In utero exposure to polychlorinated biphenyls and sensorineural hearing loss in 8-year-old children.

Early-life exposure to polychlorinated biphenyls (PCBs), a ubiquitous environmental contaminant, increases the hearing threshold at selected frequencies in rats. Among humans from the Faroe Islands with unusually high early-life PCB exposure, exposure was directly associated with increased hearing thresholds at two frequencies, although the deficits were present in the left ear but not the right. We examined PCB levels in maternal pregnancy serum in relation with audiometrically determined hearing thresholds among offspring when they were of school age. Complete data were available for 195 children with sensorineural hearing loss (SNHL) and 615 children selected at random, all of whom were born in 1959-1966 in the Collaborative Perinatal Project (CPP) U.S. cohort. The median exposure among those selected at random, as reflected by the mother's third trimester serum total PCB concentration, was 2.8 microg/l, about twofold higher than recent background levels in the United States. Based on the average hearing threshold across the frequencies essential for speech recognition in the "worst ear," the maternal serum PCB level was unrelated to the adjusted odds of SNHL or to adjusted mean hearing threshold. Overall, an adverse effect of early-life, background-level PCB exposure on SNHL was not supported by these data.