This study was carried out to make clear the chronic effect of toluene on the peripheral blood and adrenal gland. In this experiment, twenty four rats in growing period were used and divided into four groups. Rats of three groups were exposed to 200, 1000 and 2000 ppm toluene vapour for eight hours a day during 32 weeks respec-tively, and then exposed to 250 ppm benzene vapour for 39 days. Rats of the other one group were used as control and exposed to only 250 ppm benzene.
During the exposure to toluene and benzene vapour, these rats were examined on body weight, erythrocyte counts, hemoglobin contents, hematocrit values, plasma total protein, leucocyte counts, eosinophiles and appearance-ratio of Mommsen's toxic granules. When the exposure to benzene finished, all rats were killed by decapitation, and the internal organs were weighed and examined patho-histologically. The results obtained were as follows.
1. The hematopoietic system showed no remarkable change in this experiment. From this experiment, it seems inappropriate to estimate the toxicity of toluene by the results of blood examination.
2. The values of eosinophile counts in the exposed groups decreased rapidly in the first three weeks, and then showed a gradual increase till the previous values, though the process differed by the concentration of toluene. The weight of adrenal gland per body weight were significantly lighter in the exposed groups than in the control. The patho-histological examination showed the build of the secondary hypofunction of the adrenal cortex. This fact may suggest that the function of diencephalon-hypophysis-adrenal cortex system are suppressed by the chronic toluene exposure.
3. From these results, the author thinks that the present value of MAC of toluene (200 ppm) should be reconsidered in the near future.
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