Mortality among Persons Mining and Milling Attapulgite Clay

Abstract

Abstract To evaluate the possible carcinogenicity and fibrogenicity of occupational exposure to a non-asbestos mineral fibre, a cohort of 2302 males employed for at least one month between 1940 and 1975 at an attapulgite (clay fibre) mining and milling facility was followed through 1975. Among those successfully traced (94%), 317 had died compared to 388.1 expected deaths based on age-, calendar year-, and race-specific rates for United States males. A significant deficit of mortality (SMR = 43, 90% CI 23–76) due to nonmalignant respiratory disease (NMRD) was observed. A marked deficit of NMRD was seen regardless of induction-latency period, or duration employed. A statistically significant excess of mortality due to lung cancer was observed among whites (SMR = 193, 90% CI 121–293); a deficit occurred among nonwhites (SMR = 53, 90% CI 21–112). Lung cancer risk in either race was not altered substantially with induction-latency period or duration employed. The findings for NMRD are consistent with the hypothesis that short fibres ( μ m in length) are not fibrogenic.