Rat Studies’ Value Doubted

Evaluating a chemical’s cancer-causing potential by doing long-term tests in rats and mice gives uncertain results and usually is not worth the cost, new analysis suggests.

Such tests are “rarely the best approach for deciding whether to classify a chemical as a human carcinogen,” the researchers wrote last week in the British journal Nature.

Their cost-benefit analysis suggested that most chemicals should be classified on the basis of short-term lab tests instead.

The researchers said 30% of chemicals tested for cancer-causing potential in one program behaved differently in rats compared to mice. Rodent tests are probably no more predictive for humans and could be much less so, because people are more biologically different from rodents than rats are from mice, researchers said.

The researchers are from Carnegie-Mellon University in Pittsburgh, Case Western Reserve University in Cleveland and the University of Washington in Seattle.