Are the Reductions in Air Pollution Triggered by the COVID-19 Epidemic Having Health Effects?

Photo: An empty street due to social distancing measures in Leeds, UK. Dan Burton on Unsplash.

This article has been written by Xavier Querol, Research Professor at IDAEA-CSIC; Jose Luis Jimenez, Professor at Colorado University-Boulder; and Jordi Sunyer, Head of the Childhood and Environment programme

Cities all over the world are seeing record lows in air pollution. Due to the confinement measures being imposed during the current COVID-19 epidemic, ambient levels of nitrogen dioxide (NO₂)—one of the main traffic-related pollutants in our cities— have declined by between 70% and 80% in Barcelona since 21 March, according to data from the Catalan government. A study carried out by the Universitat Politècnica de València (UPV) estimates the average decline in air pollution in Spain's major cities to be as high as 64%. Similar reductions are being reported in many other cities in Europe and around the world: NO₂ levels in London have declined by approximately 40% and New York is reporting a decrease of about 50% in carbon monoxide (CO) levels.

Photo: European Space Agency (ESA)

While this news may seem very positive, air quality continues to be a long-term and deep-rooted structural issue. Even if air pollution decreases in the coming weeks or months, we believe that a temporary reduction will not be associated with any significant health benefit.

Air quality is a long-term and deep-rooted structural issue. Even if air pollution decreases in the coming weeks or months, we believe that a temporary reduction will not be associated with any significant health benefit

The following are our arguments:

1. Financial crises have never resulted in improvements in policies related to air quality and climate change

In general, the end of a financial crisis is not followed by policies that benefit air quality and combat climate change, as can be seen in the follow-up to the last crisis that started in 2008. Recent history in both Spain and Europe provides several examples of this pattern. Using the argument that a stimulus was required to bring the economy out of the crisis and that environmental policies tend to slow down economic recovery or act as a brake on economic growth, governments implemented measures to reduce the effect of such policies.

The risk to the environment in the aftermath of the current crisis is that environmental policies, including those intended to reduce air pollution, mitigate climate change and protect ecosystems, will be watered down once the acute stage is over. By this we do not mean that existing legislation will be amended, but rather that the process of developing and enacting new legislation will be stalled.

The risk to the environment in the aftermath of the current crisis is that environmental policies, including those intended to reduce air pollution, mitigate climate change and protect ecosystems, will be watered down once the acute stage is over

This was what the 2008 economic crisis, with disastrous effect on plans to implement the World Health Organisation’s guidelines for the protection of air quality by way of European Union Council Directive 1999/30/EC. This directive was supposed to come into force on January 1, 2010, but implementation was postponed until 2014, when it was decided to delay it even further until 2020.

Another example is the case of the Dieselgate emissions scandal; the authorities failed to address the problem adequately because they feared that the actions taken might affect car sales, which were already very low due to the recession. Environmental policies are often affected by fears that they will hinder economic growth. The attitude is understandable, but such fears can lead to monumental errors.

2. It is difficult to determine which reductions are due to meteorological conditions and which are due to social distancing measures

Clearly, reductions in industrial activity and transport lead to a decrease in the emission of pollutants such as particulate matter (PM₁₀ and PM_2.5), nitrogen oxides (Nox), sulphur dioxide (SO₂) and CO, among others. But how much is the actual decline?

Detailed studies are required because climate factors (rain, wind, solar radiation, African dust plumes) have affected the levels of these pollutants differently before and during containment. This means that in-depth analysis is required to determine what percentage of the reduction we are seeing is due to the health crisis and what percentage to climate factors; and to ascertain why the decrease in the levels of PM₁₀ and PM_2.5 particles has been lower than expected.

In-depth analysis is required to determine what percentage of the reduction we are seeing is due to the health crisis and what percentage to climate factors; and to ascertain why the decrease in the levels of PM₁₀ and PM_2.5 particles has been lower than expected

3. Changes in our exposure to pollution: from outdoor traffic to indoor sources

In addition to the above, our personal exposure to external pollutants such as NO₂ can be expected to be lower simply because we are not leaving our homes and are therefore not being exposed to ambient pollution caused by road traffic and other sources (industry, port, construction sites, etc.).

But, in the case of other pollutants, such as ultrafine particles and volatile organic compounds, the effects of containment measures may be to increase our exposure depending on factors such as the presence of smokers, the use of detergents and the cooking methods used in the home. It is important to bear this in mind and not to limit our calculations to the effects of external air pollution only. For example, the current crisis may trigger the use of bleach as a disinfectant—a source of highly toxic compounds that should only be used with the appropriate precautions.

4. Long-term exposure to air pollution is more harmful than short-term exposure

Air pollution has both acute and long-term health effects but the acute effects are moderate compared to the impacts of long-term exposure.

Research has shown daily variations in pollution to be associated with a 1% increase in mortality for every additional 10 ug/m³ of suspended particles (PM₁₀) in the air. It seems unlikely, therefore, that a short-term reduction in pollution could have a beneficial effect comparable in magnitude to the negative effects of the COVID-19 pandemic.

It seems unlikely that a short-term reduction in pollution could have a beneficial effect comparable in magnitude to the negative effects of the COVID-19 pandemic

However, the effects of long-term air pollution on the risk of disease or death are more serious : the same average increase of 10 ug/m³ in PM₁₀ levels over a year increases the risk of mortality by 15%. Moreover, the long-term effects of the reductions in air pollution during the COVID-19 epidemic are difficult to predict. The potential decline during this spring would have to be sustained over time for it to significantly reduce the number of deaths .

And it is likely, as we mentioned in the first point, that haste to jump-start the economy at the end of the crisis will cause air pollution to return to pre-containment or even higher levels. If this happens, the decrease in air pollution during the 2020 epidemic may have only a slight impact on the annual average . The most important objective of air quality control is to reduce each individual’s lifetime exposure, starting even before they are born; the challenge is to win the long-distance race and not a 100-meter sprint.

The long-term effects of the reductions in air pollution during the COVID-19 epidemic are difficult to predict. The potential decline during this spring would have to be sustained over time for it to significantly reduce the number of deaths

What Lessons Can We Learn from this Temporary Improvement in Air Quality?

The current situation can be seen as positive in terms of ozone because the fact that we have seen a reduction ground level ozone during this crisis contradicts the argument often put forward that we cannot affect ozone levels through our actions. Current conditions could also provide a valuable opportunity to assess to what extent it is possible to improve levels of PM and NO₂ in our ambient air and the impact of different emission sources on these levels.

Another clear lesson we can take from this crisis is that it is possible to implement major interventions in our cities for health reasons and that changes that once seemed impossible have now been implemented in just a few days. This opens up the possibility that, once the pandemic has run its course, we could choose another path than the one described above and that we could learn from this experience, leading to a change in priorities and a new situation in which clean air in the urban environment would take its place as a key concern. After all, the World Health Organisation estimates that air pollution kills seven million people worldwide every year, a figure very probably much higher than the eventual death toll from the COVID-19 pandemic.

While the outcomes achieved in previous crises have not been encouraging, we hope that this time will be different and we advocate using strategies that will improve our planet, based on fostering and promoting green energy and prioritising people’s health to tackle the threats that scientists have been warning us about for some time, such as the climate emergency and air pollution.

Ultimately, the origin of the current pandemic in the animal markets in China was a result of illegal hunting, animal abuse and the same kind of predatory and anthropocentric attitude towards nature and fellow humans that drives air pollution. And the lessons learned from this pandemic should also lead us to implement the changes needed to achieve clean air in our cities.