DECREMENTS IN NEUROBEHAVIORAL PERFORMANCE ASSOCIATED WITH MIXED EXPOSURE TO ORGANIC AND INORGANIC LEAD

In 1990, 222 current employees of a chemical facility in the eastern U nited States that manufactured tetraethyl lead were administered a neu robehavioral test battery, tests of olfactory function and peripheral vibration threshold, and questionnaires that assessed neuropsychiatric symptoms. A cumulative variable of exposure to inorganic and organic lead was derived from 12 years of personal industrial hygiene sampling data and an occupational history interview that assessed work in each of 29 exposure zones in the lead area. The range of assigned exposure intensities in these 29 zones was 4-119 mug/m3 for organic lead and 1 -56 mug/m3 for inorganic lead. Cumulative lead exposure and exposure d uration were defined as categorical variables (four groups) in multipl e linear regression models. The adjusted mean differences in neurobeha vioral test scores were estimated by comparing the average scores of t he moderate, high, and highest exposure groups with the low exposure ( reference) group. After adjustment for premorbid intellectual ability, age, race, and alcohol consumption, neurobehavioral test scores were poorer as measures of both cumulative lead exposure and exposure durat ion increased; many of the associations evidenced dose-response relati ons. Associations were observed in most cognitive and functional domai ns tested, but were most common in two domains: manual dexterity and v erbal memory/learning. On the affected neuropsychologic measures, the groups with the highest exposure averaged scores 5-22% lower than thos e of the reference groups. Overall, the data revealed generally consis tent and coherent associations between two measures of lead exposure a nd poorer neurobehavioral test performance.