PM2.5 Pollution increases the risk of COVID-19

USA. Researchers at Harvard compared COVID-19 death counts in over 3,000 counties in the United States (represent­ing 98% of the population) with PM2.5 pollution.  They found an 8% increase in COVID-19 death rates for every 1 ug/m3 of long-term PM2.5 exposure [1].

Italy. Air pollution was also linked to higher COVID-19 death rates in Italy, with  mortality rates up to 12% in the most polluted parts of northern part of Italy and only approx. 4.5% in the rest of the country [2, 3].

The virus that causes COVID-19 was identified on air pollution samples at one urban and one industrial site in Bergamo province, Italy.  Italian scientists are investigating whether this could enable the virus to be carried over longer distances and increase the number of people infected [4].

China. A peer-reviewed journal publication reported significant associations between air pollution in the previous 2 to 3 weeks and Covid-10 cases. A 10 ug/m3 increase in PM2.5 elevated the risk by almost 4% [5]. These results for short-tem PM2.5 exposure complement the analysis at Harvard of an even higher risk after years of PM2.5 exposure, similar to the effects of long- and short-term PM2.5 exposure on other health problems such as lung and heart diseases.

The Netherlands is unique because the worst air pollution is not in cities but in some rural areas, due to intensive livestock farming. This allows the “big city effect” to be ruled out, which is the idea that high air pollution simply coincides with urban populations whose density and deprivation may make them more susceptible to the virus [6]. The results suggest that a 1 ug/m3 decrease in PM2.5 would have reduced cases by 10%, hospitalizations by 12% and deaths by 21%.  If all municipalities had their pollution reduced to 6.9 ug/m3 (same as the least polluted municipality), there might have been  37% fewer cases, 45% fewer hospital admissions and 75% fewer deaths [7].

Chile. In Chile, higher PM2.5 levels were found to be associated with higher number of cases and deaths of COVID-19 In Chile, domestic wood heating is a major source of air pollution.

Flu Pandemics. Observational studies show that air pollution worsened the 1918, 1957-58 and 1968-69 flu pandemics. In China, the risk of dying from SARS more than doubled at high levels of air pollution.

Implications for NSW & Australia. Few people understand that the largest single source of air pollution in NSW is from domestic wood heaters, used as the main form of heating by only 4.4% households in Sydney.  Some of the best information is from the NSW Government research, which attributes 1,400 lost years of life (LYL) annually in Sydney to wood heater pollution (100 premature deaths every year), compared to 620 from power stations (45 premature deaths) and 990 from on-road sources (72 premature deaths).

The recent droughts and bushfires linked to global warming have also exacerbated air pollution from bushfires. Attempts to reduce wood heater pollution as the major source of avoidable air pollution, would therefore would therefore have multiple benefits, because of the impact of firewood collection on biodiversity, as because wood heaters emit substantial amounts of methane and black carbon that speed up global warming.

Some authorities recommend: Burn less wood to reduce Covid-19 risk. Some authorities are now taking action to reduce woodsmoke pollution to ease the health burden of COVID-19.  In March 2020, British Columbia’s environment ministry introduced temporary restriction on burning, saying that smoke’s impact could lead to increased numbers and severity of COVID-19 cases, adding to the burden on the province’s health care system. Michael Brauer, a respiratory and environmental health professor at the University of British Columbia, Vancouver, explained that, like the social distancing measures being widely implemented, cleaner air would help “flatten the curve”, reducing the number of patients requiring hospitalization at any one time [8].
Residents in Brighton, UK, have been asked to ‘think twice’ about lighting wood-burning stoves and other fires during the coronavirus crisis, because the smoke makes respiratory conditions worse - Don’t use wood-burning stoves during coronavirus crisis, council urges.

Further information

1.     Wu, X., et al. Exposure to air pollution and COVID-19 mortality in the United States: A nationwide cross-sectional study (Updated April 24, 2020). Available at: 2020.

2.     Science Daily. Link between air pollution and coronavirus mortality in Italy could be possible. Available at: 2020.

3.     Setti, L., et al., The Potential role of Particulate Matter inthe Spreading of COVID-19 in Northern Italy: First Evidence-based Research Hypotheses. 2020.

4.     Carrington, D., Coronavirus detected on particles of air pollution in The Guardian. Available at: 2020.

5.     Zhu, Y., et al., Association between short-term exposure to air pollution and COVID-19 infection: Evidence from China. Science of The Total Environment, 2020. 727: p. 138704.

6.     Carrington, D., ‘Compelling’ evidence air pollution worsens coronavirus – study, in The Guardian. Available at: 2020.

7.     Cole, M.A., C. Ozgen, and E. Strobl, Air pollution exposure linked to higher COVID-19 cases and deaths – new study, in The Conversation. Available at: 2020.

8.     Gardiner, B., How Air Pollution Makes The Coronavirus So Much More Dangerous, in HuffPost. Available at:  . 2020.