Merck Manual

Please confirm that you are not located inside the Russian Federation

honeypot link

Air Pollution–Related Illness


Carrie A. Redlich

, MD, MPH, Yale Occupational and Environmental Medicine Program Yale School of Medicine;

Efia S. James

, MD, MPH, Yale School of Medicine;

Brian Linde

, MD, MPH, Yale Occ and Env Medicine Program

Reviewed/Revised Nov 2023
Topic Resources

Air pollution–related illness is disease caused by harmful pollutants in the air or worsening of preexisting disease by air pollutants.

  • Some air pollutants cause the airways to narrow, leading to cough, wheezing, and shortness of breath.

  • Diagnosis is based on a history of exposure to air pollutants.

  • Doctors do pulmonary function testing to determine whether the lungs are affected.

  • Symptoms are treated.

Air pollution contributes significantly to a number of health problems. Air pollution can affect lung function, trigger asthma Asthma Asthma is a condition in which the airways narrow—usually reversibly—in response to certain stimuli. Coughing, wheezing, and shortness of breath that occur in response to specific triggers are... read more Asthma and COPD Chronic Obstructive Pulmonary Disease (COPD) Chronic obstructive pulmonary disease is persistent narrowing (blocking, or obstruction) of the airways occurring with emphysema, chronic obstructive bronchitis, or both disorders. Cigarette... read more Chronic Obstructive Pulmonary Disease (COPD) (chronic obstructive pulmonary disease) exacerbations, and increase the risk of respiratory infections and lung cancer Lung Cancer Lung cancer is the leading cause of cancer death in both men and women. About 85% of cases are related to cigarette smoking. One common symptom is a persistent cough or a change in the character... read more Lung Cancer . Air pollution also increases the risk of heart attacks Acute Coronary Syndromes (Heart Attack; Myocardial Infarction; Unstable Angina) Acute coronary syndromes result from a sudden blockage in a coronary artery. This blockage causes unstable angina or a heart attack (myocardial infarction), depending on the location and amount... read more Acute Coronary Syndromes (Heart Attack; Myocardial Infarction; Unstable Angina) , the development of coronary artery disease Overview of Coronary Artery Disease (CAD) Coronary artery disease is a condition in which the blood supply to the heart muscle is partially or completely blocked. The heart muscle needs a constant supply of oxygen-rich blood. The coronary... read more Overview of Coronary Artery Disease (CAD) , and stroke Overview of Stroke A stroke occurs when an artery to the brain becomes blocked or ruptures, resulting in death of an area of brain tissue due to loss of its blood supply (cerebral infarction). Symptoms occur suddenly... read more . People living in areas with a large volume of traffic have an elevated risk of air pollution–related health problems.

The major components of air pollution are

  • Nitrogen dioxide (from combustion of fossil fuels)

  • Ozone (from the effect of sunlight on nitrogen dioxide and hydrocarbons)

  • Carbon monoxide

  • Particulate air pollution (suspended solid or liquid particles)

  • Sulfur oxides

Outdoor air pollution is an important contributor to indoor air pollution. In addition, sources of indoor air pollution include tobacco smoke, indoor cooking (including gas stoves), construction, and renovation. Burning of biomass fuel (for example, wood, animal waste, crops) for cooking and heating is an important pollution source in countries that rely on biomass fuel.

The U.S. Environmental Protection Agency (EPA) sets air quality standards for oxides of nitrogen, ozone, oxides of sulfur, carbon monoxide, lead, and particulates established as the criteria air pollutants in the Clean Air Act.

Ozone, which is the major component of smog, is a strong respiratory irritant and oxidant. Ozone levels are highest in the summer and in the late morning and early afternoon. Short-term exposures can cause shortness of breath, chest pain, and airway hyperreactivity. Children who regularly participate in outdoor activities during days on which ozone pollution is high are more likely to develop asthma Asthma in Children Asthma is a recurring inflammatory lung disorder in which certain stimuli (triggers) inflame the airways and cause them to temporarily narrow, resulting in difficulty breathing. Asthma triggers... read more Asthma in Children .

Carbon monoxide is a product of incomplete combustion of fossil fuels and interferes with oxygen delivery to tissues by binding to hemoglobin, the protein in red blood cells that transports oxygen. Very high levels of carbon monoxide are not likely to occur outdoors.

With removal of lead from motor vehicle gasoline, lead levels in the air have decreased significantly in the United States.

Particulate air pollution is a complex mixture of solid particles and liquid droplets found in the air. The particles can originate from a variety of sources (including diesel exhaust, smoke stacks, and construction) and have both local and body-wide (systemic) inflammatory effects. Wildfire smoke, another important source of particulate air pollution, can impact people hundreds of miles from the source of the fire. Particulate air pollution increases death rates from all causes, especially heart and lung disorders.

In addition to being an important source of particulate matter, wildfire smoke also contains carbon dioxide, water vapor, carbon monoxide, hydrocarbons, nitrogen oxides, and trace minerals.

The nanotechnology industry creates extremely small particles of different substances, such as carbon, for various uses. Nanoparticles and ultrafine particles are less than 100 nanometers in size. For comparison, a human hair is about 100,000 nanometers in diameter, so it would take 1000 nanoparticles to equal the thickness of one hair. Certain nanoparticles and ultrafine particles have been associated with increased respiratory symptoms in people with asthma.

Diagnosis of Air Pollution–Related Illness

  • A history of exposure

  • Pulmonary function tests

Doctors base the diagnosis on a person's medical history, environmental exposures, symptoms, and results of lung function tests Pulmonary Function Testing (PFT) Pulmonary function tests measure the lungs' capacity to hold air, to move air in and out, and to absorb oxygen. Pulmonary function tests are better at detecting the general type and severity... read more Pulmonary Function Testing (PFT) . Doctors ask people who have lung disorders such as asthma and COPD whether their symptoms worsen when exposed to air pollution.

Tests often do not help differentiate air pollution–related illness from other causes of lung disorders. The causative role of a specific pollutant may become clear if many people in the same environment and with elevated exposures develop similar symptoms or lung disorders.

Treatment of Air Pollution–Related Illness

  • Treatment of symptoms

Prevention of Air Pollution–Related Illness

Air pollution is a leading cause of death worldwide. Preventing or reducing exposure to outdoor air pollutants is central to reducing both the acute and chronic risk of air pollution–related illness.

The levels of pollutants in the air vary based on location and environmental conditions. For example, ozone tends to remain in the air on hot sunny days, particularly in the afternoon and early evening. The Air Quality Index is used by the federal government to communicate how polluted the air is in a particular location at a given point in time. People, especially those with heart or lung disorders, can use the Air Quality Index to guide their choice of outdoor activities on days when pollution levels are high (Air Quality Index (AQI) |

Examples of risk modification include reducing strenuous outdoor exercise and/or staying indoors in spaces with high-efficiency particulate air (HEPA) filtration systems on days when air quality is poor.

Reducing exposure to indoor sources, such as smoking and cooking, and optimizing ventilation are also recommended.


More Information

The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.

  • Air Now: A resource from the U. S. Environmental Protection Agency to provide people with air quality information where they live

quiz link

Test your knowledge

Take a Quiz!