COVID-19 and exposure to air pollution

A scientist from the Netherlands has worked on a study that looked at the association between COVID-19 infections and exposure to air pollution. Researcher Bo Pieter Johannes Andrée’s study titled “Incidence of COVID-19 and Connections with Air Pollution Exposure Evidence from the Netherlands” was released prior to the peer review process on the online server Medrxiv.

Bo Andree is a researcher at the Department of Spatial Economics of the VU University Amsterdam and a data scientist with the Fragility Conflict and Violence unit at the World Bank.

Industrial Pollution - an industrial skyline in Rotterdam - Netherlands. Image Credit: Steve Allen / Shutterstock

What was the study about?

The author explains that the risk of viral respiratory infections such as COVID-19 is substantially raised in the presence of high particulate matter – an indicator of high air pollution exposure. He wrote, “Several hot-spots of Severe Acute Respiratory Syndrome Coronavirus 2 infections are in areas associated with high levels of air pollution.”

Novel Coronavirus SARS-CoV-2: This scanning electron microscope image shows SARS-CoV-2 (round gold objects) emerging from the surface of cells cultured in the lab. SARS-CoV-2, also known as 2019-nCoV, is the virus that causes COVID-19. The virus shown was isolated from a patient in the U.S. Credit: NIAID-RML

Andree wrote that this was a Policy Research Working Paper which aimed at getting to results rapidly. He explains that there had been a rapid spread of the severe acute respiratory syndrome (SARS) caused by the novel coronavirus or severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and there are several hot spots that have been identified across the world. These are all areas where most of the cases of the infection have been seen.

“Several of these are located in areas associated with high levels of air pollution. This study was essentially conducted to look at the association between exposure to particulate matter and COVID-19 incidence in 355 municipalities in the Netherlands”.

What was done?

This study looked at the association between exposures to air pollution (in the form of particulate matter) and the incidence of COVID-19 infection among 355 municipality areas in the Netherlands. The data was obtained from the confirmed cases as well as the hospital records and admissions according to the place of residence of the individuals. The air pollution levels of the residence areas of the patients were assessed using PM 2.5 (Particulate matter 2.5) and PM 10. Apart from that, the density of population at the locality and other health conditions of the patients were also recorded. Tests used to assess the association included “spatial dependence, nonlinearity, alternative error distributions, and outlier treatment,” wrote the researcher. Andree explained that these results took into consideration several factors, including preexisting diseases, the severity of symptoms, control variables. They take into account ground-measurements and satellite-derived measures of atmospheric particulate matter.

What was found?

Results showed that those exposed to PM2.5 were at a higher risk of getting COVID-19. They wrote, “PM2.5 is a highly significant predictor of the number of confirmed COVID-19 cases and related hospital admissions.” The author explained that the World Health Organization (WHO) outlines a guideline of 10mcg/m3 as a baseline. He wrote that this study revealed that cases of COVID-19 rose by 100 percent when the concentration of pollution rose by 20 percent.

Hot spot connection

Bo Andree says that the risk of some airborne viruses could rise if there are higher amounts of ambient fine particles.  These fine particles can stay suspended in the air for long and also travel far from one place to another. When inhaled, these particles can also reach deep within the lung tissues causing damage.

Measles is one such virus that has shown an increased propensity to cause infection in regions where there is more air pollution. One previous study has shown that in China, the risk of getting measles rose after 1 to 3 days of exposure to higher concentrations of PM10 and SO2 (Sulphur dioxide). The relative risk of getting influenza also rose if the air pollution levels were high in the Chinese cities, found researchers. The effect was most significant within two to three days after exposure to the fine particulate matter.

“If air pollution plays a similar role in the incidence of SARS-CoV-2, there should be a positive relationship between confirmed COVID-19 cases and particulate matter concentrations.”

He added that China is one of the worst polluted nations with the highest amount of PM2.5 concentrations. The Hubei province, where the COVID-19 infections first originated, is also one of the worst polluted regions. In another hard-hit nation Italy, one of the worst polluted areas is the Lombardy area in the northern Po valley. This region has some of the worst quality of air in the whole of Europe, say the researchers. Some studies show that most of the severely affected cases of COVID-19 in Italy were from this region. However, not all densely populated areas are badly affected by the infection, say the researchers and the connection could be the quality of air.

Conclusions and future recommendations

This study reveals a strong connection between air pollution and COVID-19. They wrote that these findings make it evident that there is a need for further studies to look at the association between air pollution and SARS CoV-2 infection risk. Bo Andree says, “If particulate matter plays a significant role in the incidence of COVID-19 disease, it has strong implications for the mitigation strategies required to prevent spreading, particularly in areas that have high levels of pollution.”

*Important Notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Journal reference:

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.

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