New York on PAUSE and traffic-related air pollution: quantifying diurnal changes in NO2 due to COVID-19 stay-at-home orders

Abstract

BACKGROUND/AIM: Policy responses to the COVID-19 pandemic, including the NY on PAUSE stay-at-home order, substantially reduced traffic and traffic-related air pollution (TRAP) in New York City (NYC). We evaluated the magnitude of TRAP decreases and identified modifying factors such as weekend/weekday, road proximity, location, and time of day—important variables for planning future traffic interventions. METHODS: Hourly nitrogen dioxide (NO₂) concentrations from 1/1/2018 through 6/8/2020 were obtained from the Environmental Protection Agency’s Air Quality System for six monitors in the NYC area. We used an interrupted time series design to determine the impact of NY on PAUSE on NO₂, using a mixed effects model with random intercepts for monitor location, adjusted for meteorology and long-term trends. We evaluated effect modification by weekend/weekday, road proximity, and time of day in stratified models, and location by including random slopes for each monitor. RESULTS: NO₂ concentrations decreased due to NY on PAUSE by -3.2 ppb (95% confidence interval [CI]: -3.5, -3.0), on average. We found no evidence for modification by weekend/weekday, but found greater decreases in NO₂ at non-roadside monitors. We found weak evidence for modification by location. For time of day, we found the largest decreases for 5 am (-4.5 ppb, 95% CI: -5.7, -3.3) through 7 am (-4.0 ppb, 95% CI: -5.2, -2.8), followed by 6 pm and 7 pm (-3.7 ppb, 95% CI: -4.8, -2.6 and -4.8, -2.5, respectively), while the smallest decreases occurred from 10 pm (-2.3 ppb, 95% CI: -3.5, -1.1) to 1am (-1.9 ppb, 95% CI: -3.1, -0.7). CONCLUSIONS: NY on PAUSE’s impact on TRAP varied greatly diurnally. For future large-scale traffic interventions, our findings suggest that blanket policies not targeting specific time windows will likely result in larger NO₂ decreases during rush hour windows. KEYWORDS: nitrogen dioxide; traffic-related air pollution; pandemic; policy; New York City