Pandemic Data May Help Scientists Understand Air Pollution

By Kylie Wolfe

Places like New York City, known for sidewalks packed with people and streets crowded with cars, were unusually quiet in 2020. As the pandemic disrupted everyday activities, temporary shutdowns laid the groundwork for an unprecedented environmental experiment.

Cities around the world suffer the effects of air pollution, a health hazard that’s often invisible but sometimes seen in the form of smog. Scientists are collecting new data to better understand this issue and what can be done to solve it. They reported their preliminary findings at the American Geophysical Union (AGU) annual meeting last December.

Recording New Data

Working from home and limiting travel this past year meant less traffic and a decrease in vehicular emissions. This led to lower levels of greenhouse gases. According to "Global Carbon Budget 2020," monthly carbon dioxide emissions decreased by 17 percent globally. By December, emissions were on the rise again but still down 7 percent compared to 2019.

New York City alone experienced a 21 percent reduction in nitrogen dioxide between March and July 2020 as reported at the AGU fall meeting. This downward trend temporarily improved air quality in the city, but it didn’t resolve the long-term problem: carbon dioxide can remain in the Earth’s atmosphere for hundreds of years.

Understanding Air Pollution

Nitrogen oxides, volatile organic compounds, and methane are gases that contribute to ground-level ozone, a pollutant in smog. When levels are high, lung damage and other respiratory complications can occur. This differs from stratospheric ozone which is found in the upper atmosphere and protects us from the sun.

Scientists began comparing concentrations of the aforementioned gases and noticed a seasonal difference. It wasn’t until summer, after the pandemic’s restrictions had been in place for a couple months, that researchers could connect a decrease in nitrogen dioxide with a decrease in ground-level ozone.

What had occurred was a photochemical reaction in the atmosphere. Sunlight and heat, characteristics of summer, interact with gases like nitrogen dioxide. The result is toxic and led Dan Jaffe, environmental chemist at the University of Washington Bothell, to point out that policy makers could better target their regulations, limiting nitrogen oxide emissions in the summer for a greater environmental impact.

Solving a Complex Problem

Scientists also saw differences in pollution by location. For example, the changes experienced in New York City weren’t as dramatic in Denver. End-of-summer wildfires added to air pollution there, reversing much of the pandemic’s impact. These natural disasters increase ozone levels, adding nitrogen oxides, carbon monoxide, and other particles to the mix.

Cities like Denver provide proof that air pollution is a complex problem. As society plans for post-pandemic life, scientists now have a unique set of data that can be used to help affect change and make a difference for our planet.