Effects of non-mining occupational silica exposure on proportional mortality from silicosis and systemic sclerosis.

Abstract

Studies report an association between mining related silica exposure and systemic sclerosis (SSc). This study evaluated associations between non-mining occupational silica exposure, silicosis, and SSc. The US National Institute for Occupational Safety and Health (NIOSH) recently identified 36 non-mining occupations in which workers face the "potential for substantial silica exposure." Data from death certificates in 25 US states during 1985-92 were analyzed to determine whether excess proportional mortality from silicosis or SSc occurred among those who worked in these occupations. Proportional mortality from silicosis in the occupations identified by NIOSH was significantly elevated among men [proportional mortality ratio (PMR) = 1.4; p < 0.0001] and women (PMR = 7.1; p = 0.002). The proportional mortality from SSc was not elevated among men (PMR = 1.0; p = 0.90) and was lower than expected among women (PMR = 0.8; p = 0.39). When cited on death certificates, the non-mining occupational categories identified by NIOSH reflect prior silica exposure; however, no evidence of excess mortality from SSc was observed in these occupations. The reported increased frequency of SSc among miners may depend on a level or mode of silica exposure unique to the mining industry.