To Marion Moses, a physician who runs the Pesticide Education Center in San Francisco, there is no need for such equivocation. “It’s become a fight over process and whether one can extrapolate animal studies to humans,” she says. “It’s a charade, and it has been going on for 12 years.” Trying to nail down unassailable proof of endocrine disruption in humans is essentially a fool’s errand, in her view. Moses, who has treated farmworkers for acute poisoning, rashes, and asthma that seem to be related to the spraying season, feels that the wildlife data alone should be enough to outlaw certain pesticides. “I spent a lot of time trying to get these awful chemicals off the market,” she says while walking in a San Francisco garden-supply store. The snail bait, lawn weed-and-feed products, fungicides, and insect repellents she pulls off the shelf all contain chemicals slated for testing.
The 2003 white paper that drew such strong criticism from Spearow, who called it “disturbing” and “misleading,” was coauthored by Rochelle Tyl, another member of the EPA advisory panel. Tyl, who runs a lab in North Carolina’s Research Triangle Park where many of the screens and tests will eventually be done, acknowledges that Sprague Dawley isn’t the perfect choice. Still, she defends the report, calling Fischer 344, for instance, a “lousy” test animal because the males have reproductive problems. Asked about rats bred to be super reproducers, she waves her arm impatiently. “I know that’s the criticism, that Sprague Dawleys are good breeders. But if you don’t have an animal that gives decent litters, how do you run a study?”
Gary Timm, a senior environmental scientist with the EPA, has been working on the endocrine disruptor program since its very first days and likewise recognizes the complexity of the process. “I’ve been totally surprised at how long it’s taken,” he says. The agency felt a constant tug between “keep it simple” and “be comprehensive.”
“Compromises have been struck,” Timm continues. He, too, cites the problem of Sprague Dawley’s virility. “People say, ‘Look, these rats suffer a 50 percent decrease in sperm and they still reproduce.’ They say, ‘If you had a guy who had a 50 percent decrease in sperm, he’d be infertile!’” Asked how he responds to such criticism, he answers, “Those are just some of the things we have to allow for.”
Representative Henry Waxman and others on the House Committee on Oversight and Government Reform are not so sure. In 2007 the committee sent a letter to the administrator of the EPA voicing concern that public health was being put at risk by the selection of Sprague Dawley. The agency responded, “While the EPA recognizes there are reasons to believe that this strain might be less sensitive, the data currently available appear to show that it is no worse (or better) than other strains for screening for endocrine activity.”
In some ways the EPA is correct, Spearow says. No one rat strain is most sensitive to all endocrine-disrupting chemicals. “However, available data show that the Sprague Dawley rat strain is least sensitive to the most endocrine-disrupting chemicals relative to other strains that have been studied,” he says. “I’m not saying it is inappropriate for all testing, but to use it as the only test animal in this program means that we could really underestimate the effects of certain kinds of chemicals. Do we make sure they’re safe for King Kong? Or do we make sure they’re safe for you and me and Bambi?”
Congress, fed up with the EPA’s delay of more than a decade, wrote into the 2008 appropriations bill that the screening of possible endocrine-disrupting compounds was to begin last summer. Testing of the first chemicals, including the herbicides 2,4-D and atrazine and the insecticide malathion, was scheduled to follow, but the EPA pushed back its deadlines yet again, to early 2009.
Endocrine disruption, with its diffuse causes and effects that may not show up for a generation, is a hydra-headed 21st-century health challenge. Thousands of chemicals will be tested and many millions of dollars will be spent. Still, opponents of using Sprague Dawley say one nagging question remains: If the whiskered workhorse in the laboratory isn’t up to the task, who will be the real lab rats?