Mice were exposed to toluene vapor at 1, 10, 100 and 1, 000ppm for six hours daily over a period of 20 days. Observations were made on the animals' wheel-turning activity during exposure and on the findings of peripheral blood and the bone marrow. In wheel-turning activity, all exposed groups showed less cumulative rounds than the control group. The group of 1 ppm ten days after exposure and the other exposed groups 6 to 8 days after exposure tended to show less rounds than the control group. Regarding peripheral blood findings, the groups of 100 ppm and 1, 000 ppm showed a decrease in red cell count. Each group of 10, 100 and 1, 000 ppm showed a decrease in thrombocyte count. All exposed groups showed an increase in white cell count in the midway of experiments and afterwards showed a recovery except the group of 1, 000 ppm. Regarding the bone marrow, the group of 1, 000 ppm showed a trend of hypoplasia and no other exposed groups showed remarkable changes. From the above findings of peripheral blood and the bone marrow, the extent of disturbances in toluene exposure seemed slighter than that in benzene exposure. It was revealed, however, that exposure to as low as 1 to 100 ppm of toluene influenced mice's spontaneous activity. In Japan, from an industrial health view point, 100 ppm has been recommended to be allowable limits for toluene in workplace air. The present authors' experimental data advocate still lower allowable limit.
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