Coronavirus patients living in areas with high levels of air pollution more likely to die, study finds
Air pollution has now been associated with significantly higher rates of death in people with COVID-19, according to the first nationwide study in the US. Scientists have found that even a small increase in long-term exposure to PM2.5 before the COVID-19 pandemic leads to a large increase in the COVID-19 death rate.
The researchers from the Department of Biostatistics, Harvard T.H. Chan School of Public Health, Boston, US found that an increase of only 1 milligram per cubic meter (μg/m3) in PM2.5 is associated with a 15% increase in the COVID-19 death rate. This indicates that patients living in areas that have high pollution levels are far more likely to die than those in cleaner parts of the country.
“We found statistically significant evidence that an increase of 1 g/m3 in long-term PM2.5 exposure is associated with a 15% increase in the COVID-19 mortality rate,” says the team.
The findings, a preprint version of which has been published, suggest that in New York County (Manhattan) if “we were to lower the long-term average PM2 exposure by only 1 g/m3 we would have expected to see 248 fewer COVID-19 deaths among a total of 1905 deaths up to April 4,” says the team.
The US government estimates that COVID-19 may kill between 100,000 and 240,000 Americans. The researchers say that 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. Accordingly, they investigated whether long-term average exposure to fine particulate matter (PM2.5) increases the risk of COVID-19 deaths in the US.
“Although the epidemiology of COVID-19 is evolving, we have determined that there is a large overlap between causes of deaths of COVID-19 patients and the diseases that are affected by long-term exposure to fine particulate matter (PM2.5),” says the research team.
Data was collected for 3,080 counties in the US (98% of the population) up to April 4. The researchers analyzed many factors such as county-level COVID-19 deaths as the outcome and county level long-term average of PM2.5 as the exposure, population size, hospital beds, number of individuals tested, weather, and socioeconomic and behavioral variables, including obesity and smoking, among others.
The experts hypothesized that because long-term exposure to PM2.5 adversely affects the respiratory and cardiovascular system, it can also exacerbate the severity of the COVID-19 infection symptoms and may increase the risk of death in COVID-19 patients.
From the results of the study, the team suggests that long-term exposure to air pollution increases vulnerability to experiencing the most severe COVID-19 outcomes. A small increase in exposure to particle pollution over 15-20 years was already known to increase the risk of death from all causes, but the current study shows this increase is 20 times higher for COVID-19 deaths.
“In a previous study of 60 million Americans older than 65 years, they found that a 1 mg/m3 in long-term PM2.5 exposure is associated with a 0.73% increase in the rate of all-cause mortality. Therefore, a small increase in long-term exposure to PM2.5 leads to a large increase in the COVID-19 death rate of a magnitude that is 20 times the one estimated for all-cause mortality,” say experts.
They add, “The findings align with the known relationship between PM2.5 exposure and many of the cardiovascular and respiratory comorbidities that dramatically increase the risk of death in COVID-19 patients. They are also consistent with findings that air pollution exposure dramatically increased the risk of death during the Severe Acute Respiratory Syndrome (SARS) outbreak in 2003, which is caused by another type of coronavirus.”
According to the researchers, the study provides a motive for expanded follow-up investigations as more and higher quality COVID-19 data become available. “These would include validating these results in other data sources and study types and studies of biological mechanisms, impacts of PM2.5 exposure timing, and relationships between PM2.5 and other COVID-19 outcomes such as hospitalization,” they explain.
The results of the study also underscore the importance of continuing to enforce existing air pollution regulations to protect human health both during and after the COVID-19 crisis, caution experts. The team noted that on March 26, the US EPA announced a sweeping relaxation of environmental rules in response to the coronavirus pandemic, allowing power plants, factories and other facilities to determine for themselves if they can meet legal requirements on reporting air and water pollution.
“Based on our result, we anticipate a failure to do so can potentially increase the COVID-19 death toll and hospitalizations, further burdening our healthcare system and drawing resources away from COVID-19 patients,” says the research team.
Link between air pollution and coronavirus death in Italy
In a separate study, researchers from Aarhus University examined whether there could be a link between the high mortality rate seen in northern Italy and the level of air pollution in the same region. The short answer is “yes possibly,” says the team.
Looking for reasons why the mortality rate is up to 12% in the northern part of Italy and only approx. 4.5% in the rest of the country, they found a probable correlation between air pollution and mortality in two of the worst affected regions in northern Italy: Lombardy and Emilia Romagna.
The figures speak for themselves. The population of the northern Italian regions lives in a higher level of air pollution, and this may lead to many complications for patients with COVID-19 in the regions, simply because their bodies may have already been weakened by the accumulated exposure to air pollution when they contract the disease, explains the team.
“Indeed, Lombardy and Emilia Romagna are Italian regions with both the highest level of virus lethality in the world and one of Europe’s most polluted areas. Based on this correlation, this paper analyzes the possible link between pollution and the development of acute respiratory distress syndrome and eventually death,” says the study published in Environmental Pollution.
“We provide evidence that people living in an area with high levels of pollutants are more prone to develop chronic respiratory conditions and suitable to any infective agent. Moreover, prolonged exposure to air pollution leads to a chronic inflammatory stimulus, even in young and healthy subjects. We conclude that the high level of pollution in Northern Italy should be considered an additional co-factor of the high level of lethality recorded in that area,” says the research team.