The Environmental Protection Agency (search) is drafting a policy to once again allow the consideration of experimental tests on humans in the setting of chemical exposure limits.

It’s the right thing to do — as long as the Bush administration is prepared to defend the policy from the savage attacks that should be expected from environmental activists.

Under the new policy being developed, manufacturers that want to test pesticides and other chemical products on human volunteers would submit proposals to the EPA for review. The agency would approve studies unless they are deemed unethical or significantly deficient in design. The data could then be considered by the agency in the setting of permissible levels of exposure to chemicals.

The Clinton administration placed a moratorium on such voluntary human testing in 1998. Environmental activists and other Bush administration-haters will no doubt try to liken the return of voluntary human testing to past instances of criminal human experimentation — such as Nazi concentration camp experiments, the Tuskegee syphilis study (search) (in which the U.S. Public Health Service purposefully left African-American men with untreated syphilis) and the U.S. government’s secret human radiation experiments (search) (in which people were unknowingly injected with plutonium).

I can even envision a twist to the 2001 television commercial produced by the Democratic National Committee in response to the Bush administration’s decision to review the Clinton administration’s eleventh hour rule concerning arsenic in drinking water. Instead of the little girl in the TV ad asking, “May I please have some more arsenic in my water, Mommy?” she might in 2005 ask, “Mommy, is it time for my pesticide pill?”

Don’t fall for this nonsense. The testing of chemicals on human volunteers (search) isn’t new, has rigorous safety standards, and helps establish more evidenced-based chemical exposure limits. What’s more, opposition to voluntary human testing (aside from the Bush-bashing aspect) is really just about restricting pesticide use — it’s got nothing to do with ethical concerns.

Until the Clinton administration moratorium on voluntary human testing, pesticide manufacturers could conduct experimental safety tests either on human volunteers or laboratory animals. Manufacturers often prefer testing on human volunteers because such tests produce results that are easier to convert into real-world permitted exposure levels.

In a typical experiment involving humans, volunteers are exposed to very low levels of a chemical, perhaps up to the point when the very first biochemical changes in the blood, or the very earliest clinical signs of the chemical (such as slight dizziness) are observed. The highest exposure level where either no significant biochemical or clinical changes are observed is then divided by 10 (an arbitrary factor used to provide a margin of safety for potentially more sensitive people in the population) to arrive at the permitted exposure level.

The procedure for setting a permitted exposure level based on laboratory animals is similar, except that the arbitrary factor used ranges from 100 to 1,000 or more, supposedly representing the increased uncertainty in extrapolating safety levels from lab animals to humans.

But testing of laboratory animals can get pretty weird. Years ago, researchers for a pesticide manufacturer debated with EPA staff about the level at which the insecticide aldicarb (search) caused the first significant clinical effects to be observed in laboratory dogs — the controversy centered around how soft was “too soft” for dog stool.

Human testing, in contrast, is much more straightforward — the effects observed during the experiment are those that the permitted exposure levels are designed to avoid. Laboratory animal testing typically results in much more stringent safety levels that make pesticide use more costly and difficult. Safety levels determined by laboratory animal testing may be set so low as to render a pesticide’s use impractical, causing a manufacturer simply to withdraw it from the market.

This was precisely the goal of the environmental extremists who pressured the Clinton administration to adopt its moratorium on human testing — a policy that forced in 2000 the withdrawal from the consumer market of the widely used insecticide Dursban. In February, the National Academy of Sciences endorsed voluntary human testing so long as the EPA ensured that such testing was necessary, scientifically valid, provided real benefits and was conducted according to ethical standards and procedures.

That sounds like a reasonable plan that will ensure that pesticides — which provide incalculable agricultural and public health benefits — can be evaluated on the basis of scientific data relevant to humans, rather than the divination of safety levels based on the texture of doggie-doo.

Steven Milloy is the publisher of JunkScience.com, an adjunct scholar at the Cato Institute and the author of "Junk Science Judo: Self-Defense Against Health Scares and Scams" (Cato Institute, 2001).

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