Interviews using a detailed questionnaire were conducted with 351 white, male, bladder-cancer patients and 855 matched controls.* "The study was designed to assess the association between bladder cancer and dietary factors, including vitamins, dietary fat, fiber, protein, total caloric intake," coffee, tea, artificially sweetened beverages, alcoholic beverages, and total daily intake of liquids—including water. "Cases were asked to refer to their usual dietary habits for the one-year prior to the onset of symptoms of their cancer, and controls were asked to refer to their usual dietary habits for the year prior to the time of the interview. . . .

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"Hypotheses that bladder cancer risk is associated with long-term ingestion of chlorinated surface water are supported by epidemiologic and experimental studies."

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"If all other variables were controlled for, tap water was associated with increased risk. . . . There was a clear dose-response relationship as consumption of [chlorinated] tap water increased: there was a 2.6-fold increase in individuals who were less than 65 years of age and a 3.0-fold risk in those 65 years of age and older. . . .

"Surface waters are usually more highly chlorinated than ground water and have much higher levels of organic contamination, which can include man-made chemicals from industrial, municipal, and sewer waste waters, or runoff. Chlorine reacts with organic compounds to form . . .a host of chlorinated nonvolatile compounds. Many of these compounds are carcinogenic in laboratory rodents or are mutagenic. . . . In fact, 18 possible, probable, or definite human carcinogens, listed by the International Agency for Research on Cancer, have been identified in varying concentrations in the finished drinking water taken from Lake Ontario. . . .

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"Surface waters are usually more highly chlorinated than ground water and have much higher levels of organic contamination, which can include man-made chemicals from industrial, municipal, and sewer waste waters, or runoff. Chlorine reacts with organic compounds to form . . .a host of chlorinated nonvolatile compounds. Many of these compounds are carcinogenic in laboratory rodents or are mutagenic. . . ."

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"Hypotheses that bladder cancer risk is associated with long-term ingestion of chlorinated surface water are supported by epidemiologic and experimental studies."

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*Vena, John E., et al, "Drinking Water, Fluid Intake, and Bladder Cancer in Western New York," Archives of Environmental Health, 48(3): 191-198, May/June 1993.