Effects of low-dose inhalation of three chlorinated aliphatic organic solvents on deoxyribonucleic acid in gerbil brain.

Young adult Mongolian gerbils (Meriones ungiculatus) were continuously exposed by inhalation to 1,1,1-trichloroethane at the Swedish occupational exposure limit (70 ppm), to methylene chloride at three times (210 ppm) the Swedish occupational exposure limit (70 ppm), and to perchloroethylene at three times (60 ppm) the Swedish occupational exposure limit (20 ppm), for three months, followed by a four-month postexposure solvent-free period. The concentrations of deoxyribonucleic acid (DNA) were then determined in different regions of the gerbil central nervous system. It was observed that the DNA concentrations in several brain regions were decreased in the exposed animals. It was found that 1,1,1-trichloroethane induced these alterations in many more brain areas at its Swedish occupational exposure limit than the other solvents studied at threefold their Swedish occupational exposure limits. The results suggest that all the solvents decrease cell density by inhibiting the slow acquisition of DNA or by inducing cell death in some sensitive brain areas and that 1,1,1-trichloroethane should not be regarded as harmless as previously stated.