Short- and long-term exposure to particulate matter (PM) pollution is a risk factor for in-hospital stroke-related death, according to a study published in Neurology. Researchers characterized the association between ambient PM of different sizes (PM ≤1 µm in aerodynamic diameter [PM1], PM2.5, and PM10) and in-hospital case fatality among patients with stroke from 2013 to 2019. Seven-day and annual averages of PM prior to hospitalization were estimated. A total of 32,140 in-hospital stroke fatalities among 3.1 million stroke hospitalizations were identified (case fatality rate, 1.03%). Each 10 µg/m3 increase in 7-day (short-term) average exposure to PM was associated with increased in-hospital case fatality, with ORs of 1.058, 1.037, and 1.025 for PM1, PM2.5, and PM10, respectively. For annual averages (long-term), similar but larger ORs were seen (1.240, 1.105, and 1.090, respectively). PM10 was associated with the largest potential reducible fraction in in-hospital case fatality for short- and long-term exposure (10% and 21.1%, respectively) in counterfactual analyses, followed by PM1 and PM2.5.