Health effects of air pollution

Around the world, nine out of 10 people breathe unhealthy air.

Air pollution is now the biggest environmental risk for early death, responsible for more than 6 million premature deaths each year from heart attacks, strokes, diabetes and respiratory diseases. That’s more than the deaths from AIDS, tuberculosis and malaria combined.

Girl using an asthma inhaler as adults look on — Unhealthy air contributes to a number of medical conditions including asthma.

Children, the elderly, people with existing diseases, and minority and low-income communities are particularly vulnerable to adverse health outcomes and economic impacts, such as missed work days, from exposure to air pollution.

Research suggests that long term exposure to some pollutants increases the risk of emphysema more than smoking a pack of cigarettes a day. And recent studies show air pollution can impact mental health, worker productivity and even stock market performance.

To understand the best way to develop air pollution solutions, it’s important to better understand this invisible threat. What we typically think of as "air pollution" is actually a mixture of small particles (pollutants), including the below.

Particulate matter (PM₁₀, PM_2.5)

Particulate matter (PM) is made up of small airborne particles like dust, soot and drops of liquids. The majority of PM in urban areas is formed directly from burning of fossil fuels by power plants, automobiles, non-road equipment and industrial facilities. Other sources are dust, diesel emissions and secondary particle formation from gases and vapors.

Coarse particulate matter (PM₁₀, particles less than 10 microns in diameter) is known to cause nasal and upper respiratory tract health problems. Fine particles (PM_2.5, particles less than 2.5 microns in diameter) penetrate deeper into the lungs and cause heart attacks, strokes, asthma, and bronchitis, as well as premature death from heart ailments, lung disease and cancer. Studies show that higher PM_2.5 exposure can impair brain development in children.

Black carbon (BC)

Black carbon is one of the components of particulate matter and comes from burning fuel (especially diesel, wood, and coal). Most air pollution regulations focus on PM_2.5, but exposure to black carbon is a serious health threat as well. Populations with higher exposures to black carbon over a long period are at a higher risk for heart attacks and stroke. In addition, black carbon is associated with hypertension, asthma, chronic obstructive pulmonary disease, bronchitis, and a variety of types of cancer.

Nitrogen oxides (NO and NO₂)

Nitrogen oxide (NO) and nitrogen dioxide (NO₂) are produced primarily by the transportation sector. NO is rapidly converted to NO₂ in sunlight. NO_x (a combination of NO and NO₂) is formed in high concentrations around roadways and can result in development and exacerbations of asthma and bronchitis, and can lead to a higher risk of heart disease.

Ozone (O₃)

Ozone high in the atmosphere can protect us from ultraviolet radiation. But ozone at ground level (where it is part of what is commonly called smog) is a well-established respiratory irritant. Ozone is formed in the atmosphere through reactions of volatile organic compounds and nitrogen oxides, both of which are formed as a result of combustion of fossil fuels. Short-term exposure to ozone can cause chest pain, coughing and throat irritation, while long term exposure can lead to decreased lung function and cause chronic obstructive pulmonary disease. In addition, ozone exposure can aggravate existing lung diseases.

Sulfur dioxide (SO₂)

SO₂ is emitted into the air by the burning of fossil fuels that contain sulfur. Coal, metal extraction and smelting, ship engines, and heavy equipment diesel equipment burn fuels that contain sulfur. Sulfur dioxide causes eye irritation, worsens asthma, increases susceptibility to respiratory infections and impacts the cardiovascular system. When SO₂ combines with water, it forms sulfuric acid; this is the main component of acid rain, a known contributor to deforestation.

The unequal burden of air pollution