SAN FRANCISCO — Two chemicals that are becoming widely used replacements for potentially toxic flame retardants in household products such as televisions and furniture have shown up in peregrine falcon eggs in California. The discovery, part of a larger study monitoring contaminants in wildlife, adds to evidence that these new flame retardants escape into and persist in the environment, as the original ones do.
While the replacement compounds were found in much smaller quantities than the flame retardants that have been on the market for years, their presence in bird eggs is cause for concern, said June-Soo Park of the California Environmental Protection Agency in Berkeley. Little is known about the toxicity of the replacement compounds and their potential to accumulate in people and wildlife, said Park, who presented the new research March 25 at the spring meeting of the American Chemical Society.
The earlier generation of fire retardants, called polybrominated diphenyl ethers, or PBDEs, was added to products such as furniture, electronics and carpeting and upholstery to reduce fire-related injuries. In California, which has especially stringent product flammability laws, people and wildlife contain some of the highest levels of PBDEs in the world, noted Park. Research on lab animals has suggested that many PBDEs mimic the effect of thyroid hormones, meddling with reproduction and nerve and tissue development. Such findings led the European Union to ban two of the most common formulations in 2004.
But researchers are still finding traces of PBDEs in the environment, where their replacements — hexabromobenzene, known as HBB, and Bis(2,4,6,-tribromophenoxy)ethane, known as BTBPE — are also now showing up.
Park’s team has been studying peregrine falcons, which became endangered after years of exposure to pesticides such as DDT but have recovered in much of the U.S. These bird-eating birds, at the top of the food chain, are considered sentinels of environmental health.
Park and his colleagues measured levels of contaminants in eggs and chicks collected from 38 nest sites between 1986 and 2007. In the eggs, PBDE levels more than tripled each decade over the last 22 years, and the levels in one chick were the highest ever reported in wildlife, Park noted. The eggs and chicks of urban falcons, living in cities such as Los Angeles, San Diego and San Francisco, had much higher levels of the flame retardants than their more rural counterparts. That may be because urban falcons consume more dust, which contains high levels of PBDEs from household items, either through preening or through eating other dusty birds like pigeons.
Preliminary data suggest the new flame retardants are also accumulating in wildlife, Park reported at the meeting. In 19 of the falcon eggs, the research team detected HBB and BTBPE, but in much lower quantities than the old standby chemicals. It isn’t clear how the falcons are accumulating the new flame retardants, Park said. “That’s a hard question — we have very limited data.” Other scientists have reported finding HBB in herring gulls around the Great Lakes and BTBPE in bedrooms and living rooms in the Boston area.
Park said the new findings suggest that further monitoring, and further testing, is necessary, as there is little toxicological data on these supposedly safer compounds. The replacement flame retardants are considered safer because they don’t break down as readily into more absorbable forms, but the flip side of that stability is that they may persist for an extremely long time. That persistence has unknown toxicological side effects.
Park’s study reflects the difficulty of balancing the benefits of compounds such as fire retardants against their unintended effects, said Sarah Rubinfeld, an environmental engineer at Stanford University. “We don’t want kids’ pajamas catching on fire,” she said. “But it’s often the case that when we realize a chemical is problematic and we start using a new one — well, sometimes we think it’s better, but it’s really just not a smoking gun.”