Neuropsychological effect of lead in occupationally exposed workers: a critical review

In their discussion of field testing of health effects of environmental and industrial toxins, Gullion and Eckerman make the following observations which can be applied to the current literature survey: "The general inattention to methodological consistency makes it difficult to integrate the research to date into a clear picture of what is known and not known about the effects of toxic substances on human behavior. In view of the variation in methods of subject selection, measurement, and statistical analysis, the completion of a series of studies of a particular toxic substance does not assure that there has been a concurrent accumulation of reliable knowledge about the effects of that substance. Apparent replications or failures to replicate a significant relationship must be evaluated carefully, since different studies may have measured different things in different populations." Therefore, the issue of psychological and neuropsychological effects of low-level lead exposure in adults remains to be resolved in the studies reviewed. The methodologies were so varied and the cultures in which the studies were conducted so diverse that it is impossible to generalize across findings. For example, studies were conducted in the U.S., Denmark, Sweden, Finland, and Australia. Although, in some instances, equivalent versions of neuropsychological and psychological tests were used, this was generally not the case. Nevertheless, a few general statements can be made. Studies that have been carried out in recent years are beginning to pay attention to more methodology and therefore do a much better job of controlling for possible confounding variables. Also, their statistical methods are more sophisticated and reporting techniques are superior to the earlier investigations in this area. The issue of whether current blood lead levels or cumulative levels are preferable is still unresolved with regard to the relationship of neuropsychological impairment. In the area of psychosocial functioning, there appears to be at least some evidence to support the observation that increased irritability and fatigue may lead to the interpersonal problems noted in various studies. However, this observation may be related to other factors which have not been controlled for, such as the workers' attitudes toward their job, level of motivation, and overall level of mental health. With regard to neuropsychological functions, there is some suggestive preliminary evidence for subtle changes in the ability to process information quickly.(ABSTRACT TRUNCATED AT 400 WORDS)