Fine particulate matter air pollution and anti-nuclear antibodies

Air pollution has been increasingly linked to systemic autoimmune rheumatic diseases (SARDs), but studies regarding fine particulate matter (PM2.5) and SARD-related serological biomarkers are limited. We aimed to assess the association between exposure to ambient PM2.5 and ANA in the general population.

Serum samples of 3548 subjects (collected between 2010 and 2013) were randomly selected from the Ontario Health Study general population cohort. We examined ANA titres using indirect immunofluorescence assay on HEp-2 cells. Annual average ambient PM2.5 levels (estimated by satellite images and a chemical transport model) for the 5-year period before sera collection were assigned based on subjects' six-character residential postal codes. We used multivariable logistic regression models to compute odds ratios (ORs) for ANA positivity by separately setting ambient PM2.5 exposure as a continuous and a categorical variable, adjusting for basic socio-demographic factors, smoking status and urban-rural status.

Comparing the highest vs lowest quartile of PM2.5 exposure, the ORs for ANA titres ≥1:640 and ≥1:1280 were 1.46 (95% CI: 1.02, 2.10) and 1.54 (95% CI: 1.06, 2.60) respectively. Although ORs were also positive for lower titres (i.e. ≥1:160 and ≥1:320), their CIs included unity. When PM2.5 was set as a continuous variable, the OR (always >1.00) was increased as the ANA titre increased but CIs always contained unity at any titre thresholds.

PM2.5 exposure was associated with ANA positivity at high titres. This strengthens the argument for systemic immune system effects of air pollution, which could in turn lead to autoimmune diseases.