Environmental Watchdogs Battle DDT, Other Controversial Pesticides

A research group here is doggedly tracking a worldwide environmental threat all but forgotten in the headlines of the Chernobyl nuclear accident and other more visible concerns.

The problem is pesticides--DDT, toxaphene and similar pesticides long banned in the United States but still showing up in air and water samples around the globe because of continued use in Third World and Eastern Bloc countries.

Another concern is chemicals still legal in the United States, with uncertain future effects.

“Residues of DDT and other pesticides are found in fish, birds and mammals from every ocean in the world, in Alpine lakes and in the snowfields of the Arctic and Antarctica,” said Terry Bidleman, a professor of marine science and chemistry at the University of South Carolina. He is leader of the school’s pesticide research group, one of only four groups in the world studying aerial transport and distribution of pesticides.

Global Contamination

The scientists have found DDT, toxaphene and similar chemicals long banned in the United States in rain and air samples almost everywhere. After monitoring pesticide movement since 1973, they conclude that continued use--and misuse--of pesticides in some countries, including the United States, has spread contamination through rainfall and ocean currents around the globe.

“What the long-term effect of these continuing low levels of pesticides will be on humankind, we just don’t know,” Bidleman said.

DDT was banned in the United States in 1972 after scientists linked it to thinning of eggshells in predatory birds and a resultant decline their in populations, among other things.

Despite the U.S. ban and the controversy surrounding Rachel Carson’s condemnatory book, “Silent Spring,” more than 6,000 tons of DDT are still applied annually in Mexico, Central America and India, Bidleman said.

DDT Still Made

According to the Chemical Manufacturers Assn., DDT is no longer manufactured anywhere in the Western Hemisphere but is still made in Italy, France, India and Indonesia.

Other U.S. scientists agree with the concerns of the South Carolina group and fear that the residue from the chemical’s manufacture and use in those and other areas may be creating a worldwide health hazard.

Although DDT is “notably nontoxic in human terms,” said Michael Corbett, a recognized expert at the University of Florida on the effect of pesticides, many researchers believe the chemical may be a “promoter” of cancerous tumors.

No Long-term Study

“DDT is present in the fat tissue in everybody,” said Corbett. “They used to spray it on humans, on immigrants for delousing. But to my knowledge no one has ever done a study of its long-term effects.”

Despite that lack of knowledge of DDT’s effects over time, many foreign governments use the chemical wantonly. Researchers cite uncontrolled handling and spraying of the chemical throughout the Third World without regard for its effect on either local or global populations.

Ineffective Against Malaria

Political leaders defend DDT use as a necessary weapon against mosquito-borne malaria. But Bidleman notes that widespread agricultural use of the pesticide has led to a resurgence of malaria as mosquitoes develop natural resistance to DDT.

“I think it is morally reprehensible,” Bidleman said of the widespread misuse. “I couldn’t say it’s criminal, because that implies legal responsibility, and there is none.”

Bidleman said areas of the Arabian Sea, bordered by heavy DDT-using countries, show levels more than 40 times higher than in the North Atlantic. Air samples from Sweden taken by the Norwegian Institute for Air Research show high levels of dangerous pesticides that apparently originate in Eastern Europe.

Contaminated Marshland

In the United States, Bidleman and his fellow researchers, monitoring the North Inlet Estuary near Georgetown, S.C., have discovered traces in rainfall of several chemicals believed to originate as far away as China. The estuary is the only salt marsh in the United States untouched by human development and certified as an experimental ecological preserve by the National Science Foundation.

In addition, “University of Minnesota scientists have found ‘fresh’ DDT and another pesticide, toxaphene, in peat bogs of southern Canada,” Bidleman said.

Toxaphene, a close relative of DDT and the most widely used pesticide in the United States until it was banned by the Environmental Protection Agency in 1982, is highly toxic to fish and causes cancer in laboratory animals.

“In the three years prior to the ban of toxaphene, 30,000 tons were applied in the United States,” said Bidleman, “A loophole in the law allows existing stocks of toxaphene to be used until the end of 1986--four years after the ban.”

Race to Use Up Chemical

Several U.S. companies are still manufacturing the chemical, the manufacturers’ association reports. Bidleman predicts a surge in toxaphene use this summer as farmers race to deplete their supplies.

“One of the reasons the EPA banned toxaphene is they were concerned about the cancer risk to people in the Great Lakes and Mississippi Delta regions who are large consumers of fish,” Bidleman said. “Another reason is that in very small amounts it is highly toxic to fish.”

He said Scandinavians are particularly distressed by apparent Eastern Bloc use of toxaphene after finding traces of toxaphene in human mother’s milk.

Toxin Limit High

U.S. toxaphene levels detected in most cases do not exceed federal limits, but Bidleman notes that the level allowed is quite high when compared to other toxic levels.

“They allow a limit of 5 parts per million, and 50 parts per million have been found to cause a significant increase in liver cancer in lab animals,” Bidleman said. “To me that doesn’t seem like a very large safety factor.”

The prohibited pesticides provide enough cause for concern, Florida’s Corbett said, but “the bottom line is there are many potentially dangerous pesticides in use that are not banned.”

Temporary Ban on Use

The New York Department of Environmental Conservation last month imposed a temporary ban on the use of diazinon for some applications, citing an unreasonable hazard to birds. But spokesmen for Ciba-Geigy Corp., developer of diazinon, call the ban unreasonable and say that “the 2,000 birds in whose deaths diazinon has been implicated over the past 30 years” represent a very minor risk when compared to the benefit of controlling pests.

And virtually every home in the Southern United States has been treated for termites with a pesticide called chlordane, Corbett said. Chlordane, another “hard pesticide” closely related to DDT and toxaphene and in use since 1947, is also thought to promote cancer. Since 1978, chlordane’s use has been limited to termite treatment. But it previously was used extensively in agriculture, household and general lawn and garden use.

Bidleman said that in controlled tests in Florida, heptachlor, a chlordane relative, showed up in the mother’s milk of a test subject within two days of its application to a test house.

Present in Blood Levels

“The problem with the 5,000 tons of chlordane applied in the South each year,” said Bidleman, “is that it doesn’t stay in the foundations. It is becoming a serious polluter of indoor air. Also, there has been noted an increase of it in the blood levels of pest control workers.”

David Schneider, former editor of Pest Control magazine and a biologist with the Chicago-based Velsicol Chemical Co., the nation’s largest manufacturer of chlordane, said that although the pesticide does show up in indoor air samples, allegations that it is a health hazard are questionable.

“Nobody doubts you can find chlordane in crawlspace air after application,” said Schneider. “It’s there.” But he added that the National Academy of Sciences concluded that “there is no adequate data to show these compounds are carcinogenic to humans,” a statement Velsicol includes on its chlordane labeling.

Pesticide Not Harmful

Schneider cited independent studies of the long-term effect of chlordane exposure on chemical manufacturing plant workers as further evidence that the pesticide is not harmful to humans. He said scientists following the health histories of present and former Velsicol workers “have discovered no pattern to their deaths, no occupational diseases clustered in some way to show that chlordane causes anything.” He added that similar studies of pest control workers have shown no patterns of chemical-related illnesses beyond the statistical norm.

“We’ve been looking for cancer (caused by chlordane) for 35 years,” Schneider said, “and we haven’t found it yet.”

But he noted that Velsicol, along with other producers in the $2-billion-a-year pest-control industry, have taken steps to encourage careful use of the products, including pictographic instructions for their use. He said the industry “probably does not favor international controls,” considered by Bidleman as the only solution to continued worldwide contamination.

“It is really quite serious,” Bidleman said. “The pesticide companies hawk their goods like snake oil, rather than as a medicine to be used carefully.

“What we need is a comprehensive set of international controls and agreements to limit the use of persistent pesticides,” the kind that do not degrade into harmless components soon after use. That may mean using less toxic--but more expensive--pesticides, or organic farming techniques in which insects become part of the producing ecosystem.

He concluded: “We must promote the use of pesticides as a medicine for a sick ecosystem, not as a panacea.”