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COVID-19: An Opportunity to Assess Global Air Quality and Its Impact on Health


With unprecedented pauses in air pollution emissions in spring 2020 and ongoing virus mitigation behaviors around the world, the COVID-19 pandemic presents an opportunity to better understand the impact of poor air quality on human health.

It is no secret that air pollution—in particular, that which is a result of climate change—has had serious ramifications on air quality and human health around the world. One recent study found that even short-term exposure to nitrogen dioxide (NO2), which largely stems from fuel combustion and automobile traffic, has a linear association with increased risk of total, cardiovascular, and respiratory death.

The COVID-19 pandemic brought several serious health conditions, like obesity and diabetes, into the limelight. But it has also provided an opportunity to better understand air pollution and the impact virus transmission mitigation behaviors have on respiratory health.

In 2003, during the severe acute respiratory syndrome (SARS) outbreak in China, those infected with SARS who lived in areas with higher air pollution were 84% more likely to die compared with those residing in less polluted areas.

Furthermore, a rapid systematic review, published in Environmental Health, concluded both acute and chronic exposure to air pollution can affect COVID-19 epidemiology.

Although the evidence is unclear for acute exposure due to bias present in existing studies, the authors wrote, “Public health interventions that help minimize anthropogenic pollutant source and socioeconomic injustice/disparities may reduce the planetary threat posed by both COVID-19 and air pollution pandemics.”

A Cause for Optimism?

Over a year into the pandemic, recently published data highlight just how much human actions impact the quality of air we breathe. In the spring of 2020, when dire COVID-19 infection projections turned into reality, metropolises around the globe stood still, and the lack of vehicular traffic led to significant air pollutant decreases seen from Mexico City to Abu Dhabi.

In a study that examined the global concentration changes in air pollutants between March and April 2020, researchers found “reductions in air pollutant concentrations have overall improved global air quality likely driven in part by economic slowdowns resulting from the global pandemic.”

Specifically, the researchers examined concentration changes in carbon monoxide (CO), NO2, sulfur dioxide (SO2), ozone (O3), and particulate matters (PM2.5 and PM10) and compared findings with those recorded during the same months between 2015 and 2019.

Analyses revealed:

  • Globally, space-borne NO2 column observations were reduced by approximately 9.19% and 9.57%, in March and April 2020, respectively
  • On a regional scale, after accounting for the effects of meteorological variability, most monitoring sites in Europe, the United States, China, and India showed declines in CO, NO2, SO2, PM2.5, and PM10 concentrations
  • An increase in O3 concentrations occurred during the same period
  • Four major city case studies in New York, New York; Milan, Italy; Wuhan, China; and New Delhi, India, showed reduction trends similar to those observed on the regional scale and an increase in ozone concentration

Generally elevated concentrations of O3 can be attributed to “lower than normal emissions of NO due to restrictions placed on industrial activities and travel. Therefore, this increase in O3 concentrations is mainly explained by an unprecedented reduction in [nitrogen oxides] emissions leading to a lower O3 titration by [nitric oxide],” the researchers explained.

“It is evident the lockdown orders associated with COVID-19 have had a profound impact on our atmospheric environment,” they concluded.

Not only will cleaner air result in superior health outcomes, it will also help reduce costs of diseases associated with air pollution, including Parkinson disease, Alzheimer disease, multiple sclerosis, diabetes, obesity, age-related macular degeneration, adverse pregnancy outcomes, and emphysema, to name a few.

Exposure reduction due to mask-wearing and stay-at-home orders have also contributed to anecdotal reports of reduced exacerbations among patients with chronic obstructive pulmonary disease (COPD).

“Many patients with COPD got the message that they were at increased risk and have been doing, I would say overall, a fairly good job of staying at home,” said Meilan King Han, MD, a professor of internal medicine in the Division of Pulmonary and Critical Care at the University of Michigan in an interview with The American Journal of Managed Care®(AJMC®).

“We know that in normal times, exacerbations would be due to things like normal colds and other non–COVID-19 viruses. The interesting thing is that overall, we're seeing patients having fewer exacerbations simply because they're heeding the CDC guidance and staying at home,” she said.

Similar situations have played out across the asthma, allergy, and immunology fields. Three recently published studies focusing on populations in the United Kingdom and South Korea found the number of individuals receiving care for asthmatic episodes decreased during the pandemic, the Center for Infectious Disease Research and Policy reports.

Although investigations were not designed to determine causation, “researchers suggest that behavioral changes in care-seeking or asthma management, lower air pollution due to lockdown, lower exposure to seasonal allergies, and the like may have contributed to the observed changes.”

Visits to allergists have gone down, too. In the spring of 2020, “our usual pollen sufferers were having a lot less exacerbations,” allergist and immunologist Courtney Blair, MD, told AJMC®. This could be due to the fact that at the time, patients were concerned about COVID-19 exposure and did not want to go to doctors’ offices.

But when it comes to mitigation efforts, “mask-wearing for our pollen sufferers seemed to benefit them quite a bit. When they did leave the house, they were inhaling less particulates from pollen especially,” said Blair, who also serves as the president of the Greater Washington Allergy, Asthma, and Immunology Society and is a fellow of the American Academy of Allergy, Asthma and Immunology.

Numerous patients and parents have reported their kids are much less sick this year, as they are either at home or the measures taken to prevent COVID-19 have cut down on rates of seasonal virus spread, she added.

Human-caused climate change has also contributed to longer and more intense pollen seasons, which not only will have implications on human health, but could also raise associated medical costs. “The strong link between warmer weather and pollen seasons provides a crystal-clear example of how climate change is already affecting peoples' health across the US,” said study author William Anderegg, PhD.

“In our patient population, we’ve had less exacerbations,” but discerning the root cause of the drop—whether it is reductions in air pollutants or mitigation efforts—is a challenge, Blair noted. However, the decrease in viral spread of all viruses in the last 12 months “probably is the most critical factor that people are just getting sick less.”

Looking Ahead

One obvious solution to the issues wrought by air pollution, as evidenced by the COVID-19 lockdowns, is to curb emissions and cut air pollution in general. A health impact assessment of data collected in 2015 found that reducing PM2.5 and NO2 in nearly 1000 European cities to World Health Organization target levels (no more than an annual mean of 10 mcg/m3 for PM2.5 and 40 mcg/m3 for NO2) could save approximately 50,000 lives each year.

Furthermore, achieving the lowest levels of the 2 pollutants measured in any European city in 2015 would prevent “an estimated 124,729 premature deaths from PM2.5 exposure and 79,435 premature deaths from NO2 exposure annually.”

In their annual State of the Air report, The American Lung Association (ALA) found more than 40% of Americans—amounting to over 135 million individuals—live in areas with unhealthy levels of ozone and particle pollution. Notably, the report also found people of color are 3 times more likely to be breathing the most polluted air compared with White individuals, a factor that could contribute to the stark racial inequities seen in COVID-19 infection and death rates in the United States.

Solutions proposed by the ALA include transitioning from fossil fuels and combustion to clean renewable electricity and zero-emission transportation.

In California, lawmakers are attempting to do just that by curbing diesel PM2.5 (DPM) emissions. According to the ALA, “Los Angeles remains the city with the worst ozone pollution in the nation, as it has for all but 1 of the 22 years tracked by the ‘State of the Air’ report... And Bakersfield, California, returned to the most polluted slot for year-round particle pollution for the second year in a row.”

However, an analysis of the effects of California’s authority under the Clean Air Act to regulate air pollution more stringently than the federal government revealed the state’s sector-based policies have been highly effective relative to the rest of the country in reducing mobile-source DPM emission.

While in office, former President Donald Trump took a more relaxed role in cracking down on environmental infractions perpetrated by industries. Within several months of him taking office, the Environmental Protection Agency prosecuted fewer alleged violations of air and water regulations, NPR reports.

“To improve health in communities disproportionately affected by these emissions, we point to opportunities to further reduce DPM emissions in California, in the US more broadly, and in parts of the world where countries have less aggressive vehicle emissions policies than the United States,” the researchers wrote.

Businesses, including Walmart, Apple, McDonalds, and Starbucks have also called on the Biden administration to reduce greenhouse gas emissions to at least half of levels reported in 2005 by 2030. In 2019, emissions were measured at just 13% below 2005 levels, marking a 1.8% decrease from the previous year, according to NPR.

But a new report from the International Energy Agency estimates global carbon dioxide emissions from energy will rise by 5% this year and noted the economic rebound from the pandemic could be “anything but sustainable” for the climate.

That increase amounts to 33 billion metric tons of emissions this year, up 1.5 billion metric tons from 2020 levels and marks the single largest increase in more than a decade, Reuters reports. For context, 33 billion metric tons is approximately equal to 73 trillion pounds.

“The expected rise in coal use dwarves that of renewables by almost 60%, despite accelerating demand for solar, wind, and hydro power. More than 80% of the projected growth in coal demand in 2021 is set to come from Asia, led by China,” the article reads.

To combat these trends, President Biden announced the United States will aim to cut carbon emissions by over 50% of its 2005 levels by the year 2030. However, the administration has not released a plan as to how it will achieve this goal. Biden is expected to announce more details at the White House’s virtual Earth Day Climate summit with world leaders being held today and tomorrow.

When it comes to a health perspective, reducing greenhouse gases and human emitted pollutants will be “the way that the world is going to get better,” said Blair. But ultimately efforts against climate change will “necessitate so many actors to make change over time, everything from politics to industry to individual choices, and then health care providers supporting the choices that are right for the patient both in the immediate, medium, and long term.”

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