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Chronic Exposure to Dioxin Increases the Risk of Cancer

October 17, 1991

LONDON (AP) _ People who work near dioxin are 24 percent more likely to die of cancer than others, but the risk to the general population is not great, according to a study of German herbicide factory employees.

Dioxin, a byproduct of chemical manufacturing, is known to cause heart, brain and genetic damage in lab animals. But the risk it poses to humans is still debated.

Dr. Alfred Manz, the investigator at the Center for Chemical Workers’ Health at the Hamburg Department of Health in Germany, said the study showed the risk was particularly great among those exposed to the heaviest doses and for many years.

The study is reported in this week’s edition of the British medical journal, Lancet.

According to the study, the factory employees who worked in departments with the heaviest exposure to dioxin for 20 years were 87 percent more likely to die of cancer, Manz said.

Overall, the study showed the employees had a 24 percent increased risk of death from cancer.

Dr. Daniel Hoffman, assistant director for Science and Environmental Health at the Centers for Disease Control in Atlanta, said the German study adds credence to a U.S. study reported in the New England Journal of Medicine in January.

That study, of the U.S. National Institute for Occupational Safety, was conducted by Dr. Marilyn Fingerhut.

Hoffman said both studies show a ″definite dose response,″ between dioxin and the risk of cancer.

At low doses, he said, dioxin does not seem to cause cancer.

Dioxin seems to be a ″weak carcinogen″ among people who are chronically exposed, like those who work for many years in herbicide factories where dioxin is a byproduct, Hoffman said in a telephone interview.

But dioxin does not seem to pose a risk to the general public, even to people living near herbicide-treated soil, he said.

The entire town of Times Beach, Mo., was bought by the federal government and evacuated in the early 1980s because of dioxin contamination. But this year, the federal health official who made the evacuation decision said it appeared the government had overestimated the hazards of dioxin.

The German study compared death rates among 1,583 herbicide plant workers to national death rates in the former West Germany.

Among the 1,184 men and 399 women plant workers in the study, 93 men and 20 women died of cancer, said Manz. The employees had all worked in the Hamburg plant for at least three months between 1952 and 1984.

The plant, operated by Boehringer-Ingelheim, was forced to close in 1984 due to public concern about exposing workers to chemical contaminants.

Manz said workers exposed to low levels for less than 20 years did not have a significantly increased risk of cancer.

Manz said heavy doses of dioxin over many years seems to stimulate tumor growth in a generalized way. There was no specific increased risk of one type of cancer, like lung or stomach cancer.

Dioxin is measured in parts per trillion. The highest measurements, about 50,000 parts per trillion, were recorded in Italy after a plant explosion, Hoffman said. He said the amount of dioxin workers are normally exposed to is substantially lower, in the hundreds to 1,000 parts per trillion.