Nitrogen dioxide levels dropped quickly as vehicle traffic plummeted during pandemic lockdowns, providing people with lung disease unexpected relief. “Many of my patients said they could run outside for the first time in 10 years,” says Toronto’s St. Michael’s Hospital respirologist Natasha Sabur.
The effects of pollution are well established. Almost 9 million deaths worldwide are attributed to the effects of air pollution on non-communicable diseases such as diabetes, stroke, lung disease and heart disease. However, there is increasing evidence of the relationship between air pollution and COVID-19.
“Data is emerging on the impact of air pollution on COVID-19 infections and mortality but there is ongoing debate about how big the effect might be,” says Boston’s Health Effects Institute’s air quality scientist Pallavi Pant.
The link between air pollution and COVID-19 severity and mortality was first established in the early days of the pandemic by Italian researchers who found COVID-19 mortality rates in the industrial regions around Milan and Bologna were two to three times higher than other, less polluted regions in northern Italy.
“In 2003, when the SARS outbreak affected several countries, especially China, there were several studies that showed the relationship of areas of high pollution with higher SARS mortality irrespective of population density,” says Pant.
Now, several studies are reporting similar findings for COVID-19 around the world, including in the U.S., Asia and Europe.
PM2.5 particles are the likely culprit. Largely the result of fossil fuel burning, the tiny particles (less than 2.5 micrometers) lodge in the lungs, leading to the expression of a receptor that binds the COVID-19 virus and increases viral load and inflammation. The source is largely from internal combustion engines in cars, trucks and trains.
In 2005, the World Health Organization (WHO) set guidelines for acceptable annual PM2.5 levels as less than 10 micrograms per cubic metre. The levels of PM2.5 throughout the world can range from seven in countries like Canada into the hundreds in countries like India where fossil fuel and waste burning are rampant and there are few other energy sources.
“The latest global data we have from 2019 shows more than 90 per cent of the world population lives in areas with PM2.5 above the recommended WHO air quality guidelines,” says Pant.
The WHO is currently revising its guidelines as recent studies show negative effects of PM2.5 on COVID-19 mortality at levels below the recommended annual concentration.
Another epidemiologic study indicated that PM2.5 particles can be responsible for the transmission of COVID-19 viruses, although Pant is cautious about that link.
“These studies are still controversial,” she says. At a recent European Parliament lung health webinar, professor and researcher Lidia Morawska from Queensland University of Technology questioned the correlation, stating that viral particles are too big to be carried efficiently by PM 2.5 particles.
Meanwhile, in an open letter to G20 leaders, more than 350 organizations representing 40 million health professionals and more than 4,500 individual health professionals from 90 different countries called on world leaders for a healthy recovery from COVID-19. It contains a call to end fossil fuel subsidies and for an energy transition that echoes the WHO Manifesto for a healthy recovery from COVID-19.
“We have to move away from fossil fuel to support health,” concluded Mary Rice, a Boston-area pulmonary and critical care physician, as she wrapped up at the EU webinar.
The newly released Canadian Net-Zero Emissions Accountability Act, Korea’s Green New Deal, China’s air pollution reduction strategies and Joe Biden’s intention to rejoin the Paris Climate Accord all provide hope that governments are responding to the air pollution public health crisis and its effect on emerging infectious diseases. But the research dollars being thrown at the effects of pollution on COVID-19 are “nowhere close to those being spent on the vaccine,” says Pant, or the subsidies for fossil fuel that globally total about US $400 billion annually.
The earlier effects of COVID-19 lockdowns on air pollution reduction have all but disappeared. However, says Pant, “this is not going to be the last time we will see a COVID-19-like virus and we have an opportunity to learn about interactions between air quality and the environment and how they impact spread, severity and mortality related to infectious disease.”
It’s an opportunity that should not be wasted, as pollution reduction will have an overarching benefit on health that goes far beyond outbreaks such as SARS and COVID-19.