Health Effects of Ozone Pollution

Ozone air pollution, sometimes known as smog, is the one of the most widespread pollutants in the United States. It is also one of the most dangerous. Scientists have studied the effects of ozone on human health for decades. Hundreds of studies have confirmed that ozone harms people at levels currently found in many parts of the United States. 

Ozone is a gas composed of molecules with three oxygen atoms. (The oxygen we need for life is made up of molecules with two oxygen atoms). Ozone forms in the lower atmosphere when a combination of other pollutants, usually nitrogen oxides (NOx) and volatile organic compounds (VOCs), “cook” together in sunlight through a series of chemical reactions. NOx and VOCs are produced primarily when fossil fuels such as gasoline, diesel, oil, natural gas or coal are burned or when solvents and some other chemicals evaporate. NOx is emitted from power plants, motor vehicles and other sources of high-heat combustion. VOCs are emitted from motor vehicles, oil and gas operations, chemical plants, refineries, factories, gas stations, paint and other sources.

If these ingredients are present under the right conditions, they react to form ozone. Sunlight is key, with higher temperatures increasing ozone production. Because the reactions take place in the atmosphere, ozone often shows up downwind of the sources of the original emissions, sometimes many miles from where it formed.

Ozone air pollution is sometimes called ground-level ozone, to distinguish it from the much higher-altitude stratospheric ozone layer that protects the Earth from damaging ultraviolet rays from the sun.

Ozone gas is a powerful lung irritant. When it is inhaled into the lungs, it reacts with the delicate lining of the airways, causing inflammation and other damage that can impact multiple body systems. Ozone exposure can also shorten lives.

Ozone has a serious effect on the respiratory system, both in the short-term and over the course of years of exposure. When ozone levels are high, many people experience breathing problems such as chest tightness, coughing and shortness of breath, often within hours of exposure. Even healthy young adults may experience respiratory symptoms and decreased lung function.1

Other breathing problems that have been tied to short-term exposure to ozone include:

  • Worsening of symptoms, increased medication use, and increased emergency department visits and hospital admissions for people with asthma and COPD;2
  • Susceptibility to respiratory infections such as pneumonia, resulting in an increased likelihood of emergency department visits and hospitalizations.3

Living with ozone pollution long-term may cause lasting damage to respiratory health, including:

  • Development of new cases of asthma in children;4
  • Damage to the airways, leading to development of COPD;5
  •  Increased allergic response.6

The inflammation and systemic stress caused by short- and long-term exposure to ozone can also do damage to tissues, DNA and proteins throughout the body, which can cause or worsen other disease conditions over time. These include:

  • Increased risk of metabolic disorders, including glucose intolerance, hyperglycemia and diabetes;7
  • Impact on the central nervous system, including brain inflammation, structural changes and possible increased risk of cognitive decline;8
  • Increased likelihood of reproductive and developmental harm, including reduced fertility, preterm birth, stillbirth and low birth weight;9,10
  • Possible cardiovascular effects – although according to the most recent EPA review, the evidence linking ozone to heart disease, heart failure and stroke is mixed.11

The damage ozone does to the body can be deadly. Recent research has affirmed earlier findings that short-term exposure to ozone, even at levels below the current standard, likely increases the risk of premature death, particularly for older adults.12 There is also a growing body of evidence that long-term exposures to ambient ozone may be associated with an increased risk of cardiovascular and respiratory disease mortality.13

Anyone who spends time outdoors where ozone pollution levels are high may be at risk. Some people face a higher-than-average risk, however, because of their underlying health and other characteristics.

 Research has shown that the groups at greatest risk from ozone pollution include:

  • children;
  •  anyone age 65 and older;
  • people with existing lung disease such as asthma and COPD;
  • · people who work or exercise outdoors;14
human figure with ways air pollution can harm people: wheezing and coughing, shortness of breath, asthma attacks, COPD, lung cancer, premature death, infections, heart attacks and strokes, impaired cognitive function, metabolic disorders, preterm births and low birth weights

Health Effects of Particle Pollution

Particle pollution – also known as particulate matter – is a deadly and growing threat to public health in communities around the country. The more researchers learn about the health effects of particle pollution, the more dangerous it is recognized to be.

Particle pollution refers to a mixture of tiny bits of solids and liquids in the air we breathe. Particle pollution comes from many sources. Factories, power plants, and diesel- and gasoline-powered motor vehicles (cars and trucks) and equipment either directly emit fine particles or generate the precursors such as nitrogen oxides (NOx) that can form into fine particles in the atmosphere. Other sources include wildfires and burning wood in wood stoves or residential fireplaces.

Many particles are so small as to be invisible, but when pollution levels are high, the air can appear thick and hazy. Researchers and regulators categorize particles according to size, grouping them as coarse, fine and ultrafine. Coarse particles, called PM10, can include wind-blown dust, ash, pollen and smoke. Fine particles, PM2.5, are most often a by-product of burning wood or fossil fuels. The tiniest are called ultrafine particles, or PM0.1, that are also produced by combustion.

The differences in size make a big difference in where and how particles affect our health. Our natural defenses help us to keep coarse particles out of the deepest parts of our lungs, although these particles do deposit in the larger airways. However, those defenses do not keep smaller fine or ultrafine particles from penetrating to the air sacs of the lungs. Many of these particles get trapped in the air sacs, while the smallest are so minute that they can pass from the air sacs into the bloodstream and disperse to other organs of the body.

Particle pollution can be very dangerous to breathe, especially at higher concentrations. It can trigger illness, hospitalization and premature death. Researchers estimate that PM2.5 is responsible for nearly 48,000 premature deaths in the United States every year.15

Short-Term Exposure

Short-term spikes in particle pollution that last from a few hours to a few days can kill. Premature deaths from breathing these particles can occur on the very day that particle levels are high, or up to a month or two afterward. Most premature deaths are from respiratory and cardiovascular causes. Particle pollution does not just make people die a few days earlier than they might otherwise—in many cases these deaths would not have occurred for years if the air were cleaner.16

Even low average daily levels of fine particles can be deadly. A 2016 study found that people aged 65 and older in New England faced a higher risk of premature death from particle pollution, even in places that met current standards for short-term particle pollution.17 A study in 2017 looked more closely at Boston, which also met the standards, and found a similar higher risk of premature death from particle pollution.18 Looking nationwide in another 2017 study, researchers found more evidence that older adults faced a higher risk of premature death even when levels of short-term particle pollution remained well below the current national standards. This was consistent whether the older adults lived in cities, suburbs or rural areas.19

Particle pollution also has many other harmful effects, ranging from decreased lung function to heart attacks. Extensive research has linked short-term increases in particle pollution to:

  • increased mortality in infants;20
  • increased hospital admissions for cardiovascular disease, including heart attacks and strokes;21
  • increased hospital admissions and emergency department visits for COPD;22
  • increased severity of asthma attacks and hospitalization for asthma among children;23,24

Year-Round Exposure

Decades of research have firmly established that breathing particle pollution day in and day out can also be deadly. Across numerous seminal studies that looked at different groups of people living in different parts of the country, the results consistently showed a clear relationship between exposure to particle matter and mortality.25 Recent research using publicly available data on a cohort of over a million adults in the U.S. reconfirmed that long-term exposure to PM2.5 was associated with elevated risks of early death. The increased risk was primarily associated with death from cardiovascular and respiratory causes, including heart disease, stroke, influenza and pneumonia. Researchers also found a similar association between exposure to fine particle pollution and an increased risk of death from lung cancer among never-smokers.26

Research has also linked year-round exposure to particle pollution to a wide array of serious health effects at every stage of life, from conception through old age. In fetuses and children, long-term particle pollution exposure is linked to:

  • Increased risk of preterm birth and low birth weight;27
  • Increased fetal and infant mortality;28
  • Reduced lung development and impaired lung function in children;29
  • Higher likelihood of children developing asthma.30

In adults, long-term particle pollution exposure is linked to:

  • Increased risk from existing cardiovascular and respiratory disease, including a worsening of heart disease, atherosclerosis and COPD;31, 32
  • Higher likelihood of developing diabetes;33
  • Higher likelihood of getting lung cancer and of dying from it;34
  • Impaired cognitive functioning and an increased risk of Parkinson’s disease, Alzheimer’s disease and other dementias later in life.35, 36

The good news is, cleaning up particle pollution makes a difference. In communities that have reduced their levels of year-round particle pollution, research has shown a consistent relationship between decreasing PM2.5 concentrations and improving respiratory health in children and adults.37

Air Pollution and COVID-19

The staggering toll of the COVID-19 pandemic in the U.S has revealed weaknesses in the underpinnings of public health that have left some communities at higher risk of severe illness and death than others. These risk factors include exposure to particle pollution.

In one study, researchers looked at the impact of long-term exposure to fine particle pollution on COVID-19 death rates. They found that just a small increase (1 microgram per cubic meter) in long-term average exposure to fine particle pollution is associated with an 11% increase in the COVID-19 death rates.38 Another study, using a mix of epidemiological data, satellite data and other monitoring information from around the world, found that long-term exposure to particle pollution made an average 15% contribution to COVID-19 mortality globally, with lower rates in cleaner places and rates as high as 58% in some of the most polluted places in the world.39

Communities of color have been especially hard-hit by COVID-19. Communities of color also are disproportionately exposed to unhealthy air. Air pollution increases susceptibility to respiratory infections. It also worsens underlying chronic conditions such as heart disease and diabetes, which are more common in communities of color, that increase the risk of serious harm from COVID-19.

One study looked at the relationships between PM2.5 and other air pollutant levels, race and COVID-19 death rates in Louisiana. It found that a higher burden of air pollution was associated with larger percentages of Black residents and increased unemployment, and higher COVID-19 death rates were associated with larger percentages of Black residents, even when accounting for diabetes, obesity, smoking, age and poverty.40

Anyone who lives where particle pollution levels are high is at risk. Some people face higher risk, however, based on their underlying health and other characteristics.

Research has shown that the groups at the greatest risk from particle pollution include:

  • Infants, children and older people (>65 years of age);41
  • People with lung disease, especially asthma, but also people with COPD;42
  • People with cardiovascular disease;43
  • People with lung cancer;44
  • People of color;45
  • Current or former smokers;46
  • People with low incomes;47 and
  • People who are obese or have diabetes.48

Sources of particle pollution include motor vehicles, factories, power plants, equipment, wood burning and wildfires.

People at Risk

The health burden of air pollution is not evenly shared. There are people more at risk of illness and death from air pollution than others. Several key factors affect an individual’s level of risk:

  • Exposure – Where someone lives, where they go to school and where they work makes a big difference in how much air pollution they breathe. In general, the higher the exposure, the greater the risk of harm.
  • Vulnerability – Children, older adults and people living with chronic conditions, especially heart and lung disease, may be physically more susceptible to the health impacts of air pollution than healthy adults.
  • Access to healthcare – Whether or not a person has health coverage, a healthcare provider, and access to linguistically and culturally appropriate health information may influence their overall health status, and how they are impacted by environmental stressors like air pollution.
  • Psychosocial stress – There is increasing evidence that non-physical stressors such as poverty, racial/ethnic discrimination, fear of deportation can amplify the harmful effects of air pollution.

These risk factors are not mutually exclusive and often interact in ways that lead to significant health inequities among subgroups of the population.

Research has shown that people of color are more likely to be exposed to air pollution and more likely to suffer harm to their health from air pollution than white people.49, 50 Much of this inequity can be traced to the long history of systemic racism in the United States. Discriminatory practices such as redlining, the systematic outlining of riskier neighborhoods by mortgage lenders, institutionalized residential segregation in the 20th century, impairing the ability of many people of color to build wealth and limiting their mobility and political power. Over the years, decision-makers have found it easier to place sources of pollution, such as power plants, industrial facilities, landfills and highways in economically disadvantaged communities of color than in more affluent, whiter neighborhoods. The resulting disproportionate exposure to air pollution has contributed to high rates of emergency department visits for asthma and other diseases.51, 52

People of color are also more likely than white people to be living with one or more chronic conditions that make them more vulnerable to the health impact of air pollution, including asthma, diabetes and heart disease.53

There is evidence that having low income or living in lower income areas puts people at increased risk from air pollution, although the correlation is not as strong as with race and ethnicity.54, 55 People living in poverty are more likely to live in close proximity to sources of pollution than people with more financial resources and have fewer resources to relocate. Poverty itself, along with the problems that beset many low-income communities, such as lack of safety, have been associated with increased psychosocial distress and chronic stress, which in turn make people more vulnerable to pollution-related health effects.56 People with low income also have lower rates of health coverage and less access to quality and affordable health care to relieve them when they get sick.

Children are both more vulnerable to harm from air pollution, and more likely to be exposed than adults. The growth and development of a child’s lungs and breathing ability starts in utero and continues into early adulthood. Exposure to air pollution at any stage of that development process can have both immediate and lasting impacts on developing lungs and children’s health. In addition, the body’s defenses that help adults fight off infections are still developing in children. Children have more respiratory infections than adults, which also seems to increase their susceptibility to air pollution.57

Children breathe more rapidly and inhale more air relative to their size than do adults. They are more likely to spend time outdoors, running around, being active and breathing hard. Consequently, they are exposed to more polluted outdoor air than adults typically are.

Much of the illness and premature death caused by air pollution occurs in older adults, who are at increased risk of harm for several reasons. As a person ages, the normal process of thinning and weakening of the lung tissue and the supporting muscle and bones of the ribcage result in diminishing lung function over time. The increased impairment that results from exposure to air pollutants then has an add-on effect, putting stress on the lungs and heart. Older people are also more likely to be living with chronic diseases, and there is evidence that co-existing chronic lung, heart or circulatory conditions may worsen following exposure to environmental pollutants.58

The strength of the immune system also declines with age, leaving older people at greater risk of contracting infections and less able to get them under control before they become serious. Because exposure to air pollution increases susceptibility to respiratory infections, including COVID-19, it also increases the risk of severe illness and death in older adults. 

For the millions of people in the U.S. living with illnesses such as asthma, COPD, diabetes, heart disease and lung cancer, exposure to air pollution places them at greater risk of harm to their health than those without disease. The cellular injury and systemic inflammation triggered by breathing ozone and particle pollution put additional stress on people’s lungs, heart and other organs already compromised by disease. This can result in a worsening of symptoms, increased medication use, more frequent emergency department visits and hospitalizations, an overall reduced quality of life and far too often premature death.

There is some recent evidence suggesting that current and former smokers are at greater risk of premature death and of lung cancer when subjected to long-term exposure to fine particle pollution compared with never smokers.59 Smoking damages the lungs, heart, blood vessels and other organs.60 This impairment leaves the person with a smoking history more vulnerable to the health risks for air pollution.

Emerging Threats

Since the passage of the Clean Air Act in 1970, the federal, state and local governments, businesses, community leaders and advocates have invested years of effort into reducing the public health threat from air pollution. By many measures, those efforts have paid off, and the air we breathe is dramatically cleaner than it was 50 years ago.  “State of the Air” has documented this long-term improvement over the past twenty-two years. In recent years, however, new threats have emerged that are causing air pollution levels to rise and the potential harm to vulnerable populations to increase.

The rising global temperatures and disruption of short- and long-term weather patterns caused by climate change are putting the health of millions of Americans at risk. The impacts of climate change currently being experienced in communities nationwide include an increase in extreme weather events, deterioration of air quality from increased ozone formation and wildfire smoke, expansion of the range of disease-carrying pests and increased stresses that affect mental health and well-being.

People and communities are differentially exposed to these climate-related hazards as well as being disproportionately affected by climate-related health risks. Populations experiencing greater health risks include children, older adults, low-income communities and some communities of color.

“State of the Air” largely focuses on the health harms linked to increases in ozone and particle pollutionbut increasing heat itself is another significant risk factor that adds to the climate vulnerability of some of the same populations who face increased risk from air pollution.61 Children are especially vulnerable to extreme heat. They spend more time playing outside and participating in vigorous activity than the average adult. Their bodies have a high surface area-to-mass ratio, so must divert more blood flow to their skin to dissipate heat, which may strain other bodily functions.62

Among older adults, increased heat and exposure to air pollution increases the risk of premature deaths, resulting in more emergency room visits and hospital admissions, especially among those older adults who spend more time outdoors. The physical changes associated with aging—including those that affect breathing and movement—can make it even more difficult to respond to climate change. In the past two decades, heat-related mortality for older persons has almost doubled, reaching a record high 19,000 deaths in 2018.63 Heat waves also significantly increase the risk of illness and death in people living with chronic lung disease.64

Wildfires are posing a growing threat to public health in many parts of the U.S. Increased heat and drought caused by climate change are resulting in larger, more frequent fires that blanket communities in smoke and leave residents gasping for air. Smoke from large fires can spread over hundreds of miles, polluting the air breathed by millions of people. In the years 2016-2019, individuals in the U.S. experienced a 19% increase in the number of days they were exposed to high wildfire risk compared to 2001-2004.65

Wildfire smoke is a complex mixture of fine and course particulate matter and gases, including carbon monoxide, nitrogen oxides, volatile organic compounds and air toxics. The chemical composition of wildfire smoke varies widely depending on the location of the fire and the material burned. The details of how these differences impact health is the subject of ongoing research.66

The biggest health threat from smoke is from fine particles. Like other sources of fine particle pollution, wildfire smoke can be extremely harmful to the lungs, especially for children, older adults and people with asthma, COPD, chronic heart disease and diabetes. Recent research has confirmed that severe wildfire episodes are associated with increased risk of hospital admissions for respiratory diseases for Medicare recipients.67 Pregnant people exposed to wildfire smoke are more likely to experience adverse pregnancy outcomes, including preterm birth.68 There is also strong evidence linking smoke exposure to increased risk of premature death.69

Shared Story Spotlight: Alex S.

Colorado’s record-breaking wildfires in 2020 filled the air with billowing smoke and pollutants for months. Alex S., who lives in the foothills west of Fort Collins, was 30 weeks pregnant. Her 3-year-old son suffered a runny nose for weeks from the poor air quality. The family’s cars were constantly covered in ash. Just days before giving birth, the Cameron Peak fire forced Alex and her family to evacuate as flames moved dangerously close to their home. While her home wasn’t damaged, the experience has made her reevaluate living in the foothills, with safety more top of mind than ever.

“We need to prioritize electing officials who will advocate for policies that help to push climate change measures forward, and on a small scale we need to be focused on our carbon footprint and teaching our children to care for their portion of the earth.”

Because COVID-19 is a new disease, the extent of possible long-term health consequences from infection are still unknown.70 But healthcare providers and researchers are reporting that severe cases of COVID-19 can cause damage to organs throughout the body, including the lungs, heart, kidneys, skin and brain. This increases the risk of long-term health problems that individuals may continue to face for months, or perhaps years, after the initial infection. Scarring of the lungs and heart, and the onset of new or worsening cases of diabetes, may lead to the development of new cases of chronic disease.71

The uncertainties surrounding the COVID-19 pandemic, including how many thousands of survivors will never regain their full health, raises the danger of a sharp and sudden rise in the size of the population of people living with underlying conditions that put them at increased risk of health harm from air pollution.


Did You Know?

  1. Nearly 5 out of 10 people live where the air they breathe earned an F in State of the Air 2020.
  2. 150 million people live in counties that received an F for either ozone or particle pollution in State of the Air 2020.
  3. More than 20.8 million people live in counties that got an F for all three air pollution measures in State of the Air 2020.
  4. Breathing ozone irritates the lungs, resulting in something like a bad sunburn within the lungs.
  5. Breathing in particle pollution can increase the risk of lung cancer, according to the World Health Organization.
  6. Particle pollution can also cause early death and heart attacks, strokes and emergency room visits for people with asthma and cardiovascular disease.
  7. Particles are smaller than 1/30th the diameter of a human hair. When you inhale them, they are small enough to get past the body's natural defenses.
  8. Ozone and particle pollution are both linked to increased risk of lower birth weight in newborns.
  9. Do you live near, or work on or near a busy highway? Pollution from the traffic may put you at greater risk of harm.
  10. People who work or exercise outside face increased risk from the effects of air pollution.
  11. Millions of people are especially vulnerable to the effects of air pollution, including infants, older adults and people with lung diseases like asthma.
  12. People of color and those earning lower incomes are often disproportionately affected by air pollution that put them at higher risk for illnesses.
  13. Air pollution is a serious health threat. It can trigger asthma attacks, harm lung development in children, and can even be deadly.
  14. You can protect your family by checking the air quality forecasts in your community and avoiding exercising or working outdoors when the unhealthy air is expected.
  15. Climate change enhances conditions for ozone to form and makes it harder to keep ozone from forming.
  16. Climate change increases the risk of wildfires that spread particle pollution and ozone in the smoke.
  17. This Administration is trying to roll back or create loopholes in core healthy air protections under the Clean Air Act. The Lung Association opposes these actions that will add pollution to the air we breathe.
  18. Cutting air pollution through the Clean Air Act will prevent at least 230,000 deaths and save $2 trillion annually by 2020.
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  1. U.S.EPA. Integrated Science Assessment for Ozone and Related Photochemical Oxidants. April 2020. EPA/600/R-20/012. Section

  2. U.S. EPA. 2020, Sections 3.1.5 and 3.1.6.

  3. U.S. EPA. 2020, Section 3.1.7.

  4. U.S. EPA. 2020, Section

  5. U.S. EPA. 2020, Section

  6. U.S. EPA. 2020, Section

  7. U.S. EPA. 2020, Section 5.1.3.

  8. U.S. EPA. 2020, Sections 7.2.1 and 7.2.2.

  9. U.S. EPA. 2020, Section 7.1.3.

  10. Mendola P, Ha S, Pollack AZ, Zhu Y, Seeni I, Kim SS, Sherman S, Liu D. Chronic and acute ozone exposure in the week prior to delivery is associated with risk of stillbirth. Int J Environ Res Pub Health. 2017; 14:731.

  11. U.S. EPA. 2020, Sections 4.1 and 4.2

  12. Di et al. 2017.

  13. Lim CC, Hayes RB. Ahn J, Shao Y, Silverman DT, Jones RR, Garcia C, Bell ML, Thurston GD. Long-term exposure to ozone and cause-specific mortality risk in the United States. Am J Respir Crit Care Med. 2019; 200(8):1022–1031.

  14. U.S. EPA. 2020, Section IS.4.4

  15. Health Effects Institute. State of Global Air. Boston MA. 2020.

  16. U.S.EPA. integrated Science Assessment for Particulate Matter. December 2019 EPA/600/R-19/188. Section 11.1.

  17. Shi L, Zanobetti A, Kloog I, Coull BA, Koutrakis P, Melly SJ, Schwartz JD. Low-concentration PM2.5 and mortality: estimating acute and chronic effects in a population-based study. Environ Health Perspect. 2016; 124:46-52.

  18. Schwartz J, Bind MA, Koutrakis P. Estimating causal effects of local air pollution on daily deaths: Effect of low levels. Environ Health Perspect. 2017125:23-29.

  19. Di Q, Dai L, Wang Y, Zanobetti A, Choirat C, Schwartz JD, Dominici F. Association of Short-Term Exposure to Air Pollution with Mortality in Older Adults. JAMA. 2017; 318:2446-2456.

  20. U.S. EPA. 2019, Section

  21. U.S. EPA. 2019, Section 6.1.2.

  22. U.S. EPA. 2019, Section

  23. U.S. EPA. 2019, Section

  24. U.S. EPA. 2019, Section

  25. U.S. EPA. 2019, Section 11.2.

  26. Pope CA, Lefler JS, Ezzati M, Higbee JD, Marshall JD, Kim S, Bechle M, Gilliat KS, Vernon SE, Robinson AL, Burnett RT. Mortality risk and fine particulate pollution in a large, representative cohort of U.S. Adults. Environ Health Perspect. 2019; 127(7):077007-1-077007-9.

  27. Bekkar B Pacheco S, Basu R, DeNicola N_Association of air pollution and heat exposure with preterm birth, low birth weight and stillbirth in the U.S.: A systemic review. JAMA Network Open. 2020; 3(6):e208243.

  28. Bekkar B et al. 2020.

  29. U.S. EPA. 2019, Section

  30. U.S. EPA. 2019, Section

  31. U.S. EPA. 2019, Section 6.2.2.

  32. U.S. EPA. 2019, Section 5.2.5.

  33. Bowe B, Xie Y, Li T, Yan Y, Xian H, Al-Aly Z. The 2016 global and national burden of diabetes mellitus attributable to PM2.5 air pollution. Lancet Planet Health. 2018; 2:e301-12.

  34. U.S. EPA, 2019. Section

  35. Kilian J and Kitazawa M. The emerging risk of exposure to air pollution on cognitive decline and Alzheimer's disease -- evidence from epidemiological and animal studies. Biomed J. 2018; 41:141-162.

  36. Shi L, Wu X, Danesh Yazdi M, Braun D, Abu Awad Y, Wei Y, Liu P, Di Q, Wand Y, Schwartz J, Dominici F, Kioumourtzoglou M-A, Zanobetti A. Long-term effects of PM2·5 on neurological disorders in the American Medicare population: a longitudinal cohort study. Lancet Planet Health. 2020; 4:e557-65.

  37. U.S. EPA. 2019, Section 5.2.11.

  38. Wu X, Nethery RC, Sabath MB, Braun, Dominici F. Air pollution and COVID-19 mortality in the United States: Strengths and limitations of an ecological regression analysis. Sci Adv. 2020; 6(4):eabd4049.

  39. Pozzer A, Dominici F, Haines A, Witt C, Munzel T, Lelieveld J. Regional and global contributions of air pollution to risk of death from COVID-19. Cardio Res. 2020; 116:2247-2253.

  40. Terrel KA and James W. Racial disparities in air pollution burden and COVID-19 deaths in Louisiana, USA, in the context of long-term changes in fine particulate pollution. Env Justice.2020. DOI: 10.1089/env.2020.0021.

  41. U.S. EPA. 2019, Section

  42. U.S. EPA. 2019, Section 12.3.5.

  43. U.S. EPA. 2019, Section 12.3.1.

  44. U.S. EPA. 2019, Section

  45. U.S. EPA. 2019, Section 12.5.4.

  46. U.S. EPA. 2019, Section 12.6.1.

  47. U.S. EPA. 2019, Section 12.5.3.

  48. U.S. EPA. 2019, Section 12.3.3.

  49. U.S. EPA. 2019, Section 12.5.4

  50. Di et al. 2017.

  51. Nardone A, Casey JA, Morello-Frosch R, Mujahid M, Balmes JR, Thakur N. Associations Between Historical Residential Redlining and Current Age-Adjusted Rates of Emergency Department Visits Due to Asthma Across Eight Cities in California: An Ecological Study. Lancet Planet Health. 2020:4(1):e24-e31.

  52. Erqou S, Clougherty JE, Olafiranye O, Magnani JW, Aiyer A, Tripathy S, Kinnee E, Kip KE, Reis SE. Particulate Matter Air Pollution and Racial Differences in Cardiovascular Disease Risk. Arterioscler Thromb Vasc Biol. 2018; 38:00-00.

  53. Centers for Disease Control and Prevention. National Center for Health Statistics. National Health Interview Survey, 2019. Analysis performed by the American Lung Association Epidemiology and Statistics Unit using SPSS software.

  54. U.S. EPA. 2019, Section 12.5.3.

  55. Mikati I, Benson AF, Luben TJ, Sacks JD, Richmond-Bryant J. Disparities in Distribution of Particulate Matter Emission Sources by Race and Poverty Status. Am J Public Health. 2018; 108(4):480–485.

  56. Kioumourtzoglou M-A, Schwartz J, James P, Dominici F, Zanobetti A. PM2.5 and mortality in 207 US cities: modification by temperature and city characteristics. Epidemiology. 2016; 27(2):221-7.

  57. Schwartz J. Air Pollution and Children’s Health. Pediatrics. 2004; 113(4):1037-1043.

  58. Simoni M, Baldacci S, Maio S, Cerrai S, Sarno G, Viegi G. Adverse Effects of Outdoor Pollution in the Elderly. J Thorac Dis. 2015; 7(1):34-45.

  59. U.S. EPA. 2019, Section 12.6.1.

  60. U.S. Department of Health and Human Services. The Health Consequences of Smoking - 50 Years of Progress: A Report of the Surgeon General. 2014.

  61. bi, K.L., J.M. Balbus, G. Luber, A. Bole, A. Crimmins, G. Glass, S. Saha, M.M. Shimamoto, J. Trtanj, and J.L. White-Newsome, 2018: Human Health. In Impacts, Risks, and Adaptation in the United States: Fourth National Climate Assessment, Volume II [Reidmiller, D.R., C.W. Avery, D.R. Easterling, K.E. Kunkel, K.L.M. Lewis, T.K. Maycock, and B.C. Stewart (eds.)]. U.S. Global Change Research Program, Washington, DC, USA, pp. 572–603.

  62. Anderko, L et al. Climate changes reproductive and children’s health: a review of risks, exposures, and impacts. Pediatr Res. 2020; 87:414–419.

  63. Watts N, Amann M, Arnell N et al. The 2020 report of The Lancet Countdown on health and climate change: responding to converging crises. Lancet 2020.

  64. Witt C et al. The effects of climate change on patients with chronic lung disease—a systematic literature review. Dtsch Arztebl Int. 2015; 112:878–83.

  65. Watts et al. Lancet. 2020.

  66. Reid CE et al. Critical review of health impacts of wildfire smoke exposure. Env Health Perspect. 2016; 124(9):1334-1343.

  67. Liu JC et al. Wildfire-specific fine particulate matter and risk of hospital admissions in urban and rural counties. Epidemiology. 2017; 28(1):77-85.

  68. Abdo M et al. Impact of wildfire smoke on adverse pregnancy outcomes in Colorado, 2007-2015. Int J Environ Res Pub Health. 2019; 16:3720.

  69. Cascio WE. Wildland fire smoke and human health. Sci Total Environ. 2018; 624: 586–595.

  70. Del Rio C et al. Long-term Health Consequences of COVID-19. JAMA. 2020; 324(17):1723-1724.

  71. Nalbandian A et al. Post-acute COVID-19 syndrome. Nat Med (2021).