Background/Purpose: Exposure to fine particles (PM_2.5) has been associated with numerous health effects including with autoimmune rheumatic diseases (SARDs). While PM_2.5 are composed of various material that are likely to present different toxicity, associations between PM_2.5  components and health outcomes remains largely unexplored. Investigate the relationships between long-term exposure to PM_2.5 and its components and the onset of new cases of SARDs in adults of Quebec.

Methods: We used a retrospective open cohort of the adult population of the province of Quebec without SARD in the previous four years, created with administrative health data from April 1, 2000 to December 31, 2019. SARD cases included lupus, dermatopolymyositis, systemic sclerosis, Sjogren syndrome, fibrosclerosis, diseases of connective tissue. Mean annual levels of PM_2.5 and its components, estimated with satellite aerosol optical depth and various models, were attributed to the six digit postal code of each participant; the components included black carbon (BC), mineral dust, sea salt (SS), nitrate, SO₄², NO₃^–, organic matter (OM). Cox models with adjustments for age, sex, year, socioeconomic status, Local Service Network and urban/rural regions were generated for PM_2.5 and its seven components. Quantile-based g– computation with similar adjustments was used to estimate the marginal hazard ratio (HR) for the mixture of PM_2.5 components.

Results: 7,482,397 individuals were analyzed, representing 98,039,304.7 person-years; 55,267 incident cases were observed. In proportion, OM was the main component of PM_2.5. The adjusted HR for SARDs was 1.022 per increase of an interquartile range of PM_2.5 (95% confidence interval (95%CI): 0.985 – 1.060). Estimates of associations for the components were positive, except for SS and SO₄^2-, although their 95%CI all included unity. Based on the quantile g-calculation, the HR of SARD was slightly positive (HR per one-decile increase in the PM_2.5 components: 1.01; 95% CI: 1.00 – 1.02). 

Conclusion: This large-scale cohort study suggests that annual exposure to PM_2.5 and the mixture of its components may be associated with the incidence of certain SARDs.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/association-between-long-term-exposure-to-fine-particles-and-its-components-and-the-onset-of-systemic-autoimmune-rheumatic-diseases-in-quebec/