PM2.5 and Ozone Air Pollution Levels Have Not Dropped Consistently Across the US Following Societal Covid Response

Abstract

<p>Analysis of a large national dataset of fine particulate matter (PM2.5) and ozone air pollution from the US Environmental Protection Agency indicate opposing differences in average concentrations during the covid response period, relative to expected levels. These are the two most important pollutants in terms of public health impacts and regulatory non-attainment in the US. Post-covid response, average PM2.5 levels are slightly higher (~6%) than expected; average ozone levels are slightly lower (~5%). The size of post-response ozone anomaly has decreased with time and by week 6 after the first stay-at-home order was enacted (April 29- May 5, 2020), ozone levels were higher than expected. In addition, no individual US state had lower-than-expected PM2.5 and ozone for all weeks post- covid response. Two non-covid factors, meteorology and regional transport, do not fully explain observed trends. These findings are unexpected given the large reduction in many household’s activities associated with “stay at home” and other covid responses. We hypothesize that this result partly arises from the fact that ozone and the majority of PM2.5 are secondary pollutants formed in the atmosphere from emissions from many sources (i.e., not just traffic). Preliminary analysis of nitrogen dioxide (NO2) data in a few cities reveals substantially lower-than-expected (~30%) concentrations post-covid. NO2 is a primary pollutant and is much more strongly associated with traffic than PM2.5 or ozone. </p><p><br></p>

UK surface NO2 levels dropped by 42 % during the COVID-19 lockdown: impact on surface O3

“…In the USA one study using EPA data showed a mean decrease of 30% of NO2 in urban areas of Seattle, Los Angeles and New York during the lockdown. The study did not show any consistent change in O3 levels (Bekbulat et al, 2020).…”

Impacts of the COVID-19 responses on traffic-related air pollution in a Northwestern US city

“…Satellite NO 2 data suggested that Western Europe and major Northeastern US cities experienced 20–38% NO 2 decreases in 2020 relative to the same period in 2019 although Iran, a region strongly affected by COVID-19, did not show clear evidence of lower NO 2 concentrations ( Bauwens et al, 2020 ). In the US, preliminary results of an ongoing study utilizing daily PM 2.5 and O 3 data obtained from US Environmental Protection Agency indicate that PM 2.5 levels were about 10% higher than expected while O 3 levels were about 7% lower than expected during the post-SHO period compared to the same period in historical years ( Bekbulat et al, 2020 ). Additionally, preliminary analysis of this study shows that NO 2 levels in Seattle were 20% lower than expected ( Bekbulat et al, 2020 ).…”

“…In the US, preliminary results of an ongoing study utilizing daily PM 2.5 and O 3 data obtained from US Environmental Protection Agency indicate that PM 2.5 levels were about 10% higher than expected while O 3 levels were about 7% lower than expected during the post-SHO period compared to the same period in historical years ( Bekbulat et al, 2020 ). Additionally, preliminary analysis of this study shows that NO 2 levels in Seattle were 20% lower than expected ( Bekbulat et al, 2020 ).…”

“…The large variation in these findings are explained by the fact that non-COVID-related factors (e.g., meteorology and emissions from regional events other than traffic) may play an important role in confounding these short-term trends ( Arya, 1999 ; Ault et al, 2009 ; Chen et al, 2017 ; Husar and Renard, 1998 ; Statheropoulos et al, 1998 ; Vu et al, 2015 ; Zhao et al, 2020 ). The effects of meteorology and regional events can be partially adjusted by comparing the current year data with historical year data ( Bekbulat et al, 2020 ). Another recent study tried to exclude meteorological impacts on the change of air pollution by using the Weather Research and Forecasting (WRF) model and the Community Multiscale Air Quality (CMAQ) model combining with some attributing analyses ( Zhao et al, 2020 ).…”

COVID-19 Prevention and Air Pollution in the Absence of a Lockdown

“…Brodeur and NO2 in New York City (NYC), when using a linear time series model to compare pollutant levels following the NYC shutdown to the same weeks in 2015 -2019. One consideration in the interpretation of estimates by Bekbulat at al. (2020) is that they analyzed data from across the U.S., where restrictions and compliance with federal directives was very heterogeneous.…”