Epidemiological update on solvent neurotoxicity.

Epidemiological studies of occupational mixed solvent exposure were reviewed for evidence of exposure-related neuropsychiatric disorders, mental symptoms, and neurobehavioral performance. Studies of workers receiving disability pensions found consistent evidence of an increased risk of neuropsychiatric disability among solvent-exposed workers. Study results differed, however, with respect to relations between solvent exposure and specific diagnostic entities. These differences may be attributed to cross-country differences in diagnostic entities and criteria for disability pension eligibility. Psychiatric morbidity studies found no relation between occupational solvent exposure and admission to a hospital for psychiatric illness. Alcohol abuse and solvent exposure in combination seemed to be a risk factor for dementia and cerebral degeneration. Cross-sectional studies supported the hypothesis that occupational, low-level, long-term solvent exposure may cause adverse central nervous system effects. Several studies that used complex measures of lifetime cumulative and average exposure demonstrated significant dose-response relations between exposure, mental symptoms, and neurobehavioral performance. There were discrepancies, however, in the degree of exposure causing these adverse effects. The cumulative findings strongly suggest that occupational solvent exposure may be the cause of mental and cognitive impairment that may become chronic and disabling. The adverse central nervous system effects observed in these studies seemed to occur at exposure levels well below accepted threshold limit values. Lowering these values should be considered.