The removal of a chemical from Scotchgard stain repellent and other products has led to a major drop in levels of the chemical found in ring seals in the Arctic, according to a new study.

Scientists say they've seen as much as a two-thirds decrease in the presence of perfluorooctane sulphonate, or PFOS, in liver samples taken from ring seals in Resolute Bay, and a drop to one-fifth of maximum levels in seals from Arviat since 2000.

That's when the 3M corporation, the largest commercial user of the chemical, stopped using it chiefly in Scotchgard, a stain and water repellent product.

"It takes a long time sometimes, but in the case of PFOS, the unusual feature is a very fast change in the amounts that we're seeing in the animals," said Derek Muir, a research scientist with Environment Canada.

PFOS had been found to be a persistent organic pollutant, and was detected in low levels in humans and wildlife across the U.S., before 3M voluntarily stopped its use in 2000. It also traveled through the atmosphere, ending up all over the world — including the Arctic.

PFOS is linked to bladder cancer and liver problems.

One researcher says samples taken from 35 years of seal harvests show a peak in PFOS levels in 2000. Since then, levels have dropped significantly, and quickly.

"So to us what it represents is that once the production levels have been shut off or pulled, then the Arctic animals are actually clearing these contaminants quite quickly from their systems," said Craig Butt, a PhD student at the University of Toronto.

Researchers are studying contaminants in 11 seal populations from Nain, Labrador, to Sachs Harbour, Northwest Territories. They've been working with local hunters and trappers associations to analyze tissue samples and seal livers.

Scientists now want to find out if there's a similar drop in the high PFOS contamination rates in polar bears, since ring seals are their main meal.

Muir says other persistent organic pollutants such as PCBs are also showing a decline in animals in the North, "but nothing as remarkable as PFOS."

Problems with PFOS aren't over yet, however, since the chemical is still used in products such as fire-fighting foam and floor polishes.

3M has insisted the chemical is not harmful to humans.