Higher Air Pollution Can Increase COVID-19 Transmission

AP Photo/Cha Song Ho

In a new study, Chinese experts have found out that higher air pollution concentrations can increase the risk of COVID-19 transmission. The new study was published in a pre-print on the online platform medRxiv today and has not been peer reviewed yet.

Along with higher pollution, lower temperature, relative humidity and wind velocity may also favor COVID-19 transmission, according to the scientists.

Air pollution is a major public health threat in the world. Pollution is especially severe in fast-growing urban areas, which combine high population density with a large number of motorized vehicles and construction work, uncontrolled solid waste burning, and heavy use of polluting sources of energy.

Source: WHO

Till date evidence and data regarding the effects of ambient air pollutants and meteorological factors on COVID-19 transmission is very rare. In this new study scientists wanted to see if there were significant associations of air pollutants and meteorological factors with COVID-19 confirmed cases across 31 Chinese provinces during the outbreak period.

For this purpose, they gathered data on number of COVID-19 confirmed cases, air pollutant concentrations and meteorological factors in 31 Chinese provinces from January 25 to February 29, 2020 from authoritative electronic databases.

This data was then used to analyze the region-specific trends regarding diverse air pollution levels and weather conditions. The scientists found data regarding 77,578 COVID-19 confirmed cases across Chinese provinces during the study period.

After analysis, they found an increase of each interquartile range in PM2.5, PM10, SO2, NO2, O3 and CO at lag4 corresponded to 1.40, 1.35, 1.01, 1.08, 1.28, and 1.26 at odds ratios of daily COVID-19 confirmed new cases, respectively.

The time series distribution of daily COVID-19 confirmed new cases, air pollutant concentrations, and meteorological factors in 31 Chinese provinces from January 25 to February 29, 2020. Columns represent daily COVID-19 confirmed new cases while curves represent daily mean air pollutant concentrations and meteorological factors. –Source: medRxiv

For each increase in temperature, relative humidity and wind velocity, the odds ratios were at 0.97, 0.96, and 0.94, respectively.

This means that the estimates of PM2.5, PM10, NO2 and all meteorological factors were statistically significant when it came to the transmission of COVID-19 cases.

This led the scientists to conclude that higher concentrations of air pollutants and lower meteorological factors were associated with daily COVID-19 confirmed new cases increasing.

Researchers around the world suggest that air pollution has significantly worsened the impact of COVID-19 and may have led to more deaths.

Source: Encyclopedia of the Environment

Scientists have also suggested that harmful air particles found in polluted environments may be predisposing people to the virus. Another theory suggests that these particles may also act as vehicles for viral transmission.

A study in Europe found that 78 percent of the deaths related to COVID-19 in northern Italy and Spain occurred in the five regions that had the worst combination of nitrogen dioxide levels and airflow conditions, which prevent dispersal of air pollution.

A high level of correlation between COVID-19 cases and air pollution has also been reported in similar studies in the United States and the Netherlands.

Among all of these pollutants the most dangerous perhaps are PM2.5 particles which are so named due to their size. They are so small that they can be only seen by electron microscope.

Source: PM2.5 in Beijing

These atmospheric particulate matters (PM) come from various sources such as motor vehicles, airplane, power plants, volcanic eruptions, dust storms, and forest fire along with wood burning and agricultural burning.

They are quite dangerous for humans and animals. They are so small that they stay longer in the air. This increases the chance of animals and humans inhaling them. Due to their small size they can end up in the blood circulatory system by bypassing smallest of gaps in cells of the lungs.

Previously it has been seen that these particles are closely linked with premature death due to lung and heart disease. Their long-term exposure can cause plaque deposits in arteries that carry blood. This can cause vascular inflammation and hardening of arteries which can lead to stroke and a heart attack.

Source: UN Environment Program (GRID-Arendal)

They can also increase the intensity of heart attack, bronchitis, asthma, and other multiple respiratory health issues. American Heart Association warns that exposure to these particles over a few hours to weeks can trigger cardiovascular disease-related mortality and nonfatal events.

Long-term exposure can reduce life expectancy by several months to a few years. These particles have also been linked to birth defects in infants where mothers were exposed to it.

When countries started enforcing lockdowns to contain the COVID-19, major cities around the world recorded significantly lower levels of nitrogen dioxide and sulfur dioxide, both harmful chemicals released in part by motor vehicles and power plants.

Cities with historically high particulate matter (PM2.5) concentration levels also experienced a substantial reduction in pollution. But it is difficult to say where these levels will fall as economies begin to reopen.

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