Inadvertent admixture of the fire retardant chemical polybrominated biphenyl (PBB) with farm feed occurred in Michigan late in 1973; important animal disease resulted. Delay in detection allowed wide and prolonged distribution of contaminated food, and as a result most of Michigan’s 9 000 000 citizens currently have detectable levels of PBB in serum and body tissues. Almost all samples of breast milk in the State have been found to have PBBs as well as PCBs. A clinical field survey of more than 1000 dairy farm residents and others demonstrated an unusual prevalence of specific but not pathognomonic clinical complaints, particularly neuro-behavioural. These were far fewer among a control group of Wisconsin dairy farm residents not exposed to PBB. Similar contrasts were noted in two laboratory studies: liver function test results (enzyme levels) were much more likely to be abnormal in Michigan than in Wisconsin, possibly related to the fact that the halogenated biphenyl is a powerful enzyme inducer; in addition, T cell and B cell abnormalities and impaired lymphoblastogenesis were the rule in Michigan dairy farmers, but these findings, consistent with immunosuppression, were absent in the Wisconsin group.The long-term significance of the observations is not at present known. This is being studied, as is the status of the general population of Michigan presumed to have lower tissue burdens than the farmers.
Formation of brominated dibenzofurans from pyrolysis of the polybrominated biphenyl fire retardant, firemaster FF-1.
