Polybrominated diphenyl ethers (
PBDEs) are brominated
flame retardants that act as
endocrine disruptors, affecting
thyroid hormone homeostasis. As a follow-up to a recent study showing high
PBDE levels in household cats and linking
PBDE levels with cat
hyperthyroidism, we measured
PBDEs,
polychlorinated biphenyls (
PCBs), and organochlorinated pesticides (OCPs) in serum samples from 26 California household cats (16
hyperthyroid, 10 controls) using liquid-liquid extraction and high-resolution gas chromatography/high-resolution mass spectrometry. In the present pilot study, we found that
PBDE levels in California house cats were extremely high (ΣPBDEs median = 2,904 ng/g
lipid; range, 631-22,537 ng/g
lipid). This is approximately 50 times higher than levels in California residents (ΣPBDEs geomean = 62 ± 8.9 ng/g
lipid, National Health and Nutrition Examination Survey), who have among the highest human levels in the world.
Polybrominated diphenyl ethers congener patterns (BDE-99 major congener, BDE-209 significant) differed markedly from patterns found in California residents (BDE-47 major) or wildlife but resembled patterns found in
house dust.
Polychlorinated biphenyls and OCPs in cats were highly correlated, consistent with a shared dietary source or pathway of exposure, but did not correlate with
PBDEs. This suggests a different source or pathway of exposure for
PBDEs, which was most likely
house dust. The authors found no evidence that linked levels of
PBDEs,
PCBs, or OCPs with
hyperthyroidism. This may be because of the small sample size, competing or confounding risk factors, or complicated causal mechanisms.