A study reports that areas with higher concentrations of air pollution also have higher death rates from COVID-19.

Air pollution, especially the tiny particles known as fine particulate matter (PM2.5) has been linked before to respiratory and cardiovascular disease. But the pollution is also highest in cities where many people live and work closely together. It is hard to tell whether an increase in deaths from COVID-19 is due to pollution or simply to more cases of COVID-19 where people are more densely concentrated.

New research looked at US deaths from COVID-19 up to the 4th of April, and historical pollution data. The researchers adjusted their figures to take population density and other factors into account. They estimated each 1 microgram per metre squared increase in PM2.5 was linked to a 15% increase in a region’s death rate from COVID-19.

The study results are important, but the study has not yet been published in a peer-reviewed journal. This means they need more scrutiny.


Where did the story come from?

The Guardian and several other media outlets reported the study, which was released on the 5th April by the Harvard TH Chan School of Public Health. Prior to this report, the European Public Health Alliance warned in March that air pollution was likely to increase complications or deaths from COVID-19.


What is the basis for the claim?

The study used historical air quality monitoring data from 3,080 counties in the US, collected from 2000 to 2016, to get an idea of people’s long-term exposure to pollution. The researchers used a US-wide registry of deaths attributed to COVID-19, reported by county. Researchers calculated the ratio of deaths to county population size to get the county level death rate.

The researchers found that counties with higher death rates also had higher levels of PM2.5 pollution. Average levels were 8.4 micrograms per metre squared across the US, with a range from less than 3 to more than 12.

They adjusted their figures to take account of factors including population density, the proportion of people aged over 65, the proportion with deprivation markers, ethnic background, the proportion of smokers, number of hospital beds, weather, and number of COVID-19 tests.

After adjustment, they said that each additional 1 microgram per metre squared rise in a county’s air pollution increased death rates by 15%. They calculated that in New York County (where the disease has hit hardest) a reduction of 1 microgram per metre squared in PM2.5 pollution might have prevented 248 of 1,905 deaths.

A study from 2003 looking at deaths from SARS in China, found that people with the disease were more likely to die if they lived in polluted regions. The study looked at different measures of air pollution than the US study and used numbers of people who died compared to the number of cases reported. It did not account for important factors such as whether people smoked.


What do trusted sources say?

The WHO has not commented on links between air pollution and COVID-19 deaths. However, in 2014 the organisation said that air pollution may cause 7 million premature deaths annually worldwide, contributing to deaths from cardiovascular disease, respiratory disease (including acute respiratory infections such as SARS and COVID-19) and cancer.

Dr Maria Neira, Director of WHO’s Department for Public Health, Environmental and Social Determinants of Health, said at the time: “Few risks have a greater impact on global health today than air pollution; the evidence signals the need for concerted action to clean up the air we all breathe.”

Analysis by EIU Healthcare, supported by Reckitt Benckiser



  1. Xiao Wu et al. Exposure to air pollution and COVID-19 mortality in the United States. medRxiv 2020.04.05.20054502; doi: https://doi.org/10.1101/2020.04.05.20054502 Available at https://projects.iq.harvard.edu/files/covid-pm/files/pm_and_covid_mortality.pdf (Accessed 8 April 2020)

Reading list

  1. Cui, Y., Zhang, Z., Froines, J. et al. Air pollution and case fatality of SARS in the People’s Republic of China: an ecologic study. Environ Health 2, 15 (2003). https://doi.org/10.1186/1476-069X-2-15 (Accessed 8 April 2020)
  2. European Public Health Alliance. Coronavirus threat greater for polluted cities. March 16 2020. https://epha.org/coronavirus-threat-greater-for-polluted-cities/ (Accessed 8 April 2020)