Persistence of polybrominated biphenyls (PBB) in human post-mortem tissue.

Polybrominated biphenyl (PBB), a fire retardant, was accidentally substituted for an animal feed supplement in Michigan 10 years ago. This led to widespread livestock contamination and ultimately to contamination of virtually every human residing in the State at that time. In order to evaluate the extent of PBB persistence and distribution in human tissues 10 years after this accidental poisoning, a study was conducted on a series of autopsy cases from the Grand Rapids ("high" exposure) area of the State. No attempt was made to relate cause of death to PBB exposure or tissue concentration. Samples of 196 tissues from 15 subjects were analyzed for PBB content, and levels were determined by measurement of the hexabromobiphenyl peak using electron capture gas chromatography. Only 4 of the 196 samples analyzed did not have PBB concentration above the limit of detection (0.5 ng/g). As expected, fat and fat-rich tissue had the highest PBB concentration. Perirenal fat had the highest mean concentration (475 ng/g). Adrenal, atheromatus aorta and thymus had mean concentrations about half that of perirenal fat; all other tissues had mean concentrations one-tenth or less of perirenal fat. The results document that PBB is still present in human tissue and that PBB was distributed in all tissues examined. The PBB fat elimination half-time was estimated to be at least 7.8 years. If this is approximately correct, PBB will persist in tissues throughout the lifetime of humans so contaminated.