Toxic flame retardants, which are building up at a rapid pace in people’s bodies throughout the United States and Canada, are being spread by an array of store-bought foods as well as dust inside homes and offices, scientists have discovered.
Three new studies, released at an international conference this month, detected for the first time high concentrations of the flame retardants in a variety of fish, meat and fowl in the United States, including California grocery stores.
The findings, combined with other new tests that found the chemicals in household dust and on computer keyboards, have convinced environmental scientists that exposure to them is unavoidable.
“There is more or less a continuous exposure, and there is absolutely no way to really control it. You have almost a 24-hour exposure, except for the time you are outside,” said Aake Bergman, head of environmental chemistry at Stockholm University in Sweden and a leading authority on flame retardants.
Created by chemical companies to make hard plastic and polyurethane foam less flammable, polybrominated diphenyl ethers, or PBDEs, are added to computers, TVs, furniture cushions, upholstery textiles, carpet backings, mattresses, cars, buses, aircraft and construction materials.
California has banned two types of flame retardants effective in 2008, and the manufacturer has agreed to stop producing them by the end of this year. But others, including the most widely used PBDE, are unregulated.
For the last year, scientists have been struggling to figure out how people are exposed, particularly in the United States, where human bodies carry 20 times more on average than in Europe and other areas.
Toxicologists are mystified by the high levels in some Americans, saying there are no obvious patterns to explain the phenomenon. People are exposed to other well-known chemicals, such as PCBs and mercury, almost entirely through the food web, especially fish. But while some fish have high concentrations of PBDE, people who eat a lot of fish are not necessarily among the most highly contaminated.
Many scientists suspect that the exposure of some people --particularly children -- is more direct and individualized, dependent on what products are inside their homes and not just what they eat. But they have yet to prove which of the two -- food or dust -- is the major source, or what, if anything, people can do to reduce their risk.
“We have two sources: Food is one and indoor air is another. We now know that the sources are inside our houses, inside our buildings,” said Mehran Alaee of Canada’s National Water Research Institute, who led a conference of scientists in Toronto this month to share the findings of about 100 studies of flame retardants. “I’m convinced that we are in intimate contact with PBDEs. It’s on the seat cushion you’re sitting on, the computer monitor you’re using.”
The flame retardants have been detected in virtually every person and animal tested, even newborns and fetuses, around the world, including Australia, Arctic Canada and Svalbard, Norway, near the North Pole. Amounts in people and wildlife are doubling in North America every four to six years, a pace unmatched for any contaminant in at least 50 years.
PBDEs build up in fatty tissues and pose a particular risk to babies because they pass through the womb and taint breast milk. Low doses in lab animals have disrupted brain growth and altered estrogen hormones, affecting male fertility and ovary development.
About 5% of people in the United States -- an estimated 15 million -- have PBDE levels considered high, based on breast milk and blood samples from more than 2,000 women around the country. Some are carrying doses similar to those that impaired brain development of newborn laboratory rats.
In one of the new studies, two California laboratories found the chemicals in fish, meat and fowl purchased at three Sacramento-area grocery stores from December to February.
Swordfish, farm-raised salmon and catfish, and duck had the highest concentrations. Farm-raised fish contained 5 to 6 times more than wild fish, except for swordfish, which had the most of any food tested, according to Alta Analytical Laboratories in El Dorado Hills and Environ in Emeryville. Beef had the lowest levels, followed by goose, pheasant, scallops, canned tuna and wild coho salmon. Chicken contained moderate amounts.
In nationwide tests conducted by the USDA and revealed at this month’s conference, bacon and beef fat had fairly low levels while fat trimmed from pork chops had fairly high.
At three Dallas supermarket chains, the amounts in meat products also varied significantly. Pork sausage, hot dogs and duck had fairly high levels of contamination while bacon and ground beef had low levels.
“PBDEs are found in almost all foods of animal origin; and some have very high levels of these chemicals,” said a report by University of Texas environmental scientist Arnold Schecter, based on the Dallas supermarket tests he conducted. He reported that diet is “most likely the primary route of exposure.”
The lack of any pattern in the food puzzles toxicologists and makes “prediction of the amount one ingests very difficult,” said researcher Thomas McDonald of California’s Office of Environmental Health Hazard Assessment. However, because PBDEs bind to fat, trimming excess fat, eating lean meats and avoiding large, predatory fish is advised--especially for pregnant and nursing women.
Other experts aren’t convinced. Bergman says European and North American diets are not different enough to explain the huge variation of human concentrations on the two continents. Instead, he suspects that the explanation lies in Americans breathing the much higher levels found in their household dust compared with European homes.
Last month, the Environmental Working Group, an activist organization, reported finding the contaminants in dust in all 10 homes it sampled in nine states, including two in California. Two other environmental groups found them in dust on all 16 computer keyboards sampled in universities, government offices and in a children’s museum. PBDEs apparently escape as a gas from hard plastic and polyurethane foam -- especially newer computers, furniture and other products -- and then adhere to dust. Spread by waterways and winds, they are ingested by plants and animals and transported thousands of miles.
One of the contaminants is a PBDE compound called deca, widely used in electronics equipment and upholstery textiles.
Deca is not subject to the California ban. Scientists initially thought it would not accumulate in the environment, but in recent months it has been found in humans and breast milk as well as wild animals. The compound “hides” by transforming itself in the environment into other PBDEs that are absorbed more readily by body tissues.
“I am convinced we are building a huge, ticking time bomb in our environment today,” said Bergman, who has studied toxic contaminants since the 1970s. “The 55,000 or 56,000 tons of deca used per year are slowly transformed into lower brominated compounds, which stay around for hundreds of years. I don’t see any solution to this but to substitute the PBDEs, and that goes for all the PBDEs, including deca.”
Manufacturers of deca say it protects people from fires and there is little evidence that it is dangerous or building up to high levels. Some companies, including Apple and Dell, are redesigning products to avoid flame retardants and still meet fire safety standards.
In April, Maine enacted a law banning deca in 2008 only if safer flame retardants are nationally available. The European Union, the international leader in restricting industrial compounds, decided last month that there was insufficient evidence to ban deca as it had the other flame retardants.