Studies on the Chronic Toxicity (Inhalation) of Wollastonite in Fischer 344 Rats

Abstract

Wollastonite is a naturally occurring calcium metasilicate acicular mineral that is used in a variety of commercial applications and has been proposed as an asbestos substitute for selected products. Male Fischer 344 rats were exposed by inhalation to 10 mg/m³ (360 fibers/cm³) wollastonite (NYAD-G) for 6 h/d, 5 d/wk for 12 or 24 mo. They were compared to untreated chamber controls and positive controls [chrysotile asbestos, 70 mg/m³ (-7000 fibers/cm³) for 12 mo]. Six rats from each exposure group were killed after 3, 12, and 24 mo. The remaining rats were held for lifetime observation (until 90% mortality). The results of this study showed that wollastonite was slightly toxic to the lung, producing an alveolar macrophage response that resolved after exposure ceased. There was no evidence of wohstonite-induced neoplasms, although the chrysotile asbestos administered under similar conditions produced a high incidence of bronchoalveolar carcinomas.