Air Pollution and Smoking May Increase Coronavirus Risks, Worsen Outcomes

By Jeffrey Norris

Lung damage is the cause of most COVID-19 deaths, and lung damage also is a public health concern for smokers and anybody living under polluted skies. The assault to the lungs in COVID-19 and due to inhaled smoke and chemicals has led researchers to suspect that there is a synergy at work for many with the disease.

Diabetes, high blood pressure and heart or chronic respiratory disease put those infected with SAR-CoV-2, the newly pandemic coronavirus that causes COVID-19, at risk for worse outcomes. But beyond these pre-existing health conditions, there’s good reason to believe that smoking and long-term exposure to air pollution also are likely to shift the odds.

Researchers, including pulmonologists at UC San Francisco, are working to find out more about the links between smoking, air pollution and infection, including fatal coronavirus infection. For instance, Michael Matthay, MD, along with UCSF intensive care physician Jeffrey Gotts, MD, PhD, and postdoctoral fellow Shotaro Matsumoto, MD, are investigating how lung injury and susceptibility to infection may be affected not only by smoking, but also by vaping.

Acute Respiratory Distress Syndrome

The leading cause of death in COVID-19 patients is acute respiratory distress syndrome (ARDS), a form of oxygen starvation associated with the flooding of the tiny air sacs within the lungs called the alveoli.

Although treatment has greatly improved over the past two decades, ARDS arising from influenza infections still kills thousands of patients each year in the United States, notes UCSF pulmonologist and critical care specialist Matthay. The number of COVID-19 deaths due to ARDS is expected to be much greater.

“Most of the mortality in COVID-19 is due to severe ARDS,” Matthay said. “Somewhere between about 17 percent to 30 percent of hospitalized COVID-19 patients are ending up with ARDS, and about 40 to 50 percent who develop ARDS are dying, based on data from China and some regions of the U.S.”

Normally blood passing through the lungs is able to take in oxygen and get rid of carbon dioxide by diffusing these gases across healthy alveoli and adjacent capillaries through a thin, delicate membrane of tissue. But as the immune system responds to worsening infection and initial lung injury associated with viral pneumonia, it may trigger so much inflammation that it causes further damage and disruption to the cells involved in this gas exchange.

As the alveoli begin to fill with fluid the body becomes increasingly starved for oxygen. At this stage the patient’s condition is likely to quickly deteriorate, creating an urgent need for mechanical ventilation.

Where There’s Smoke

COVID-19 can attack a healthy person’s lungs, but the disease can be worse for people whose lungs are vulnerable, including from smoking. Smoking damages some lung tissue directly, according to Matthay, including hair-like cilia that help sweep mucus out the lungs.

“It’s well known that tobacco smokers are at greater risk for bacterial pneumonia as well as viral pneumonia,” Matthay said.

In addition, compared to non-smokers, smokers who contract viral pneumonia are probably more likely to die from ARDS. Early research on the current pandemic already indicates that the fatality rate is higher among smokers with COVID-19.

Damage to the lungs doesn’t have to be from just smoke. Although vaping products are heated, not burned, they still pose health risks to lungs. Since last year more than 2,800 who vape have been hospitalized and 68 have died, many from ARDS, according to the CDC. A large majority of the hospitalizations are attributed to THC products containing the oil vitamin E acetate.  

“We found that vitamin E acetate is injurious to lungs both in mice and to human lung alveolar epithelial cells grown in the lab,” Matthay said.

But the chemical components of other vaping formulations, including nicotine products, also are likely to prove harmful, according to UCSF pulmonologist and epidemiologist John Balmes, MD.

“I suspect that whenever you inhale a heated chemical aerosol it’s going to increase the risk for lung infection,” Balmes said.

Compromised Lungs From COPD, Asthma

Smoking accounts for a great majority chronic obstructive pulmonary disease (COPD), including bronchitis. Smoking rates for people diagnosed with COPD, or with asthma, a chronic lung disease in which the lung’s airways easily constrict, are about the same as for the general population, according to UCSF pulmonologist Stephen Lazarus, MD.  

“Asthma, and to a lesser extent COPD, are inflammatory diseases,” Lazarus said. “The inflammation is exacerbated by viral infections, and by smoking and air pollution. Early data indicate that outcomes are worse for COVID-19 patients with asthma or COPD, but does not show that they are at any increased risk of becoming infected.”

Lazarus urges asthma patients who are worried about their COVID-19 risk to continue taking medications prescribed to help prevent their airways from contracting so easily, including any prescribed inhaled steroids, which are less immunosuppressive than oral steroids, Lazarus said. Patients with chronic respiratory disease who smoke might want to reconsider the possibility of quitting.

Will Wildfires Rage Alongside the Pandemic?

Like smoking, air pollution increases inflammation, Balmes said. Lung diseases might be the most obvious chronic conditions affected, but they are not the only ones. Epidemiological studies have found associations between air pollution levels and diabetes, heart disease, lung disease, and high blood pressure. Much of the mayhem caused by air pollution appears to be due to small-particle air pollution.

Even relatively short-term increases in ambient air pollution, as occurs with large wildfires, have been associated with increased hospital admissions for heart conditions, asthma and pneumonia. A 2003 study of the related coronavirus that caused thousands of SARS cases in China found an association between air pollution levels and fatality.

Balmes suggests that a good share of the biological underpinnings for these epidemiological associations is likely due to inflammation.  Immune cells called macrophages are tasked with gobbling up and getting rid of all the tiny particles from combustion products that enter the lungs.

“The macrophages in the alveoli can become overloaded, and this probably contributes to infection risk,” he said.

About half of California and much of the West are abnormally dry now, possibly priming these regions for major wildfires that in a few months may again torch populated areas and blanket millions with hazardous, smoke-filled air.

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“There really is growing concern that wildfires may hit us before the spread of COVID-19 is under control,” Balmes said. “That would really be a double whammy.”