Covid-19 death rate rising in countries with high air pollution, study finds


“We found that an increase of only 1 gram per cubic meter of fine particles in the air was associated with a 15% increase in the Covid-19 mortality rate,” said lead author Francesca Dominici, co-director of Harvard Data Science. Initiative.

The study defined high pollution levels as fine particulate matter (PM 2.5) levels greater than 13 micrograms per cubic meter of air, much higher than the US average of 8.4.

“The results suggest that long-term exposure to air pollution increases vulnerability to the most serious results from Covid-19,” said Dominici.

The new information should be used by federal, state and local authorities to make informed decisions about the application of social distancing and the preparation of local hospitals and health care systems for a potential influx of more serious cases that will require extreme measures such as fans, said Dominici.

“We historically know the countries that have higher levels of pollution,” she said. “We know that even if they [the counties] have not yet experienced a high number of deaths, this would be one of their highest risks. “

Average PM2.5 concentrations at the American county level (2000-2016)
Citation: Exposure to air pollution and mortality from COVID-19 in the United States. Xiao Wu, Rachel C. Nethery, Benjamin M. Sabath, Danielle Braun, Francesca Dominici. medRxiv 2020.04.05.20054502

As for areas that currently do not have high mortality rates that should prepare, “Atlanta stands out as one of the clearest examples,” said co-author Xiao Wu, a doctorate. student in the Department of Biostatistics at Harvard University.

“DeKalb and Gwinnett counties all have PM 2.5 levels greater than 13 micrograms per cubic meter of air during our study period, and still have a relatively small number of confirmed cases and deaths”, said Wu. “Baltimore also stands out as a place with high exposure to particles, but a low death toll so far. “

Wu said other counties with high pollution levels with current Covid-19 mortality rates below the average in the United States include:

  • Fresno, Kings, Los Angeles, Orange and Tulare Counties in California
  • Vanderburgh County, Indiana
  • Butler, Hamilton and Montgomery Counties in Ohio
  • Allegheny and Westmoreland Counties in Pennsylvania

“This means that in these countries, we need to monitor social distancing measures more closely and we must make sure that they are equipped to respond to people hospitalized with Covid-19,” said Dominici. “It really makes sense to me. “

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The study is a “pre-press”, which means that it has not been peer reviewed and has been accepted by a journal for publication. Preprints are becoming more common during the pandemic as researchers scramble to provide results of studies that may provide clues to the fight against the virus.

The results provide “dramatic new information on the deadly toll from particulate pollution,” said president and CEO of the American Lung Association, Harold Wimmer, who was not involved in the study.

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“The nation has known for some time that long-term exposure to particulate pollution can worsen symptoms of lung disease, increase susceptibility to lung infections, trigger a heart attack and stroke, and can even cause lung cancer and premature death, “Wimmer said in a statement. declaration.

“This new Harvard research now links exposure to particulate pollution to a considerably higher mortality rate from Covid-19. “

Fine particles

The study analyzed the levels of fine particles in each county in the United States between 2000 and 2016.

Particulate matter is a mixture of solids and liquids in the air. The dust, dirt and smoke particles are larger, but there are also extremely small inhalable particles that cannot be seen with the naked eye. These are called PM 2.5 because their size is generally 2.5 micrometers or less.

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It’s really tiny – for comparison, an average human hair is 30 times larger than a PM 2.5 particle. Because they are so small, these particles can penetrate deep into the lungs and wreak havoc with our lungs and bodily functions.

The researchers then compared these county-level air pollution maps to the current number of Covid-19 deaths until April 4, a number calculated by Johns Hopkins University.

There is a large overlap between the underlying conditions that put many Covid-19 patients at risk – such as lung, kidney, and heart disease – and illnesses worsened by long-term exposure to fine particles.

A previous study of 60 million Americans over the age of 65 by the same research group found that every 1 gram increase per cubic meter of long-term PM 2.5 exposure was associated with an increase of 0 , 73% of the mortality rate whatever the cause.

Compared to these results, the new study has shown that the same small increase leads to a “Covid-19 mortality rate of a magnitude that is 20 times that estimated for all-cause mortality.”

According to the study, these results hold true after taking into account a large number of socioeconomic, demographic, weather, behavioral and healthcare-related confounders.

The study has some limitations, according to the authors, including the fact that the data were averaged at the comteti level.

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“If they knew on an individual level the deaths due to Covid-19, and knew if the dead person smoked, suffered from hypertension, had diabetes or any of the other known risk factors, that would be a more in-depth analysis “Said pulmonologist Dr. John Balmes, a professor of medicine at the University of California at San Francisco, who was not involved in the study.

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The maps also show more danger from the virus in communities of color, said Balmes, who is also a professor of environmental health sciences at UC Berkeley.

“The same counties that have the highest air pollution, they also have more poor people, more poor people of color. And it is probably at the neighborhood level that there is the greatest risk, “he said.

“You can use these cards to better target scarce resources, especially resources for the safety net hospitals that these poor people of color usually have to go to,” said Balmes.

And there is a global need to analyze the impact of air pollution on risk levels around the world.

“I think that by and large the general beliefs that long-term exposure to PM 2.5 increases the risk of death from Covid-19 is probably generalizable globally,” said Yifang Zhu, professor the health and environmental sciences department at UCLA, which did not participate in the study.

“So I think the study provides solid evidence to underscore the importance of further improving air quality as a whole,” said Zhu.


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