Toxaphene, the most widely used insecticide in the United States, has been shown to cause large increases of cancer in animals in tests at the National Cancer Institute. Although the cancer institute has not published its results, the test data have been evaluated by a panel of scientists at the Environmental Protection Agency who verified that toxaphene is a carcinogen.

Based upon EPA's scientific analysis, the EPA working group on toxaphene has recommended that the agency begin legal action to ban the insecticide, which is manufactured at an annual rate of more than 100 million pounds and is used in hundreds of farm applications on crops, including cotton, soy beans, wheat, corn, alfalfa, tomatoes, spinach, peaches, sunflowers, beans, lettuce, sorghum, potatoes, and other vegetables.

In making its recommendation, the toxaphene working group reported that EPA's scientific carcinogen assessment group had verified the cancer institute data and found increased malignancies in treated rats and, "in the instance of toxaphene-treated male and female mice, a highly significant dose-related increase in hepatic carinomas (liver cancers) was found. The working group therefore recommends issuance of a rebuttable presumption against toxaphene registrations."

The issuance of a rebuttable presumption means that EPA presumes on the basis of evidence that a chemical use should be suspended or canceled. The users and manufacturers would have to rebut EPA's findings. A Newsday study of the cancer institute data showed that more than 60 per cent of treated mice developed liver cancer. EPA's policy is that if a substance causes cancer in animals, it is considered hazardous to humans and should be banned.

The largest manufacturer of toxaphene, which has a significant share of the $2.5 billion pesticide market in the United States, is Hercules Chemical Co. of Wilmington, Del., the firm that first patented toxaphene in 1947. The firm's manager of ecological research, Chuck Dunn, said, "We think it [toxaphene] is safe as far as humans are concerned." Toxaphene is used almost exclusively in agriculture and almost never in home use products, but the EPA is worried because the heavily used chemical leaves residue on foods and has been shown to contaminate water supplies and accumulate in the flesh of fish, oysters, shrimp and other seafood.

Dunn said his company's scientists examined the cancer institute's data after its release to EPA. "They said as far as the rat is concerned it's not much of a problem, but in the mouse, it was pretty evident you had a tumorgenic [tumor-producing] response," Dunn said.

According to EPA attorney Tom McGarity, it took his agency nine months to obtain even the preliminary data on toxaphene from the cancer institute. "We asked for it the first part of last summer," McGarity said. "They're pretty slow over there, we finally got it a month or two ago." McGarity said that when he prodded the officials at the cancer institute during the waiting period, "they always said that we've just got such a big backlog that we can't get things going."