There’s an epidemic of cats with hyperthyroidism, and researchers at Oregon State University believe the flame retardants often found in household furniture may be the culprit.
According to OSU, the number of cats diagnosed with hyperthyroidism in 1980 was 1 in 200. Today it’s estimated that 1 in 10 cats are afflicted.
For the Oregon State study, a silicone pet tag developed by Kim Anderson, an environmental chemist in the Oregon State College of Agricultural Sciences, was attached to the collars of 78 hyperthyroid and non-hyperthyroid cats. The cats wore the tags for a week, after which chemicals the cats had been exposed to could be extracted from the tags with a solvent.
“The tags are porous and chemically very similar to human cells,” Anderson said, in an OSU press release. “Molecules of contaminants embed themselves in the silicone in the same way they’d go into the cells in your body. The silicone is a pretty good mimic of the types of chemicals that you can absorb – what we call passive sampling.”
The same material was used in the silicone wrist bands for measuring exposure to environmental chemicals in humans, including after Hurricane Harvey in Houston in 2017. Notably, the material was actually invented in Anderson’s lab.
But, back to the cats. The research, led by Carolyn Poutasse, a doctoral student in Anderson’s lab, found over 20 individual flame retardants in at least one tag.
But what differed between tags on the hyperthyroid and non-hyperthyroid cats were the levels of a flame retardant commonly applied to foam in upholstered furniture, some plastics, and gel air fresheners.
The retardant, tris(1,3-dichloro-2-isopropyl) phosphate, or TDCIPP, was discontinued in children’s sleepwear during the 70s.
According to the press release from OSU, the research found that even in healthy cats, higher TDCIPP levels were correlated with thyroid hormone levels.
“The way a cat is diagnosed with feline hyperthyroidism is by extremely elevated concentrations of thyroid hormones,” Anderson said. “Seeing the correlation is suggestive of a connection between thyroid function and exposure to TDCIPP.”
Two cats in the same household can have different levels of TDCIPP, Poutasse said, because one cat may spend more time on furniture and the other on windowsills or other areas without flame retardant. Covering furniture to provide a barrier and reducing air freshener use may help lower a cat’s TDCIPP exposure.
According to the OSU press release, this could affect humans.
The findings have led researchers to think about hyperthyroidism in humans. Even at the cellular level the benign tumor associated with feline hyperthyroidism is identical in cats and humans. Extrapolating from that, hyperthyroid cats could be sentinels for humans, warning of a possible link between flame retardants and human hyperthyroidism.
The amount of the chemical in use in the U.S. continues to rise, Poutasse noted. In 1997, demand for TDCIPP was 450 tons and in 2006 it was 22,700 tons. Scientists are beginning to look not only at the organophosphates in flame retardants, but also the derivatives. Anderson and Poutasse plan to continue evaluation of over 1,500 chemicals not measured in the current study.
The study was recently published in Environmental Science & Technology. OSU partners included Dr. Mark E. Peterson of the Animal Endocrine Clinic in New York City, the first veterinarian to document feline hyperthyroidism. The study was a partnership between OSU’s Food Safety and Environmental Stewardship Program, the OSU Carlson College of Veterinary Medicine, Columbia University, the Animal Endocrine Clinic and the New York Cat Hospital.