WATER HAZARD?

By LEON JAROFF

Just when you thought it was O.K. to go back in the water, new studies raise questions about the safety of the chlorine used to purify everything from swimming pools to municipal drinking-water supplies.

In the latest study a team of Finnish scientists reported in the Journal of the National Cancer Institute last week that MX, a compound produced when chlorine reacts with organic material in water, causes cancer in laboratory rats when swallowed in large quantities. "Although these findings cannot be extrapolated to humans," they concluded, "MX should be studied as a candidate risk factor."

As a disinfectant, chlorine is one of the public-health success stories of the 20th century. After it was first used to purify water supplies in the early 1900s, typhoid fever, cholera and dysentery virtually disappeared from the U.S. But the chemical has been under attack in recent years by environmentalists for contributing to the destruction of the earth's ozone layer. Greenpeace's "Chlorine Kills!" campaign is focused primarily on paper bleaching and other industrial uses, but the organization also urged pool operators to look for an alternative to chlorine.

An editorial in the NCI journal last week tried to put the drinking-water problem in perspective. It pointed out that at the highest levels of MX found in U.S. water supplies, the additional lifetime cancer risk was only 2 in 1 million. But it encouraged further investigation of the effects of MX and other chlorination by-products, and last week the National Institutes of Health announced that it was launching a two-year study. The NCI editorial also warned about the perils of abandoning drinking-water chlorination too hastily. It noted that when Peru did that in 1991, some 300,000 Peruvians were stricken in a cholera epidemic.

--By Leon Jaroff