Embryotoxicity of polybrominated biphenyls

Abstract

A mixture of polybrominated biphenyls (PBB) was accidentally mixed with livestock feed in Michigan, and resulted ultimately in prolonged periods of exposure to large numbers of farm animals. Several writers have reviewed the episode1–4, and the following account is a brief summary of their chronologies. PBB was manufactured solely by Michigan Chemical Company as a fire retardant, under the trade name of Firemaster. The company also manufactured magnesium oxide as a feed supplement for lactating cows, under the trade name of Nutrimaster. Somehow, some PBB was packaged in the colour bags usually reserved for magnesium oxide and, although labelled Firemaster, was shipped to the Michigan Farm Bureau as part of a shipment of the Nutrimaster. Substitution of the toxic PBB for magnesium oxide in feed went unrecognized. Compounding the problem of feed contamination was the cross-contamination that occurred to all other feeds handled in the facilities that had been exposed to PBB, thereby resulting in contamination of other livestock and poultry. Widespread contamination of farms further resulted from the rendering of PBB contaminated animals for feed, and by feed swapping between individual farms and between feed mills. The Michigan PBB episode has resulted in thousands of farm animals killed and buried, and in the destruction of huge quantities of eggs and dairy products, at great economic loss to Michigan dairy farmers.