New research finds association between cat hyperthyroid disease and flame retardant levels in dust

Donna Mensching's informative new study of 72 cats (including my cat Midnight) with abstract below confirmed that domestic cats have high concentrations of the PBDE flame-retardant in their blood. Midnight's blood levels were very high and my house dust at 95mg/g was the highest in this Illinois study.

Donna compared blood levels in healthy and hyperthyroid geriatric cats and found no significant difference. She also found that household dust PBDE levels were significantly higher in homes with hyperthyroid cats.

Happily the level of flame retardants in my house dust went down to from 95 mg/g to 3mg/g in dust three years after I discarded all my toxic furniture.

My high dust levels were probably due to California's outdated and ineffective flammability standard Technical Bulletin 117(TB117). To learn more about the lack of fire safety of TB117, read our paper:
Flame Retardants in Furniture Foam: Benefits and Risks.

Analysis of several commercially available canned cat foods suggested that food is not a major source of PBDEs. Ingestion of dust from grooming, however, is proposed as the main source of the cats' PBDE exposure. The estimates for PBDE exposure calculated from her data indicate that domestic cats are at risk for adverse thyroid effects from these chemicals.

Treatment options for feline hyperthyroidism include surgery, drug therapy (methimazole), radioactive iodine treatment, and a new treatment for the disease which is a prescription diet called Hill's y/d which is very low in iodine.

The Feline Thyroid Gland: A Model for Endocrine Disruption by Polybrominated Diphenyl Ethers (PBDEs)
Mensching DA, Slater M, Scott JW, Ferguson DC, and Beasley VR. (2012). Journal of Toxicology and Environmental Health, Part A, 75:201-212.

Abstract
The role of polybrominated diphenyl ethers (PBDE) was investigated in the occurrence of feline hyperthyroidism (FH) by evaluating 15 PBDE congeners in serum from 62 client-owned (21 euthyroid, 41 hyperthyroid) and 10 feral cats. Total serum PBDE concentrations in euthyroid cats were not significantly different from those of hyperthyroid cats. Total serum PBDE in feral cats were significantly lower than in either of the groups of client-owned cats. Total serum PBDE did not correlate with serum total T4 concentration. Ten samples of commercial canned cat food and 19 dust samples from homes of client-owned cats were analyzed. Total PBDE in canned cat food ranged from 0.42 to 3.1 ng/g, and total PBDE in dust from 510 to 95,000 ng/g. Total PBDE in dust from homes of euthyroid cats ranged from 510 to 4900 ng/g. In dust from homes of hyperthyroid cats, total PBDE concentrations were significantly higher, ranging from 1100 to 95,000 ng/g. Dust PBDE and serum total T4 concentration were also significantly correlated. Estimates of PBDE exposures calculated from canned cat food and dust data suggest that domestic cats are primarily exposed through ingestion of household dust. These findings indicate further study of the role of PBDE is needed in the development of FH, which might identify the cat as a model and sentinel for humans with toxic nodular goiter (TNG).