Occupational Exposures and Smoking in Eosinophilic Granulomatosis With Polyangiitis: A Case–Control Study

Objective: Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare antineutrophil cytoplasmic antibody (ANCA)–associated vasculitis. Environmental agents and occupational exposures may confer susceptibility to EGPA, but data are scarce. This study was undertaken to investigate the association between occupational exposures (e.g., silica, farming, asbestos, and organic solvents) and other environmental agents (e.g., smoking) and the risk of EGPA. Methods: Patients with newly diagnosed EGPA (n = 111) and general population controls (n = 333) who were matched for age, sex, and geographic area of origin were recruited at a national referral center for EGPA. Exposures were assessed using a dedicated questionnaire administered by a specialist in occupational medicine, under blinded conditions. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated. Results: Exposures to silica (OR 2.79 [95% CI 1.55–5.01], P = 0.001), organic solvents (OR 3.19 [95% CI 1.91–5.34], P < 0.001), and farming (OR 2.71 [95% CI 1.71–4.29], P < 0.001) were associated with an increased risk of EGPA. Co-exposure to silica and farming yielded an OR of 9.12 (95% CI 3.06–27.19, P < 0.001), suggesting a multiplicative effect between these 2 exposures. Smoking (current and former smokers combined) was significantly less frequent among patients with EGPA compared to controls (OR 0.49 [95% CI 0.29–0.70], P < 0.001). The pack-year index was also lower among patients with EGPA (OR 0.96 [95% CI 0.94–0.98], P < 0.001). The association of silica and farming was primarily aligned with ANCA-positive EGPA, while the association of smoking status and organic solvents was primarily aligned with ANCA-negative EGPA. Conclusion: The environment can influence susceptibility to EGPA. Exposure to silica, farming, or organic solvents is associated with an increased risk of EGPA, while smoking is associated with a lower risk. These exposures seem to have distinct effects on different EGPA subsets.