A scientific advisory subcommittee convened by the US Environmental Protection Agency (EPA), Washington DC, to study the bioethics of testing pesticides on humans, has failed to reach a consensus, delaying EPA rulings on the issue. Even if the subcommittee eventually favors accepting data from human tests, it is likely to exclude industry-sponsored research projects like those that have recently come under fire in the UK.

Under the Food Quality Protection Act passed by Congress in 1996, the EPA was required to begin re-certification of all pesticides in use in the US, including a re-evaluation of human exposure limits, by August 3rd this year. When exposure limits are based on animal models, the agency requires an additional tenfold margin of safety to allow for species differences. Pesticide manufacturers have lobbied the EPA to accept data from human trials, which demonstrate that higher exposure levels can be tolerated. The subcommittee of bioethicists, toxicologists, and public health experts was formed in 1998 to address the ethics of testing non-therapeutic chemicals on volunteers, and was expected to issue a consensus report before the August deadline either favoring or opposing data from human testing.

Nurse sprays hospital bed with 5% kerosene

Committee members contacted by Nature Medicine revealed that the 14-member group was split 10–4, with the majority in favor of accepting human test data. "I've been with the board 11 years. We've never had a group that could not come to some kind of a consensus, or we had a majority and the report provided a statement of the minority position as well," says Sam Rondberg, the federal official responsible for overseeing the committee, but the latter option was rejected by the subcommittee.

Bernard Weiss, a professor of environmental medicine at the University of Rochester, downplays the disagreement: "I don't think it's a really sharp division, I think it's more in the matter of tone." While the minority would refuse data from any human pesticide testing, the majority would permit such tests only when they would clearly advance scientific knowledge. "Simply undertaking human studies to revise or restore an older regulatory standard is not kosher," says Weiss.

Although the committee plans to meet again in late October to try to reach an agreement, human tests may never form a basis for US pesticide regulations because of recent high-profile cases overseas. Some chemical companies have drawn criticism for tests done in Britain, where human testing of pesticides is not illegal.

In one case, Bayer AG hired Inveresk, a company based in Edinburgh, UK, to carry out human exposure tests on azinphos methyl. Volunteers were offered £460 (US$770) and asked to swallow small doses of the compound, an organophosphate pesticide so toxic that the EPA recently established strict limits for its use on food crops. Bayer contends that its trials were carried out in accordance with international ethical and safety guidelines.