Beryllium carcinogenesis. I. Inhalation exposure of rats to beryllium sulfate aerosol.

Abstract

One hundred fifty rats (with equal number of controls) were exposed to the inhalation of beryllium sulfate aerosol at a mean atmospheric concentration of 34.25 µg of Be/cu m, and sacrificed in monthly groups during 72 weeks of exposure. Average lung weight towards the end of exposure was 4.25 times normal. Histopathologic examination disclosed 2 gradually developing pathologic processes: ( a ) an inflammatory response chiefly characterized by marked accumulation of histiocytic elements forming clusters of macrophages in the alveolar spaces; and ( b ) a proliferative response, progressing from early epithelial hyperplasia of the alveolar surfaces, through metaplasia and anaplasia, to lung cancer. The first tumors were found after 9 months of exposure, the incidence rapidly rising, and reaching 100% at 13 months ( vs. 0% in controls). All tumors appeared to be alveolar adenocarcinomas, in some instances with focal intermixture of other types. Out of 56 tumors studied, 3 reached a very large size comparatively early. Females appeared to be more vulnerable to the exposure than males in terms of attritional mortality and body weight loss.