New research points to another potential factor that might play into a person’s risk of death due to Covid-19: prolonged exposure to high levels of air pollution. In a study published Wednesday in Science Advances, researchers estimated long-term air pollution levels for more than 3,000 U.S. counties, which also had Covid-19 mortality data available through June 2020. While the study wasn’t designed to show whether pollution exposure directly affected a person’s risk of death due to Covid-19, it did demonstrate an association between increased pollution levels and higher Covid-19 death tolls.