There has recently been concern about carcinogens in drinking water.
In Duluth, Minnesota, asbestos in substantial amounts has been found in the water supply, which has apparently been contaminated since 1955 with industrial waste from taconite ore discharged into Lake Superior.1 Asbestos, when inhaled, is known to be carcinogenic in man. It causes pleural and peritoneal mesothelioma, lung cancer, and gastrointestinal neoplasia in factory workers exposed to the fibers,2-5 and mesothelioma of the pleura or peritoneum among persons living in the neighborhoods of these factories and perhaps in the households of workers.3,6-9 An increase in the frequency of bronchogenic carcinoma has also been reported among persons with low-level (nonoccupational) exposures to asbestos.10
Asbestos is believed to be carcinogenic because of its physical rather than its chemical properties—specifically, the length and diameter of the fibers are related to their carcinogenicity in rats.11,12 Long thin fibers seem to be more harmful than short thick ones, but short fibers cannot yet be regarded as harmless.13
Millions of asbestos fibers are found per liter of water drawn from the taps in Duluth.1 Most are of short length, less than 5µ. Studies of cancer mortality through 197114,15 showed no increase that was attributable to contamination of the water supply, but the latent period for asbestos-induced cancer is known to be two or more decades, well beyond the interval for which data were available.
The problem, if indeed there is one, may not be limited to Duluth, since other water supplies contain asbestos fibers leached from serpentineor amphibole-rock or from asbestos-containing cement pipes.16,17
- Copyright © 1976 by the American Academy of Pediatrics