Each panel
member made a brief presentation on investigating environmental lead
sources and pathways.
Dr.
Isabella Romieu
Dr. Isabelle
Romieu presented a case study of the sources of lead exposure in the
population of Mexico City. The variability of potential sources of exposure
between different population was acknowledged, as well as the differences
in the relative role of specific sources as contributors to blood lead
levels in different populations depending on lifestyles and environmental
setting.
In Mexico,
studies have been carried out to determine major sources of exposure
in order to focus control strategy through the linkage between biological
and environmental monitoring in exposed population. In urban setting
the main sources and pathways of exposure among children 5 years of
age or less were air, lead, the use of leaded glaze ceramics and children’s
hand dirt. Such sources of exposure have also been identified in other
populations and implementation of control strategies, in particular
the introduction of unleaded gasoline, had a dramatic impact on blood
lead levels of the population of Mexico City, which fact was confirmed
by data from sequential cross-sectional evaluation of blood lead levels.
The impact of the use of leaded ceramic has also been identified in
different subgroups of the Mexican population and is currently considered
as the major remaining source of lead exposure in non-occupational exposed
population in Mexico. The use of lead isotope fingerprint has confirmed
the importance of this source in their blood lead levels.
An
update: In Mexico’s largest-ever environmental clean-up, the
Government of Mexico started evacuating a 20-block area surrounding
the Met-Mex Penholes silver refinery plant in Torreon. While there were
limits set in 1995 on the amount of lead it can expel, enforcement has
been largely voluntary and monitoring did not start until 1998. Environmental
activists say that the government protected the plant from any bad publicity
until now. A study of 2397 children under the age of 12 years living
near the plant showed that only 157 had "acceptable" blood
lead levels below 10 mcg/dl., and many had seriously elevated levels
of lead. The government has accepted a plan that calls for temporary
evacuating residents from around the plant, cleaning the houses and
removing the top-soil in the area.
Dr.
Dinesh Parikh, Dr. C.B. Pandya and Dr. S.K. Kashyap
Dr. Parikh
presented an overview of the lead exposure and toxicological/epidemiological
studies carried out in India with reference to occupational exposure,
community exposure and traditional sources like herbal medicine. He
also explained the facilities available in India at various institutions/centers/universities
and medical colleges regarding sampling and analysis of lead in environmental
and biological specimens. However, he commented that rigid QA/QC program
is not performed by many laboratories in India. He suggested that a
training program is required in this area. Further, there is no standard
reference material in India. The National Institute of Occupational
Health (NIOH), Ahmedabad, has taken up the work of preparing lead standards
for blood on behalf of the Dept. of Science and Technology, Govt. of
India.
Human
exposure to a pollutant occurs when a person comes in contact with that
pollutant through the air, water and food, or through skin absorption.
After knowing the intensity of exposure, it is necessary to study the
effect on health and to suggest appropriate control strategies. In recent
year, many new techniques are developed to monitor such exposures, assess
them accurately and evaluate contributions from the individual sources
(Marie Vahter and Stuart Slorach, 1990). WHO and UNEP through the GEMS
had carried out successfully international pilot studies known as "Human
Exposure Assessment Location studies (HEAL)" for selected pollutants
in many countries. The National Institute of Occupational Health (NIOH),
Air Quality Monitoring and Research Laboratory (AQMRL), Mumbai Municipal
Corporation and Maharashtra Pollution Control Board (MPCB), Mumbai,
participated on behalf of the country. Groups of metals and chemicals
like lead and cadmium, pesticides like Hexachloro Benzene (HCB) and
Dichloro Diphenyl Trichloroethene (DDT); and the gaseous pollutants
like Nitrogen Dioxide were monitored in this program. In this article
attempt has been made to present the exposure monitoring data on Lead
at Chembur, Mumbai which is the HEAL site for India, and to describe
the issues related to exposure monitoring.
Chembur
area of Mumbai City was selected as the HEAL site which have conglomeration
of industries and heavy traffic density. High Exposure Areas (HEA) and
Low Exposure Areas (LEA) of Chembur were selected for the study. 16
non-smoking housewives, 25-50 years of age, living in the Chembur area
of Mumbai (7 were staying in high exposure area and 9 were staying in
low exposure area) were selected for the study. The samples of blood,
air, diet were collected as per the HEAL sample collection protocol
given by Technical Coordinating Centre, Sweden (Marie Vahter & Stuart
Slorach, 1990). Feces samples could not be collected from the subjects
due to non-cooperation.
Lead in
blood analysis was carried out using Delve's cup flame AAS (Atomic Absorption
Spectrophotometer) with BC (Background Corrector). Environmental Samples,
i.e. air, water and food, were wet oxidized and put in proper form for
AAS analysis. The samples were analyzed using AAS with BC.
In order
to ensure the validity and reliability of the monitoring data, an extensive
and rigid quality assurance program was implemented. Samples collected
from HEA and LEA of Chembur, Mumbai are compared with the results of
the other HEAL sites of the world in Table1. The mean value of 432.4
ng pb/m3 air was reported for Zagreb. It is also remarkable that there
is significant difference of ambient air lead level reported in Chembur,
Mumbai both from HEA and LEA.
Lead
content in water and its exposure
Lead levels
of water consumed by the subjects of Chembur, Mummbai area are given
in Table 2. Lead was found in an average range of 2.77 ug/L (in HEA)
to 4.48 ug/L (in LEA). This suggested a significant difference (p <
0.05) in water lead levels.
Exposure
to lead via the diet
Every content
of lead in duplicate diets collected from Chembur, Mumbai is compared
with the data from the HEAL site in Table 3. The values: mean (26.0±.7.7
ug); median (25.0 ug) and range (6.4 to 76.9 ug) of lead in daily diets
are comparable to similar values reported from the HEAL sites. Assuming
that 10% ingested lead is absorbed in the gastro intestinal tract, it
can be estimated that the housewives in Chembur, Mumbai, absorb an average
2.6 ug of daily-ingested lead.
Lead
in blood
The concentration
of blood samples of the women of Chembur, Mumbai are compared with the
result of the various HEAL sites studied under WHO/UNEP-HEAL Program
(Table 4). The blood lead were found in ranges from 37 to 124 Ug/dL
with an average of 71.0 Ug/dL and median of 70 Ug/dL.
Issues
Related to Exposure Monitoring
Exposure
monitoring should concentrate on assessing total human exposure to various
pollutants to be studied. This ensures the establishment of proper,
cost effective control standards designed to protect human health. Thus,
the following issues related to exposure monitoring require deliberations.
- Environmental
control strategies to protect human health
- Risk
assessment
- Quality
Assurance
- Epidemiological
studies
- Cost
effective control strategies
- Technology
transfer and information exchange
Human exposure
monitoring of Lead at Chembur, Mumbai was studied and data were compared
with other HEAL sites like Beijing, Stockholm, Yokohama and Zagreb.
The results of these studies indicate that the levels of our data are
comparable with other HEAL sites and it also indicates that diet is
an important route in exposure to lead.
Reference
Marie Vahter
& Stuart Siorach (1990). "Exposure Monitoring of Lead and Cadmium":
An international Pilot Studies within the WHO/UNEP Human Exposure Assessment
Location (HEAL) Program; pp. 1--82.
Table
1: Concentration of Lead in the Breathing zone Air (Personal Monitoring)
collected by the HEAL study groups
|
HEAL site
|
No. of
subjects
|
Mean'
|
Meana
|
S.D.
|
Ng Pb.m3
Median
|
Range
weekly
averageb
|
Range
daily
averagec
|
|
Beijing
|
12
|
|
116d
|
20
|
118
|
77-153
|
21-318
|
|
,
Stockholm
|
15
|
116d
64
|
64
|
14
|
66
|
42-94
|
15-169
|
|
Zagreb
|
17
|
412
|
412
|
195
|
400
|
140-840
|
0-2530
|
|
Mumbai
(HEA)
|
07
|
432.4
|
432.4
|
57.3
|
41.7
|
367-51.4
|
131.864
|
|
Mumbai
(LEA)
|
09
|
268.8
|
268.8
|
94.8
|
241.3
|
151-400
|
147-476
|
a) Mean
of the weekly average air concentrations for all subjects,
b) Range of the weekly average air concentrations among subjects.
c) Range of all daily average concentrations measured.
d) Six of the subjects were monitored for 4 days
Table
2: Lead Levels in Drinking Water (ug/L) of Mumbai HEAL Site
|
|
|
HEA
|
LEA
|
|
.... .. .. .......... , .-
|
Mean
+S.D.
|
2.77+0.84
|
448+1.65*
|
|
|
Range
|
1.84-4.06
|
1.73-6.61
|
|
m
|
Median
|
2.47
|
3.71
|
|
|
Number
|
7
|
9
|
*P<
0.05
Table3:
Lead in the Daily Duplicate Diets, Including Beverages, Collected
By the
HEAL Study Groups
|
|
HEAL site
|
No. of
subjects
|
Meana
|
S.D.
|
Ng Pb.m3
Median
|
Range
weekly
averageb
|
Range
daily averagec
|
|
|
Beijing
|
10
|
46
|
18
|
41
|
29-91
|
12-174
|
|
|
Stockholm
|
15
|
26
|
7.9
|
26
|
13-40
|
4.4-130
|
|
|
Yokohama
|
3
|
31
|
-
|
-
|
26-34
|
12-60
|
|
|
Zagreb
|
17
|
15
|
7.2
|
15
|
6.1-37
|
2.1-99
|
|
|
Mumbai
|
6
|
26
|
7.7
|
25
|
16.5-47.2
|
6.4-76.9
|
Table
4: Concentration of Lead in Blood Collected by the Heal Study Groups
| |
|
|
|
Ug/Pb/1
|
|
|
|
HEAL Site
|
No. of
Subjects
|
Mean
|
S.D.
|
Media
|
Range
|
|
|
Beijing
|
12
|
73
|
20
|
69
|
48-124
|
|
|
Stockholm
|
15
|
29
|
8.3
|
28
|
15-44
|
|
|
Yokohama
|
12
|
31
|
12
|
32
|
13-60
|
-
|
|
Zagreb
|
17
|
50
|
17
|
47
|
25-101
|
|
|
Mumbai
|
16
|
71
|
22
|
70
|
37-124
|
|
Dr.
Gary Noonan
Dr. Noonan
discussed issues of environmental sampling and reiterated the need for
QA/QC program and analytical standards. He also emphasized the need
to develop environmental sampling protocols that closely mimic the work
that has been already done in developed and other developing countries.
He also talked about various new analytical instruments available to
screen/measure lead levels in environmental media. There is a critical
need for standard operating procedures (SOP’s) for sample collection.
He stressed a real need to co-ordinate between various government ministries,
departments, and institutions both within the country and at international
levels.
Dr.
Brain Gulson
Dr. Gulson
discussed isotopic finger printing for exact identification and characterization
of lead exposure. He presented case studies that were funded by the
national Institute of Environmental Health Sciences in the US at two
different sites in Australia. He discussed advantages and disadvantages
of using isotopic technique. This technique identifies exact sources
but is not adopted by the developing countries because of its high cost
of instrumentation and infrastructure including training of personnel
who are required to run the operation. Further more he discussed the
use of this technique in a study recently conducted on Biokinetics of
Lead in Human Pregnancy.
Dr.
Xai Ming Shen
Dr. Shen
described sources of lead exposure in Chinese children. He focussed
his presentation on industrial emission, leaded gasoline and other consumer
products such as food and traditional Chinese medicine. He stated that
lead content in gasoline in China is 0.78 gm/lt. i.e., second highest
in the world. In 1998 Chinese policy-makers made a decision to phase
out lead in gasoline from all urban centers by year 2000. He presented
data indicating 30.4% of toys contain soluble lead with levels as high
as 250ppm. Recent survey in China also indicated that 66.7% of painted
pencils have soluble lead above the allowable level of 3ppm. He also
pointed out that "take home exposure" is a serious problem
in China. The coal combustion at home is also a major source of lead
exposure (18 times more than control).
Dr.
B. Sonawane
Dr. Sonawane
stated that in the US lead base paint clearly remains a major source
of childhood and occupational lead poisoning. It is the principal source
of elevated blood lead levels for over one million US children between
the ages of 1 and 5 years. Lead-based paint represents a difficult challenge
because it is source that is both highly concentrated and widely dispersed.
Lead abatement is relatively a costly affair.
The extent
of lead-based paint exposure could be analyzed by collecting data on
the amount of
- Lead
used in the production of new paint
- Old
lead-based paint in the existing houses.
- Toys,
furniture and consumer items.
- Nonresidential
setting-principally old bridges and other steel structures
In 1998
USEPA proposed an interim guidance for correcting actions for lead in
soil. This proposal identified hazardous paint as well as residential
dusts and soils that have levels of lead considered to be hazardous,
regardless of whether they were contaminated with paint or other lead
sources. When environmental levels exceed the contamination level of
EPA’s baseline, expectation is that children may be at risk of having
elevated blood lead levels.
He further
stated that the residential screening level for lead has been calculated
using the Agency’s new Integrated Exposure Uptake Biokinetic Model (IEOBK)
using default parameters. This model recognizes multimedia nature of
lead exposure, incorporated important absorption information and allows
the risk manager to consider the potential distributions of exposure
and risk at a particular site.
He further
noted that both the Guidance Manual and the IEUBK model are available
to the public through the National Information Service (Ph: 703-487-2650).
Discussion
- What
is the best strategy to identify major sources of lead exposure in
India?
Environmental
sampling should be carried out at two levels:
- Routine
monitoring of major potential sources of lead exposure including air,
water, food, and soil should be conducted. This activity should be
the responsibility of Federal /state agencies.
- Specific
assessment should be conducted in susceptible population including
simultaneous biological and environmental sampling in order to determine
major sources of lead exposure in these populations and focus control
strategies.
- Who
should be responsible for monitoring environment lead content?
In the
ministry of environment, central population control boards (CPCB)
in collaboration with the national environmental engineering research
institute (NEERI), should co-ordinate and carry out environmental
sampling and monitoring. The identification of major sources of exposure
should be made by a national institute such as ITRC/NIOH, in collaboration
with the local universities/medical colleges. The scientific body
should develop guidelines for Protocol Development, Quality Assurance
(QA) and Quality Control (QC), Reference Material, and Sampling strategies
so that data can be collected in a comparable manner by different
centers allowing comparison and pooling of data. For rapid assessment,
portable instruments that can be used in the field and which require
little maintenance is a good alternative to the use of more sophisticated
equipment.
- Where
should standards be set?
It was
recognized that because of the extensive multimedia in lead exposure,
strict standards may not be achievable in a short time frame. Therefore
a stepwise approach may be more feasible in order to keep the impetus
for moving in the right direction. A time frame should be formulated
to allow progressive control of environmental Lead exposure.
- How
to be develop an effective approach to capacity building and training?
Training
of public health and laboratory personnel is essential and should be
coordinated through a central agency. Training module should be developed
and taught in local universities/medical colleges in a comprehensive
and standardized manner. Quality assurance and quality control programs
are an essential part of this, and they must be developed in strict
adherence to ensure validity of the data. It cannot be stressed enough
that the main goal of collecting quality environmental/biological data
is to provide policy makers with the information required for implementing
control programs and to evaluate the importance of interventions. For
any of the programs to be effective, public awareness of the problem
and educational out reach programs need to be implemented at the community
level using NGOs, public health personal, and private medical providers.
Dr.
Venkatesh Iyengar
Various
sources are responsible for the excessive presence of lead in the Indian
environment. Among these, vehicular emissions and waste water (effluent)
streams from battery industries contribute to the problem to a great
extent and therefore, require priority attention. These are the emissions
from vehicles using leaded petrol, and the emissions/discharges from
industries involved in the manufacture of lead-acid batteries. The vehicular
emissions need greater attention as they have a direct impact on the
health of human population. In other words, urban areas with high density
vehicular traffic need priority attention. Sources like adulterants,
cooking utensils and indigenous medicines also contribute to some extent,
but the severity in this case is much less significant in comparison
with that arising from vehicular emissions.
Vehicular
Emissions
The total
production of petrol is 5.1 million tonnes per year (MTPY). Out of this
4.8 MTPY is regarded as low leaded petrol with a maximum permissible
limit of 0.15 gm/litre. Further, 0.3 MTPY is the unleaded type, which
contains up to 0.013 gm/litre due to presence of lead in the crude oil
itself. The total estimated release of lead from vehicular emissions
is 640 TPY (1). At least 50%, and possibly up to 70% of this is expected
to be released as emissions into the environment, and the rest gets
deposited in the exhaust system. As per the Central Pollution Control
Board’s (CPCB) annual report of 1993-94, the annual mean values of particulate
lead in ambient air during the years 1989 to 1992 remained within the
limit of 1000 ng/m3 as prescribed by the WHO, except in the Shahdara
area of Delhi where it exceeded in some cases. However, the report also
covers maximum encountered values of as high as 8500 ng/m3 in the year
1990. Particulate lead is being monitored at six locations in Delhi
as per the details given in this report (1).These annual mean values
have come down to 350 ng/m3 in 1996 and about 220 ng/m3 in 1997 as reported
in the CPCB’s annual report of 1997-98. This report also indicates highest
emissions of lead in Delhi, followed by Calcutta, Mumbai and lowest
levels in Chennai, as far as these four mega cities are concerned. The
lead emission for Delhi in 1996 has been estimated as 259 tonnes. It
may be noted that Delhi has about 2.5 Million petrol driven vehicles
out of which 1.83 million are two wheelers alone (2). As far as the
control measures are concerned, the following steps have been taken:
regulatory restriction enforcing the use of unleaded petrol by all vehicles
manufactured after 1.4.1995; all the petrol-driven vehicles in Delhi
adopting the use of unleaded petrol with effect from 1.9.1998; and banning
of vehicles aged 15 years or more from the city traffic.
Battery
Industries
The total
production of the lead-acid batteries in the country is about 8 million
batteries per year (3). Nearly 10,000 kg of lead is consumed in the
production of every 1000 such batteries, and the estimated release of
lead from various sources in the production of 1000 such batteries is
nearly 11.35 kg i.e. 11.35 kg/1000 batteries. Out of this 11.35 kg,
5.45 kg is estimated to be released as emissions and 5.90 kg as part
of the waste water or effluents (3). These are governed by the relevant
environmental legislation. It may be noted that even the discharge of
lead within the limit of 0.1 mg/litre results in the release of significant
quantities of lead due to large volumes of such effluents released.
Permissible
Concentration Limits for Lead in Various Media
The permissible
limits of lead in (a) ambient air is 0.75 µg/cum for sensitive areas
such as bird sanctuary, 1.0 µg/cum for residential areas and 1.5 µg/cum
for industrial areas (4); (b) drinking water is 0.05 mg/litre and c)
industrial effluents for their discharge in inland surface water is
0.10 mg/litre.
Absorption
of Lead
Absorption
of lead by humans is highly variable. For example, lead absorption is
highly dependent on the chemical form, constituents of the diet, and
also on the nutritional status of the subjects just before ingestion
(e.g. fasting and non-fasting situations). It can also be influenced
by the ill health of the subjects. A few examples drawn from the literature
are presented in Table 1 (5). It should also be noted that , the absorption
phenomenon varies widely between the young and the adults for heavy
elements, and this has been demonstrated in several species (6); e.g.
lead (5 folds in humans).In general, infants and young children absorb
minerals from the diets to a higher degree in comparison with adult
subjects.
Priority
Needs for Action Concerning Lead Emissions in India
In order
to investigate children for exposure to lead, the selection criteria
has to be designed carefully. Because of the differences in schooling
opportunities available to various population groups (e.g. most of the
children in India start their education at the age of 5+ as far as the
government schools are concerned), it will be necessary to consider
at least two different types of groupings: selecting the 5 to 15 years
or so age group for the exposure studies, is one possibility; the other
option is to carefully identify the groups that start attending the
Kindergarten system before the age of 5 years, and build a group in
the age span of 3 to 5 years of age. It would be necessary to harmonize
the conditions by choosing the schools from selected localities with
comparable vehicular traffic pattern.
Occupational
health studies are required more in the lead-acid battery manufacturing
activities which involve direct emission of lead into the working environment.
The mining activities segment is also important if there is evidence
of contaminated dust containing <10 micron size lead particles. It
is also recommend that workers in the soldering sections in electronic
goods manufacturing units be investigated. Among others, investigation
of the bioavailability of lead from various sources merits attention.
Blood lead levels during pregnancy are relevant because of the effects
on the unborn. The human placenta, which is an easily accessible specimen,
offers the possibility to carry out biomonitoring at a population level.
References
1. Personal
Communication (1998), Mr. C.P. Jain, Dy. General Manager (Safety and
Environment Protection), Indian Oil Corporation Ltd., Scope Complex,
New Delhi.
2. Dutta,
S.A. & Sengupta, B. (1998), Air Quality Goals for Delhi-options
to meet by the year 2005", proceedings of the Workshop on Integrated
approach to Vehicular Pollution Control, April 16-18, 1998, World Bank,
New Delhi.
3. "Comprehensive
Survey of the Battery Industries in India, CPCB, 1993".
4. Standards
for liquid effluents, gaseous emissions, Automobile exhaust,
Noise and
Ambient Air Quality, CPCB Publication No. PCL/4/1995-96 page 61-62
5. G.V.
Iyengar, Gastrointestinal absorption of trace elements, In, Trace Elements
in Medicine, Health and Atherosclerosis, F. Reis et al (Eds), Smith-Gordon
Publishers, London 1995, pp.79-90.
6. Similarities
and Differences between Children and Adults, P.S. Guzelian et al. (Eds),
ILSI Press, Washington DC, 1992.
