Biochemical effects of subacute formic acid vapor exposure.

Male Wister rats were exposed to 20 ppm of formic acid vapor for three and eight days, 6 h daily. Analyses for neurochemical effects and effects on drug-metabolizing enzymes in liver and in kidneys revealed significant changes. Cerebral glutathione increased initially above the control range and decreased at eight days while lysosomal acid proteinase increased at the same time. Liver ethoxycoumarin deethylase increased somewhat above the control level at the end of the exposures while hepatic glutathione decreased. Kidney cytochrome P-450 was below the control range at all times as was its glutathione content. Formic acid is an end-product of methanol metabolism as well as a thermal degradation product of polyethylene plastics, and therefore, its metabolic effects may play a role in methanol or polyethylene fume exposures.