Fig 2. Flexible association between short-term exposure to PM_2.5 and violence cases.

Each Blue and Green dashed lines indicate WHO: World Health Organization air quality guidelines (daily average PM_2.5: 15 μg/m³), NAAQS: National Ambient Air Quality Standards (daily average PM_2.5: 35 μg/m³) in the United States, and KAS: Korean Air Quality Standards (daily average PM_2.5: 35 μg/m³), respectively. A conditional logistic regression model, adjusted for holiday and daily mean temperatures, within a time-stratified case-crossover design, was used to estimate odds ratios and 95% confidence intervals.