Kim JH, Hong J, Jung J, et al. - Researchers aimed at ascertaining how meteorological factors and air pollutants affect out-of-hospital cardiac arrest (OHCA) according to seasonal variations. From the Korean nationwide emergency medical service database, they obtained data of 38,928 OHCAs of cardiac origin that occurred within eight metropolitan areas between 2012 and 2016. Observations revealed independent association of particulate matter ≤ 2.5 µm, average temperature, daily temperature range and humidity with OHCA occurrence in a season-dependent manner. Importantly, particulate matter ≤ 2.5 µm alone was noted to be the independent risk factor for OHCA occurrence irrespective of seasonal changes.