Flame retardant may sicken cats

An epidemic of thyroid disease among pet cats could be caused by toxic flame retardants that are widely found in household dust and some pet food, government scientists reported Wednesday.

The often-lethal disease was rare in cats until the 1980s, when it began appearing widely. That was at the same time industry started using large volumes of brominated flame retardants in consumer products, particularly furniture cushions, electronics, mattresses and carpet padding.

Scientists from the Environmental Protection Agency noted a possible connection between hyperthyroidism, which has become increasingly common in older cats, and flame retardants. The chemicals — known as polybrominated diphenyl ethers, or PBDEs — mimic thyroid hormones, so experts have theorized that high exposure in cats could cause overactive thyroids.

"We know there is an association between indoor living for cats and hyperthyroidism," said Linda Birnbaum, a senior author of the study published in the journal Environmental Science and Technology and the EPA's director of experimental toxicology. "Our paper does show cats are highly exposed and hyperthyroidism may be due to the high PBDEs. More studies are needed to fully determine this."

A major unanswered question is whether humans face the same health dangers. So far, no link has been established between human thyroid disease and exposure to flame retardants.

Brominated flame retardants are ubiquitous in the environment and inside homes. The chemicals have been building up in people and wildlife over the past two decades, particularly in the United States, where human concentrations have doubled every few years.

People in the United States have the highest PBDE levels in humans worldwide, but U.S. cats are even more exposed — some with levels 100 times greater, according to the study.

Twenty-three cats were tested in the EPA's study, including 11 with hyperthyroidism. The researchers found that the hyperthyroid cats had substantially higher levels of a PBDE compound. Symptoms of the disease, which is a leading cause of death in cats, include weight loss, rapid heartbeats and irritability.

Cats, while sleeping, often come in direct and prolonged contact with upholstery, carpeting and mattress materials that contain flame retardants. "Because of their meticulous grooming behavior, cats would effectively ingest any volatilized PBDEs or PBDE-laden dust that deposited on their fur during such activities," the scientists wrote.