Potential neuropsychological profiles in welders occupationally exposed to manganese: an examination of effect size patterns.

This study used effect sizes to examine two recently published articles by Bowler et al. (2003, 2006) that purport to show that welders who had been occupationally exposed to manganese demonstrate a specific pattern of neuropsychological impairment. In the two articles, the welding groups were composed of different participants, but the control group was composed of the same participants in both studies. A similar neuropsychological battery was administered across studies. Effect size differences between welders and controls were quite different across both studies, and the pattern of effect sizes within each study for neuropsychological domains was different. Taken together, these articles do not support the claim that chronic manganese exposure in welders results in a specific and identified pattern of neuropsychological impairment.