Neurotoxic effects of organic solvents in exposed workers: two controlled follow-up studies after 5.5 and 10.6 years.

The findings of acute and/or chronic central and peripheral neurotoxic effects of organic solvents in workers from a previous controlled cross-sectional study (65 exposed and 33 unexposed) were re-assessed to ascertain whether the neurotoxic symptoms and signs had become chronic. These follow-ups were performed 5.5 years later by occupational medical and clinical neurological examination (59 exposed and 30 unexposed) and again 10.6 years later by a mailed questionnaire (53 exposed and 30 unexposed). Both follow-ups revealed more acute neurotoxic symptoms in the exposed workers than in the unexposed workers, but fewer than previously, and indeed, the current exposure to solvents had been reduced. However, at both follow-ups, the exposed workers showed significantly more symptoms of chronic encephalopathy, in particular, memory and concentration impairment. These latter symptoms had also significantly worsened in the workers who were still being exposed, while they were presently unchanged in the previously exposed workers who had been free of exposure for 6.6 years at the latter follow-up. On the other hand, symptoms of chronic encephalopathy had not appeared in the unexposed group. Among workers, both still and previously exposed, there were also social consequences in the form of occupational disqualification. According to the findings, long-term occupational exposure to organic solvents in concentrations that are not unusual at workplaces may lead to development of chronic neurotoxic symptoms.