The major components of air pollution in developed countries are
Burning of biomass fuel (such as wood, animal waste, and crops) is an important source of particulate matter indoors in developing countries. Secondhand smoke is also an important source of indoor air pollution.
High levels of air pollution can trigger attacks (exacerbations) in people with asthma or chronic obstructive pulmonary disease (COPD). Air pollution–related lung disease increases the risk of heart and blood vessel disorders and may increase the risk of lung cancer. People living in areas with high traffic are at particular risk.
Most air pollutants cause the muscles in airways to contract, narrowing the airway (airway hyperreactivity).
Among members of the general population, especially children, long-term exposure to air pollution may increase respiratory infections and symptoms of respiratory disorders (such as cough and difficulty breathing) and decrease lung function.
Ozone, which is the major component of smog, is a strong lung irritant. Levels tend to be higher in the summer compared to other seasons and relatively higher in the late morning and early afternoon compared to other times of the day. Short-term exposures can cause breathing difficulties, chest pain, and airway hyperreactivity. Children who participate in outdoor activities on days on which ozone pollution is high are more likely to develop asthma. Long-term exposure to ozone causes a small, permanent decrease in lung function.
Combustion of fossil fuels that are high in sulfur can create acid particles that are easily deposited in the upper airway. These particles, called sulfur oxides, can cause the airways to become inflamed and constricted, causing symptoms such as breathing difficulty, and increase the risk of chronic bronchitis (inflammation of the bronchi, or large airways).
Particulate air pollution derived from fossil fuel combustion (especially diesel fuel) is a complex mixture. The particles can cause inflammation of the airways or can affect other parts of their body, such as the heart. Data from some studies suggest that particulate air pollution increases death rates from all causes, especially heart and lung disorders.
Particles affect the lung differently depending on what substances they are made from. Particles of the same material also may have different effects depending on their size and shape. 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. Testing in animals as well as laboratory tests shows that high concentrations of nanoparticles or ultrafine particles can be dangerous. Some workers accidentally exposed to very large amounts have developed fluid around the lungs or damage to the small lung airways. But doctors do not know for certain the effects on workers in the nanotechnology industry of the amounts and types of nanoparticles that they are exposed to. Studies are being done to evaluate the risks and to ensure that workers are protected.
The levels of pollutants in the air vary based on location and environmental conditions. For example, ozone tends to remain in the air on warm, humid days, particularly in the afternoon and early evening. Carbon monoxide tends to be high during periods when there are many commuters driving to or from work. The Air Quality Index is used to communicate how polluted the air is 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*
Doctors base the diagnosis on a person's history of exposure, symptoms, lung function tests, and exposure to high concentrations of known pollutants in the air at work and at home. 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 lung disorders. The diagnosis may become clear if many workers in the same occupation and with similar exposures develop the same lung disorder, including after sudden, very large exposures.
Workers with air pollution exposures should comply with recommendations issued by major governmental agencies that limit exposure to air borne gases, dusts, and fumes. Children, older people, and people with asthma, COPD and other lung disorders should avoid exercising outdoors when the air has high levels of pollutants.