(NewsTarget) Approximately 10,000 chemicals currently on the market need to be retested for possible toxicity, according to a study published in the journal Science.

The study authors warn that approximately one-third of carbon-based chemicals currently in commercial use may need to be retested, based on limitations of the tests previously used to determine toxicity.

The danger rests on a class of chemicals referred to as "bio-accumulative," or "persistent organic pollutants," which concentrate in the bodies of animals. The concentrations of these pollutants tend to increase higher up in the food chain, as animals absorb the toxins stored in the body of their prey. Because of the health and ecological danger posed by persistent organic pollutants, 12 varieties have been globally banned under the Stockholm Convention, including DDT, dioxins and PCBs.

In the current study, researchers warn that many chemicals currently classified as safe may actually be persistent organic pollutants.

The accumulation test most often used, KOW, measures how soluble a chemical is in fat as compared with water. Chemicals with a high fat-to-water ratio are presumed to be bio-accumulative. Another test, KOA, measures how efficiently a chemical can cross lung membranes. The researchers hypothesized that KOA will be a better measure of accumulation in air-breathing animals and that KOW will be a better measure for gill-breathers.

The scientists also tested the accumulation of two different chemicals -- PCB-153 and beta-HCH -- in three different food chains: plankton to fish; lichen to caribou to wolves; and plankton to fish to marine mammals. They found that PCB-153, with a high KOW, accumulated in all three food chains. Beta-HCH, which has a low KOW and high KOA, accumulated only along the two air-breathing food chains and not among fish.

Due to their results, the researchers warned that many chemicals should be re-tested.

"They won't all be bio-accumulative, but they all have the potential," said Frank Gobas of Simon Fraser University in British Columbia. 10/29/2007 11:00 AM