Small rise in long-term air pollution exposure may increase risk for COVID-19 death
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An increase of 1 microgram per cubic meter in a U.S. county’s long-term average exposure to fine particle pollutants appeared to raise that area’s COVID-19 mortality rate, data from a preliminary ecological regression analysis show.
“The SARS‐CoV‐2 virus can attack a patient’s lungs as well as cardiovascular system,” Xiao Wu, a PhD candidate in the department of biostatistics at the Harvard T.H. Chan School of Public Health, told Healio Primary Care. “Therefore patients, especially those with preexisting conditions, may require extra measures to protect themselves from severe air pollution.”
Previous research, Wu said, has linked long-term exposure of particulate matter less than 2.5 micrometers in diameter (PM2.5) to several adverse health outcomes, including asthma, worsening COPD, slowed lung function growth and increased risks for myocardial infarction, stroke and death from CVD. According to the Environmental Protection Agency’s website, the largest fine PM2.5 particle is about 30 times smaller than the average human hair, which is about 70 micrometers in diameter.
For the current analysis, Wu and colleagues analyzed daily PM2.5 exposures from 2000 to 2016 in 3,089 counties, accounting for 98% of the United States’ population, using what they described as “well-validated atmospheric chemistry and machine learning models.”
The researchers wrote in Science Advances that their analysis showed for each microgram per cubic meter increase in a county’s long-term average PM2.5, there was an 11% (95% CI, 6-17) increase in that area’s COVID-19 mortality rate. This rate remained stable as more data accumulated, according to the researchers.
In addition, age distribution, days since the first COVID-19 case was reported in a county, median household income, percent of owner-occupied housing, percent of the adult population with less than high school education, percent of Black residents and population density were important predictors of the COVID-19 mortality rate. Wu and colleagues reported a 49% (95% CI, 38-61) increase in COVID-19 mortality rate for every one standard deviation increase in the percent of Black residents in a county.
Wu said that more representative and individual-level data are needed to validate the findings.
“Physicians are often the first group of people to collect these data,” Wu said. “If physicians can collect and share these data in a privacy‐protected manner, foster collaborative data consortium and are willing to collaborate with environmental scientists and data scientists to analyze data for rigorous evaluation, this would be a significant step to prompt environmental policy change.”
In a related editorial, Jeremy Jackson and Kip Hodges, both members of Science Advances’ editorial team, wrote that COVID-19 is the latest “potentially severe emerging zoonotic disease” aggravated by air pollution that “remains a long-term threat to our species.” They encouraged future research to build on the findings of Wu and colleagues’ study.
References
EPA. Particulate Matter (PM) pollution. https://www.epa.gov/pm-pollution/particulate-matter-pm-basics. Accessed November 12, 2020.
Jackson J, Hodges K. Science Advances. 2020;doi:10.1126/sciadv.abf1897.
Wu X, et al. Science Advances; 2020:doi:10.1126/sciadv.abd4049.
Perspective
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Emanuela Taioli, MD, PhD
This paper makes it very clear that air pollution can cause death from COVID-19. Like all environmental studies, it looked at population-level risk factors and population-level outcomes rather than individuals.
Having said that, environmental studies are great tools to generate hypotheses for real studies that gather an individual person’s data. It also makes sense to use environmental studies to raise a red flag and say these things require further study. For example, environmental studies first made us aware that air pollution triggered some instances of respiratory and cardiovascular disease. Patients with these two conditions are also among those at risk for very serious COVID-19 outcomes.
It is very difficult make changes on an individual basis to mitigate the risk caused by environmental factors. If we had addressed air pollution 5 or 10 years ago in a more substantial way, Wu and colleagues might not have found the association that they did. We should use their paper to realize that we need to tackle air pollution on a steady, constant level with policies geared towards public health.
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