Research

Frank Gobas

Chemicals in humans: New concerns

July 12, 2007

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By Barry Shell

Thousands of common chemicals from insecticides to perfumes are not being recognized for their potential to accumulate to high levels in humans and other air-breathing animals, according to SFU-led research. The findings will appear in the journal Science on July 13.

A team of Canadian chemists and toxicologists led by Frank Gobas (above), a professor in SFU’s School of Resource and Environmental Management, reports that the degree of exposure may be greatly under-estimated in some classes of chemicals.

"We need to reevaluate our methods for how we’re screening for persistent toxic chemicals," says lead author Barry Kelly, Gobas’ former PhD student. Researchers estimate about a third of all industrial chemicals are "currently wrongly assessed in terms of their potential effects in mammals, birds and humans."

Methods used by Canadian and U.S. Environmental Protection Agencies as well as the United Nations are currently based on water-breathing animals such as fish rather than mammals, birds or humans.

Gobas says the fish is not a good model to assess the environmental behaviour of chemicals in most air-breathing organisms.

"Toxic chemicals dissolve to different degrees in air, water and fat. Since fish breathe water, chemicals with a low tendency to dissolve in water accumulate because they cannot be eliminated easily in the water that fish pump across their gills," he says.

"However, in air-breathing animals such as humans it is the low tendency of chemicals to evaporate to the air that determines whether the chemical has the potential to accumulate."

There is a difference between water-respiring and air-respiring animals and the way they bioaccumulate, adds Kelly, referring to the tendency of fat-soluble chemicals to build up in biological organisms.

For instance, the widely used pesticide lindane accumulates in rats (as well as humans). Yet lindane is easily eliminated by fish because it does dissolve in water. The same is true for some perfumes such as musk-xylene, as well as the degradation products of common fluorinated chemicals such as Teflon and ScotchGuard.

The Canadian researchers are hopeful that environmental protection authorities will change their assessment procedures to reflect the way humans and other mammals accumulate environmental toxins.

Their paper can be found at www.eurekalert.org

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