Clean skies and longer vistas have been one of the few silver linings in the current COVID-19 crisis. Delhi residents saw the Himalayas again in April and May as particulate matter in the Indo-Gangetic Plain reached a 20-year low. Evidence from ground monitors and satellites shows widespread drops in lung-damaging nitrogen dioxide: 20-40% over cities in China, Europe and the U.S. Particulate matter also dropped in many cities during lockdown.
To be clear: the COVID lockdown has not “solved” the air-quality problem. Sharp drops in movement, manufacturing, and (in some places) electricity needs visibly cleared the air, but they neither removed all pollution, nor achieved these changes at anything like a reasonable cost. Ground-level ozone pollution in the U.S., for example, remained high during the lockdown, in part due to the underlying chemistry of how it is formed, but also because trucks, power plants, refineries and other major contributors were still running. And some of the underlying structural drivers of air pollution — energy poverty, cutting corners on emission controls, and weak regulations and enforcement — appear to be growing stronger as economies reopen. The U.S. president has issued two executive orders in recent weeks that limit environmental review and pollution control requirements for infrastructure, citing the need to avoid hindering economic recovery. India, on the other hand, is maintaining its Budget 2020-2021 financial commitment to substantially increase investment in cleaning up urban air, even as the lockdown has created economic stress and is likely to have increased exposure to indoor air pollution.
The coronavirus crisis, however, has brought the clean air stakes into sharp relief. The slow-down has provided a fleeting glimpse of a clean air future — one with fewer asthma cases; longer life spans; healthier crops, forests and ecosystems; less warming; and more predictable rainfall. It also has highlighted the far-reaching health implications of living with air pollution. Not only does pollution increase vulnerability to infectious disease, but COVID-19’s effects on lungs will almost surely increase vulnerability to pollution’s effects on asthma patients and those with other respiratory complications.
We need to act now to achieve a healthier clean air future. Air pollution is not only the leading environmental risk for premature death, but a bigger threat to sustainable development than most people realize.
The evidence on the science of pollution sources and the political economy of air quality action points to three steps that can help make a clean-air future a reality.
1. Tackle the real sources.
One lesson from the COVID-19 economic slowdown is that cutting fossil fuel combustion cleans up the air, another is that there’s a lot of pollution left over after that. The sources vary by place and time, but generally speaking, we need to reduce fossil fuel use, stop burning things — especially solid waste — and accelerate changes already underway in food systems, from agricultural practices to food waste management. Many of these changes would also bring substantial emissions reductions and other environmental benefits, not to mention new employment opportunities.
There is no silver bullet, but better air is a big reason to accelerate transformations in energy and transport, waste management and food systems.
Fossil fuel emissions account for nearly 60% of the premature mortality associated with particulate matter and ground-level ozone, two of the most prominent pollutants from a health and crop yield impact perspective. And these emissions continue to grow: fossil fuels powered nearly 70% of the rise in total energy demand in 2018, for the second year in a row. Natural gas use grew faster than coal use — good news for particulate matter and carbon dioxide emissions, but mediocre for other forms of air pollution and the climate. Gas production is a substantial contributor to emissions of methane, a powerful warming gas and precursor for ground-level ozone.
Across the world, we use fossil fuels to produce electricity in power plants that emit various harmful pollutants, including particulate matter laced with metals and other toxics, sulfur dioxide, nitrogen oxide and volatile organic compounds (VOCs). We use them in the combustion engines of cars, trucks and ships that are a primary source of air pollution in cities and account for a quarter of global carbon dioxide emissions. We use them to cook food and heat buildings, burning them in boilers that create emissions hotspots for neighborhoods and areas beyond.
Part of the solution is to shift to cleaner alternatives such as solar, wind, geothermal and hydro-electric power, use more efficient energy carriers — electrify more, in other words — and control the emissions that are left. This will require a deeper dive into the energy system to deliver cleaner air at the lowest possible cost. Wealthier countries have historically improved air quality by tightening emissions controls at the end of the tailpipe, but today there are cheaper alternatives to avoid emissions before they get into the tailpipe. It will require some updates in the scope of what we consider “air quality management” to include high-level choices about infrastructure investment as well as the more conventional focus on emission controls, but there is growing precedent for this kind of mainstreaming of air quality and other environmental goals into core development strategies.
We need to stop burning things. NASA’s satellite sensors track numerous small and large fires, both man-made and natural. Some estimates indicate that open burning and other agricultural activities account for more than a third of all black carbon (essentially, darker particulate matter) emitted globally. In Southeast Asia, a large concentration of fires was visible from space in early March as farmers cleared vegetation for the upcoming growing season. This practice is also evident in sub-Saharan Africa and South Asia, as well as some parts of Latin America.
Other fires are not as readily visible from the sky but have significant consequences on the ground. Household burning of charcoal and peat for cooking and domestic heating can heavily influence indoor and regional air quality. Some household burning is due to energy poverty; 3 billion people rely on traditional, inefficient cookstoves and solid fuel for their cooking and heating. Other cooking and heating-related pollution comes from pizza ovens, fireplaces and biomass boilers. Waste burning also contributes to particulate matter, air toxics and other hazards. Emissions from incineration in waste-to-energy plants can be controlled, but the technology is not always applied. And open burning or dump fires — which affect landfills in high- and low-income countries alike — don’t even have that option. The World Bank estimates that 93% of waste in low-income countries and more than half of the waste in South Asia, the Middle East and North Africa, and sub-Saharan Africa ends up in open dumps prone to fires as well as gaseous emissions.
And we need to change our food system. Wasted food (about 30% of all food produced) releases methane as it rots. Agricultural production contributes to air pollution. Gaseous emissions from agriculture — methane and nitrogen oxide from rice beds, ammonia from animal feedlots and fertilizer use — contribute to ground level ozone and the formation of particulate matter. One 2016 study found that ammonia emissions from farms — which interact with other emissions, largely from combustion, to create particulate matter — outweigh other human sources of fine-particulate air pollution in much of the United States, Europe, Russia and China. Fertilizer is still going to be needed to ensure food security, but must be used carefully, along with other steps to reduce the impact of agricultural emissions on air pollution. The same study found that reducing emissions from fossil fuel combustion and open burning could limit the conversion of ammonia into particulate matter enough to allow more food production with less pollution.
This means a broad, integrated approach is the way to achieve and maintain cleaner air: recognizing the main sources of emissions, acknowledging the interactions in the atmosphere that convert emissions to ambient pollution, and managing the air through actions that cut across sectors and geographies.
The choices we make in the coming months can have a positive effect on nearly every Sustainable Development Goal.
2. Reduce “Embedded Pollution”
Facing up to the full range of pollution contributors is one part of our reality check; acknowledging the role of global consumption is a second. Air pollution is often linked to particular places: cities, countries, regions on the map. But its roots run much deeper. Supply chain emissions — those linked to the production and delivery of goods to the end consumer — are significant and inequitably distributed.
In China, for example, much of the pollution is associated with manufacturing goods consumed elsewhere. One group of researchers estimated that 50-60% of China’s pollution was associated with consumption in provinces and countries other than where it was produced. Another study found that emissions from export-focused production continued to rise during 1997-2010, even as national policies helped to clean up household energy and close inefficient factories. Sixty percent of the primary emissions of small particulate matter (PM2.5) were linked to exports to OECD countries.
The same problem — pollution suffered by (often less-affluent) people in one area to produce goods enjoyed by (often higher-income) people elsewhere — happens within the United States. One study compared how much air pollution different demographic groups experienced in their daily lives versus how much was produced to make the goods they consumed. Non-Hispanic white populations experienced 17% less air pollution than was caused by producing the goods and services they consumed, while black and Hispanic minorities experienced 56% and 63% more pollution, respectively, than was associated with their consumption. These and other findings from the growing literature on pollution embodied in supply chains suggest that it is significant, and its impacts are almost always regressive. It is important to keep this gap in mind as countries ramp up production — and relax regulations — in the post-pandemic restart. Human demand drives those impacts.
Freight-related pollution also matters. In the United States, heavy-duty trucks are the fastest-growing contributor to transportation pollution, which in turn accounts for over 20% of particulate matter emissions, 30% of VOCs and more than half of the nitrogen oxides. Pollution around ports, transshipment depots and shipping routes is readily visible from space.
National air pollution footprints — the land area affected by pollution related to goods consumed in that country — are estimated to be growing faster than carbon footprints. Wealthier countries tend to see more of this growth abroad, while lower-income countries experience growth domestically.
Rapid advances in air pollution source monitoring is pushing companies to reduce air pollution associated with their supply chains. Remote sensing, lower-cost monitors for citizen science, and the digitization of records on commercial relationships and goods movement is making it easier to hold specific firms accountable for specific pollution hotspots. Such tracking is becoming higher resolution, moving from national to sub-national to plant and facility level. As a result, corporate CEOs are discovering that reducing previously out-of-sight, out-of-mind pollution is necessary to maintain business continuity, reduce regulatory and operating risks, and maintain a positive reputation. Investors and consumers are learning that they can drive air pollution clean-up by supporting firms that act early and avoiding those who continue to pollute.
3. Aggregate Local Actions for Global Change
Global air quality advocacy has often started from the top down, with priority lists based on global analysis of pollution sources. But these lists are only approximately true for any particular place. The roots of pollution vary by location and season. Delivering clean air cost-effectively and building support for more ambitious plans requires more specific guidance.
A global campaign for clean air will requires two strategic shifts. First, global research and scientific organizations must support local air quality movements with data, analysis and platforms offering location-specific, customized guidance on pollution sources and ways to tackle them. Second, these bottom-up movements must be supported to come together and catalyze national and regional changes. Much of energy and impetus for change comes from local initiative. Global actors wanting to reduce air pollution must find ways to support them and reduce the frictions that limit scale.
Linking pollution to its sources involves three components: spatially referenced information on emissions; models that trace how emissions move and interact; and monitoring of where the resulting pollution goes. Acting on this information will require coordinating emissions control strategies across sectors and administrative or even national boundaries. Cross-border scientific collaboration is growing and can provide a foundation for other types of collaboration, such as green investment coordination between neighbors.
Each of the scientific components reinforces the others: good data on emissions and pollution helps improve models of pollution movement and chemistry. Strong models and accurate emissions data make it possible to identify gaps in monitoring. And better monitoring plus models helps track unreported emissions. There is substantial ongoing innovation — and room for much more — in each of these components. Constantly improving satellite data will help to fill gaps in monitoring and emissions inventories. Combining these with ground referencing improves the accuracy and extent of inferences that can be made for areas without monitors. Analysis of data thrown off by an increasingly digital economy and large-scale citizen science experiments can yield additional insights that further sharpen the picture.
International initiatives can bring these scientific developments together for rapid vetting and refinement, accelerating learning across regions with differing initial conditions, air chemistry and levels of readily available information. For example, the World Meteorological Organization’s Global Air Quality Forecasting and Information System and Integrated Global Greenhouse Gas Initiative are two such initiatives. Similarly, the International Global Atmospheric Chemistry Project is a scientific network that supports rapid development of the intelligence we need to manage our atmosphere more effectively.
These scientific platforms are essential for translating existing and emerging air quality detection, attribution and forecasting techniques into tools for local champions, engaging local leaders and communities. Even when scientific advice exists, it is hard to build the necessary broad coalition for change if people don’t understand how the scientific conclusions were reached. Reducing emissions imposes costs, and polluters are often the first to dispute the facts and point fingers at other sources. Trust in the underlying science is also important for detecting and rewarding progress, which cannot always be judged by visible changes in air quality.
The COVID-19 crisis presents an opportunity to build a cleaner, healthier, more sustainable world. Global alliances, driven by local demand for clean air, can make that shared goal real. But it will require an active network of cities and communities, all raising their collective voices on national energy, agriculture, waste, urban policies and their representation in international arenas. City networks such as ICLEI and C40, and cohort-based programs such as the WRI-NASA CityAQ project and WRI’s TheCityFix Labs and the GEF-financed Sustainable Cities Impact Program, provide a starting point.
The coronavirus pandemic has allowed a glimpse of a clean air future, at a tragic physical and economic cost to millions of people. The hope is for a clean air future achieved without this painful cost. The solutions exist. Now is the time to start working together to achieve them.