Clinical course of neuropsychological functioning after chronic exposure to organic and inorganic lead.

This case series describes the clinical course (12- to 28-month follow-up) of neuropsychological functioning in 23 workers who had chronic occupational exposure to a mixture of organic and inorganic lead. Significant improvement in performance was seen in 123 tests and deterioration in 323 tests. However, there was no significant change in the majority of tests (1923). Tests that showed deterioration were all tests of psychomotor/motor speed. In addition, 10 of 13 workers who completed a symptom checklist twice reported more frequent physical, cognitive, and affective symptoms at follow-up. This increase in symptoms was associated with psychomotor/motor slowing as compared to initial test performance. Many workers subjectively reported an increased frequency of memory and concentration problems at follow-up, although this change could not be documented objectively. Individual worker demographic and exposure characteristics were not predictive of changes in neuropsychological performance at retest. We propose a psychosocial mechanism to explain the increase in symptom severity and the psychomotor/motor slowing because environmental levels of lead declined during the inter-test interval.