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Covid-19 pandemic raises new questions about the health impacts of air pollution

Against the backdrop of the Covid-19 pandemic, SEI conducted a group question-and-answer session to discuss known and emerging issues about air pollution. Senior Research Fellow Chris Malley, Research Leader Johan C.I. Kuylenstierna, and Acting Africa Centre Director Philip Osano answered questions posed by Communications Officer Karen Brandon.

Published on 23 April 2020
Empty Plaza del Zócalo in Mexico City during lockdown

Empty Plaza del Zócalo in Mexico City during lockdown. Photo: Hector Vivas / Getty Images.

The Covid-19 pandemic has cast a spotlight on the risks to human health posed by air pollution. Though scientists are investigating possible connections between exposure to air pollution and vulnerability to the Covid-19 virus, an extensive body of work has already established that air pollution harms human health in myriad ways.

SEI’s work on the air pollution agenda is twofold. SEI researchers have worked to expand understanding of air pollution’s negative impacts on human health and well-being. In addition, SEI has sought to help countries find and wield policy levers that can simultaneously reduce air pollution at local and regional levels, and reduce emissions that contribute to climate change at the global level.

A large body of evidence from almost all corners of the world demonstrates that it is possible to improve air quality and human health without compromising economic growth.

Let’s begin with the basics about air pollution’s health effects. How does air pollution harm human health? How does air pollution exposure increase health risk factors for disease?

Exposure to air pollution, outdoors and indoors, was associated with approximately 4.9 million premature deaths per year in 2017, according to the Global Burden of Disease project. Premature deaths attributable to air pollution exposure result from respiratory diseases such as chronic obstructive pulmonary disease, cardiovascular diseases such as ischemic heart disease and stroke, lung cancer and acute respiratory infections in children.

Is premature death the main effect of air pollution on health?

Pemature deaths predominantly affect older people, but air pollution threatens young people, too – for example, through increased infant mortality from respiratory infections. And air pollution’s effects aren’t limited to mortality. Exposure to fine particulate matter and ozone air pollution was estimated to be responsible for at least 5 million asthma-related emergency room visits in 2015. Such pollution led to an estimated 2.7 million preterm births in 2010. These data result from research that SEI has undertaken with partners. Air pollution exposure leads to increased numbers of emergency room visits for respiratory and cardiovascular diseases.

Will the short-term reduction in air pollution that appears to be emerging during the lockdowns result in improved health?

These health impacts of air pollution result from both short-term peaks in air pollution that happen on a given day, and long-term exposure that accrues over years. Therefore, short-term reductions in air pollution concentrations have been shown to yield benefits for human health. However, the World Health Organization (WHO) has concluded that the health impacts of long-term exposure are substantially greater than just the sum of the impacts from short-term peaks in air pollution concentrations.

What can be said about the increased risk of Covid-19 as a result of air pollution exposure? What is known at this point?

Air pollution is a risk factor for certain illnesses, such as respiratory and cardiovascular diseases. These same diseases put people at a higher risk from Covid-19. That said, substantially more research is needed to assess the association between exposure to high levels of air pollution and increased risk of developing severe symptoms from Covid-19, as well as the causal, biological mechanism by which this would occur.

Different groups are starting to publish results that indicate that there may be statistical relationships between death rates from Covid-19 and levels of air pollution in some countries, but more time and work are needed before any relationship is established with confidence.

Streets in New Delhi, India during Covid-19 lockdown

Street in New Delhi, India during the Covid-19 lockdown. Photo: Stringer / Getty Images.

Even though understanding of the relationship between Covid-19 and air pollution is evolving, can the pandemic experience begin to inform air pollution policies going forward?

The improved air quality that has been measured in many cities after implementation of measures to slow the spread of Covid-19 has coincided with reduced economic activity globally. However, a large body of evidence from almost all corners of the world shows that air quality can improve without compromising economic growth. In many regions, the reduction in air pollution that has been seen during the Covid-19 pandemic is emerging on top of long-term declines in air pollution that had occurred over decades.

For example, recent research by SEI has shown that in Paris between 2009 and 2018, annual average levels of fine particles (PM2.5) decreased on average by one-third. Over the same period, the GDP of France rose by 13%, according to the World Bank. Across Europe, SEI research has shown that nitrogen dioxide concentrations decreased at over 60% of monitoring sites between 2000 and 2014. Over that time, GDP across the European Union increased by 19%, according to the World Bank. Sustainable reductions in particulate matter and other air pollution concentrations were achieved in Canada and the US over a 20-year period, in which GDP rose by 40%, and over a five-year period in China, where GDP grew by almost 30%.

These air pollution reductions, achieved through public policy, technological improvements and changes in behaviour, have yielded substantial health benefits. For example, clean air policies implemented between 1970 and the present – long before the appearance of any pandemic-related measures – enabled Europe and North America to avoid up to 500,000 premature deaths per year. As these examples unequivocally demonstrate, it is possible to improve air quality, and human health, without compromising economic growth.

What steps could move the world in that direction? Do we need technological innovations to make further progress?

While new technologies have the potential to improve air quality, we already know the actions that need to be taken to reduce air pollutant emissions. These are technically feasible and, in many cases, cost effective. Many countries are already taking these steps.

In 2019, a report, “Air Pollution in Asia and the Pacific: Science-based Solutions”, identified 25 “Clean Air Measures”, which, if implemented, would provide clean air (exceeding the guidelines for air quality set by the WHO) for an additional 1 billion people in Asia. These measures included traditional steps, including “end-of-pipe” actions to control emissions from industry, and vehicle emission standards already used in Europe. But they also included next-generation air quality measures, such as reducing ammonia emissions from fertilizer.

Measures with significant sustainable development benefits, such as replacing traditional cookstoves that use wood or charcoal with cleaner fuels, would also contribute to providing clean air, both outdoors and in homes. This last group of measures also substantially reduces the emission of greenhouse gases causing climate change – underscoring that policies and measures, carefully chosen, can have multiple development benefits.

The pictures of clearer skies in cities do not convey the complexity of the situation regarding the make-up and sources of air pollution.

London on lockdown

London on lockdown. Photo: Dan Kitwood / Getty Images.

Pictures from all over the world are showing dramatically clearer skies, particularly in cities that are usually shrouded in smog.  What is happening with air pollution now? What is the role of the pandemic in changes taking place?

Worldwide, a view has emerged that measures to respond to the Covid-19 crisis have substantially reduced air pollution, and in many cities this is true. However, this narrative is incomplete. The pictures are likely to be different in different places around the world, and for different groups of people in any given place.

This can seem counterintuitive. If everyone is staying at home, and industries have closed, one might logically conclude that air pollution must have fallen. However, the situation reveals the complexity of air pollution itself, which isn’t made up of a single thing. Fine particles (PM2.5), which are responsible for the majority of health impacts from air pollution, and nitrogen oxides (NOx) from vehicles have declined as people have used transportation less. But, this is not the case for all pollutants or emission sources. Take ozone as an example. In contrast to PM2.5 and NOx, ozone  interacts with other pollutants in complex ways. The reductions of other pollutants because of reduced transportation appear to have led to increases in ozone within London, for instance.

Differences in the prevailing sources of emissions for cities and regions matter, too. The most important sources of particulate matter air pollution in certain parts of the world are from different sources: from agriculture in Europe and China; the use of wood and charcoal for cooking in India and China; biomass burning in Africa, Latin America and South East Asia; and power generation in southern Africa and parts of the US. Covid-19 measures may not affect these emission sources as much as transport and industry sources. Therefore, where these sources make large contributions, the reduction in air pollution may be lower than where transport dominates.

Can we measure and compare the effects of the pandemic on air quality and human health in these different places?

In many ways, this pandemic underscores the disparity between developed and developing countries. Air pollution is no different in that respect. For example, most developing countries lack sufficient monitoring to reliably and consistently measure air pollution, or the effects on air pollution resulting from measures implemented to address the spread of the virus – or from any other policy, for that matter. Monitoring is especially scarce in the very cities and regions where air pollution concentrations are believed to be the world’s highest.

In fact, in many developing countries, Covid-19-related measures requiring people to stay indoors and at home could result in higher exposure indoors to emissions from residential wood and charcoal burning, particularly for the world’s poorest and most vulnerable populations. For example, recent research by SEI showed that, in those households using charcoal for cooking in Accra, Ghana, the personal exposure to air pollution was twice as high for household members who spent more time at home than for those who worked outside the home. Lower-income households tend to be more likely to cook with wood and charcoal.

The pandemic only underscores the importance of integrated thinking and approaches to address air pollution, protect human health, and deliver benefits for climate change and sustainable development.

Air pollution from cooking in China

For millions of people, the main source of exposure to air pollution comes from cooking. Photo: Guang Niu / Getty Images.

Using cleaner energy would have other benefits, such as helping to address climate change. Tell us more about that perspective, and how it relates to the current situation and recovery measures.

Actions to improve air quality have multiple, additional benefits. For example, if Asia were to fully implement the 25 measures to achieve cleaner air, global temperatures would fall by 0.3 degrees by 2050, helping to achieve international climate change goals. Those 25 steps also contribute to multiple other Sustainable Development Goals (SDGs), such as access to clean, renewable energy (SDG 7), reducing poverty (SDG 1), and improving health (SDG 3).

Countries have to rethink how they conduct planning so that they can consider and evaluate potential cross-over effects of policies on air quality, climate change, human health, and other areas of sustainable development. Recognition of the potential of such joined-up approaches is growing. Within SEI, for example, we are working on a new initiative that focuses on integrated climate change and development planning. We are developing tools and approaches that allow countries to do this kind of planning more effectively so that they can consider the multiple benefits, including improved air quality, reduced climate change and other sustainable development goals, from different policy and planning decisions.

The pandemic is taking a huge economic toll. What can be said about integrated approaches as countries recover?

If anything, the pandemic only underscores the importance of integrated thinking and approaches. Many countries are now considering large investments to recover from the Covid-19 epidemic. As they make decisions about where these investments should be targeted, considering actions that will sustainably reduce air pollution concentrations can help to protect the health of their populations, as well as deliver other benefits for climate change and development.

Empty Aqueduct of Valens during lockdown in Istanbul

Istanbul on lockdown. Photo: Burak Kara / Getty Images.

What is important in the near future? How should efforts to aid recovery address the issue of air pollution?

Many people have experienced a welcome improvement in air quality during the pandemic. To maintain these improved conditions, investments will need to be made to avoid emissions. Otherwise we will return to the same high levels of air pollution that people have suffered for a long time, and we will continue to suffer the related, debilitating effects on human health, well-being and longevity. Progress in reducing air pollution in many parts of the world has proven that reducing emissions does not prevent economic growth. In fact, cleaner air will promote quality of life, reduce economic impacts related to ill health, and make people more resilient to respiratory diseases.


Chris Malley

Senior Research Fellow

SEI York

Johan C.I. Kuylenstierna

Reader / Research Leader

SEI York

Philip Osano
Philip Osano

Centre Director

SEI Africa

Karen Brandon
Karen Brandon

Senior Communications Officer and Editor


SEI Oxford

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