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Long-term exposure to air pollution linked to severe Covid

A recent study led by the Barcelona Institute of Global Health (ISGlobal) has found that long-term exposure to air pollution increases the risk of developing severe forms of Covid-19, being admitted to the hospital or intensive care units (ICUs) after infection, and dying. The analysis was based on a large cohort of 4,660,502 adults residing in Catalonia in 2020, the year this Spanish autonomous community had a particularly high incidence of Covid-19.

The experts used data from COVAIR-CAT, a large population-based study examining the relation between Covid-19 and air pollution in Catalonia, as well as from the SARS-CoV-2 surveillance system (SUVEC), which collected information on PCR and rapid antigen test results in cohort participants. 

In addition, the team determined the mean annual levels of fine particulate matter (PM2.5), nitrogen dioxide (NO2), black carbon (BC), and ozone (O3) at the residential address of each of the participants.

The researchers examined data on severe cases of Covid-19 in 2020, such as the number of hospital and ICU admissions, the length of hospital stays, and the number of deaths. They found that an increase in exposure to PM2.5 of 3.2 µg/m3 was associated with a 19 percent rise in hospital admissions, an increase in exposure to NO2 of 16.1 µg/m3 with a 42 percent rise in ICU admissions, and an increase in exposure to BC of 0.7 µg/m3 with a six percent rise in mortality.

“One of the strengths of our analysis is that the population is very well represented. The study covers both large urban conglomerations and rural areas and we were able to obtain detailed individual-level data on the participants’ exposure to ambient air pollution in a country heavily affected by the pandemic in 2020,” said senior author Cathryn Tonne, an environmental epidemiologist at ISGlobal.

According to the researchers, several biological mechanisms could explain why long-term exposure to air pollution increases the risk of severe Covid. 

First, exposure to air pollution increases the risk of developing chronic comorbidities linked to severe infections, such as hypertension. 

Second, air pollution may facilitate the infection, since exposure to fine particulate matter was shown to increase the expression of the receptors the virus binds to, especially in the lungs. 

Finally, exposure to air pollution is strongly associated with changes in the immune defenses used to fight the virus, such as a decrease in type II interferon and antibody responses.

While many studies on the effects of short- and long-term exposure to air pollution on chronic respiratory diseases have already been published, this is one of the first to examine the impact long-term exposure has on the incidence and severity of acute respiratory infections. 

 “Our findings add further compelling evidence on the importance of reducing levels of air pollution to improve the health of the population in general and, in particular, to reduce the incidence of severe acute respiratory infections,” concluded lead author Otavio Ranzani, an epidemiologist at ISGlobal.

The study is published in the journal Nature Communications.

More about air pollution and respiratory infections 

Air pollution has been linked to various adverse health effects, including respiratory infections. When people are exposed to polluted air, particularly those containing high levels of harmful particles or gases, it can have detrimental effects on their respiratory system and increase the risk of developing respiratory infections. Here’s how air pollution and respiratory infections are interconnected:

Increased susceptibility

Exposure to air pollution weakens the immune system and makes individuals more susceptible to respiratory infections. Pollutants can irritate the airways, damage lung tissues, and impair the body’s defense mechanisms, making it easier for infectious agents like bacteria or viruses to invade the respiratory system.

Respiratory symptoms

Air pollution can cause or exacerbate respiratory symptoms such as coughing, wheezing, shortness of breath, and chest congestion. These symptoms can make individuals more vulnerable to infections by compromising the respiratory system’s ability to clear pathogens effectively.

Inflammatory response

Air pollution triggers an inflammatory response in the respiratory system. Prolonged exposure to pollutants leads to chronic inflammation, which can impair the immune response and increase the likelihood of respiratory infections.

Impaired lung function

Long-term exposure to air pollution can result in reduced lung function. Weakened lung capacity makes it more difficult for the body to defend against respiratory infections and can prolong the recovery time from such infections.

Interaction with pathogens

Air pollutants can interact with infectious agents, such as bacteria and viruses, altering their behavior and increasing their virulence. This interaction may enhance the pathogen’s ability to infect the respiratory system and cause more severe respiratory infections.

Indoor air pollution

Indoor air pollution, caused by factors like cooking stoves, tobacco smoke, and volatile organic compounds (VOCs), can also contribute to respiratory infections. Poor ventilation in indoor spaces can lead to a buildup of pollutants and increase the risk of respiratory infections, particularly among vulnerable populations such as children and the elderly.

It is worth noting that while air pollution can increase the risk of respiratory infections, it is usually not the sole factor responsible. Other factors such as individual susceptibility, overall health status, and the presence of other risk factors also play significant roles in determining the likelihood of developing respiratory infections.

Efforts to reduce air pollution through policies, regulations, and individual actions can have a positive impact on respiratory health by reducing the risk of infections and improving overall respiratory well-being.

By Andrei Ionescu, Staff Writer

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