Air Pollution and Your Health

Air pollution is a familiar environmental health hazard. 

We know what we’re looking at when brown haze settles 

over a city, exhaust billows across a busy highway, or 

a plume rises from a smokestack. Some air pollution is 

unseen, but its pungent smell alerts you.

When the National Ambient Air Quality Standards were 

established in 1970, air pollution was regarded primarily 

as a threat to respiratory health. Over the next decades 

as air pollution research advanced, public health concern 

broadened to include cardiovascular disease; diabetes; 

obesity; reproductive, neurological, and immune system 

disorders; and cancer. In 2013, the International Agency 

for Research on Cancer of the World Health Organization 

(WHO) classified air pollution as a human carcinogen.

Over its 50-plus year history, NIEHS has been a leader in 

air pollution research. The institute continues to fund and 

conduct research into how air pollution affects health 

and the population groups who are most affected.

What Is Air Pollution?

Air pollution is a mix of hazardous substances from both 

human-made and natural sources. Some dangerous 

substances are released into the air naturally, such as ash 

and gases from volcanic eruptions. Other emissions can 

be caused by both human and natural activity, such as 

smoke from wildfires, which are often started by people; 

and methane, which comes from decomposing organic 

matter in soils as well as animal feedlots.

The primary sources of human-made air pollution are 

vehicle exhaust; fuel oils and natural gas to heat homes; 

by-products of manufacturing and power generation, 

particularly coal-fueled power plants; and fumes from 

chemical production.

TRAP and Its Components

Traffic-Related Air Pollution (TRAP), from motor 

vehicle emissions, contains most of the elements 

common to all air pollution, including various forms 

of carbon, nitrogen oxides, sulfur oxides, volatile 

organic compounds, polycyclic aromatic hydrocarbons, 

fine particulate matter, and ground-level ozone.

Noxious gases, including carbon dioxide, carbon 

monoxide, nitrogen oxides (NOx), and sulfur oxides 

(SOx), are components of motor vehicle emissions and 

byproducts of industrial processes.

Particulate matter (PM), made of chemicals such as 

sulfates, nitrates, carbon, or mineral dusts, are created 

during the combustion of fossil fuels and organic matter.

Volatile organic compounds (VOC) are released during 

the combustion of fossil fuels, and given off by paints, 

cleaning supplies, pesticides, and even craft materials 

like glue. 

Polycyclic aromatic hydrocarbons (PAH) are organic 

compounds released during combustion, power 

generation, and some manufacturing. PAHs are also 

found in particulate matter.

Ozone, an atmospheric gas, is created when pollutants 

emitted by cars, power plants, refineries, and other 

sources chemically react in the presence of sunlight. 

We call this smog.

Learn more about common air pollutants from 

the U.S. Environmental Protection Agency (EPA) at 

https://epa.gov/criteria-air-pollutants.

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Phone: 919-541-3345 • https://niehs.nih.gov

August 2020

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U.S. Department of Health and Human Services

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How Air Pollution Affects Health

Fine particulate matter (PM 2.5) is 30 times thinner than 

a human hair and can be inhaled deeply into lung tissue. 

It accounts for most health effects3

 due to air pollution 

in the U.S. Other significant contributors and outcomes 

follow.

Respiratory disease 

Air pollution can affect lung development and is 

associated with emphysema,4

 asthma, and chronic 

obstructive pulmonary disease5

 (COPD). PM and 

nitrogen oxide have been linked to chronic bronchitis.6

How your genes interact with the environment also plays 

a critical role in the health of your respiratory system. 

NIEHS-funded research discovered that people with 

specific gene variants7

 that made them more likely to 

have lung inflammation had a greater chance of suffering 

from asthma if they lived close to major roadways.

Cardiovascular disease

Air pollution can aggravate your heart and cardiovascular 

system in many ways. PM 2.5 can impair blood vessel 

function8

 and speed up calcification in arteries.9

Researchers also found:

• Short-term daily exposure to nitrogen oxides by 

post-menopausal women can increase the risk of 

hemorrhagic stroke.10

• For a cross-section of older Americans, exposure to 

TRAP can result in lowered levels of high-density 

lipoprotein (HDL),11 sometimes called good cholesterol, 

increasing their risk for cardiovascular disease.

Cancer

Many types of cancer are associated with air pollution.

• Researchers found that occupational exposure to 

benzene, an industrial chemical and component of 

gasoline, can cause leukemia and is associated with 

non-Hodgkin’s Lymphoma.12

• A long-term study, 2000-2016, found an association 

between lung cancer13 incidence and increased reliance 

on coal for energy generation.

• The risk of developing breast cancer from exposure to 

air pollution is of special concern. A study of more than 

57,000 women found living near major roadways may 

increase a woman’s risk for breast cancer.14

Whom Does Air Pollution Affect the Most? 

Pregnant women and children

Air pollution has been shown to have many negative 

effects for pregnant women and their fetuses.

• Prenatal exposure to PAHs was associated with various 

prenatal and childhood neurological problems, such as 

brain development effects, slower processing speed, 

and attention-deficit and hyperactivity disorder (ADHD) 

symptoms.15

• Prenatal exposure to particulate matter was associated 

with low birth weight.16

• Women exposed to high levels of PM 2.5 during 

pregnancy, particularly in the third trimester, may have 

up to twice the risk of having a child with autism.17

• Second and third trimester exposure to PM 2.5 might 

increase the chance of those children having high 

blood pressure in early life.18

• In California’s agricultural San Joaquin Valley, women 

exposed to high levels of carbon monoxide, nitrogen 

oxide, or nitrogen dioxide during their first eight weeks 

of pregnancy were more likely to have a baby with neural 

tube defects.19

National Institute of Environmental Health Sciences

National Toxicology Program

According to a systematic review, TRAP exposure 

increases a pregnant woman’s risk for dangerous 

changes in blood pressure, known as hypertensive 

disorders, which are a leading cause of preterm 

birth, low birth weight, and maternal and fetal 

illness and death.1

The 14th Report on Carcinogens, prepared by NTP 

on behalf of the U.S. Department of Health and 

Human Services, lists 15 PAHs as carcinogens.2
National Institute of Environmental Health Sciences

Older adults

In older adults, long-term exposure to TRAP may 

significantly hasten physical disabilities.24 The risk is more 

pronounced among racial minorities and lower-income 

people. PM 2.5 is associated with accelerated memory 

problems and Alzheimer’s-like brain declines25 among 

women 65 years of age and older.

Rural dwellers

Many people believe that air pollution is an urban 

problem. But rural residents, especially those in 

agricultural areas, also face health risks from air pollution.

• An NIEHS-funded study found that concentrations of 

PM 2.5 in rural Washington state were comparable to 

those in urban Seattle, resulting in increased asthma 

symptoms for rural children26 that include wheezing, 

nighttime waking, and limitations on activities.

• Large-scale animal feeding operations might 

compromise regional air quality through emission of 

pollutants, such as ammonia gas27 and methane. A 

study found acute lung function problems in children 

with asthma in such areas.

The Children’s Health Study

Begun in 1992 at the University of Southern 

California, this study is one of the largest on the 

long-term effects of air pollution on children’s 

respiratory health. With major funding from NIEHS, 

it includes data collected from more than 11,000 

children in 16 communities across Southern 

California. Published findings include:

• Higher air pollution20 levels increase short-term 

respiratory infections, which lead to more school 

absences.

• Children who play several outdoor sports21 and live 

in communities with high ozone are more likely to 

develop asthma.

• Children living near busy roads22 are at increased 

risk for asthma.

• Children with asthma who were exposed to high 

levels of air pollutants were more likely to develop 

bronchitis23 symptoms.

• For more information: https://healthstudy.usc.edu

NIEHS and Community Involvement

NIEHS has a long history of direct involvement in 

communities, from close cooperation with native peoples 

in identifying the sources and impacts of pollution on 

tribal lands, to understanding issues of environmental 

justice in inner cities, to citizen science initiatives that 

improve the quality of data crucial to air pollution 

research. Among these initiatives, researchers found: 

• Breathing dust from mine tailings, created by active 

and abandoned mining operations, affects lung 

function.28 NIEHS grant recipients address health 

hazards in disadvantaged communities, such as among 

Native American people in the West, through culturally 

relevant health communication.

• NIEHS also helps residents of Imperial County, California, 

track air pollution through a network of 40 communityrun monitors. In this county, long-term improvements 

in air quality were associated with significant lungfunction improvement29 in children.

• Community-level tactics30 can also help reduce 

exposure to TRAP:

– Using high-efficiency particulate air (HEPA) filtration.

– Building land-use buffers and vegetation barriers.

– Improving urban design with gardens, parks, and 

street-side trees.

– Creating active-travel options, such as bicycling and 

walking paths.
Why Improving Air Quality Matters

Success stories in cleaning up our air demonstrate the 

benefits of these efforts for public health.

• Among children in Southern California, decreases in 

ambient nitrogen dioxide and PM 2.5 were associated 

with fewer cases of asthma.31

• In the Los Angeles region, bronchitis symptoms 

declined32 as pollution levels dropped.

• When fossil-fuel power plants close, nearby air 

pollution is reduced. A study found the incidence of 

preterm births33 went down within 5 kilometers of 

retired coal and oil-powered plants.

• An NIEHS-funded study found that a mixture of 

several B vitamins may protect DNA34 from changes 

attributable to PM 2.5 air pollution.

National Institute of Environmental Health Sciences

Resources

• AirNow, a tool developed in partnership by several 

government agencies, allows anyone to monitor 

air quality in real time anywhere in the U.S. Simply 

enter a zip code, as indicated on the website. 

https://airnow.gov

• EPA’s Air Sensor Toolbox provides information on 

the operation and use of air sensor monitoring 

systems for technology developers, air quality 

managers, citizen scientists, and the public. 

https://epa.gov/air-sensor-toolbox

For more information on the 

National Institute of Environmental Health Sciences, 

go to https://niehs.nih.gov.

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Research Triangle Park, NC: National Toxicology Program. Monograph 7 

2 NTP (National Toxicology Program). 2016. Report on Carcinogens, Fourteenth Edition.; Research Triangle Park, NC: U.S. Department of Health and Human Services, 

Public Health Service. https://ntp.niehs.nih.gov/go/roc14 3 Nolte CG, et al. 2018. Air Quality. In Impacts, Risks, and Adaptation in the United States: Fourth National Climate Assessment, Volume II (Reidmiller, D.R., et al., eds.). U.S. 

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