Monday, February 18, 2008


Old chemicals used by businesses for decades are causing new problems in the environment as scientists turn their attention toward compounds that are accumulating in rivers, lakes and oceans.

While new commercial chemicals are extensively reviewed before they are approved for use, thousands of "grandfathered" substances were never subject to the same testing. Scientists are now raising questions about their effects as new testing methods reveal their presence.

"A lot of our problems are related to those old chemicals," said Derek Muir, an Environment Canada scientist, who was to present his findings Saturday at the American Association for the Advancement of Science conference in Boston.

Muir and his colleagues found that of about 30,000 chemicals used commercially in the United States and Canada, about 400 don't readily break down and have been slowly accumulating in the environment. About three-quarters of these chemicals have not been studied.

Some of them are very similar to other chemicals that have been banned or restricted, such as brominated flame retardants, said Muir.

"They aren't produced in as large amounts; nevertheless, they appear to have the same sort of environmental behaviour and may accumulate in marine food webs and possibly in humans as well."

Chemicals such as polycyclic aromatic hydrocarbons, which enter the environment from sources such as oil spills, car exhaust or urban waste, have been shown to create heart deformities in fish.

Substances used to create non-stick coatings and stain repellents accumulate in animals such as mussels and damage the livers and immune systems of turtles that eat them.

Nor do scientists understand what effect these older commercial chemicals have when they get mixed together in a river or along a coastline.

"We can measure the exposure to the mixture," said Muir. "But when it comes to assessing what the effect of that mixture is, we are really challenged."

The effects of combining some highly studied chemicals such as PCBs or dioxins are fairly well understood. But there is little knowledge with regard to hundreds of other compounds circulating in waterways.

Do effects from different chemicals simply add up? Do they amplify each other, or even cancel each other out?

"There's progress being made on that, but it's really a challenge on the ecotoxicology side," Muir said.

The particular chemical cocktail in a finished product may not even be known, as one manufacturer buys raw material from another, adds something during processing, then sells it to the next business up the supply line. European regulations are just now attempting to sort out which chemicals are used in each manufacturing or packaging step.

"As a consumer, you don't know where it's come from," Muir said.

One of the researchers in his group documented hormone disruptions in fish near some California wastewater pipes so severe that male fish were producing female hormones - and even proteins to form egg yolks.

Scientists are beginning to work their way through the backlist of unstudied chemicals. Canada is a leader in that effort, Muir said.

All of the 23,000 chemicals grandfathered in 1986 have since been reviewed.

"Now, Environment Canada is actually acting to remove chemicals from commerce if there's any evidence of adverse effect."

However, chemicals removed from the Canadian market can still enter the environment through Europe and the U.S., which are just starting on similar steps.

The risks to consumers are low and long-term but nevertheless real, said Muir.

"We always have to be vigilant about this. We certainly haven't gotten to the point where we know enough about the chemicals in commerce to be comfortable."


Post a Comment

<< Home