Outdoor air pollution is a major environmental health problem affecting everyone in low-, middle-, and high-income countries. People living in low- and middle-income countries disproportionately experience the burden of outdoor air pollution with 91% (of the 4.2 million premature deaths) occurring in low- and middle-income countries, and the greatest burden in the WHO South-East Asia and Western Pacific regions. The latest burden estimates reflect the very significant role air pollution plays in cardiovascular illness and death. More and more, evidence demonstrating the linkages between ambient air pollution and the cardiovascular disease risk is becoming available, including studies from highly polluted areas.
Air pollution threatens the health of people in many parts of the world. New estimates in 2018 reveal that 9 out of 10 people breathe air containing high levels of pollutants. Both ambient (outdoor) and household (indoor) air pollution are responsible for about 7 million deaths globally per year; in the Western Pacific Region alone, around 2.2 million people die each year. These two are the most prevalent types of air pollution. Smog, or "ground-level ozone, " as it is more wonkily called, occurs when emissions from combusting fossil fuels react with sunlight. Soot, or "particulate matter, " is made up of tiny particles of chemicals, soil, smoke, dust, or allergens, in the form of gas or solids, that are carried in the air. The EPA’s "Plain English Guide to the Clean Air Act" states, "In many parts of the United States, pollution has reduced the distance and clarity of what we see by 70 percent." The sources of smog and soot are similar. "Both come from cars and trucks, factories, power plants, incinerators, engines—anything that combusts fossil fuels such as coal, gas, or natural gas, " Walke says. The tiniest airborne particles in soot—whether they’re in the form of gas or solids—are especially dangerous because they can penetrate the lungs and bloodstream and worsen bronchitis, lead to heart attacks, and even hasten death.