Are Cleaning Activities a Source of Exposure to Crystalline Silica in Women with Rheumatoid Arthritis? A Case-control Study

Introduction: Inhalation of crystalline silica (silicon dioxide, SiO) is associated with a wide range of acute and chronic diseases, including rheumatoid arthritis (RA). The objectives of this work were to identify the main sources of exposure to SiO in a series of patients with RA not selected on the basis of their professional activity, compared with a representative sample of the French general population, and to assess the association between silica exposure and disease features.

Methods: The Dust Exposure Life-Course Questionnaire (DELCQ) is a tool that enables retrospective quantification of both occupational and non-occupational lifetime exposure to SiO. DELCQ-previously validated in a large representative sample of the French general population-was administered to 97 consecutive RA patients, and exposure scores were compared between cases and age, gender and smoking status-matched controls (1:4). The main sources of SiO exposure were identified in cases and controls, and source-specific exposure levels were compared. The association between DELCQ scores and disease variables in cases was tested via univariable and multivariable analyses.

Results: In women with RA, the main sources of SiO exposure were cleaning activities and dusty clothes laundry, with higher exposure levels from these sources versus the general population (p<0.005). Across the whole series of RA patients, high SiO exposure was independently associated with mediastinal lymphadenopathy (OR 6.3, 95% CI 1.4 to 27.7).

Conclusion: Cleaning activities and dusty clothes laundry may be underestimated sources of SiO exposure in women with RA.