To Your Health

Most people have no trouble drinking water with either chlorine or chloramine at the levels used in municipal water supplies

Q. This is a follow-up question concerning a recent column about the hazards of chlorine in shower water [July 16]. Our city water supply has converted from chlorine to chloramine as a disinfectant. Are the risks different with chloramine? Does a filter that works for chlorine work for chloramine?

A. Chloramines (there are several) have been used as disinfectants since the 1930s. As a water treatment, chloramines are weaker but longer-lasting than chlorine, and so are often used in combination with chlorine to maintain residual disinfectant strength throughout the distribution system so that drinking water is kept safe all the way to the point of use.

Public drinking-water providers are required by the Environmental Protection Agency to protect water supplies at the source and to use disinfectants to prevent growth of dangerous bacteria in the water pipes. The EPA offers drinking-water providers only two chemical disinfectant choices: chlorine and chloramine. Other nonchemical options such as ultraviolet light and charcoal filtration are prohibitively expensive for large-scale water treatment, so usually the chemical treatments will be used. The KDF filter that effectively removes chlorine does not remove chloramine, although charcoal, zeolite, or ascorbate filters appear to reduce it.

Most people have no trouble, other than an offensive taste or smell, drinking water with either chlorine or chloramine at the levels used in municipal water supplies. A search of the medical literature did not reveal any studies showing problems with chloramine except for a possible allergic reaction. The principal advantage of chloramine is the reduction in the formation of chlorinated hydrocarbons, which is a major concern when showering with hot chlorinated water. In that respect chloramine appears to be less damaging than chlorine.

There are still a couple of worries about chloramine. N-Nitrosodimethylamine, a carcinogen, is formed by both chlorine and chloramine water treatment. NDMA is a concern when even trace amounts are present in drinking water. However, the NDMA concentration in drinking water is negligible compared to other NDMA sources, such as tobacco smoke, cured meats, beer, fish, cheese, shampoos, cleansers, and household pesticides. Public drinking-water providers monitor for NDMA and other byproducts and do not allow high levels to develop.

Chloramine can cause serious problems for kidney dialysis patients, and with the advent of home dialysis machines, patients could be adversely affected. Dialysis equipment can be adjusted to remove chloramine and chlorine. The treated water must be monitored to be certain that the final chloramine concentration is minimal.

Chloramine is a much more serious hazard to fish. People who are accustomed to getting rid of chlorine in tap water by simply letting it sit in an open vessel for a day or two before using it in their aquarium will find that they cannot do this if their tap water is treated with chloramine. Furthermore, some of the water treatments used to get rid of chlorine leave behind a residue of ammonia when used on chloramine-treated water. Ammonia produced by chlorine removal will kill fish in a matter of hours.

The ideal water treatment has yet to be found, but the combination of chlorine and chloramine appears to be as safe as any of the alternatives.

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