The relationship between blood lead levels and neurobehavioral test performance in NHANES III and related occupational studies.
Krieg-EF; Chrislip-DW; Crespo-CJ; Brightwell-WS; Ehrenberg-RL; Otto-DA
Public Health Rep 2005 May-Jun; 120(3):240-251
The goals of this study were two-fold: (1) to assess the relationship between blood lead levels and neurobehavioral test performance in a nationally representative sample of adults from the third National Health and Nutrition Evaluation Survey and (2) to analyze the results from previously published studies of occupational lead exposure that used the same neurobehavioral tests as those included in the survey. Regression models were used to test and estimate the relationships between measurements of blood lead and performance on a simple reaction time, a symbol-digit substitution, and a serial digit learning test in adults aged 20-59 years who participated the survey. Mixed models were used to analyze the data from the occupational studies. The blood lead levels of those participating in the survey ranged from 0.7 to 41.8 ug/dl. The estimated geometric mean was 2.51 ug/dl, and the estimated arithmetic mean was 3.30 ug/dl. In the survey, no statistically significant relationships were found between blood lead concentration and performance on the three neurobehavioral tests when adjusted for covariates. In the occupational studies, the groups exposed to lead consistently performed worse than control groups on the simple reaction time and digit-symbol substitution tests. Conclusions. The results from the survey and the occupational studies do not provide evidence for impairment of neurobehavioral test performance at levels below 25 ug/dl, the concentration that the Centers for Disease Control and Prevention define as elevated in adults. The average blood lead level of the exposed groups in the occupational studies was 41.07 ug/dl, less than 50 ug/dl, the minimum concentration that the Occupational Safety and Health Administration requires for medical removal from the workplace. Given the evidence of impaired neurobehavioral performance in these groups, the 50 ug/dl limit should be reevaluated.
Blood-analysis; Lead-compounds; Sampling; Sampling-methods; Behavioral-tests; Behavioral-testing; Occupational-exposure; Models; Demographic-characteristics; Age-factors; Age-groups; Exposure-levels; Exposure-assessment
Edward F. Krieg Jr, Ph.D, National Institute for Occupational Safety and Health, Robert A Taft Laboratories, 4676 Columbia Parkway, MS C-22, Cincinnati, OH 45226
Public Health Reports