Reductions in mortality resulting from reduced air pollution levels due to COVID-19 mitigation measures

To control the novel coronavirus disease (COVID-19) outbreak, state and local governments in the United States have implemented several mitigation efforts that resulted in lower emissions of traffic-related air pollutants. This study examined the impacts of COVID-19 mitigation measures on air pollution levels and the subsequent reductions in mortality for urban areas in 10 US states and the District of Columbia. We calculated changes in levels of particulate matter with aerodynamic diameter no larger than 2.5 μm (PM(2.5)) during mitigation period versus the baseline period (pre-mitigation measure) using the difference-in-difference approach and the estimated avoided total and cause-specific mortality attributable to these changes in PM(2.5) by state and district. We found that PM(2.5) concentration during the mitigation period decreased for most states (except for 3 states) and the capital. Decreases of average PM(2.5) concentration ranged from 0.25 μg/m(3) (4.3%) in Maryland to 4.20 μg/m(3) (45.1%) in California. On average, PM(2.5) levels across 7 states and the capital reduced by 12.8%. We estimated that PM(2.5) reduction during the mitigation period lowered air pollution-related total and cause-specific deaths. An estimated 483 (95% CI: 307, 665) PM(2.5)-related deaths was avoided in the urban areas of California. Our findings have implications for the effects of mitigation efforts and provide insight into the mortality reductions can be achieved from reduced air pollution levels.