COVID-19 Pandemic Highlights the Urgent Global Need to Control Air Pollution

Boston – More than 91 percent of the world's population lives in areas that exceed air quality guidelines recommended by the World Health Organization, and more people are impacted by worsening air quality each year. Ambient air pollution – including potentially harmful pollutants such as small particles and toxic gases emitted by industries, households, cars and trucks – has been shown to worsen viral respiratory infections. Now, new studies are showing a similar association between ambient air pollution and worse COVID-19 outcomes.

In a new commentary reviewing current research on the potential relationships among pollution, respiratory viruses and health disparities, physician-researchers at Beth Israel Deaconess Medical Center (BIDMC) discuss several ways that the COVID-19 pandemic highlights the urgent need to address the global problem of air pollution and improve respiratory health and equity worldwide. The commentary appears in the Annals of the American Thoracic Society.

"A multitude of studies show that exposure to higher long-term ambient air pollution is associated with both increased risk of infection and death from COVID-19," said corresponding author Stephen Andrew Mein, MD, a physician in BIDMC's Department of Medicine. "Historically, air pollution has been linked with worse health outcomes, including higher mortality, due to other respiratory viruses like influenza. Now, new research on COVID-19 adds further evidence of the adverse effects of ambient air pollution and the urgent need to address the public health crisis of pollution."

In one of the most prominent studies modeling COVID-19 mortality Mein and colleagues reviewed, researchers at the Harvard T.H. Chan School of Public Health found that each small (1 μg/m³) increase in long-term fine inhalable particle (PM_2.5) exposure was associated with an eight percent increase in mortality during the pandemic, per an examination of county level data. Another study concluded that air pollution has contributed 15 percent to COVID-19 mortality worldwide. "The studies we reviewed evaluated whether long-term, ambient air pollution exposure that occurred years prior to the pandemic was associated with worse COVID-19 outcomes," said Mein, who is also an Instructor in Medicine at Harvard Medical School.

The exact mechanisms of the association between long-term pollution and poor COVID-19 outcomes are not fully known. However, scientists have suggested that long-term exposure to air pollution may impair the immune system, leading both to increased susceptibility to viruses and to more severe viral infections. Higher air pollution exposure — a burden disproportionately shouldered by communities of color in the Unites States — is also associated with higher rates of heart disease and metabolic disorders such as diabetes, which are known to be risk factors for severe disease and death from COVID-19. These long-term chronic effects occurred well in advance of the reported reductions in air pollution during the COVID-19 pandemic.

The authors noted that recent models predict that improved air quality (due to less travel and industrial activity) during the pandemic may have reduced morbidity and mortality from non-communicable diseases, but more study is necessary.

"Research evaluating associations between the dramatic reduction in ambient air pollution during global lockdowns and health care utilization for respiratory conditions would further confirm the impact of ambient air pollution on non-communicable diseases and the need to reduce air pollution to improve overall health," said Mary Rice, MD, physician in the Pulmonary, Critical Care & Sleep Medicine Department at BIDMC and senior author of the commentary.

"While the primary association between air pollution and COVID-19 outcomes has been generally consistent, there is still much research to be done," added Rice, who is also Assistant Professor in Medicine at Harvard Medical School. "In particular, there is a need for studies that adjust for individual-level risk factors, since current studies have been restricted to county or municipal-level exposure and outcome data. Research is also needed to evaluate whether air pollution contributes to the stark differences in COVID-19 outcomes among communities of color.

Racially and ethnically diverse communities are more likely to be located in areas closer to industrial pollution such as PM_2.5 and nitrogen dioxide, and to work in types of businesses that expose them to more air pollution. These inequalities in residential and occupational air pollution exposure may be one of the causes of the stark disparities of the COVID-19 pandemic along racial and ethnic lines.

"The COVID-19 pandemic has highlighted the widespread health consequences of ambient air pollution, including acute effects on respiratory immune defenses and chronic effects that lead to higher risk of chronic cardiopulmonary disease and acute respiratory distress syndrome (ARDS)," said Mein. "These chronic health effects likely explain the higher COVID-19 mortality among those exposed to more air pollution. The pandemic has also provided a glimpse into the health benefits of cleaner air. COVID-19 is a wakeup call for the need to adopt stricter air quality standards and end our tolerance for pollution in disadvantaged neighborhoods. As part of our post-COVID-19 recovery, we must clean up the air to improve respiratory health and equality worldwide."

Editor's note: This release is adapted from a press release issued by the American Thoracic Society.