The research, published in the journal Science Advances, investigated the impact of long-term exposure to PM 2.5 pollutants – tiny particles in the air that are two and one half microns or less in width – on Covid-19 mortality rates in 3089 counties in the US, “covering 98 per cent of the population.”
It found that “higher historical exposure” to these particulate pollutants is associated with greater county-level Covid-19 mortality rates after accounting for several area-level risk factors.
While the study could not provide insights into the mechanism underlying the relationship, the scientists, including those from Harvard University in the US, believe chronic exposure to PM 2.5 may cause over production of the ACE-2 receptor in the lungs, which the novel coronavirus uses to enter host cells.
They believe the prolonged exposure to air pollution may also impair people’s immune system.
“Chronic exposure to PM2.5 causes alveolar ACE-2 receptor overexpression and impairs host defences. This could cause a more severe form of Covid-19 in ACE-2-depleted lungs, increasing the likelihood of poor outcomes, including death,” the scientists wrote in the study.
Citing the limitations of the study, the scientists said they were unable to adjust for individual-level risk factors such as age, race, and smoking status as such data were unavailable.
“This approach leaves us unable to make conclusions regarding individual-level associations,” the scientists said.
However, the researchers said the analyses provide strong justification for follow-up investigations as more and higher-quality Covid-19 data become available.
“Research on how modifiable factors may exacerbate Covid-19 symptoms and increase mortality risk is essential to guide policies and behaviours to minimise fatality related to the pandemic,” they noted in the research.