LEAD
POISONING IN INDIA - NIOH EXPERIENCE
Dr.
H. N. Saiyed
Importance
of Lead Removal from the Viewpoint of Health and Environment
Lead is ubiquitous
in nature. It affects virtually every system in the body. Blood lead
levels as low as 10 ug/dl are associated with adverse health effects
in children. The children and fetuses are particularly more vulnerable
to the effects of lead. Although the effects of low lead level may not
be severe in an individual child, on a population basis they are extremely
important. The important sources of lead are automobile exhaust, and
industrial processes such as smelting of lead, recycling of lead batteries,
manufacturing of lead based paints etc. Exposure to lead can occur through
the drinking water and food contaminated with lead. The population of
developing nations like India is particularly more susceptible to lead
poisoning because of the problem of malnutrition. Iron deficiency anemia,
a common nutritional problem in Indian women (particularly during pregnancy)
and children, can lead to greater absorption and therefore greater toxic
effects at the same level of lead exposure. Ironically, the lead poisoning
leads to anemia. Because of the greater susceptibility of children,
and since lead poisoning is a preventable condition, all necessary steps
should be taken for its prevention.
Studies by the
National Institute of Occupational Health /NIOH), Ahmedabad
National Institute
of Occupational Health, Ahmedabad, a permanent institute under the Indian
Council of Medical Research (ICMR), is dedicated to the cause of the
workers and environment. The importance of lead toxicity has been well
recognized by the Institute and is working on this issue since 1970.
The Institute has carried out research pertaining to various health
issues related to lead exposure in different groups like general population,
children and workers. In the following paragraphs, some important studies
have been summarized.
Exposure Monitoring
of Lead and Cadmium -An International Pilot Study within WHO/UNEP
a) Human Exposure
Assessment Location Program.
This international
collaborative study was undertaken with the objectives to develop and
test methods for monitoring of lead and cadmium and to get first hand
information on sources of pathways of lead and cadmium in selected locations
in selected countries. The study was carried out in Mumbai (India),
Beijing (China), Stockholm (Sweden), Yokohama (Japan), and Zagreb (Yugoslavia).
The study in Mumbai consisted of exposure assessment of sixteen (nine
from high exposure and seven from low exposure areas) subjects from
air, water and food. For estimation of lead exposure from air, each
subject was attached with a personal sampling device for 24 hours a
day for the whole week. The samples of food and beverages consumed by
each participant during the whole study period were collected and the
actual quantity consumed was also noted. The venous blood samples for
lead and cadmium were collected on the first and last days of the study.
The study results showed that the mean concentrations of lead in high
and low areas of Mumbai were 432.2 ± 57.ng/M3 of air and 268.8
± 94.8 ng/M3 of air. The mean concentrations in Beijing, Stockholm
and Zagreb were 116 ± 20, 64 ± 14 and 412 ± 195 ng/M3
of air respectively. The daily (mean of seven days) intake of lead in
Mumbai subjects through food and beverages was 26 ug/day. In Beijing,
Stockholm, Yokahama and Zagreb the mean values were 46, 26, 31 and 15
ug/day respectively. The mean blood lead levels in Mumbai, Beijing,
Stockholm, Yokahama and Zagreb were 7.1, 7.3, 2.9, 3.1 and 5 ug/dL of
blood respectively. This preliminary study suggested relatively higher
levels of lead in blood in Mumbai subjects resulting from exposure through
air and food.
b) Levels
of Lead in children and its effect on sexual maturity
This is an ongoing
study which is based on the observations in rodents of a possible association
between lead exposure even at lower level and sexual maturity. To verify
such association in human beings a three-year longitudinal study is
being carried out in 632 school children (348 boys and 284 girls). On
the basis of blood lead levels, they have been divided into two groups:
(1) those having blood lead levels less than 10 ug/dL; in this group
there are 392 children (214 boys and 178 girls). Their mean blood level
is 7.41 t 1 .49 ug/dL. and (2) those having blood lead levels 10 ug/dL
or more. In this group there are 240 children (134 boys and 106 girls).
· Their mean blood level is 13.48 t 3.13 ug/dL. The blood lead levels
were measured by Delve's Cup Technique on Atomic Absorption Spectro-photometer.
The Sexual Maturity Rating (SMR) was carried out by senior pediatricians
as per Marshall Tanner Classification.
The results of the
first examination show that the mean age at various stages of the SMR
was higher in boys belonging to high blood lead group. In girls also
SMR was higher in those belonging to high blood lead group. Both in
boys as well as girls, the differences in mean age was greater at higher
stages of development. These differences were statistically non-significant.
However, since these differences were observed at most of the stages
of development in both sexes, the preliminary results indicate possible
delaying effect of relatively low lead levels on sexual maturity. The
final conclusions can be drawn only at the end of this longitudinal
study.
c) Blood lead
levels in certain high-risk occupational groups
Since the 1970s,
the National Institute of Occupational Health, Ahmedabad, has been carrying
out surveys in various industrial workers having high occupational risk
of lead exposure. These surveys have shown that the blood lead levels
were as follows: Welders-28 ug/dL, Iron Foundry Workers-62.11 ug/dL,
Glaze workers-53 ug/dL, Type Foundry Workers-61 u,g/dL, Printing Press
Workers-38 ug/dL, Workers of Battery attached with a personal sampling
device for 24 hours a day for the whole week. The samples of food and
beverages consumed by each participant during the whole study period
were collected and the actual quantity consumed was also noted. The
venous blood samples for lead and cadmium were collected on the first
and last days of the study. The study results showed that the mean concentrations
of lead in high and low areas of Mumbai were 432.2 ± 57.ng/M3 of
air and 268.8 ± 94.8 ng/M3 of air. The mean concentrations in Beijing,
Stockholm and Zagreb were 116 f 20, 64± 14 and 412 ± 195 ng/M3
of air respectively. The daily (mean of seven days) intake of lead in
Mumbai subjects through food and beverages was 26 ug/day. In Beijing,
Stockholm, Yokahama and Zagreb the mean values were 46, 26, 31 and 15
ug/day respectively. The mean blood lead levels in Mumbai, Beijing,
Stockholm, Yokahama and Zagreb were 7.1 , 7.3, 2.9, 3.1 and 5 ug/dL
of blood respectively. This preliminary study suggested relatively higher
levels of lead in blood in Mumbai subjects resulting from exposure through
air and food.
Accumulator . -55.5
ug/dL, Lead Smelting-21 .1 ug/dL, and in Silver Foundry Workers-17.29
ug/dL. In all these industries the blood levels exceeded the danger
levels of 40 ug/dL in many individuals.
Prevention
For prevention
of lead poisoning in workers, following Code of Practice should be followed
at plant level:
- Assessment of
work which exposes persons to lead
- Information,
instruction and training
- Control measures
for materials, plant and processes
- Use and maintenance
of control measures
- Respiratory protective
equipment and protective clothing
- Washing and changing
facilities and cleaning
- Separate eating,
drinking and smoking areas
- Duty to avoid
spread of contamination by lead
- Air monitoring
- Medical surveillance
and biological tests
- Keeping of records.
For Prevention
of lead poisoning in workers, the Government should ensure the following
steps:
- Ensure the enforcement
of the Lead Schedule of the Factories Act by each of the state government.
- Creation of infrastructure
facilities like proper equipment, chemicals and trained staff essential
for monitoring of lead in environment as well as in blood as per the
requirement of the Factories Act.
- Review of the
standards as laid down in the Factories Act from time to time on the
basis of new scientific findings.
Finally, it may
be concluded that lead poisoning is an important preventable public
health problem which particularly affects the children of low socio-economic
status and various industrial workers. In the light of recently acquired
scientific knowledge, it is established that the lead exposure, even
at a relatively low level, can have serious health and economic consequences.
It is therefore essential that we should work out a national policy
on lead taking into account the cost benefit analysis.
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