Human solvent exposure. Factors influencing the pharmacokinetics and acute toxicity

The purpose of this review has been to discuss human and environmental factors which may influence the acute irritative and neurotoxic effects of organic solvents. The review is based on a field study and on four human experimental studies. Several studies have shown that printers and other workers exposed to mixtures of solvents experience an increased frequency of work related irritative and neurological symptoms although the exposure has been far below the occupational exposure limits. A series of controlled human exposure studies was carried out. Different groups of persons were exposed to the most frequent solvent, toluene. Toluene in alveolar air and the urinary excretion of the metabolites were measured and the acute effects of toluene were assessed by the performance in a series of test of the perceptual and psychomotor functions as well as a standardized registration of annoyance and symptoms. The pharmacokinetics of toluene is complex and there is a large individual variation in the excretion of the metabolites. This variation can only to a limited extend be related to known variables. Intake of alcohol during exposure inhibits the metabolism of toluene and increases the internal dose. Normal therapeutic doses of cimetidine or propranolol have no measurable effect on toluene metabolism. Exposure to 100 ppm during 7 h causes irritation in the eyes and airways as well as feeling of intoxication, dizziness, and headache. There are signs of impairment in the performance in test concerning visual perception, colour vision, vigilance as well as the psychomotor functions. However, the influence on the performance tests was not seen in all studies. Variations in the air concentration of toluene with peaks op to 300 ppm causes fluctuation in the alveolar concentrations, but no acute effect of these peaks or of increased physical activity during exposure could be detected. However, the importance of peek concentrations and of workload for the development of chronic solvent encephalopathy is still unknown. The influence of a 9-25 years occupational exposure to solvents was investigated. A group of printers occupationally exposed to mixtures of solvents were compared with a matched unexposed control group. There was no difference between printers and controls in the performance in the psychological test, but in two of the tests there were tendencies to increased sensitivity to toluene in the group of printers. It is concluded that exposure to toluene corresponding to the occupational limit in several countries cause irritative and prenarcotic symptoms and possibly a lowered performance.(ABSTRACT TRUNCATED AT 400 WORDS)