Comparative Inhalation Hazards of Titanium Dioxide, Synthetic and Natural Graphite.
Thomson-SA; Burnett-DC; Carpin-JC; Bergmann-JD; Hilaaki-RJ
NIOSH 1990 Nov:1277-1283
The inhalation toxicity of titanium-dioxide (13463677) (TiO2) and synthetic (SG) and natural graphite (7782425) (NG) were investigated in rats. Male Fischer-344-rats were exposed to 0 or 100mg/m3 TiO2, SG, or NG dust 4 hours daily for 4 consecutive days in an inhalation chamber and observed for clinical signs of toxicity. Twenty four hours or 14 days after the last exposure the rats were killed and the lungs were removed and lavaged. Total and differential lavage fluid cellularity was determined. The lavage fluid was assayed for alkaline-phosphatase (ALP), beta-glucuronidase (bG), lactate- dehydrogenase (LDH), and protein. No signs of clinical toxicity were observed. All rats gained weight at the same rate. All dusts caused a significant increase in lavage fluid protein concentration 24 hours post exposure. By 14 days the protein concentrations had returned to the control value. Both graphite dusts induced significant increases in lavage fluid bG and ALP 24 hours after exposure ended. Lavage fluid LDH activity was significantly increased by TiO2 at this time. Fourteen days later all enzyme activities had returned to the control values. NG caused a significant increase in total lavage fluid cells 14 days postexposure and an increase in white blood cell counts at 24 hours. All dust increased the influx of polymorphonuclear leukocytes into the lavage fluid; NG causing the largest increase. NG, SG, and TiO2 caused a mild brown to black pigmentation of the lungs and alveolar macrophages. Epithelial hyperplasia of the alveoli and terminal bronchioles was noted in three of 20 rats exposed to SG and one of 20 exposed to TiO2. The authors conclude that repeated inhalation exposure of Fischer-344-rats to 100mg/m3 TiO2, SG, and NG dusts causes a mild inflammatory response 24 hours post exposure.
Mineral-dusts; Laboratory-animals; In-vivo-studies; Inhalation-studies; Physiological-chemistry; Enzyme-activity; Lung-tissue; Lung-cells;
Proceedings of the VIIth International Pneumoconioses Conference