COVID-19 death rates increase due to long-term exposure to PM2.5

More and more we are seeing results from recent studies showing a correlation between higher COVID-19 death rates and people who live in air pollution riddled areas. Both in Italy and the United States, people that reside in areas with higher concentrations of PM2.5 in the atmosphere are at least 12% more likely to not survive a bout with COVID-19. These findings are consistent with the findings from the 2002-2003 SARS outbreak that claimed 349 lives in China. 

2002 SARS in China

When the Severe Acute Respiratory Syndrome (SARS) outbreak took the lives of 349 people, Universities studied the relationship between people exposed to poor air quality in the short- and long-term and the rate of death from SARS. It has been shown through multiple studies that air pollution is linked to asthma attacks, COPD exacerbation, acute respiratory inflammation, and cardiorespiratory disease related deaths.

The universities studied 5 regions that had 100 or more SARS cases. Their analysis showed people in regions with moderate to high APIs had an increased risk of passing from SARS.

SARS patients from regions with moderate APIs had an 84% increased risk of dying from SARS compared to those from regions with low APIs. Similarly, SARS patients from regions with high APIs were twice as likely to die from SARS compared to those from regions with low APIs.

The biological explanation might be that long-term or short-term exposure to certain air pollutants could compromise lung function, therefore increasing SARS fatality. Both long-term and short-term exposure to air pollution has been associated with a variety of adverse health effects including acute respiratory inflammation, asthma and COPD. Air pollution may predispose the respiratory epithelium of SARS patients, leading to severe respiratory symptoms and an increased risk of deaths. 

(Cui, Zhang, Froines, 2003)

While the study had some limitations, one can see the connection of SARS case fatality rising with increased levels exposure to air pollution.  Similarly to SARS, the below COVID-19 studies are showing a correlation between an increased fatality rate among those who have the disease and those who have been exposed to higher levels of air pollution over longer periods of time. 



In the United States, the following was a national study on long-term exposure to air pollution and COVID-19 mortality done by Harvard University: 

Background: United States government scientists estimate that COVID-19 may kill between 100,000 and 240,000 Americans. The majority of the pre-existing conditions that increase the risk of death for COVID-19 are the same diseases that are affected by long-term exposure to air pollution. We investigate whether long-term average exposure to fine particulate matter (PM2.5) increases the risk of COVID-19 deaths in the United States.

Methods: Data was collected for approximately 3,000 counties in the United States (98% of the population) up to April 04, 2020. We fit zero-inflated negative binomial mixed models using county level COVID-19 deaths as the outcome and county level long-term average of PM2.5 as the exposure. We adjust by population size, hospital beds, number of individuals tested, weather, and socioeconomic and behavioral variables including, but not limited to obesity and smoking. We include a random intercept by state to account for potential correlation in counties within the same state.

Results: We found that an increase of only 1 μg/m3 in PM2.5 is associated with a 15% increase in the COVID-19 death rate, 95% confidence interval (CI) (5%, 25%). Results are statistically significant and robust to secondary and sensitivity analyses.

Conclusions: A small increase in long-term exposure to PM2.5 leads to a large increase in COVID-19 death rate, with the magnitude of increase 20 times that observed for PM2.5 and all-cause mortality. The study results underscore the importance of continuing to enforce existing air pollution regulations to protect human health both during and after the COVID-19 crisis. The data and code are publicly available.

(Wu, Nethery, Sabath, Braun, Dominici)



Researchers at Aarhus University in Denmark, looked at similar correlations between communities living in Emilia Romagna and Lombardy who have had long-term exposure to higher air pollution than the rest of the country and who were experiencing a higher morbidity rate of COVID-19 infected persons. 

The two northern Italian regions are among the most air-polluted regions in Europe. The recently published article took its outset in data from the NASA Aura satellite, which has demonstrated very high levels of air pollution across precisely these two regions. The group compared these data with the so-called Air Quality Index; a measurement of air quality developed by the European Environment Agency. The index gathers data from several thousand measuring stations all over Europe, providing a geographical insight into the prevalence of a number of pollutant sources in the EU.

(Aarhus University, 2020)

With mortality in Northern Italy up to 12% comparatively to 4.5% in the reset of the country, air pollution plays a heavy role. We knew that those living in areas with higher levels of pollution are more likely to have respiratory conditions. What we see now is the original impairment from air pollution to a person's health is quickening the destruction of Severe Acute Respiratory Syndrome CoronaVirus 2.

Among elderly living in such a region and affected by other comorbidities, the cilia and upper airways defenses could have been weakened both by age and chronic exposure to air pollution, which, in turn, could facilitate virus invasion by allowing virus reaching lower airways. Subsequently, a dysregulated, weak immune system, triggered by chronic air pollution exposure may lead to ARDS and eventually death, particularly in case of severe respiratory and cardiovascular comorbidities. Moreover, since the prolonged exposure to atmospheric pollution could induce persistent modifications of the immune system (Tsai et al., 2019), short-term changes in the air quality may not be sufficient to break this vicious circle. This might be supported by the persistent high fatality rate, despite the dramatical reduction of air pollution levels in Lombardy since the start of the outbreak. 

(Conticini, Frediani, & Caro 2020)


Cleaner air could have saved lives

With a 15% increase in death rate in the United States and a 12% increase in death rate across the globe in Italy, the research shows a strong correlation of poor air quality damaging individual's health and ultimately leading to untimely deaths. 

“Previous work showed that air pollution exposure dramatically increased the risk of death from [the] Sars [coronavirus] during the 2003 outbreak,” said Rachel Nethery, one of the Harvard team. “So we think our results here are consistent with those findings.”

Xiao Wu, a fellow team member, said: “This information can help us prepare by encouraging populations [with high pollution exposure] to take extra precautions and allocate extra resources to reduce the risk of poor outcomes from Covid-19. It is likely that Covid-19 will be a part of our lives for quite a long time, despite our hope for a vaccine or treatment. In light of this, we should consider additional measures to protect ourselves from pollution exposure to reduce the Covid-19 death toll.”

(Carrington, 2020)

Communities, knowing of this correlations, can support populations which have seen higher air pollution levels over the past 15-20 years by allocating additional resources and encouraging community members to take extra precautions against COVID-19.

Since the correlation is a result of long-term exposure to high pollution levels, society should strive to keep the decrease in air pollution from the stay-at-home orders down long term. 



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  • Air pollution linked to far higher Covid-19 death rates, study finds
  • Citation: Carrington, Damian. “Air Pollution Linked to Far Higher Covid-19 Death Rates, Study Finds.” The Guardian, Guardian News and Media, 7 Apr. 2020,

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