Evaluation of a possible styrene-induced damage to the haematopoietic tissues in the rat.

The aim of this study was to determine a possible risk of malignancies in the haematopoietic tissues of rats treated with styrene, either by injection or by inhalation. Two experiments were carried out: in the first (acute treatment), 12 male rats were treated intraperitoneally with different doses of styrene (40 mg/Kg/2 ml/die and 400 mg/Kg/2 ml/die) for 3 consecutive days. A control group (6 rats) was administered corn oil 2 ml/kg/die for the same period of time. In the second experiment (chronic treatment), 12 male rats were exposed to styrene inhalation (300 ppm/6 hour day/5 days a week for 2 weeks) for 3 weeks and sacrificed at the end of the experiment or after 3 weeks. The rats treated with the highest doses of styrene by injection (400 mg/kg, acute treatment) showed a hyperactivity of the erythropoietic series while the granulocytopoietic series was at the normal value. The rats exposed to 300 ppm styrene vapour (chronic treatment) showed a statistically significant increase in erythropoietic cells (basophilic, polychromatophilic and orthochromatic erythroblasts). A temporary block of immature cells of the granulocytopoietic series was also evident. These results indicate an alteration of the erythropoietic series independently of method of administration. However, these findings do not show a possible risk of preleukemic or leukemic disorders in rats exposed or treated with styrene.