The general connection between polluted air and health problems has been a recurring theme here on air-Q's air quality blog. For example, breathing bad air leads to respiratory stress - and can be a trigger for allergic asthma, hay fever or neurodermatitis(read more in this blog post). In 2016, the European Environment Agency attributed more than 410,000 premature deaths in 41 European countries to air pollution from particulates(PM2.5), another 71,000 to nitrogen oxides and 15,100 deaths to exposure to ground-level ozone(post dated 17 October 2019).
Scientists at the Harvard T.H. Chan School of Public Health have now investigated in a recent statistical evaluation what influence air pollution in American counties has on the death rate from the coronavirus (SARS-CoV-2):
With an increase in particulates particles of only 1 μg/m³, the Covid-19 death rate increases by 15 per cent.
Patients who breathe bad air for more than 15 years are more likely to develop pre-diseases because the particulates particles can penetrate the bloodstream via the alveoli and the human cells all the way to the lungs and brain. In the lung tissue, this often leads to protracted inflammation, which in extreme cases can lead to cancer. These pre-existing conditions are subsequently decisive in determining whether a covid disease is mild or severe or even fatal.
Impact of air pollution in Manhattan
The findings of the Harvard study are clear: if the borough of Manhattan had reduced its air pollution accordingly to 1 μg/m³ of air over the past decades, there is a high probability that there would have been about 250 fewer deaths by 4 April.
Besides lung damage, diabetes and cardiovascular problems are among the most common pre-existing conditions found in Covid 19 ICU patients in the US. Four out of five of these patients have a corresponding pre-existing condition.
According to study leader and biostatistics professor Dr Francesca Dominici, this association between PM2.5 air pollution and the Covid 19 death rate is 20 times stronger than previously established associations between air pollution and an overall death rate. The so-called Medicare study (2017) had shown a 0.7 percent increase in the death rate with a one unit increase in air pollution.
Other risk factors were removed from the statistics as far as possible: This concerns, for example, the density of available beds in intensive care units in relation to the size of the population or the obesity of patients.
In the short term, the Harvard scientists' findings mean that American counties with traditionally high levels of air pollution should prepare for more severe courses of the coronavirus epidemic. This also affects the supply of ventilators and respirators within a state. According to the report, there could be a particularly high number of severe cases in the Central Valley district (California), which is dominated by agriculture, or in the Cuyahoga district (Ohio), which has a particularly high number of industrial plants.
Differentiated measurements of particulates of any size necessary
For the time after the Corona crisis, however, additional consideration should be given in the medium term - also in Europe - to broader measurements, especially of the smallest particulates particles (ultra-particulates). "New studies show that smaller particulates particles and ultra-particulates remain in the air for a very long time, in some cases indefinitely, because these particles only fall to the ground once they have docked with larger particles," says particulates expert Frank Hoferecht, Managing Director of ETE EmTechEngineering GmbH - the first spin-off from the DBFZ Deutsches Biomasseforschungszentrum gemeinnützige GmbH.
To date, however, there are no comprehensive studies on the number of such ultra-particulates particles in the ambient air, for example in cities. "In modern combustion engines, this circumstance is even deliberately exploited," says Hoferecht - smaller and more dangerous particulates is produced here in favour of a reduction in coarse particulates. Hoferecht: "For example, the most modern high-pressure direct injection engines cause significantly more ultra-particulates compared to conventional engines, because the fuel is already broken down into ultra-fine particles before combustion."
In order to recognise the dangers to one's own health, corresponding particulate matter measurement data should be collected and published in a more differentiated manner, demands Mario Körösi, Managing Director of Corant GmbH. "The mass data is misleading for normal citizens. It suggests that the same mass per volume means the same harmfulness. However, scientific findings indicate that it is rather the number of particles that is important. For example, up to one million particles more are hidden in ultraparticulates PM0.1 compared to PM10 for the same mass."
Instead of focussing solely on the misleading mass figure, a distinction should be made for particulate matter according to particle size up to ultra-particulates (PM0.1), according to mass per volume (µg/m³) and additionally according to the number of particles," says Körösi. "If these data are not measured in a differentiated way and made accessible to people, misinterpretations will occur that can prevent developments and ultimately affect the health of many people.
Harvard scientists want to analyse more data
The Harvard scientists have submitted their study "Air Pollution and Mortality in the Medicare Population" to the New England Journal of Medicine for publication in a peer-reviewed journal. The researchers have published the underlying data sets here. Further research will include data that further delineates coronavirus disease regionally. Furthermore, socio-demographic factors will be examined in addition to the death rate.
