Received for review April 6, 2007

Revised manuscript received July 10, 2007

Accepted July 10, 2007

Abstract:

Co-incident with the introduction of polybrominated diphenyl ethers (PBDEs) into household materials nearly 30 years ago, feline hyperthyroidism (FH) has increased dramatically. Risk of developing FH is associated with indoor living and consumption of canned cat food. We hypothesized that increases in FH were, in part, related to increased PBDE exposure, with key routes of exposure being diet and ingestion of house dust. This study was designed to determine whether body burdens of PBDEs in hyperthyroid (HT) cats were greater than that of young or sick non-HT cats. Serum samples and clinical information were collected from 23 cats. Serum and dry and canned cat food were analyzed for PBDEs. A spectrum of BDE congeners was detected in all cats, with BDE-47, 99, 207, and 209 predominating. Mean ± standard error (and median) cumulative PBDE serum concentrations of young, old non-HT, and HT cats were 4.3 ± 1.5 (3.5), 10.5 ± 3.5 (5.9), and 12.7 ± 3.9 (6.2) ng/mL, respectively. Due to high variability within each group, no association was detected between HT cats and PBDE levels. Indicative of age- or disease-dependent changes in PBDE metabolism, BDE-47/99 ratios were inversely correlated with age, and 47/99 and 100/99 ratios in HT cats were significantly lower than those in the other cats. Overall, PBDE levels in cats were 20- to 100-fold greater than median levels in U.S. adults. Our results support the hypothesis that cats are highly exposed to PBDEs; hence, pet cats may serve as sentinels to better assess human exposure and adverse health outcomes related to low-level but chronic PBDE exposure.

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