I/.
United States
Environmental Protection
Agency
Health Effects Research
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S1 -85-003 Feb. 1985
&ER& Project Summary
Asbestos Sampling Plan for the
San Francisco Bay Area,
California
Carole J. Leong and Michael E. Tarter
This research project was initiated to
facilitate the use of waterborne asbestos
data for a possible case-control epide-
miological study of ingested asbestos in
five Bay Area counties near San Fran-
cisco, California. For each county, and
each census tract within the area,
information about historical water sup-
ply and distribution, water treatment
practices, and asbestos levels has been
compiled. It was determined that none
of the major water districts servicing
the San Francisco Bay Area are free of
asbestos fibers. Individual asbestos
measurements range in value from less
than 10* fibers/liter to 1.8 x 10"
fibers/liter of finished water. It was
determined that a sampling protocol to
augment the current asbestos data base
should include sampling the largest
flows of water and should take into
consideration: variation within the dis-
tribution system, possible seasonal
variation, the drought of 1976-1978,
and the historical wateborne asbestos
levels.
The final report was submitted in
fulfillment of Purchase Agreement No.
(3253NAET) by the Department of
Biomedical and Environmental Health
Sciences of the University of California,
Berkeley, California, under the sponsor-
ship of the U.S. Environmental Protec-
tion Agency
This Project Summary was developed
by EPA's Health Effects Research Labo-
ratory. Research Triangle Park. NC, to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
A study of asbestos in drinking water
supplies and cancer incidence from
1971 -1976 was conducted at the Univer-
sity of California at Berkeley. The indirect
epidemiological approach used (the cen-
sus tract was the smallest unit) in that
study showed the existence of a statistical
association between the presence of
asbestos fibers in drinking water and the
incidence of certain cancers among resi-
dents served by those water supplies. In
particular, the incidence of cancer of the
digestive tract and digestive related
organs was associated with increasing
amounts of asbestos in the drinking water
supply of the San Francisco Bay Area.
In order to take into account more fully
the effects of other variables such as
smoking, alcohol consumption, and oc-
cupation on the association found, a
case-control study could be conducted.
To conduct such an epidemiological study
of ingested asbestos fibers and cancer, it
is necessary to determine an individual's
exposure to waterborne asbestos over
the past 30 or 40 years. A review of the
waterborne asbestos data base amassed
during the indirect study and recommen-
dations as to how to augment the data
was necessary.
Results
The available data show that the
presence of asbestos fibers in Bay Area
drinking water is a result of water coming
in contact with serpentive rock, either as
runoff (Marin County) or through reser-
voirs (Crystal Springs), and the major
water systems within this study area
have not changed much over the past 30
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to 40years. Any historical changes in the
asbestos levels found in tap water
probably result from the use of different
treatment practices. The contribution of
asbestos-cement pipe to the level of
asbestos found in drinking water has yet
to be determined. The University of
California indirect epidemiology study
was not specifically designed to measure
the risk that might be attributed to the use
of asbestos-cement pipe.
The available data show that none of
the major water districts servicing the
San Francisco Bay Area are free of
asbestos fibers. Individual asbestos
measurements range in value from less
than 10* fibers/liter to 1.8 x 108 fibers/
liter of finished water. A number of graphs
and charts have been developed to show
the fiber exposures determined for vari-
ous water distribution areas.
Conclusions
The individual asbestos fiber concen-
trations available in the full report are the
values for single grab samples of tap
water taken from a census tract. Water
sampling sites wre chosen on the basis of
(1) being representative of a specif ic water
distribution system, and (2) convenience
of sampling. In order to more fully char-
acterize the asbestos content of these
water systems, it may be necessary to
make composite samples by combining
samples of water over a period of time.
This would minimize the problems of
utilizing grab samples and reduce the
number of water samples to be analyzed.
This would also take into account the
intermittent and non-uniform occurrence
of asbestos in water from various sources.
Recommendations
A sampling protocol to augment the
current asbestos data base should ad-
dress the following points:
1. Drought of 1976-1978. Most of the
data on asbestos in Bay Area
drinking water were collected dur-
ing the extreme drought years of
1976-1978. It is not known if the
waterborne asbestos concentra-
tions are truly representative of a
year with normal rainfall.
2. Seasonality. It has not been deter-
mined if there is any variation in
waterborne asbestos at different
times of the year.
3. Variation within a distribution
system. Finished water from each
system and corresponding tap water
samples from various census tracts
within the system should be ana-
lyzed and compared. Different dis-
tribution systems having the same
source should also be compared.
4. Historical waterborne asbestos
levels. The history of water supply
for the area has been well docu-
mented. Since changes have oc-
curred mainly in the treatment
practices employed by the water
suppliers, source water prior to
treatment should be fairly repre-
sentative of historical asbestos
levels, and extensive sampling and
analysis should be carried out
Carole J. Leong and Michael E. Tarter are with the Department ofBiomedicaland
Environmental Health Sciences, University of California, Berkeley, CA 94720.
James R. MfHettt is the EPA Project Officer (see below).
The complete report, entitled "Asbestos Sampling Plan for the San Francisco Bay
Area, California," (Order No. PB 85-151 207'/AS; Cost: $11.50, subject to
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Health Effects Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
it US GOVERNMENT PRINTING OFFICE; 1985 — 559-016/7906
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45260
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