The Improvement of the Air Quality due to Traffic Halting in Los Angeles and Potential Health Care Risk during the COVID-19 Outbreak

TL;DR

The COVID-19 lockdown in Los Angeles led to significant reductions in traffic and pollutants like NO2, CO, and PM2.5, offering insights for future air quality management and policy planning.

Contribution

This study quantifies the impact of traffic reduction during COVID-19 lockdowns on air quality in Los Angeles using real-time data and spatial analysis.

Findings

Traffic flow decreased by 20.86% during lockdown.

Significant declines in NO2, CO, and PM2.5 levels observed.

Truck flow changes strongly correlated with pollutant reductions.

Abstract

Background: On March 19, 2020, the government of California ordered all 40 million Californians to stay at home in the coming weeks as the result of the escalation of the coronavirus disease 2019 (COVID-19) pandemic. As lockdowns were implemented, the significant changes caused by these restrictions brought a dramatic improvement in air quality in metropolitan cities such as Los Angeles (LA Basin).Methods: We use real-time data from The South Coast Air Quality Management District (South Coast AQMD), and the California Department of Transportation to evaluate the drivers of the pollution sources. We also mapped monthly spatial variations and constructed hourly heatmaps of those pollutants in 2020 to understand the impacts of the lockdown on different locations and times of day in the LA Basin. Results: Compared to the same dates in 2019, traffic flow on highways in the Los Angeles Basin dropped by 20.86 % when the stay at home order was initiated and it continued to decrease along with dramatic declines in NO2, CO, and PM2.5. The correlation (Pierson r) between truck flow change and changes of NO2, CO, and PM2.5 is statistically significant. Conclusion: The declines in truck flow are mainly responsible for the drop of NO2 and CO, with traffic having a slightly smaller effect on PM2.5. The lockdowns provided a large-scale experiment into air quality research. The result of this research would provide an important reference for the policy markers regarding truck management in light of air quality control to prepare for the 2028 Summer Olympics in LA.