Irreversible effects of trichloroethylene exposure on the central nervous system.

Mongolian gerbils (Meriones Unguiculatus) were continuously exposed to 320 ppm (1.72 g/m3) of trichloroethylene (TCE) for nine months. During this period the spatial memory of the animals was tested. No major differences were found between the TCE group and the air-exposed control group. Eleven days after the end of TCE exposure, the animals were again tested. Every second day during this test, they were exposed to 2,300 ppm (12.6 g/m3) of 1,1,1-trichloroethane for 6 h. It was found that, on days when exposed to 1,1,1-trichloroethane, the animals previously exposed to TCE made more correct choices in the maze than on days when not exposed, whereas the control group made less. This test was repeated 75 d after the end of TCE exposure. The results were predominantly the same as 11 d after TCE exposure. The results are interpreted as showing that irreversible effects on the central nervous system are caused by exposure to 320 ppm (1.72 g/m3) of TCE during nine months. The effects cannot be directly observed as changes in the behavior of the animals but can be revealed in almost every single animal by treatment with 1,1,1 trichloroethane. The possibility that covert toxicologic effects might exist in humans exposed to volatile solvents and that the effects may be unmasked by alcohol, stress, or age is discussed.