- The Washington Times - Monday, June 12, 2000

The Environmental Protection Agency is restricting over-the-counter sales of the insecticide Dursban, also known as chlorpyrifos. Oddly enough, junk ethics rather than junk science drives the agency's action. The EPA refuses to use scientific data that would obviate the need for action against Dursban because the data allegedly are "unethical."

Dursban is one of the most common home-and-garden insecticides, having been used in millions of homes every year since the late 1960s. But popularity is also Dursban's Achilles heel. The big product is a big target for the anti-pesticide mob, including some at the EPA. They targeted Dursban for eradication years ago. But Dursban survived because it's safe when used according to its label.

Now Dursban is being attacked through the Food Quality Protection Act of 1996, which requires the EPA to conduct a systematic review of pesticide safety. One of the law's supposed aims is to ensure children are sufficiently protected from overexposure to pesticides. For Dursban's opponents, though, implementation of the law is another opportunity to take a whack at the product and its manufacturer, Dow Agro Sciences.

There is a twist, however, in the current attack. Dursban is not being done in by science or by the "better safe than sorry" pabulum of the precautionary principle. Not even anti-pesticide hysteria is being employed by the EPA. Instead, the agency is using so-called ethics to restrict Dursban use.

Existing Dursban regulations are based on data obtained from testing the insecticide on paid human volunteers given nontoxic doses. The tests show how much of the chemical can be ingested without any noticeable effect on people. As opposed to testing chemicals on animals, there is less scientific uncertainty from such human testing because there is no need to extrapolate results between species.

When animal tests are used to determine safe levels of human exposure, a good deal of extrapolation is involved. Scientists record the highest tested dose having no adverse effect. Then, they divide the "no effect dose" by a "safety factor," usually 100, to provide a wide margin of safety for humans. The large safety factor is intended to account for uncertainties in extrapolating animal data to human exposure. But the safety factor is a judgment call; it is not a scientifically determined need or number.

There is much less uncertainty if human testing is involved, so acceptable exposure levels are usually set 10 times lower than the "no effect" dose. Because human testing involves a lower safety factor, it often leads to higher permitted exposure levels. But pesticide opponents want lower permitted exposure levels preferably so low that pesticide use is not practical.

So human testing is under attack, and the rationale is ethics. Lynn Goldman, former assistant administrator in EPA's Office of Prevention, Pesticides and Toxic Substances, wondered if it's ethically justified to perform a human test "merely so you can sell a product." The head of the Environmental Working Group said, "We've got to make a stink out of this." The EPA stopped using human data in 1998 pending an as-yet unfinished review of the ethics. And it's not enough that no new human testing will be allowed. Even human data from past tests is being called unethical and considered unfit for regulatory use.

For Dursban, this means available human data does not exist for regulatory purposes, allowing the EPA to base permissible exposure levels on the basis of animal testing.

Scientists oppose this rejection of data. Jay Goodman, a professor of pharmacology and toxicology at Michigan State University, wrote to EPA, "I view the testing in question as being similar to the clinical trials of potential new drugs and I do not see that it presents an ethical problem. A very large body of animal data provides a strong base to embark on human testing."

Steven Cohen, professor of toxicology at the University of Connecticut School of Pharmacy, wrote: "Reverting to animal-based end points for chlorpyrifos risk assessment is clearly a step backwards [from sound science] in that injects greater uncertainty into the process."

With the human data out of the way, the EPA points to a recent study reporting brain damage in the offspring of female rats fed such very high doses of Dursban that the mother rats were sickened. Normally fetal effects secondary to maternal toxicity are considered an experiment artifact. But the EPA is treating these effects as though they were real and predictive of human effects.

Pretending the artifact is a true adverse effect permits the EPA to employ yet another the safety factor of 10 in determining Dursban's permitted exposure level. So the allowable exposure level determined by the EPA is 1,000 times lower than the tested dose causing no adverse effect in humans.

To keep potential exposures that low, Dow must give up some uses of the popular and effective Dursban. Consumers will have to find another way to control insects around their home.

The EPA's action against Dursban is primarily an exercise in convenient ethics coupled with the arbitrariness of safety factors to fulfill the intellectually and morally bankrupt anti-pesticide agenda. Anyone for ethic cleansing at the EPA?

Steven J. Milloy is a lawyer, biostatistician, publisher of Junkscience.com and adjunct scholar at the Cato Institute.

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