Coronavirus and climate change | Coronavirus and heatwaves | Preventing Pandemics at the Source

We know that air pollution can cause health problems, like heart attacks, strokes, diabetes and high blood pressure, that have been identified as the pre-existing medical conditions that raise the chances of death from COVID-19 infection. Emerging research, including a study from Harvard T.H. Chan School of Public Health, finds that breathing more polluted air over many years may itself worsen the effects of COVID-19.

The Harvard Chan study led by Xiao Wu and Rachel Nethery and senior author Francesca Dominici found an association between air pollution over many years with an 11% increase in mortality from COVID-19 infection for every 1 microgram/cubic meter increase in air pollution (for comparison, many Americans breathe air with 8 micrograms/cubic meter of particulate matter).

While the study does not show that air pollution directly affects an individual’s likelihood of dying from COVID-19 because individual-level COVID data is not yet publicly available, it does show an association between long term exposure to air pollution and higher COVID-19 mortality rates.

“The results of our study suggest that in counties with high levels of pollution is where we need to implement social distancing measures now more than ever, knowing that people here will be more susceptible to die from Covid-19” Dominici told STAT News.

Dr. Aaron Bernstein, former Director at the Center for Climate, Health, and the Global Environment at the Harvard T.H. Chan School of Public Health (Harvard Chan C-CHANGE), who was not involved in the Harvard study, says that higher death rates that have been observed among the poor and people of color in the United States reflect existing health and economic inequalities that both contribute to, and result from, greater exposure to air pollution.

“In places where air pollution is a chronic problem, we have to pay particular attention to individuals who may be more exposed or vulnerable than others to polluted air, such as the homeless and those with chronic medical problems,” says Dr. Bernstein. “These individuals may need more support than they did even before coronavirus came along.”

Research on Air Pollution and Coronavirus

The Harvard study is one of several that suggest air pollution is affecting COVID-19 mortality. Researchers analyzing 120 cities in China found a significant relationship between air pollution and COVID-19 infection, and of the coronavirus deaths across 66 regions in Italy, Spain, France and Germany, 78% of them occurred in five of the most polluted regions. There’s also evidence from previous outbreaks like SARS, which was also a coronavirus, as well as many other respiratory infections including influenza, that breathing more polluted air increased risks of death.



United States

  • Zhou et al found that there were nearly 20,000 extra coronavirus infections and 750 deaths associated with exposure to high levels of PM2.5 from 2020 wildfires in 92 western U.S. counties (Science Advances, August 13, 2021).
  • Lipsitt et al found annual nitrogen dioxide exposure (a pollutant that comes from tailpipe emissions) to be associated with COVID-19 incidence and mortality in Los Angeles County neighborhoods while adjusting for numerous confounders, with an 8.7 ppb increase in NO2 to be associated with a 35–60% increase in mortality rate (Environment International, August 2021).
  • Wu et al found an association between air pollution over many years with an 11% increase in mortality from COVID-19 infection for every 1 microgram/cubic meter increase in air pollution. (Science Advances, November 4, 2020)
  • Liang et al found that people living in communities with more long-term exposure to tailpipe emissions were associated with higher rates of dying from COVID-19, with a 4.6ppb increase in NO2 exposure (which primarily comes from urban traffic) resulting in an 11% increase in the case fatality rate after controlling for other factors that may increase risk of dying from the disease. (The Innovation, September 21, 2020)
  • Petroni et al found an increase in exposure to hazardous air pollutants (HAPs) is associated with a 9% increase in COVID-19 mortality. (Environmental Research Letters, September 11, 2020)

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