WASHINGTON -- Environmentalists called for phasing out industrial uses of chlorine yesterday in the wake of a new government finding that minute amounts of dioxin found in food, air and water may cause cancer, infertility and other health problems.
But Environmental Protection Agency officials said that there was no need for drastic action as a result of their scientific reassessment of the hazards of dioxin, and spokesmen for some of the industries identified in the study as sources of the toxic chemical took issue with the study.
The EPA released the preliminary results of its 3 1/2 -year review of scientific research on the health risks posed by dioxin, reaffirming an earlier finding that it was a probable human carcinogen while raising new concerns that tiny doses of the chemical may harm human reproduction and immune systems.
Dioxin is the name for a group of chemical compounds that are unintentionally produced as a result of burning medical waste and trash, some chemical manufacturing, and chlorine bleaching of paper. Many industrial processes using chlorine-and-carbon chemical compounds generate trace amounts of dioxins as byproducts.
The EPA estimates that only about 30 pounds of dioxin are generated annually from all sources nationwide, and officials said emissions appear to have declined in recent years. But the substance is considered highly toxic and has been the focus of stringent government regulation.
The EPA launched its reassessment in 1991 in response to questions raised by regulated industries and some scientists about how harmful it is. After spending $4 million so far on research and evaluation, agency officials said they still consider dioxin the most toxic man-made pollutant, though less harmful than cigarette smoking.
Likening the 2,000-page EPA report to the 1964 surgeon general's report that tied smoking to lung cancer, Sierra Club President J. Robert Cox said the EPA has finally settled the dioxin controversy.
"We no longer need to discuss if dioxin is deadly. We need to act," Mr. Cox said. Sierra and other environmental groups called on the EPA and industry to phase out industrial uses of chlorine because of their tendency to produce dioxins and other toxic contaminants, and they likewise called for an end to incineration of medical waste and trash.
But EPA officials stressed that there is much still unknown about the health risks of dioxin and similar compounds, especially at the low levels at which they are found in food and the environment.
"We don't think they [dioxin levels] are so high that people need to fear or panic over them," said Dr. Lynn Goldman, an assistant EPA administrator who oversaw the review. "But we do think they're high enough to warrant public health concern."
The EPA already has stringent limits on dioxin in water, and the agency is proposing new pollution controls for municipal waste incinerators and for pulp and paper mills. Similar regulations for medical waste burners will come by early next year.
Further requirements to reduce dioxin exposure may be considered, EPA officials said, after the study is finished next year. Incineration of medical waste and municipal garbage produces about 95 percent of all known dioxin emissions, according to the report, but the EPA acknowledged that it could not pinpoint the sources for as much as half the contaminants found in the environment.
Airborne dioxins emitted by incinerators and other sources settle on plants. They enter the food chain through grazing animals, and they concentrate in fatty tissues.
EPA officials stressed, however, that there is no direct scientific evidence that humans with everyday levels of exposure are experiencing any of the noncancerous health effects found in laboratory animals. Dr. Goldman said, "The benefits from a balanced diet far outweigh any theoretical risks from dioxin exposure."
Spokesmen for chemical manufacturers and the pulp and paper industry noted that companies have reduced dioxin releases significantly in recent years, and they pledged to do more. But they rejected environmentalists' calls for phasing out chlorine use and continued to question the scientific evidence that dioxin is harmful to humans at everyday low levels.