. It is generally assumed that hair texture 
might be related either to the sulphur content or the carbon: sulphur ratio of scalp hair in some 
way. The data obtained supported this assumption. A significant difference in the carbon: sulphur 
124 
ratio was found between the East Indian and African racial groups.These two groups have 
different hair texture as mentioned before. It should be noted that the physical structure of scalp 
hair is different among the racial groups. It is therefore also possible that because of this, lead 
particles are entrapped to varying extents by the scalp hair of individuals from different races, 
resulting in the significant differences in lead levels among the races. It may also be that factors 
not studied in this project are responsible for the differences in scalp hair lead values observed. 
In the East Indian and Mixed racial groups, scalp hair, pubic hair and blood lead values 
between males and females were significantly different. No significant difference was found in 
the African group. Differences in hormonal activity or hair growth rate between males and 
females as well as the loss of blood (menstrual discharge) could have influenced the lead values 
among the East Indian and Mixed groups. It is also possible, that the extent of genetical mixing 
in the Mixed group (rather than hormonal activity) maybe responsible for the differences 
observed in this category. Other factors which were more influential to lead accumulation than 
hormonal activity and which were not influenced by sex may account for the lack of a significant 
difference in lead levels between sexes in the African group. 
A significant difference in lead levels was found between scalp hair and pubic hair of 
persons within the general population. This difference has been attributed to the difference in 
growth rate of both types of hair. Pubic hair grows more slowly than scalp hair and therefore 
lead accumulation in pubic hair would be less than that of scalp hair. In addition, scalp hair is 
more exposed to exogenous lead contamination than pubic hair. 
125 
No significant difference was found in blood lead values between occupationally exposed 
groups and the general population. This is because blood lead levels reflect intake prior to the 
time the sample was taken, whereas hair provides a time averaged estimate. The significant 
difference found in scalp hair lead and pubic hair lead between occupationally exposed groups 
and the general population suggests that in occupations like that of battery plant employees and 
traffic police personnel, the increased atmospheric lead concentrations contribute significantly 
to their scalp and pubic hair lead levels. In spite of the possibility of exogenous lead 
contamination, it seems that the elevated lead found in occupationally exposed workers is suffi­
ciently different to assume that their occupations are responsible for the difference. 
No significant correlation was found between the time spent in "traffic jams" and the lead 
levels in scalp hair. This was unexpected, but similar to the results of Hall et al26. Since the 
speed at which motor vehicles travel in a "traffic jam" is slow, it may be that the lead 
particulates emitted from their exhaust systems are deposited close to the ground and are not 
elevated sufficiently to be inhaled by their occupants. 
There was also no significant correlation between the total time spent on the road in 
motor vehicles and the scalp hair lead levels. It was assumed that at high speeds, automobiles 
consume larger quantities of gasoline which should result in the emission of larger quantities of 
lead. However, the force and velocity with which exhaust gases are emitted at high vehicular 
speeds could result in the lead particulates being elevated to heights beyond the reach of persons 
travelling. 
126 
There was also no significant correlation between the total time spent on the road 
in motor vehicles and the scalp hair lead levels. It was assumed that at high speeds, automo­
biles consume larger quantities of gasoline which should result in the emission of larger 
quantities of lead. However, the force and velocity with which exhaust gases are emitted at 
high vehicular speeds could result in the lead particulates being elevated to heights beyond 
the reach of persons travelling. 
When the scalp hair lead values and the blood lead values were compared, no 
significant correlation was found. This reinforced the point that each of the bioindicators 
mentioned represents different time scales. Blood reflects lead intake in the previous hours 
or days whereas hair provides a lasting record. 
Many problems associated with the use of hair as a bioindicator for detecting 
exposure to lead still exist. For example, there is the difficulty in obtaining scalp hair from 
newborn babies and balding adults. Inspite of these limitations, hair analysis is likely to 
gain more international recognition as ane ffective bioindicator for determining lead levels. 
127 
RECOMMENDATIONS 
The following are the recommendations for further work: 
(1) A larger sample population should be investigated in order to obtain a sample 
population which is more representative of the Trinidad population. In addition, 
the sample population should include more Chinese in the control and 
occupationally-exposed groups so that suitable statistical analyses can be done. 
(2) The sample population studied in this project consisted of only one major age 
group and therefore no comparison between age groups was possible. Further 
studies should be done on a population that includes all the major age groups ie. 
pre-adolescent, adolescent and adult. 
(3) Individuals sampled should be instructed to accurately determine the time spent 
on the road and the time spent in "traffic jams". 
(4) Closer medical scrutiny should be carried out on individuals to ascertain whether 
medical symptoms observed are actually related to lead exposure or are due to 
other factors. 
128 
(5) Air-lead levels at the battery plant and along routes where individuals travel 
should be monitored. Air currents and rainfall data should also be collected and 
utilized in the interpretation of the data. 
(6) Other occupationally exposed groups such as gas station attendants, taxi drivers, 
auto-mechanics, persons handling tetraethyllead for gasoline blending etc. should 
be included in the sample population. 
(7) More work should be done to establish a suitable washing procedure which 
removes all exogenous particulates but avoids removal of endogenous material. 
(9) Hair lead determination should also be done by other methods (e.g the X-ray 
fluorescence (XRF) method) and the results compared with that obtained by 
atomic absorption spectroscopy (AAS). 
(10) An investigation of the growth rate of hair of persons belonging to different racial 
groups should be conducted so as to determine what impact, if any, it has on lead 
levels in hair. 
129 
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