The chemicals, known as polybrominated diphenyl ethers or PBDEs, were introduced around 30 years ag, for use in households as a flame retardant. This coincides with the increasing incidence of overactive thyroid disease in cats. Hyperthyroidism was rare several decades ago, and is now one of the leading causes of death in pet cats. It’s known that key risk factors for feline hyperthyroidism are for indoor cats and those who eat canned foods.
One of the study authors, EPA veterinarian Janice Dye, told Reuters, "We definitely found evidence that cats are being exposed to these compounds based on the level of compounds in their blood…Cats are in this perfect position to be near the products these chemicals were put in to reduce flammability. They're in our homes. They're sleeping on our mattresses and furniture." Dye believes that house cats are ingesting the PBDEs, which are present in household dust, as they carefully groom themselves.
Linda Birnbaum, director of the Experimental Toxicology Division at the U.S. Environmental Protection Agency, told HealthDay news, "Cats are very highly exposed to these chemicals, and the levels in cats are higher than the levels in people. But cats may be a good indicator of indoor exposure to humans.”
In the study, researchers compared levels of PBDE in healthy cats and cats with hyperthyroidism, and found that the cats with an overactive thyroid had PBDE levels 20 to 100 times higher than the average adult human in the United States. All the cats had detectable levels of PBDEs, but the highest levels were seen in cats with hyperthyroidism.
The researchers also found that the PBDE content of certain canned cat foods –- in particular, seafood flavors like salmon and whitefish –- is substantially higher than dry or non-seafood canned cat food.
Symptoms of hyperthyroidism in cats include hunger, increased appetite, weight loss, increased thirst, vomiting, diarrhea, irritability, and vocalizing.
According to Dye, “Our results showed that cats are being consistently exposed to PBDE. Because they are endocrine-disrupting agents, cats may well be at increased risk for developing thyroid effects.”
According to Dye, cats and humans are the only mammals with high incidences of hyperthyroidism. The paper suggests that cats are, in a way, the canaries in the coal mine, suggesting a possible thyroid risk of PBDEs to humans. While a causal link between the PBDEs and feline thyroid problems has not been proven, more research will be done to investigate. If the relationship is proven, then similar research on the effects of PBDEs on humans will be conducted.
Mary Shomon, About.com's Thyroid Guide since 1997, is a nationally-known patient advocate and best-selling author of 10 books on health, including "The Thyroid Hormone Breakthrough: Overcoming Sexual and Hormonal Problems at Every Age," "The Thyroid Diet: Manage Your Metabolism for Lasting Weight Loss," "Living Well With Hypothyroidism: What Your Doctor Doesn't Tell You...That You Need to Know," "Living Well With Graves' Disease and Hyperthyroidism," "Living Well With Autoimmune Disease," and "Living Well With Chronic Fatigue Syndrome and Fibromyalgia." Click here for more information on Mary Shomon.
Betts, Kellyn, “PBDEs, cats, and children,” Science News, August 15, 2007,
Environmental Science and Technology site.
Dye, Janice et. al. “Elevated PBDE Levels in Pet Cats: Sentinels for Humans?“
Environ. Sci. Technol Abstract, August 15, 2007.
Steenhuysen, Julie, “Household chemicals may be causing cat disease”
Betts, Kellyn, “PBDEs, cats, and children,” Science News, August 15, 2007, Environmental Science and Technology site.
Dye, Janice et. al. “Elevated PBDE Levels in Pet Cats: Sentinels for Humans?“ Environ. Sci. Technol Abstract, August 15, 2007.
Steenhuysen, Julie, “Household chemicals may be causing cat disease” Reuters .