Chlorination: residues cloud water safety.

Chlorination: Residues cloud water safety

Roughly 200 million U.S. residents drink water disinfected with chlorine. Decades of research have demonstrated chlorination's benefits in limiting outbreaks of typhoid fever and other acute diseases from microbial contaminants. However, four groups of federal researchers report that these benefits may come at the expense of a small added risk of chronic disease -- most likely heart disease or cancer.

Each team stresses that the disinfecting benefits of chlorination still appear to far outweigh any potential side effects. But validation of their preliminary findings could prompt calls for stricter limits on soil runoff and industrial releases of chlorinated pollutants into water, says Ellen K. silbergeld of the Environmental Defense Fund in Washington, D.C.

In 1985, a study of Wisconsin farmers by Elaine Zeighami and her co-workers at Oak Ridge (Tenn.) National Laboratory suggested that "hard" water, characterized by high levels of calcium and magnesium, reduces mortality from heart attacks and stroke. Reasoning that hard water's minerals might affect blood pressure or how the body uses lipids -- primarily cholesterol and the lipoproteins that shuttle it around the body -- Zeighami recently returned to survey blood factors in 1,520 residents of 46 Wisconsin towns.

The only correlation she found was between water chlorination and serum cholesterol, especially in women. After adjusting for age and other possible confounding factors, Zeighami found mean cholesterol levels about 4 percent higher (248 milligrams per deciliter) in women who drank municipally chlorinated water than in women drinking unchlorinated well water. As a rule of thumb, cardiovascular researchers estimate that each 1 percent increase in serum cholesterol elevates heart attack risk by roughly 2 percent.

In men from homes with chlorinated tapwater, Zeighami observed a statistically significant 1 percent cholesterol increase, to 236 mg/dl. In women and men, chlorinated drinking water was also linked to comparable increases in low-density lipoproteins -- the so-called "bad" lipoproteins that carry cholesterol into the bloodstream -- but without any changes in the "good" high-density lipoproteins that remove cholesterol from blood. Zeighami reported her findings in Cincinnati this week at a conference sponsored by the University of Missouri System.

At the same meeting, J. Peter Bercz and his colleagues at EPA's Health Effects Research Lab (HERL) in Cincinnati described similar small "abnormalities" in the lipid metabolism of mice drinking highly chlorinated water (15 parts per million) and eating diets with a fat content comparable to that in most Americans' diets. With dietary fat factored out, their lipids -- "subtly but noticeably shifted from the high-density to the low-density lipoproteins" -- offer the first "unimpeachable" evidence that chlorinated drinking water can change the way the vertebrate body handles cholesterol and lipids, Bercz told SCIENCE NEWS.

Two other HERL teams report data on mutagens that form in drinking water when chlorine interfacts with humic material -- soil products formed by plant decay. One of these is a chlorinated furanone known as MX. Trace quantities of MX have shown up in every chlorinated drinking water source where researchers have looked for it, and it appears to be the single largest contributor of mutagenic activity in those waters as measured by the Ames bacterial assay, according to EPA chemist H. Paul Ringhand. Scientists use mutagenicity -- the ability to cause genetic mutation -- as a rough gauge of potential carcinogenicity.

DCA, another mutagen found in chlorinated water, is known to cause liver cancers. F. Bernard Daniel and his coworkers report new data showing that DCA is a peroxisome proliferator. Such chemicals, often capable of exerting powerful effects on cholesterol metaolism, have been shown to trigger uncommon liver cancers (SN: 2/25/89, p.119). HERL researchers are now trying to determine whether the trace levels of DCA and MX in chlorinated water pose human hazards.