Impact of wildfires and PM _2.5 on ST-elevation acute coronary syndrome in Rosario City: a case-crossover study

We conducted a modified case-crossover study to examine whether wildfires in the Paraná River Delta departments surrounding Rosario, Argentina, during 2021-2022 increased PM₂.₅ concentrations in this city and if this rise subsequently elevated the risk of ST-elevation myocardial infarction (STEMI). We first observed that daily PM₂.₅ levels in Rosario were significantly higher on wildfire days compared to non-wildfire days (34 µg/m³ vs. 25.75 µg/m³, <i>p</i> < 0.01). In the case-crossover analysis, we found that the odds of STEMI were significantly higher on days when PM₂.₅ concentrations exceeded 20 µg/m³ (OR 2.2 [95% CI 1.2-4.2, <i>p</i> = 0.02]). Additionally, the odds of STEMI increased with higher PM₂.₅ concentrations, with a significant difference when comparing the first and fourth quartiles concentration (OR 1.76 [95% CI 1.06-2.92, <i>p</i> = 0.03] and OR 2.02 [95% CI 1.25-3.27, <i>p</i> < 0.01], respectively). In conclusion, wildfires in the surrounding departments of Rosario City in the Paraná River Delta led to elevated PM₂.₅ levels, and this increase was associated with a higher risk of STEMI hospital admissions.