Wegener’s granulomatosis and environmental factors in Western Montana

The objective of our study was to determine whether exposure to silica or other environmental factors is associated with developing Wegener’s granulomatosis (WG), in a geographically isolated region of Western Montana. We sought to identify and interview all cases of WG diagnosed during 1993-2006 among residents of a ten-county region of Western Montana, as well as a group of demographically similar controls (n=39) without autoimmune disease. In the interview, we ascertained occupational silica and other exposures (metals, solvents, pesticides, tobacco). We enumerated 32 cases of WG, of whom 27 were included in the case-control study. Overall, a history of silica exposure was not associated with WG (OR = 0.68, 95% CI: 0.13-3.27), although there was a suggestion of increase in risk among persons with relatively recent (OR=2.67, 95% CI: 0.54-17.2), heavy (OR=1.82, 95% CI: 0.09-112.9), and prolonged (OR=1.53, 95% CI: 0.16-20.0) exposures. A history of having worked in the mining industry was associated with WG (six cases including three with no silica exposure, zero controls, lower 95% CI: 1.53). Risk was not associated with occupational or aerial pesticide exposure, but with residential rodenticide use (OR=12.15, 95% CI: 1.54-552). Occupational exposure to metals or solvents was not associated with WG, nor was a history of cigarette smoking. Results of earlier studies of WG support the hypothesis that silica exposure adversely influences the risk of developing WG. Our small study of WG failed to identify an association with silica overall, but the results are compat­ible with an increased risk in persons with relatively heavy, prolonged, and/or recent exposure.