A new study published today in the journal Occupational & Environmental Medicine claims that exposure to air pollution could increase the spread of COVID-19

According to research published online in the journal Occupational & Environmental Medicine, long-term exposure to ambient air pollution may increase the incidence of COVID-19 infection.

The strongest correlation was seen for particulate matter, with a 1 g/m3 increase in the infection rate being connected to a 5 percent increase in the rate. This translates to an additional 294 cases/100,000 people every year, according to the data, which are based on residents of a single Northern Italian city.

While additional research is necessary to establish cause and effect, the researchers believe the findings should strengthen efforts to reduce air pollution.

The coronavirus pandemic has wreaked havoc on northern Italy, with Lombardy being the worst-affected region in terms of both infections and deaths. Different testing methodologies and demographics have been offered as possible explanations.

However, according to estimates from the European Union Environmental Agency, Northern Italy is home to the majority of the 3.9 million Europeans who live in places where air pollution exceeds European norms.

According to the researchers, recent research has indicated airborne pollution as a risk factor for COVID-19 infection, however, study design issues and data collection only until mid-2020 have limited the findings.

To get around these problems, they looked at long-term exposure through airborne contaminants and COVID-19 infection trends among residents of Varese, Lombardy’s eighth largest city, from the beginning of the pandemic to March 2021.

More than 97 percent of the 81,543 residents as of 31 December 2017 were successfully connected to the 2018 annual average exposure levels for the major air pollutants based on their residential address.

Regional COVID-19 infection data, as well as information on hospital discharge and outpatient medicine prescriptions, were collected for 62,848 adults who had not been infected with SARS-CoV-2, the virus responsible for COVID-19, between the end of 2019 and the end of March 2021.

By the end of March 2021, only 3.5 percent of the population in the entire region had been properly vaccinated, according to official estimates.

Data of seasonal and annual average levels of five airborne pollutants were obtained for 2018 across a 40-kilometer-wide area: particulate matter (PM2.5, PM10), nitrogen dioxide (NO2), nitric oxide (NO), and ozone (O3).

PM2.5 and NO2 levels averaged 12.5 and 20.1 g/m3, respectively. In Italy, population-weighted average yearly exposures were 15.5 and 20.1 g/m3, respectively, for the same year.

The research involved 4408 new COVID-19 cases that were recorded between February 25, 2020, and March 13, 2021. This translates to 6005 cases per 100,000 people per year.

The study found no link between population density and the probability of infection. However, staying in a residential care home was linked to a 10-fold increased risk of infection.

A history of stroke, drug treatment for diabetes, high blood pressure, and obstructive airway disease, as well as a history of stroke, were all linked to a 17 percent, 12 percent, 17 percent, and 29 percent increased risk, respectively.

Both PM2.5 and PM10 were substantially related with an elevated COVID-19 infection rate after accounting for age, gender, and care facility residency, as well as concurrent long-term illnesses.

Every 1 µg/m3 increase in long-term PM2.5 exposure was linked to a 5 percent increase in the number of new cases of COVID-19 infection, or 294 more cases per 100,000 people each year.

Similar results were obtained when seasonal rather than yearly averages were used, and these findings were validated in additional studies that removed care home residents and controlled for local levels of deprivation and public transportation use. PM10, NO2, and NO were shown to have similar results.

According to the researchers, the observed relationships were even more pronounced across older age groups, indicating a higher effect of pollutants on the COVID-19 infection rate among 55–64 and 65–74-year-olds.

As being an observational study, it is impossible to determine cause. Moreover, despite taking into consideration a variety of potentially important aspects, the researchers were unable to account for mobility, social interaction, humidity, temperature, and some underlying illnesses such as mental illness and kidney disease.

Long-term air pollution exposure increases the risk of respiratory and cardiovascular diseases by causing chronic inflammation and a weakened immune system. According to the researchers, these identical processes may be involved in the relationship between air pollution and greater COVID-19 infection rates.

“Our findings provide the first solid empirical evidence for the hypothesised pathway linking long-term exposure to air pollution with the incidence of COVID-19, and deserve future generalisation in different contexts,” they concluded.

“Meanwhile, government efforts to further reduce air pollution levels can help to mitigate the public health burden of COVID-19.”

Source: 10.1136/oemed-2021-107833

Image Credit: Getty

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