Systemic onset juvenile idiopathic arthritis and exposure to fine particulate air pollution

Fine particulate matter (PM2.5) is a measurable component of ambient pollution, and positive associations of short-term PM2.5 exposure with the clinical presentation of systemic onset juvenile idiopathic arthritis (SJIA) in young children have been described in a regional cohort. Our objective was to further establish associations between short-term pollution exposures and the reported clinical event of SJIA onset in cases residing from multiple metropolitan regions. A case-crossover study design was used to analyse associations of short-term PM2.5 exposures with the event of SJIA symptom onset from cases residing in five metropolitan regions. Time trends, seasonality, month, and weekday were controlled for by matching. Selected exposure windows (to 14 days) of PM2.5 were examined. Positive, statistically significant associations between PM2.5 concentrations and elevated risk of SJIA were not observed. The most positive associations of short-term PM2.5 exposure with SJIA were in children