Particle Pollution Increases Coronavirus Mortality, According to Harvard

Michael Tobias
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    The global scientific community is trying to understand the new coronavirus better, and research results are being published daily. On April 7, the Harvard University T.H. Chan School of Public Health published a study of the relationship between coronavirus death rates and fine particulate matter - suspended particles with a size up to 2.5 microns, abbreviated as PM2.5. According to their research, a PM2.5 increase of only one microgram per cubic meter (µg/m3) increases coronavirus mortality by 15%, and the results have a 95% confidence interval.

    The World Health Organization (WHO) and many other institutions have studied the negative effects of fine particulate matter. The health consequences of PM2.5 include respiratory and cardiac illnesses, which are among the conditions that make patients vulnerable to COVID-19.

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    The US Environmental Protection Agency developed the National Ambient Air Quality Standard, where the limit for PM2.5 is 12 µg/m3 annually. The WHO provides an even lower guideline value of 10 µg/m3 annually. If you are a real estate developer who wants to earn the WELL Certification for a building, the indoor PM2.5 concentration must be kept below 15 µg/m3 (35 µg/m3 in commercial kitchens).

    Why Is Fine Particulate Matter so Harmful?

    There are air pollutant particles of all sizes. However, particles smaller than 2.5 microns are especially dangerous, since they can reach deep into the lungs and even the bloodstream.

    • With short-term exposure, fine particulate matter can irritate the eyes, throat and respiratory system. PM2.5 can also cause sneezing, coughing, a runny nose, and heavy breathing.
    • In the case of asthma patients, PM2.5 can worsen symptoms or cause flare-ups.
    • With long-term exposure, PM2.5 can have more severe health effects like lung cancer and heart disease.

    Fine particulate matter is released in large amounts by combustion devices, including motor vehicles and oil-fired heating systems. When there is a high concentration of PM2.5 in urban areas, visibility is reduced and the outdoor air becomes hazy. Many governments monitor the PM2.5 concentration, and they emit public alerts when dangerous levels are detected. Fine particles can reach very high concentrations in urban areas when there is little or no wind.


    The health issues caused by particle pollution are also among the risk factors for severe cases of coronavirus. To study this relationship, Harvard University analyzed coronavirus cases in more than 3,000 US counties, with the data available by April 4, 2020.

    • As mentioned above, a PM2.5 increase of 1 µg/m3 causes a 15% increase in coronavirus mortality. A similar behavior was observed for the Severe Acute Respiratory Syndrome (SARS) in 2003, which is also caused by a coronavirus.
    • Even in the absence of pandemics like coronavirus, air pollution causes 5.5 million premature deaths around the world each year.
    • A previous Harvard study found that a PM2.5 increase of 1 µg/m3 causes a 0.73% increase in overall mortality. The effect on coronavirus mortality alone is over 20 times larger than the effect on overall mortality.

    Considering how particle pollution makes coronavirus cases more severe, there are now stronger reasons to reduce emissions in urban areas. The NYC Green New Deal is one step in that direction, introducing mandatory emissions cuts for buildings in 2024 and 2030.

    Improving Public Health by Reducing Particle Pollution


    In building interiors, particle pollution can be controlled by providing adequate ventilation for combustion appliances, and not allowing indoor smoking. Particulate matter can also be captured by high performance filters such as MERV 16 or HEPA.

    Outdoor particle pollution is a more difficult challenge, since removing particles from the air is unfeasible. To reduce PM2.5 levels in urban areas, the most effective solution is reducing emissions from all sources - vehicles, buildings, manufacturing, power plants, etc.

    Living in a city with polluted air does not necessarily mean that you are more vulnerable to coronavirus. Consider that the severity of symptoms depends on factors like age and lifestyle. In general, city governments in highly polluted areas should prepare for a larger fraction of severe coronavirus cases. Reduced levels of particle pollution can improve public health in the long run, making the population less vulnerable to acute respiratory diseases like COVID-19.

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    Tags : indoor air quality coronavirus air quality particulate matter PM2.5

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