The most common air pollutants include particulate matter (PM), nitrogen oxides (NOx), sulfur oxides (SOx), ozone (O3), and carbon monoxide (CO). These pollutants can come from a variety of sources, including transportation, industry, agriculture, and natural sources like wildfires and dust storms.

According to the WHO, air pollution is responsible for an estimated 7 million premature deaths each year, making it one of the leading causes of death globally.

Fine particulate matter (PM2.5) is one of the most harmful air pollutants, as it can penetrate deep into the lungs and bloodstream, causing respiratory and cardiovascular problems. In 2019, the global average concentration of PM2.5 was 25 micrograms per cubic meter, but levels varied widely across different regions.

Air pollution can also have a significant economic impact, due to healthcare costs, lost productivity, and damage to crops and ecosystems. The World Bank estimates that air pollution costs the global economy $5 trillion per year in welfare losses.

Governments and international organizations are taking steps to address air pollution through policies and regulations aimed at reducing emissions from transportation, industry, and other sources. However, progress has been slow in many areas, and air pollution remains a significant public health and environmental challenge.