The Clean Air Act has dramatically improved air quality averages across the United States. Over the past 30 years, sulfur dioxide is down 89 percent and ground-level ozone is down 21 percent—and in the past 20 years, fine particulate matter is down 34 percent. However, when it comes to air pollution regulation worldwide, the Clean Air Act is the exception rather than the rule. According to a new study, half of the world’s population continues to breathe increasingly polluted air.
The Problem with Particulates
The study, published in the journal Climate and Atmospheric Science, focused on the type of air pollution known as fine particulate matter, or PM 2.5—microscopic bits of airborne particles and condensed liquid droplets that are often the byproduct of burning fossil fuels. After traveling down the human windpipe, fine particulate matter penetrates deep into the interior of the lungs, triggering inflammation that causes or exacerbates a wide variety of respiratory ailments, some of which can be fatal. The smallest bits also manage to enter the bloodstream, where they set off a chain reaction that can lead to heart attacks, cancer, and stroke.
PM 2.5 in outdoor air kills 4.2 million people worldwide each year. But it’s a complicated problem to solve, because unlike most air pollutants, these particles can consist of many substances from a range of sources. Ozone smog is one particular thing. Sulfur dioxide is another. Carbon monoxide is also a thing. But fine particulate matter is a unique threat in that it is defined by its size (at 2.5 microns or fewer across, it can be half the size of a typical bacteria cell) rather than its chemical composition.
The sources of PM 2.5 air pollution include some of the usual suspects, like coal-fired power plants and cars. Those sources are relatively straightforward to address through emissions controls or switching to cleaner energy sources, such as wind and solar power, and setting stronger fuel efficiency standards for cars.
But smoke from wildfires is also a major source of PM 2.5. Desert sand particles, dirt from farms, and simple dust also contribute to particulate matter exposure. Governments can’t directly control the spread of sand, fire, or dust, and such particles can also travel hundreds of miles with no respect for national boundaries, presenting challenges for countries that would have to coordinate with their neighbors.
A Patchwork of Progress
The U.S. Clean Air Act of 1970 and its amendments were a major effort to control dangerous air pollution in the United States. An international agreement to better manage air pollution across international borders followed, with the European Union setting its own standards in the 1990s. Those landmark laws have been incredibly successful in reducing air pollution and improving public health. (That, however, hasn’t stopped the Trump administration from attacking the Clean Air Act and jeopardizing those gains.)
But here’s the problem. While fine particulate matter pollution has dropped considerably in Europe and North America, it remains a menace to public health worldwide. Between 1960 and 2009, fine particulate matter levels grew 38 percent globally, with the highest regional increases occurring in India and China. Over those same decades, deaths attributable to that pollution rose 124 percent, again with the steepest rises in India and China.
According to the study, which gathered data from nearly 10,000 ground-based air monitoring stations over a seven-year period, 55 percent of the world’s population was exposed to more PM 2.5 in 2016 than in 2010. This is obviously a situation that must be addressed. But, since the sources are varied, the authors note that “cooperation across sectors”—energy, transportation, industry, agriculture, residential, etc.— “and at different levels—urban, regional, national and international—is crucial.”
The increased burning of coal for electricity and the expansion of car ownership are two major contributors to rising fine particulate matter levels. Their combination led to the high air pollution levels seen in the United States and Europe last century and, in more recent decades, have been lowering the quality of India and China’s air. As an example, India’s coal consumption more than doubled between 2003 and 2013, and car ownership in the country increased by nearly 70 percent between 2013 and 2018. While India’s National Clean Air Programme and local leadership are addressing the problem at national and community levels, significant health risks from its air pollution remain.
The PM 2.5 problem and its solutions, of course, vary from place to place. Much of the increase in sub-Saharan Africa’s particulate matter is attributed to windblown desert dust. As temperatures rise and precipitation diminishes in that part of the world, dust from the Sahara can travel downwind and harm people’s lungs. It should be noted that this isn’t just a problem for the health of Africans. Desert dust also affects the air quality in the Middle East and parts of Asia, and research shows that the Sahara’s dust travels into Europe and across the Atlantic into South and North America. (Just last week, the largest and most intense such dust storm in nearly two decades hit the southeastern U.S. coast.)
While transoceanic dust storms are beyond anyone’s control, the fine particulate matter from such sources as the burning of fossil fuels is something we can fix. Global action on this front—anything from investments in renewable power and energy efficiency to low-emission automobiles and stronger air quality standards—would not only do wonders for the mitigation of climate change, but would benefit the health of literally billions of people.
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David Doniger, senior strategic director of the Climate & Clean Energy Program, has helped shape federal and global climate-related policies since he joined NRDC in 1978.
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