Several new scientific studies link death rates for cancer - mainly of the bladder - with the extend to which water is chlorinated to make it safe to drink.
One study showed that women in seven New York state counties served by chlorinated water ran a 44 per cent greater risk of dying from cancer of gastrointestinal or urinary tract organs than comparable women whose water was not chlorinated.
Another study of cancer mortality and chlorinated water sources in 200 counties across the country found increased rates of fatal cancer of the bladder and large intestine in older persons, particularly those over 60, but very low rates in persons under 40.The latent period for bladder cancer is 30 years or more, so it is unlikely to be detected in young persons.
The principal suspected cause of the death is chloroform which is produced in reactions between chlorine and organic chemicals. Such chemicals occur naturally in water systems, run off the land into them, or enter a sewage or effluents. Chloroform is a known cancer-causing agent, or carcinogen in laboratory animals.
In 1974, the Environmental Protection Agency and a Dutch scientist each reported the presence of chloroform and other known or suspected chlorine-related carcinogens in treated drinking water.
Later in 1974, the EPA reported that drinking water taken from the Mississippi River at New Orleans contained these carcinogens.
In the same year, the Environmental Defense Fund, a non-profit group, disclosed that a year-long study showed that in New Orleans and other communities in southern Louisiana that derive drinking water from the Mississppi, fatal cancer in organs of the gastrointestinal and urinary tracts was 10 to 20 per cent more common than in parts of Louisiana where water comes from other surface sources and wells.
Cancer deaths attributed to the use of Mississippi River drinking water accounted for 15 to 20 per cent of the total in southern Louisiana, the EDF estimated.
After launching a nationwide survey, the EPA reported in 1975 that it had discovered chloroform and other carcinogens in small but measurable amounts iin the drinking water systems of 80 communities. Among them were the District of Columbia, Fairfax County, Baltimore, Philadelphia, Miami, Cincinnati and Seattle.
And last September, Dr. Nancy A. Reiches of Ohio State University reported on a study of cancer mortality in the 3.5 million to 4 million Ohioans whose drinking water comes from heavily polluted sources: the Ohio River, which forms that state's southern boundary, and Lake Erie, which bounds much of the state on the north.
She said their cancer mortality is 8 per cent higher than that of about 1 million other Ohioans - residents of Columbus and three rural counties whose water comes from the Scioto River. The EDF and Resources for the Future & NG., cooperated in her study.
Until now, scientists did not have the evidence to incriminate any paritcular chemical. But chloroform was incriminated Friday in the New York State and other studies discussed at a meeting here of the EPA's National Drinking Water Advisory Council.
In addition, Reiches, director of the Division of Epidemiology at Ohio State's Comprehensive Cancer Center, who did the nationwide 200-county study, said in a phone interview that still-unpublished results further incriminated chloroform.
The EPA commissioned Dr. Michael Alavanja and two associates at the Columbia University School of Public Health to investigate cancer mortality in seven New York state counties. The countries - Allegamy, Cattaraugus, *Chautauqua, Erie, Rennsseleaer, Schnectady and Saint Lawrence had, for 15 years, relatively stable populations and water-supply systems.
The scientists examined each female death from cancer of gastrointestinal or urinary tract organs in the years 1968-1970. They confined the study of women because 85 per cent of them in the seven counties are housewives and, as such, much more likely than men to consume water mostly at home, and much less likely than men to be exposed to workplace carcinogens.
The number of such female deaths - in a total populations of 1.81 million - was 1.595. The relative death risk was 1.44 times higher than in comparable women in the same counties whose water supply was not chlorinated.
In urban areas only, the relative risk was 2.24 times higher where surface water was chlorinated than where it was not. This amounts to an excess over normal of 400 cancer deaths per 1 million population per year.
"To our knowledge, this is the first time a significant statistical relationship had been demonstrated between human gastrointestinal and urinary tract cancer mortality and chlorinated drinking water," the scientists wrote in a report to the EPA. They did not break down rates by paritcular body sites.
Dr. Reiches' study of the 200 counties encompassed major cities, including the District of Columbia, New York, Boston, Chicago, Milwaukee, Minneapolis and Cleveland. It excluded blacks because there are too few of them in some of the counties to permit reliable statistical analyses.
She said that among person relying on chlorinated water, fatal bladder cancer occured more often in women than in men. She said this is significant partly because men are more often exposed to bladder cancer in the workplace.
Fatal cancer at other body sites particularly the large intestine (colon) and rectum, however, occured more often among men than among women.
Overall, Reiches found that for each 1 million women of all ages, the rate of fatal bladder cancer was 27.5 when parts per billion - 38 per cent more the exposure to chloroform was 100.
She cautioned against concluding that chloroform alone was necessarily responsible, pointing out that humans are exposed to numerous environmental carcinogens, including sacharin, and that in some persons the chemicals interact in ways that make them more dangerous.
Reiches said that a third study, done for the EPA, Dr. Kenneth P. Cantor of the National Cancer Institute generally supports her research.
Cantor analyzed data in the 1975 EPA study on 79 urban counties where at half of the population relied on a single source of chlorinated drinking water. Like Reiches, he found elevated rates of fatal bladder cancer, especially in women. He also found some statistical association with brain malignancies, Reiches said.
Dr. Joyce Salg, while in the University of North Carolina Department of Epidemiolgy, examined cancer data for 346 Ohio River Valley counties with a population of 18.7 million in seven states. She found a correlation between prechlorination - the addition of chlorine to water before it goes through treatment plants - and increased rates of bladder, colon, rectal and other forms of cancer.
Michael Hogan of the National Institute of Environmental Health Sciences studied levels of chloroform in drinking water and their possible association with bladder and other cancer mortality in 83 water systems in EPA's Region V. embracing Illinois, Indiana, Michigan, Minnesota, Ohio Wisconsin.
He reported "some correlation" between chloroform levels and rectalcon and bladder cancer deaths, but was cautions about extrapolations of the data to overall cancer-mortality patterns. His data suggest that at 100 ppd., chloroform could cause 20 extra rectal-colon cancer deaths per million population annually.
The EPA, which is expected propose water-chloroform standards within a few weeks, considers 100 ppd. the maximum that should be allowed. In a test last summer of the Occoquan Reservoir, which supplies most of Northern Virginia, the EPA found a concentration of 232.6 ppd.