Early workplace exposure to lead may affect cognitive abilities, study finds
Researchers from the Graduate School of Public Health and the School of Medicine at the University of Pittsburgh found that both the developing brain and the aging brain can suffer from lead exposure. For older individuals, a buildup of lead from earlier exposure in the workplace may be enough to result in greater cognitive problems after age 55. The study appeared in the January issue of Neuropsychology, a publication of the American Psychological Association.
For the report, researchers followed up on a 1982 lead occupational study, which assessed the cognitive abilities of 288 lead-exposed and 181 non-exposed male workers in eastern Pennsylvania. The lead-exposed workers came from three lead battery plants while the unexposed workers made truck chassis at a nearby location. At both points in time, all the workers were given the Pittsburgh Occupational Exposures Test battery, which includes measures of five primary cognitive domains -- psychomotor speed, spatial function, executive function, general intelligence, and learning and memory.
In 1982, lead-exposed workers were found to have an average blood lead level of 40 micrograms per deciliter, well above normal. Pennsylvania workers found to have 25 micrograms per deciliter or more must be taken off the job. That same year, the unexposed workers had an average blood level of 7.2 micrograms per deciliter, within normal limits.
In 2004, the current study followed up with 83 of the original lead-exposed workers and 51 of the original non-exposed workers. Researchers measured lead levels in their blood and cumulative lead levels through special X-rays of the lower leg bone. Researchers also readministered the test battery to assess cognitive performance relative to both measures of lead. Among the lead-exposed workers, men with higher cumulative lead had significantly lower cognitive scores. The linkage was more significant in the older lead-exposed men, of at least age 55.
"Increased prevention measures in work environments will be necessary to reduce [lead exposure] to zero and decrease risk of cognitive decline," the authors wrote.
March 5, 2009
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