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Long-term exposure to ambient air pollution may increase the risk of Covid-19 infection, suggests research published online in the journal
«Occupational & Environmental Medicine».
The average annual increase of 1 µg / m3 of particles is linked to a 5% increase in the infection rate. This is equivalent to 294 additional cases / 100,000 people per year, the findings indicate, which focus on the inhabitants of a northern Italian city.
While more research is needed to confirm cause and effect, the results should bolster efforts to reduce air pollution, the researchers say.
Northern Italy has been hit hard by the coronavirus pandemic, with Lombardy being the most affected region in terms of cases and deaths. Several reasons have been suggested for this, including different testing strategies and demographics.
But estimates of the
European Union Environmental Agency show that most of the 3.9 million Europeans residing in areas where air pollution exceeds European limits live in northern Italy.
Recent research has linked air pollution as a risk factor for Covid-19 infection, but errors in study design and data capture only until mid-2020 have limited the findings, the researchers write.
To address these issues, they analyzed long-term exposure to airborne pollutants and Covid-19 infection patterns from the start of the pandemic through March 2021 among residents of Varese, the eighth largest city in Lombardy.
Among the 81,543 residents as of December 31, 2017, more than 97% were linked to the 2018 annual average exposure levels for the main air pollutants, depending on the address.
Regional data on Covid-19 infection and information on hospital discharge and prescription of medications for outpatients were collected from 62,848 adults who have not yet been infected with SARS-CoV-2, the virus responsible for Covid-19 since the end of 2019 until the end of March 2021.
Official figures show that only 3.5% of the population in the entire region was fully vaccinated at the end of March 2021.
Estimates of the annual and seasonal average levels of five airborne pollutants were available for 2018 in an area over 40 km wide: particulate matter (PM2.5, PM10); nitrogen dioxide (NO2); nitric oxide (NO); and ozone (O3).
The average values of PM2.5 and NO2 were 12.5 and 20.1 µg / m3, respectively. The weighted average annual exposures for the population in Italy for the same year were 15.5 and 20.1 µg / m3, respectively.
About 4,408 new cases of Covid-19 were included in the study, which were registered between February 25, 2020 and March 13, 2021. This is equivalent to a rate of 6,005 cases / 100,000 inhabitants / year.
Population density was not associated with an increased risk of infection. But live in a residential care home was associated with a risk of infection more than 10 times greater.
Drug treatment for diabetes, high blood pressure, and obstructive airway diseases, as well as a history of stroke, were also associated with an increased risk of 17%, 12%, 17%, and 29%, respectively.
After taking into account age, gender, and residence in the care home, in addition to concurrent long-term conditions, the averages, both PM2.5 and PM10 were significantly associated with a higher rate of Covid-19 infection .
The associations found were even more notable among the older age groups, indicating a stronger effect of the pollutants in the rate of infection by Covid-19 among people 55 to 64 and 65 to 74 years old, the researchers suggest.
This is an observational study and as such cannot establish the cause. And although the researchers considered several potentially influential factors, they were unable to account for the mobility, social interaction, the humidity, temperature, and certain underlying conditions, as the poor mental health and kidney disease.
Long-term exposure to air pollution increases the risk of respiratory and cardiovascular diseases through persistent inflammation and compromised immunity. Thus, these same pathways may be involved in the link between air pollution and higher rates of Covid-19 infection, the researchers suggest.
«Our findings provide the first solid empirical evidence of the hypothetical pathway that links long-term exposure to air pollution with the incidence of Covid-19, and they deserve future generalization in different contexts, “they concluded. Meanwhile, government efforts to reduce air pollution can help end Covid-19 pollution.
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