Comments on the California studies.

I became interested in asbestos in drinking water supplies in the spring of 1973 when Mr. Jack Murchio, our electron microscopist, pointed out that a number of San Francisco Bay Area reservoirs were situated on geologic formations that are known to contain asbestos, i.e., serpentine rock. Thus we set out to examine the raw drinking water associated with these reservoirs for the presence of asbestiform fibers. This required the development and refinement of a method for the determination of concentration, enumeration, and identification of fibers in water using electron microscopy. The results of our preliminary investigations indicated that fiber counts as high as 2 x 108 fibers/L were present. These results were published in September 1974 (1). To my knowledge, this was one of the first reports of the presence of asbestos fibers in drinking water associated with natural geologic formations rather than with asbestos mining or other industrial activities. The potential public health problem associated with asbestos in water supplies, particularly in light of the 1974 reports from Duluth, MN, seemed obvious. An epidemiologic study appeared feasible, since the San Francisco Bay Area was serviced by a number of water supplies, some from asbestos-rich geologic formations. Tumor morbidity data for the geographic area involved was available through the San Francisco Bay Area Resource for Tumor Epidemiology. Our epidemiologic study was funded in 1976 by the EPA Health Effects Laboratory. Dr. Marty Kanarek (a doctoral student at the time) was the project manager and Mr. Paul Conforti was assigned as project statistician. The resultant study was subject to all the problems of such projects. The most time-consuming task was to develop water supply information as it related to the 1970 census tracts of the involved counties and to determine whether or not such