It is well understood that adverse health effects—lung cancer, respiratory disease, cardiovascular disease, asthma, premature mortality—can be caused by nitrogen dioxide (NO2) exposure, and a variety of biological mechanisms are thought responsible. NO2 is a traffic-related air pollutant, meaning most of its anthropogenic emissions come from vehicle combustion and industry. The COVID-19 pandemic brought about large-scale changes in human mobility. Due to the impact of lockdown on these emission sources, many hypothesized pollutant emissions would decrease.

Dr. Himes and I wanted to explore whether these predicted trends would apply on a global scale. Specifically, we studied NO2, which, because of its short lifetime in the air, can be taken alone as a predictor of decreased emissions. To achieve this aim, we retrieved a variety of data, including both satellite NO2 and ground-level NO2, COVID-19 counts, country demographics, and COVID-19 lockdown policy indices. We modeled the data in an R software environment with an interrupted time series analysis, which allowed us to quantify the difference in NO2 over lockdown and determine if this difference is significant when considering seasonal trends and historical data. Preliminary results show that the major decrease in NO2 in China seemed to drive the worldwide trend. We predict that making policy decisions informed by the relationship between different lockdown measures and air quality on a country-by-country basis can address environmental health concerns moving forward.