Improved method developed to test carci...( CORVALLIS Ore. Researchers at Orego...)

CORVALLIS, Ore. Researchers at Oregon State University recently completed the largest animal study ever done in the field of toxicology, and the findings challenge some basic concepts about how to determine what level of a cancer-causing compound can be considered safe.

The study found that acceptable levels of at least one carcinogen may be 500 to 1,500 times higher than is currently believed. It also indicates that for many purposes trout may be a superior animal model than laboratory rats, and that traditional methods of assessing the risk of carcinogens need to be re-evaluated.

The health impact of carcinogens is not always "linear," the OSU researchers reported in this study. This means experiments that are done using high concentrations of a carcinogen a common practice made necessary by cost and logistics may not accurately predict the actual risks of the compound when exposure in the real world is at lower levels over long time periods.

In practice, this suggests that some chemicals or toxins are safe at levels far higher than is currently believed, and that some previous research may have significantly erred on the side of conservatism. Such studies have been "severely limited by inadequate experimental data at environmentally relevant exposures," the researchers wrote in their report.

"The whole foundation of modern toxicology is that the dose makes the poison," said George Bailey, an OSU distinguished professor emeritus of molecular and environmental toxicology. "You can die from eating a few tablespoons of ordinary table salt at one time, but that doesn't mean that table salt is a poison at the doses that humans normally consume.

"With compounds that we know can cause cancer, the real question is how much is too much," Bailey said. "What we have found is that traditional approaches to making that evaluation, which are almost always based on studies done at very high doses with laboratory rodents, may
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