Substantial Decreases in U.S. Cities’ Ground-Based NO2 Concentrations during COVID-19 from Reduced Transportation

Abstract

A substantial reduction in global transport and industrial processes stemming from the novel SARS-CoV-2 coronavirus and subsequent pandemic resulted in sharp declines in emissions, including for NO2. This has implications for human health, given the role that this gas plays in pulmonary disease and the findings that past exposure to air pollutants has been linked to the most adverse outcomes from COVID-19 disease, likely via various co-morbidities. To explore how much COVID-19 shutdown policies impacted urban air quality, we examined ground-based NO2 sensor data from 11 U.S. cities from a two-month window (March–April) during shutdown in 2020, controlling for natural seasonal variability by using average changes in NO2 over the previous five years for these cities. Levels of NO2 and VMT reduction in March and April compared to January 2020 ranged between 11–65% and 11–89%, consistent with a sharp drop in vehicular traffic from shutdown-related travel restrictions. To explore this link closely, we gathered detailed traffic count data in one city—Indianapolis, Indiana—and found a strong correlation (0.90) between traffic counts/classification and vehicle miles travelled, a moderate correlation (0.54) between NO2 and traffic related data, and an average reduction of 1.11 ppb of NO2 linked to vehicular data. This finding indicates that targeted reduction in pollutants like NO2 can be made by manipulating traffic patterns, thus potentially leading to more population-level health resilience in the future.

Effect of COVID‐19 lockdown on ambient air quality

“…In this regard, it should not be overlooked that trucks/vans, as well as automobiles, have a significant influence on the rise in NO 2 levels. [ 39 ] However, due to COVID‐19, people opt for automobiles instead of using public transportation, and also the increased usage of diesel‐powered automobiles contributed to the increase in NO 2 levels. According to Turkish Statistical Institute statistics, when cars registered for traffic were evaluated in terms of fuel type, it was determined that the rate of diesel cars increased from 38.1% in 2019 to 38.3% in 2020.…”

A Novel Method for Traffic Estimation and Air Quality Assessment in California

“…Many countries around the world have restricted usual daily routines and restrained domestic and international travel simply to minimize the spread of the virus. As a result, there has been a reasonably unusual trend of vehicular traffic operations and also changes in air quality levels reported in various recent studies [16][17][18][19][20][21][22]. It is clear that the implementation of such restrictions changes commuting flows and leads to prominent changes in air pollution levels.…”

Efficacy of Low-Cost Sensor Networks at Detecting Fine-Scale Variations in Particulate Matter in Urban Environments

“…A limitation of the studies that use PM 2.5 in relation to human health outcomes is that due to the high cost and maintenance of regulatory monitors, most US cities have few monitors to gauge air quality and health burdens, sometimes just one or two sensors for millions of people. Enhanced spatial and temporal detail in monitoring is critical as a host of studies show the important role that local sources play in driving air pollution [14,17,18].…”