Blood lead, hearing thresholds, and neurobehavioral development in children and youth.

NHANES II audiometry data were used to confirm a previously observed link between blood lead (PbB) level and hearing threshold. Other indicators of neurological development, such as age at which a child first sat up, walked, and spoke, and the presence of speech difficulties and hyperactivity were also examined to determine if they were significantly related to lead exposure. The probability of elevated hearing thresholds at 500, 1000, 2000 and 4000 Hz increased significantly (p less than .0001) with increasing PbB for both ears. PbB levels were also significantly related to delays in the age at which children first sat up, walked, and spoke and to the probability that a child was hyperactive. Lead was not related to the probability of a child having a previously diagnosed speech impairment.