Quantifying the Health Impact of “Shelter in Place” Policies from NO2 Emissions: An Empirical Assessments of the West Coast of the United States

Abstract:

California, Washington and Oregon enacted shelter-in-place policies in late March, effectively reducing traffic, and hence, traffic-related air pollution. This unprecedented action creates a natural experiment to observationally quantify the impact of traffic on NO2 emissions, and the consequent health benefits of reduced NO2. We compare NO2 concentrations on the West Coast in April 2020 to emissions April 2019, using data from the Sentinel-5P TROPOMI instrument. Column NO2 measurements in moles/m2 are converted to surface concentrations in ppb using EPA’s ground-based monitoring network. Preliminary analysis shows pronounced decrease over large urban centers (e.g. Los Angeles, San Francisco, Seattle); while a few areas show an increase in NO2. Using BenMAP-CE, we estimate the improvement in respiratory outcomes associated with this reduction in NO2. The results suggest that health impacts from NO2 emissions vary by geographic context, and that regional atmospheric conditions and built environments may drive the variation.