For the past 30 years, flame retardants have been found in every Canadian home, added liberally as a safety precaution to everything from mattresses and carpets to stereos, televisions and computers.
Now Canada is poised to add flame retardants -- or polybrominated diphenyl ethers (PBDEs) -- to its toxic-substances list.
If a draft proposal it is circulating is any guide, the federal government is expected to virtually eliminate some varieties of the chemical and place tight controls on others.
Regulators are considering drastic action because laboratory studies using animals have linked the chemicals to behaviour changes that bear an uncanny similarity to attention-deficit and hyperactivity disorders common in children. Some researchers believe PBDEs could offer a clue for the sudden rise of these childhood disorders in recent years.
The animal findings on their own would not be a major concern, except for a second disturbing discovery: Flame retardants are not staying put in consumer products. They have been migrating from mattresses and computers, in ways that are not completely understood, into the environment and into people.
A significant number of North Americans, estimated at about 5 per cent to 10 per cent of the population, are considered "super accumulators." They have become highly contaminated with PBDEs and can have levels about 1,000 times higher than people with the lowest body burdens of the chemicals, according to tests of breast milk, blood and tissue.
What is more, people with the highest readings in Canada have body burdens of the chemicals that exceed those producing harmful effects in laboratory animals, according to Jake Ryan, a Health Canada researcher who retired from the federal agency in April after helping to discover that flame retardants in the breast milk of Canadian women are at one of the highest levels in the world.
The meaning of the animal experiments "to the human situation is unclear," Dr. Ryan said. However, the exposure used in one of the laboratory tests that found hyperactivity effects is lower than the exposure present in some humans.
In reaction to the surprising discoveries that flame retardants can migrate from consumer products into people and affect health, officials at the federal health and environment departments say they are close to issuing rules to restrict the chemicals, which are currently unregulated and were not evaluated by federal authorities before their commercial introduction.
Such are the concerns about flame retardants that if they were introduced now, they might not be allowed, particularly in the form found in mattresses.
"It may well be that it would not have been allowed on the market," said Robert Chernier, who evaluates chemical safety at Environment Canada.
Federal officials are not recommending that people throw out their mattresses and computers to reduce exposure. However, some researchers are expressing concern that without tight controls on the safe disposal of these products when they reach the end of their useful lives in homes and offices, the chemicals will become imbedded in the environment and become a long-term problem.
In Europe, regulators were so alarmed by flame retardants that they issued a ban on two of three formulations in 2004. They outlawed the type used in mattresses and a second type used mainly in computer casings and monitors.
In the United States, a number of states have take similar action. The Environmental Protection Agency reached a voluntary agreement with the major U.S. manufacturer of the same two varieties to end production two years ago. It is widely expected that Canada, like Europe, will take tough action against the computer and mattress formulations, which together accounted for about 15 per cent of the market for the chemicals in 2001.
People in North America have the highest burdens of the chemicals in the world, about 10 times higher than Europeans. That is seen as a reflection of their more widespread use in North America and earlier moves in Europe to phase them out.
"We've surrounded ourselves with them, before we've really thought about what they might do," said Thomas Zoeller, a biology professor at the University of Massachusetts. He is is studying the health threat associated with the flame retardants for the U.S. Environmental Protection Agency.
Given the animal studies, Dr. Zoeller said, "it's not outrageous to conjecture that some of the increase in [childhood]attention deficit, or attentional disorders, is related to these types of compounds."
Some parents are so worried about the flame retardants they have taken steps to reduce their children's exposures. Tonya Surman, a Toronto environmental activist, said that when her two sons, now aged four and six, graduated from cribs to beds, she made sure their new mattresses did not contain any PBDEs by purchasing them from a company that does not stock products containing the controversial chemicals.
"We specifically went out and bought our mattresses from IKEA because they had a PBDE policy," Ms. Surman said. "I want to take a precautionary approach. . . . I want to do everything I can to protect my kids."
The flame retardants were never manufactured in Canada, indicating that industrial releases are not a factor contributing to the exposures. These are "pollutants in consumer products, as opposed to pollutants that are pumped out of smokestacks or pumped out of exhaust pipes," said Rick Smith, executive director of Environmental Defence, a Toronto-based activist group that tested a number of Canadians last year and found flame retardants in each.
There is speculation that super accumulators are either middle-class people whose homes are filled with electronic gadgets, or those who are exposed to old, crumbling foam-filled furniture, according to Dr. Miriam Diamond, a professor in the University of Toronto's department of geography.
The rest of the North American population carries low flame-retardant levels, although amounts found have been doubling every two to five years. If the trend continues, many more people will be at risk of moving into the ranks of the highly contaminated, although some scientists suspect the dramatic increase seen from the 1980s up to the early 2000s is slowing.
Ironically, flame retardants were introduced in the late 1970s as a consumer-safety boon. They reduced the tendency of TV and computer casings, made from flammable hard plastics, to burst into flames, preventing many serious blazes. They have also saved many a drowsy smoker from self-immolation by making it more difficult for foam-filled sofas and mattresses to burn rapidly.
Because flame retardants merely slow the pace of blazes, some firefighters are worried that if consumer products containing them are a potential health hazard, breathing in the smoke when they burn is even worse.
"I'm strongly in favour of banning these things," said Tim Baillie, a firefighter and vice-president of the British Columbia Professional Fire Fighters Association.
Studies on flame retardants began in the 1990s, after Swedish researchers made the surprising discovery that concentrations in human breast milk were rising sharply, indicating that the chemicals were managing to get out of consumer products.
Researchers have also determined that the chemical structure of flame retardants resembles that of polychlorinated biphenyls (PCBs), but with a shape that suggests they are much more biologically active than their outlawed chemical cousin.
Much of the subsequent study into the chemicals has been done in Canada by scientists at Environment Canada, the Department of Fisheries and Oceans, Health Canada and the University of Toronto, including the finding that most of the human exposure in North America appears to be coming from within homes, where microscopic traces of flame retardant are breaking off consumer items and accumulating in household dust.
Products can shed large amounts because they contain so much of it in a form that is only loosely mixed into plastics and foams. Computer casings may be up to 18 per cent flame retardant, and mattress foam about 2 per cent or 3 per cent.
When flame retardants started showing up in people, researchers initially thought they were coming from food, an exposure route observed with other persistent pollutants. But testing of dust has found their concentrations can be thousands of times higher than in foods, indicating that unlike PCBs or the banned pesticide DDT, the chemicals have not yet contaminated the human food chain in a big way.
The dust finding means that each time people breathe in house dust, or get dust on their fingers and put their hands to their mouths, they are getting small doses of flame retardants.
In tests of dust, researchers have found the percentage of homes with high levels of flame retardants -- at about 10 per cent -- matches the percentage of the population with elevated body readings. It raises the question "whether there is a relationship there," said the U of T's Dr. Diamond.
She said the dust finding is particularly important with regard to toddlers, who spend a lot of time crawling and have a lot of hand-to-mouth activity and so are likely more exposed than adults.
"The main exposure is indoors," said Dr. Diamond, who recommends people minimize household dust, avoid buying new products containing PBDEs and remove any crumbling foam furniture.
For reasons unknown, the amount of contaminants in dust does not bear any relationship to the number of computers or TVs people have, although small houses tended to have higher concentrations than big ones.
Given that scientists have found the chemicals indoors, Dr. Diamond is concerned that without the safe disposal of the thousands of tonnes of flame retardants imbedded in consumer products, it will be only a matter of time before the chemicals start building up in the environment in a big way.
That means they will eventually get into the food chain, just like PCBs, and it will take many decades for exposures to fall to low levels.
In a paper this year in the journal Atmospheric Environment, Dr. Diamond warned that flame retardants in products are a potential "time bomb" waiting to go off.
"Every home has this stuff," she said. "It should be appropriately disposed of, or we should at least understand the implications of not disposing of them."
TOMORROW: A plastic chemical mimics the hormone estrogen when absorbed by humans.
Chemicals are everywhere, so how can you live contact free?