As we discussed in our previous article, COVID-19 has become a global public health problem, arising questions about its relation to many global issues that humanity is facing these years, such as climate change and air pollution, all of which still remain under careful scrutiny from scientists all around the world.

One of these important topics is COVID-19’s relation with air pollution. Luckily, many articles have now been issued on this argument, leaving us with no doubt about the existence of a significant correlation between air pollution and COVID-19 infection.

A new study

In particular, Yongjian Zhu, Jingui Xie, Fengming Huang, Liqing Cao’s study aimed to explore the relationship between ambient air pollutants and the infection caused by the novel coronavirus. Daily confirmed cases, air pollution concentration and meteorological variables in 120 cities were obtained from January 23, 2020 to February 29, 2020 in China.

They applied a generalized additive model to investigate the associations of six air pollutants (PM2.5, PM10, SO2, CO, NO2 and O3) with COVID-19 confirmed cases. They observed significantly positive associations of PM2.5, PM10, NO2 and O3 in the last two weeks with newly COVID-19 confirmed cases. A 10-μg/m3 increase (lag0–14) in PM2.5, PM10, NO2, and O3 was associated with a 2.24% (95% CI: 1.02 to 3.46), 1.76% (95% CI: 0.89 to 2.63), 6.94% (95% CI: 2.38 to 11.51), and 4.76% (95% CI: 1.99 to 7.52) increase in the daily counts of confirmed cases, respectively. However, a 10-μg/m3 increase (lag0–14) in SO2 was associated with a 7.79% decrease (95% CI: −14.57 to −1.01) in COVID-19 confirmed cases.

Their results indicate that there is a significant relationship between air pollution and COVID-19 infection, which could partially explain the effect of national lockdown and provide implications for the control and prevention of this novel disease.

The research continues

Another study, this time from England, explored potential links between major fossil fuel-related air pollutants and SARS-CoV-2 mortality. They compared current SARS-CoV-2 cases and deaths from public databases to both regional and subregional air pollution data monitored at multiple sites across England. After controlling for population density, age and median income, positive relationships were shown between air pollutant concentrations, particularly nitrogen oxides, and COVID-19 mortality and infectivity. Using detailed UK Biobank data, they further show that PM2.5 was a major contributor to COVID-19 cases in England, as an increase of 1 m3 in the long-term average of PM2.5 was associated with a 12% increase in COVID-19 cases.

The relationship between air pollution and COVID-19 withstands variations in the temporal scale of assessments (single-year vs 5-year average) and remains significant after adjusting for socioeconomic, demographic and health-related variables. They conclude that a small increase in air pollution leads to a large increase in the COVID-19 infectivity and mortality rate in England.

These findings were confirmed by the European Society of Cardiology, whose research estimated for the first time the proportion of deaths from the coronavirus that could be attributed to the exacerbating effects of air pollution for every country in the world.

Their results, published in Cardiovascular Research, suggested that air pollution is an important cofactor increasing the risk of mortality from COVID-19. This provides extra motivation for combining ambitious policies to reduce air pollution with measures to control the transmission of COVID-19. These scientists estimated that about 15% of deaths worldwide from COVID-19 could be attributed to long-term exposure to air pollution. In Europe the proportion was about 19%, in North America it was 17%, and in East Asia about 27%. These are alarming numbers that should awake all of us to the dangers of air pollution.

Other scientists found a more modest but always present link between air pollution and COVID-19, also stressing out the importance of following all precautions by the rule, since weather’s changes alone (such as a warmer weather and/or a lower air pollution level) cannot eliminate the risk of infection.

Finally, several academics also underline how assessing whether long-term exposure to air pollution increases the severity of COVID-19 health outcomes, including death, remains an important public health objective. Limitations in COVID-19 data availability and quality remain obstacles to conducting conclusive studies on this topic. At present, publicly available COVID-19 outcome data for representative populations are available only as area-level counts. Therefore, studies of long-term exposure to air pollution and COVID-19 outcomes using these data must use an ecological regression analysis, which precludes controlling for individual-level COVID-19 risk factors. They describe these challenges in the context of one of the first preliminary investigations of this question in the United States, where they found that higher historical PM2.5 exposures are positively associated with higher county-level COVID-19 mortality rates after accounting for many area-level confounders. Motivated by this study, they lay the groundwork for future research on this important topic, describe the challenges, and outline promising directions and opportunities.

Conclusions

The stakes for the world are enormous, and the results of robust research studies are urgently needed in order to provide information that could help in developing strategies for facing the current pandemic as well as future pandemics. Several academics’ recommendations for future research focus on (but are not limited to) the investigation, both outdoors and indoors, of airborne transmission routes, lifetimes and dynamics, dosimetry and infection thresholds within the human body, and the physical/chemical/biological/toxicological/virological properties of virus-laden bioaerosol particles, with all of these factors properly adjusted for a wide number of potential confounders. This research should come from a multidisciplinary approach, involving a strong collaboration between traditionally distinct disciplines of science.

 

Read the full articles here:

 

  1. Yongjian Zhu, Jingui Xie, Fengming Huang, Liqing Cao, Association between short-term exposure to air pollution and COVID-19 infection: Evidence from China, April 2020 (https://www.sciencedirect.com/science/article/abs/pii/S004896972032221X)
  2. Marco Travaglio, Yizhou Yu, Rebeka Popovic, Liza Selley, Nuno Santos Leal, Luis Miguel Martins, Links between air pollution and COVID-19 in England, October 2020 (https://www.sciencedirect.com/science/article/pii/S0269749120365489)
  3. Andrea Pozzer, Francesca Dominici, Andy Haines, Christian Witt, Thomas Münzel, Jos Lelieveld, Regional and global contributions of air pollution to risk of death from COVID-19, October 2020 (https://academic.oup.com/cardiovascres/article/116/14/2247/5940460)
  4. Daniele Contini, Francesca Costabile, Does Air Pollution Influence COVID-19 Outbreaks?, April 2020 (https://www.mdpi.com/2073-4433/11/4/377/htm)
  5. Ran Xu, Hazhir Rahmandad, Marichi Gupta, Catherine DiGennaro, Navid Ghaffarzadegan, Heresh Amini, Mohammad S. Jalali, The Modest Impact of Weather and Air Pollution on COVID-19 Transmission, May 2020 (https://www.medrxiv.org/content/10.1101/2020.05.05.20092627v3)
  6. X. Wu, R. C. Nethery, M. B. Sabath, D. Braun, F. Dominici, Air pollution and COVID-19 mortality in the United States: Strengths and limitations of an ecological regression analysis, September 2020 (https://advances.sciencemag.org/content/6/45/eabd4049?utm_campaign=SciMag&utm_source=JHubbard&utm_medium=Twitter)
  7. Frédéric Dutheil, Julien S. Baker, Valentin Navel, COVID-19 as a factor influencing air pollution?, August 2020 (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7144597/)