Chlorine in water linked to bladder, rectal cancers
Special to the Tribune

Chlorine used to purify drinking water supplies across the nation is lined to at least 4,200 cases of bladder cancer and 6,500 cases of rectal cancer a year, according to a new study that calls for safer purification methods.

The report provides the strongest evidence so far of a link between chlorination byproducts and cancer. But the authors do not call for eliminating chlorination, acknowledging that use of chlorine has dramatically reduced such potentially fatal waterborne diseases as typhoid and cholera in the United States.

This past week, however, an environmental group called for stricter regulation by the Environmental Protection Agency of chlorination byproducts, which can form when chlorine added to reservoirs interacts with such organic compounds as decayed leaves.

"We actually have dead bodies out there," said Erik Olson, a lawyer monitoring drinking-water issues for the Natural Resources Defense Council, a private non-profit organization that works to improve public health and the environment through litigation and research. "The agency must respond and must respond immediately."

Robert D. Morris, lead author of the study in the July issue of the American Journal of Public Health, agreed that the current EPA drinking water standard for trihomethanes, as the chlorination by products are called, should be looked at closely. He also urged research into better ways of killing bacteria and viruses in drinking water that would not create cancer-causing chemicals.
"The whole thing should be looked at in the context of public health trade-offs, between protecting against infectious diseases and avoiding, or al least minimizing, the risk of cancer," said Morris, an epidemiologist at the Medical College of Wisconsin. Other researchers came from the Harvard University School of Public Health.

"The whole thing should be looked in the context of public health trade-offs, between protecting against infectious diseases and avoiding, or at least minimizing, the risk of cancer."
Robert Morris, epidemiologist

Chlorination is used mainly to purify surface-water supplies, since those are most at risk of contamination by bacteria or viruses. As much as 75% of the nations drinking water is chlorinated, according to the new study. The new study found that people who drink chlorinated water are at a 21 percent higher risk of developing bladder cancer and at a 38 percent higher risk of developing rectal cancer.

Morris said other countries, such as Japan, use ozone to purify water rather than chlorine, although he acknowledged that one drawback to ozone is that it does not have the long-lasting disinfection power of chlorine.

The study's estimate of 4,200 cases of bladder cancer linked to chlorination represent about 9 percent of all such cancers diagnosed every year, and the 6,500 cases of rectal cancer represent about 18 percent of all such cancers diagnosed every year, Morris said. These figures are based on exposure to chlorinated drinking water beginning 20 to 30 years ago, because that is about how long it would take for cancer to develop, according to Morris.

SLIGHTLY LOWER NUMBERS

With the first EPA standard put into place in 1978, Morris said, the number of cancers based on the level of exposure over the next 20 to 30 years may be slightly lower but still in the thousands.

In 1969, Joseph M. Price, a medical doctor, authored a popular book called "Coronaries, Cholesterol, Chlorine" in which he linked chlorine in drinking water supplies to heart attacks. He wrote that the rate of heart attacks soared followed the introduction of chlorine into public water supplies, and that heart attacks were almost unknown in countries without chlorinated water. Chlorine, he wrote, is the chemical catalyst that initiates damage to the arteries and buildup of cholesterol deposits. This "clogging" can ultimately lead to a heart attack. Price, too, called for switching from chlorine to ozone as the anti-bacterial method for public drinking water.

His theory was discounted by mainstream medicine. Thomas C. Chalmers, a doctor and co-author of the new chlorine-cancer study, said it took more than a year and rejection by three journals before the team got its analysis published. Science, the Journal of the American Medical Association, and the American Journal of Public Health all rejected the paper, Chalmers said.

Generally, scientific journals only tell the authors why they turn down a paper. But Chalmers said the experts who reviewed the paper "were uneasy about informing people about this problem until some alternative was available: for fear that people would demand an end to chlorinating water. "But we felt people oughtt to have the data, not suppress it," Chalmers said. So when The American Journal of Public health appointed a new editor, the authors sent their paper in again, it was accepted.