Study links house dust to cat illness

updated 11:37 a.m. ET Aug. 16, 2007

WASHINGTON - A new federal study suggests that household dust containing a common flame retardant may be linked to an increase in cats getting sick from overactive thyroids.

That could be a warning sign for how young children could get exposed to the chemical, said Linda S. Birnbaum, director of experimental toxicology at the U.S. Environmental Protection Agency and co-author of the study.

The small study looks at chemical flame retardants called polybrominated diphenyl ethers (PBDEs), which were used in foam, plastics, furniture, electronics, fabrics and carpet padding. The sole American manufacturer in 2004 agreed to phase out the types of PBDEs included in the study because of concern about toxicity in animals.

But PBDEs remain in American homes.

The study of 23 cats found the older felines with high levels of certain types of PBDEs tended to have overactive thyroids, the researchers reported online Wednesday in the peer-reviewed journal Environmental Science and Technology.

Hyperthyroidism is treatable in both cats and humans. In cats, the disease started soaring in America in the late 1970s and 1980s, soon after PBDEs became common, according to the researchers.

The EPA study adds to recent research that raises serious questions about human exposure to PBDE. One study found a significant relationship between indoor dust exposure and PBDE levels in first-time mothers in the Boston area. Another found PBDE levels in Americans are three to 10 times higher than in Europeans. And small studies in California and Norway show that children, especially toddlers, have higher PBDE levels than adults.

Tom Webster, a professor of environmental health at Boston University, said animal research has found PBDEs to damage the nervous system and disrupt hormones, but studies haven’t been done to look at people’s health.

“I don’t think we know about (human) health yet, but I don’t like the sound of this,” said Webster, who co-authored the Boston dust study but was not part of the EPA research, which he praised. “Levels in people are going up.”

But because the cat study is so preliminary, Birnbaum said people shouldn’t overreact and sell their furniture or rid themselves of carpets. However, she said she makes sure to wash her grandchildren’s blankets more frequently and checks on flame retardant use when buying furniture.

Most people don’t have PBDE levels that are anywhere near that of cats, Birnbaum said. PBDE is just one of many chemicals that accumulate in our body with unknown effects, but the dust exposure route is unusual, Birnbaum said.

The EPA study suggests household dust as the key way PBDE gets into cats, and likely, people. It also found elevated PBDE levels in certain cat food, mostly fish, but tests showed food couldn’t be blamed for the high levels in cats, Birnbaum said.

She said if PBDEs get into bodies through household dust, that means children are likely to be more exposed than their parents.

“To me, it’s a consumer product issue,” said Myrto Petreas, chief of the state of California’s environmental chemistry branch and co-author of other studies looking at PBDE levels in women and San Francisco Bay harbor seals. “You get exposed while you’re in your home.... It’s in the carpet. It’s in the monitor. It’s in your chair.”

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