Pollution Facts

Particulate pollution comes in the top 5 threats to human health globally.

The AQLI establishes that the impact of PM2.5 on global life expectancy is comparable to that of smoking, more than 3 times that of alcohol use and unsafe water, more than 5 times that of transport injuries like car crashes, and more than 7 times that of HIV/AIDS.

Particulate matter (PM) air pollution, which is predominantly the result of fossil fuel combustion, is recognized as the most deadly form of air pollution globally. The AQLI demonstrates that averaged across all women, men, and children globally, particulate air pollution cuts global life expectancy short by nearly 2.3 years relative to if particulate concentrations everywhere were at the level deemed safe by the World Health Organization (WHO). This life expectancy loss makes particulate pollution much more devastating than communicable diseases like  HIV/AIDS, behavioral killers like tobacco and alcohol use and conditions like child and maternal malnutrition, mental disorders, etc. Some areas of the world are impacted more than others. For example, in the United States, where there is less pollution, life expectancy is cut short by just 3.6 months as a result of not being compliant with the WHO guideline. In China and India, where there are much greater levels of pollution, bringing particulate concentrations down to the WHO guideline would increase average life expectancy by 2.5 and 5.3 years, respectively.

“Particulate air pollution shortens lives globally, even more than cigarettes. There is no greater current risk to human health.”  – Michael Greenstone,
Milton Friedman Distinguished Service Professor in Economics,
University of Chicago


How Does Particulate Air Pollution Impact Health?

Particulate matter (PM) refers to solid and liquid particles – soot, smoke, dust, and others – that are suspended in the air. When the air is polluted with PM, these particles enter the respiratory system along with the oxygen that the body needs.

When PM is breathed into the nose or mouth, each particle’s fate depends on its size: the finer the particles, the farther into the body they penetrate. PM10, particles with diameters smaller than 10 micrometers (μm) whose concentration in the air is included in measures of “total suspended matter” (TSP), are small enough to pass through the hairs in the nose. They travel down the respiratory tract and into the lungs, where the metal elements on the surface of the particles oxidize lung cells, damaging their DNA and increasing the risk of cancer.[1] The particles’ interactions with lung cells can also lead to inflammation, irritation, and blocked airflow, increasing the risk of or aggravating lung diseases that make breathing difficult, such as chronic obstructive pulmonary disorder (COPD), cystic lung disease, and bronchiectasis.[2]

More deadly is an even smaller classification: PM2.5, or particles with diameter less than 2.5 μm—just 3 percent the diameter of a human hair. In addition to contributing to risk of lung disease, PM2.5 particles pass even deeper into the lungs’ alveoli, the blood vessel-covered air sacs in which the bloodstream exchanges oxygen for carbon dioxide. Once PM2.5 particles enter the bloodstream via the alveoli, they inflame and constrict blood vessels or dislodge fatty plaque, increasing blood pressure or creating clots. This can block blood flow to the heart and brain, and over time, lead to stroke or heart attack. In recent years, researchers have even begun to observe that PM pollution is associated with lower cognitive function. They speculate that PM2.5 in the bloodstream may cause the brain to age more quickly due to the inflammation. In addition, it may damage the brain’s white matter, which is what allows different regions of the brain to communicate.[3] White matter damage, such as due to the decreased blood flow that PM2.5 may cause, has been linked to Alzheimer’s and dementia.[4]

The tiny size of PM2.5 particles not only makes them harmful from a physiological perspective, but also allows these particles to stay in the air potentially for weeks and to travel hundreds or thousands of kilometers.[5] This increases the likelihood that the particles will end up inhaled by humans before depositing onto the ground.

The Air Quality Life Index translates long-term exposure to particulate pollution concentrations into their impact on life expectancy. The AQLI’s core finding is that sustained exposure to an additional 10 micrograms per cubic meter (μg/m3) of PM2.5 reduces life expectancy by 0.98 years. This means that Shanghai’s residents could expect to live 2 years longer if it permanently reduced concentrations to the WHO guideline. In the United States, residents of California’s Central Valley are now consistently exposed to average particulate pollution levels above both the WHO guideline and the nation’s own air quality standard. In 2021—a year in which California experienced its second worst wildfire season, in terms of acreage burned and its largest single wildfire[6][7]—20 out of the top 30 most polluted counties in the US were in California, where average pollution concentrations ranged from 5.5 μg/m3 in Monterey County to 26.6 μg/m3 in Plumas County.


How Does Particulate Air Pollution Stack Up Against Other Health Threats?

Though we know it is possible for people to live to 80, 90, or even longer, the average infant born in 2019 is expected to live to be 73. Life expectancies are cut short for many reasons, including illnesses such as smoking, child and maternal malnutrition, and HIV/AIDS—some of the deadliest culprits. The AQLI shows that particulate air pollution cuts life expectancy shorter than all of these causes.

According to the AQLI, if current particulate pollution levels persist, today’s global population will lose a total of 16.7 billion years of life directly due to this particulate pollution. That means, the average person loses about 2.2 years of life. But, if particulate pollution around the world was reduced to the WHO guideline of 5 μg/m3 and everything else stayed the same, global average life expectancy at birth would increase by 2.2 years (from 73 years) to about 75 years.

According to the AQLI, if current particulate pollution levels persist, today’s global population will lose a total of 17.8 billion years of life directly due to this particulate pollution as a result of not being compliant with the WHO PM5 guideline. That means, the average person loses 2.3 years of life. So, this means that if particulate pollution around the world was reduced to the WHO guideline of 5 μg/m3 and everything else stayed the same, global average life expectancy at birth would increase by 2.3 years to about 75.7 years.[8]

To put this in perspective, measured in terms of life expectancy, the AQLI reveals that ambient particulate pollution is consistently one of the world’s greatest risks to human health. While particulate pollution is set to reduce global average life expectancy by 2.3 years, tobacco use, for instance, reduces global life expectancy by 2.2 years. Child and maternal malnutrition reduces life expectancy by 1.6 years; alcohol use by 7.2 months; unsafe water, sanitation and handwashing, 7.2 months; HIV/AIDS, 3.6 months; and nutritional deficiencies, just 1.2 months (see Figure 1.1). Thus, the impact of particulate pollution on life expectancy is comparable to that of tobacco use, 3.8 times that of alcohol use and unsafe water sanitation and handwashing, 5.8 times that of transport injuries, 7.6 times that of HIV/AIDS, and 23 times that of nutritional deficiencies.[9] The figure below shows select major global threats to life expectancy.

Sources: Global Burden of Disease ( level-2 causes and risks data and WHO Life Tables ( were combined with the Life table method to arrive at these results. “PM2.5 relative to WHO Guideline” bar displays the reduction in life expectancy relative to the WHO guideline as calculated by latest AQLI (2021) data.

Comparing the impact of particulate pollution to other health threats can be surprising. As an example, the health discourse in Sub-Saharan Africa has centered on infectious diseases such as HIV/AIDS and malaria. However, a comparison shows that particulate pollution’s impact on life expectancy is no less serious. In Cameroon and the Democratic Republic of the Congo, air pollution is one of the biggest threats to human health in terms of its impact on life expectancy—shaving off more years than HIV/AIDS, unsafe water and sanitation and malaria. In fact, it ranks as the second deadliest of all threats in Cameroon and the third deadliest in the DRC. In Nigeria, air pollution’s impact on life expectancy is greater than that of HIV/AIDS but less than malaria.

What accounts for particulate pollution’s enormous overall impact? The key difference is that residents of polluted areas can do very little to avoid particulate pollution, since everyone breathes the air. In contrast, it is possible to quit smoking and take precautions against diseases. Thus, air pollution affects many more people than any of these other conditions: 98.4 percent of the global population, or 7.6 billion people, live in areas where PM2.5 exceeds the WHO guideline of 5 µg/m3. So, although other risks such as HIV/AIDS, tuberculosis etc.  have a larger impact among the affected, they affect far fewer people. For example, the Global Burden of Disease estimates that those who died from HIV/AIDS in 2019 died prematurely by an average of 52.9 years. However, since the 36 million people affected by the disease is tiny compared to the 7.6 billion people breathing polluted air, the overall impact of air pollution is much greater.


Where Is Particulate Air Pollution Cutting Life Expectancy The Most?

Just like with other public health threats, the burden of air pollution is not borne equally by everyone around the world. Developing and industrializing Asian countries are impacted the most by particulate pollution.

If all areas not in compliance with the WHO PM5 guideline in 2021 were to permanently reduce their particulate pollution levels to meet the guideline, then, globally:

  • Practically all of the Northern Plains’ 521.2 million people, 38.9 percent of India’s population, live in areas where the annual average particulate pollution level is 17.3 times higher than the WHO guideline.
  • 815 million people would live at least 5 years longer on average. These include 91.7 percent of Bangladeshis, 74.9 percent of Indians, 40.4 percent of Nepalis, 16.4 percent of Pakistanis and others in Bhutan, Cameroon and Mongolia.
  • 1.9 billion people would live at least 3 years longer on average. This includes 100 percent of Bangladeshis, 78.1 percent of Nepalis, 75.9 percent of Indians, 72 percent of Pakistanis, 46.4 percent of the citizens of Democratic Republic of the Congo, 28.4 percent of Chinese and others in Bhutan, Bolivia, Guatemala, Mongolia, Myanmar, Vietnam, etc.
  • An additional 7.6 billion people around the world are exposed to particulate pollution concentrations above the WHO guideline. They would gain an average of 2.3 years.
  • No other location on the planet illustrates the stubborn nature of the pollution challenge more than South Asia, where pollution continued its upward trend in 2021. Bangladesh, India, Nepal, and Pakistan—where 22.9 percent of the global population lives—are the top four most polluted countries in the world. South Asia accounts for more than half, 52.8 percent, of the total life years lost globally due to high pollution. The average South Asian would live 5.1 years longer if these four countries reduced pollution to meet the WHO guideline.
  • Measured in terms of life expectancy, particulate pollution is the greatest threat to human health in India, taking 5.3 years off the life of the average Indian. In contrast, cardiovascular diseases reduce the average Indian’s life expectancy by about 4.5 years, while child and maternal malnutrition reduce life expectancy by 1.8 years.
  • By contrast, the United States and Europe—which make up 15.4 percent of the world’s population—account for only about 4.1 percent of the health burden from particulate pollution.. In the United States, average pollution was 7.8 µg/m3 in 2021, slightly above the WHO guideline of 5µg/m3. At this level, residents could expect to gain roughly 3.6 months if the air they breathed permanently met the WHO guideline, equivalent to 99.2 million total life years. The average European in 2021 was exposed to a particulate pollution concentration of 12.4 µg/m3, meeting the European Union’s air pollution standard of 25 µg/m3 but falling short of the revised WHO guideline. If particulate pollution were to meet this standard, average life expectancy across Europe would improve by 8.4 months, equivalent to 602.4 million total life years.

Learn more about the impact of air pollution policies here. To learn how many years of life expectancy are lost in countries and regions around the world under current pollution levels, see The Index.


Where Does Particulate Air Pollution Come From?

Though some particulates arise from natural sources such as dust, sea salt, and wildfires, most PM2.5 pollution is human-induced.

The fact that burning coal pollutes the air has been known for some time. Around 1300, King Edward I of England decided that the punishment for anyone who burned coal in his kingdom would be death. Today, fossil fuel combustion is the leading global source of anthropogenic PM5[10] acting through three distinct pathways[11]:

  • First, because coal contains sulfur, coal-fired power plants and industrial facilities generate sulfur dioxide gas. Once in the air, the gas may react with oxygen and then ammonia in the atmosphere to form sulfate particulates.
  • Second, combustion that occurs at high temperatures, such as in vehicle engines and power plants, releases nitrogen dioxide, which undergoes similar chemical reactions in the air to form nitrate particulates.
  • Finally, diesel engines, coal-fired power plants, and burning of coal for household fuel all involve incomplete combustion. In this type of combustion, not enough oxygen is present to generate the maximum amount of energy possible given the amount of fuel. Part of the excess carbon from the fuel becomes black carbon, a component of PM5 that is also the second- or third-most important contributor to climate change after carbon dioxide and perhaps methane.
  • In addition to fossil fuel combustion, humans generate PM2.5 through the combustion of biofuels such as wood and crop residue for household cooking and heating. Biofuel burning emits black carbon and organic particulates. In many parts of the world, biofuel combustion’s contribution to particulate pollution is comparable to that of fossil fuels. The burning of biomass—forests, savannah, and crop residue on fields—to clear land for agriculture is also a significant source of anthropogenic particulate pollution.[12]


Why Is There So Much Particulate Pollution?

Fossil fuels are today the cheapest form of energy, and energy is crucial to raising living standards through economic growth.

As the first figure shows, there simply aren’t examples of countries attaining high levels of living standards without consuming high levels of energy. It should then come as no surprise that today’s developing (i.e. non-OECD) countries are expected to consume more energy with time as they grow.

Much of the world’s rising demand for energy is projected to continue to come from fossil fuels. Based on policies in place and committed at the end of 2016, fossil fuels should supply 74% of the world’s primary energy in 2040, compared to 81% in 2014, according to International Energy Agency.

Why is the world projected to continue to rely so heavily on fossil fuels, even though we know they lead to air pollution and climate change? This is because they are inexpensive and their price does not take into account the costs of pollution and climate change—or what economists call “negative externalities.”

For example, a kilowatt-hour (kWh) of energy from a new coal plant that had all the environmental controls required in the United States would cost only about 8 cents. And without those environmental controls, the cost would be only about 3 cents per kWh. Due to the hydraulic fracturing revolution, the cost of a kWh of electricity from a combined cycle natural gas plant is about 5.5 cents per kWH in the United States.  In contrast, the cost of low-carbon sources such as nuclear or renewables (with natural gas back-ups to deal with intermittency) are two or three times as much.

Not only are fossil fuels cheap, they are also abundant. The world is not going to run out anytime soon.  There is about 55 years-worth of oil alone, more than a century of natural gas, and endless amounts of coal, while oil and gas companies will continue to innovate to find more.


How Has The Impact of Particulate Pollution Changed Over Time?

Air pollution is a stubborn problem. Over the last two decades, from 1998-2021, particulate pollution cut global life expectancy short on average by 6.1 months. In 2021, global average PM2.5 pollution stood at 28.2 µg/m3. If this were reduced to meet the WHO guideline, it would add 2.3 years onto the life expectancy of an average person.  Global pollution exposure peaked in 2011. If that year’s pollution levels had been sustained, average life expectancy would be 2.7 years shorter.

To make a sense of this global average trend, it is necessary to decompose it by region. Asia and Africa bear the greatest burden yet lack key infrastructure. No other location on the planet illustrates the stubborn nature of the pollution challenge more than South Asia, where pollution continued its upward trend in 2021. Bangladesh, India, Nepal, and Pakistan—where 22.9 percent of the global population lives—are the top four most polluted countries in the world. Since 2013, about 59 percent of the world’s increase in pollution has come from India alone. The African countries of the Democratic Republic of the Congo, Rwanda, Burundi, and the Republic of the Congo are amongst the ten most polluted countries in the world. Central Africa has consistently remained more polluted than West Africa from 1998 till 2021. Given the latest AQLI 2021 data, air pollution is shortening lives by 2.4 years for the average resident of Central Africa, relative to the WHO guideline. In comparison, an average resident of West Africa loses 1.2 years of life expectancy.

At the same time, after periods of industrialization led to pollution that choked Europe and the United States decades ago, the two regions have largely been successfully creating and enforcing strong pollution laws. In the United States, legislative measures like the Clean Air Act have helped to reduce pollution by 64.9 percent since 1970, extending the average lifespan by 1.4 years. In Europe, policies such as the European Union’s Air Quality Framework Directive have helped to reduce pollution by 23.5 percent since 1998, allowing residents to gain 4.5 months. Primarily due to these pollution reductions, the United States and Europe—which make up 15.4 percent of the world’s population—account for only about 4.1 percent of the health burden from particulate pollution. But, in spite of major advancements in reducing pollution over several decades, fresh data reveal inequalities persist in the amount of pollution residents breathe in regions within the United States and Europe. Those in some of the most polluted areas would gain 2.5 years onto their lives if pollution were reduced to meet the WHO guideline, underlining the importance of continuing to strengthen and innovate air quality policy.

Meanwhile, China is one example of staggering success in combating pollution since declaring a “war on pollution” in 2014. From 2020 to 2021, pollution levels in China fell another 5.3 percent. In fact, the small decline in global pollution levels from 2013 to 2021 is entirely due to China’s progress. China has had such success in reducing pollution because of strict public policies. After China reached its highest pollution levels in 2013, the public began to call for change. China responded with a National Air Quality Action Plan in the fall of 2013, laying out specific targets to improve air quality by the end of 2017, including a 270 billion USD initiative to reduce pollution in the densely populated regions. At the 2014 annual meeting of the People’s Congress, Premier Li Keqiang declared a “war against pollution.” The timing of this declaration marked an important shift in the country’s long-standing policy of prioritizing economic growth over concerns about environmental protection. Pollution dropped 42.3 percent between 2013 and 2021. Even though China’s overall particulate pollution average is in compliance with the national standard, 30.9 percent of the population still lives in areas that exceed the national standard of 35 µg/m3. If these areas were to comply with the national standard, it would result in a gain of 216.7 million total life years. As China enters the next phase of its “war against pollution,” the country has an opportunity to place more emphasis on market-based approaches in order to more sustainably reduce pollution at a lower cost. Such approaches of reducing pollution have been successful in other parts of the world.


Have Countries Overcome The Particulate Pollution Problem?

The dual challenges of economic growth and environmental quality faced by places like Beijing and Delhi today are no different from those once confronted by London, England, Los Angeles, California, or Osaka, Japan—once respectively known as “the big smoke,” “the smog capital of the world,” and the “smoke capital”—during their periods of industrialization.

The legacy of environmental improvement in these former pollution capitals—but now, rich, vibrant, and much cleaner cities—is evidence that today’s pollution does not need to be tomorrow’s fate. However, the air did not become cleaner in these countries by accident. It was the result of forceful policies. In the United States, legislative measures like the Clean Air Act have helped to reduce pollution by 64.9 percent since 1970, extending the average lifespan by 1.4 years.  Similarly, in England, pollution has reduced since the passage of the Clean Air Act of 1956. In Japan, a series of lawsuits and environmental protection laws that began in the 1960s have helped to reduce air pollution to levels similar to those in Europe.

These changes, however, cannot happen overnight. Learn more about the impact policies around the world have had in reducing air pollution.


Does Particulate Pollution Have Anything To Do With Climate Change?

While the current air pollution challenge is largely concentrated in developing countries, decisions in these countries about fossil fuels usage, which is the primary source of particulate air pollution, will affect the entire world. That’s because the combustion of the same fossil fuels that releases life-threatening air pollution also involves the release of greenhouse gases that increase the odds of disruptive climate change. And, unlike air pollution that is highly localized, climate change doesn’t care where you live. It will impact all countries. For example, unmitigated climate change will make the United States poorer and more unequal—with the poorest third of U.S. counties projected to sustain economic damages costing as much as 20% of their income if warming proceeds unabated, according to research from the Climate Impact Lab, a a first-of-its-kind multidisciplinary effort working to enhance understanding of the social and economic costs of climate change.[13]

[1] Xing, et al., 2016

[2] E.g. Ling & van Eeden, 2009

[3] Gibbens, 2018

[4] Iadecola, 2013

[5] Wilson & Suh, 1997

[6] National Interagency Coordination Centre. 2021. “Wildland Fire Summary and Statistics Annual Report.”

[7] California State Portal. 2022. “Fire Season Incident Archive.”

[8] WHO, the Global Health Observatory; Global life expectancy in 2019:

[9] Calculations based on GBD 2019

[10] Philip et al., 2014

[11] NRC, 2010

[12] Philip et al., 2014

[13] Hsiang et al., 2017


Notes and Sources

Gibbens, S. (2018). Air pollution robs us of our smarts and our lungs. National Geographic. Retrieved from

Global Burden of Disease. (2019). Retrieved from

Hsiang, S., Kopp, R., Jina, A., Rising, J., Delgado, M., Mohan, S., … & Larsen, K. (2017). Estimating economic damage from climate change in the United States. Science, 356(6345), 1362-1369.

Iadecola, C. (2013). The pathobiology of vascular dementia. Neuron, 80(4), 844-66.

India Ministry of Statistics and Programme Implementation. (2017). Motor vehicles – Statistical year book India 2017.

Ling, S. H., and van Eeden, S. F. (2009). Particulate matter air pollution exposure: role in the development and exacerbation of chronic obstructive pulmonary disease. International journal of chronic obstructive pulmonary disease, 4, 233-43.

National Research Council. (2010). Global Sources of Local Pollution: An Assessment of Long-Range Transport of Key Air Pollutants to and from the United States. Washington, DC: The National Academies Press.

Pakistan Bureau of Statistics. (2006). Pakistan statistical pocket book 2006.
Pakistan Today. (2019, June 16). Registered vehicles in Pakistan increased by 9.6% in 2018.

Philip, S., Martin, R.V., van Donkelaar, A., Lo, J.W., Wang, Y., Chen, D., …, Macdonald, D.J. (2014). Global chemical composition of ambient fine particulate matter for exposure assessment. Environmental Science & Technology, 48(22), 13060-13068.

US Energy Information Administration. (n.d.). International: Electricity [Data set].

Wilson, W.E. and Suh, H. H. (1997). Fine particles and coarse particles: Concentration relationships relevant to epidemiological studies. Journal of the Air & Waste Management Association, 47(12), 1238-1249.

Xing, Y. F., Xu, Y. H., Shi, M. H., & Lian, Y. X. (2016). The impact of PM2.5 on the human respiratory system. Journal of thoracic disease, 8(1), E69-74.

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