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Media Relations

Scientists at work: Ronald Hites and Marta Venier

A study by Indiana University Bloomington and U.S. Environmental Protection Agency researchers found high levels of chemical flame retardants in house cats and raised the possibility that exposure to the chemicals could be linked to feline hyperthyroidism, a serious disease in cats.

The study, published online in August by Environmental Science & Technology and featured on the cover of the journal Sept. 15, concluded cats could serve as "sentinels" for human exposure to the chemicals, polybrominated diphenyl ethers (PBDEs).

The authors included Indiana University doctoral student Marta Venier and Ronald Hites, IU distinguished professor at the IU School of Public and Environmental Affairs. They collaborated with veterinary researchers at the National Health and Environmental Effects Research Laboratory of the U.S. Environmental Protection Agency.

The study of 23 indoor house cats found PBDE concentrations in their blood serum that were 20 to 100 times as high as the levels in North American adults -- which, in turn, are the highest concentrations that have been found in adult humans anywhere. (A 2003 study by Hites and others found PBDE levels in U.S. mothers and babies that were 20 times higher than those in Scandinavian mothers and babies.)

PBDEs have been used since the late 1970s as flame retardants in upholstered furniture, carpet padding, and electronics. During the same time period, feline hyperthyroidism has gone from being almost never reported to being a common disease in older cats, prompting researchers to wonder if there was a connection. The chemicals have been shown in lab tests to impair thyroid and liver function.

Manufacture of the penta and octa varieties of PBDE was phased out in 2004, but the more heavily brominated deca PBDE remains in use. The chemicals persist in the environment and bioaccumulate in the tissues of animals.

The recent study, while involving a small number of cats, found a correlation between blood concentrations of PBDEs and the likelihood that the cats had hyperthyroidism, symptoms of which include increased appetite, weight loss, hair loss, and irritability.

The researchers believe cats are exposed to PBDEs in household dust and ingest the chemicals through their meticulous grooming behavior. That raises concern about potential exposure in toddlers, who crawl on the floor and put things in their mouths.

Venier and Hites also tested dry and canned cat food purchased at a Bloomington discount store and found surprisingly high concentrations of PBDEs in some varieties. They said more detailed studies are needed to determine how much of the cats' exposure comes from household dust and how much comes from diet.

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