HALF-LIFE OF POLYBROMINATED BIPHENYL IN HUMAN SERA

Polybrominated biphenyl (PBB), a flame-retardant material, was introdu ced into the toed chain in Michigan in 1973 due to a manufacturing and distribution mistake. Following public concern about the longterm hea lth effects of PBB in humans, a cohort of PBB-exposed Michigan residen ts was assembled in 1975. We initiated this study to determine the hal f-life of PBB in human sera and to understand how continued body burde n relates to the possible adverse health consequences of PBB exposure. To determine the half-life, eligible persons were selected from the c ohort if they had at least two PBB measurements 1 year apart and had a n initial level greater than or equal to 20 pbb. There were 163 person s who met the criteria with a median PBB level of 45.5 ppb. The estima ted half-life is 10.8 years (95% CI, 96-14.7 years). The body burden o f PBB in exposed persons will decrease only gradually over time. For p ersons with an initial level of 45.5 ppb of PBB, it will take more tha n 60 years for their PBB levels to fall below the current level of det ection of 1 ppb.