Key Facts

  • Air pollution is one of the greatest environmental health risks. By reducing air pollution levels, countries can reduce the burden of disease from stroke, heart disease, lung cancer, and chronic and acute respiratory conditions, including asthma.
  • Short- and long-term cardiovascular and respiratory health of the population is inversely related to the level of air pollution.
  • The WHO Global Air Quality Guidelines 2021 assess the health effects of air pollution and provide threshold values above which it is harmful to health.
  • In 2019, 99% of the world’s population lived in places that did not meet the thresholds recommended in the WHO air quality guidelines.
  • In 2016, an estimated 4.2 million premature deaths were caused by ambient (outdoor) air pollution in cities and rural areas around the world.
  • Some 91% of these premature deaths occurred in low- and middle-income countries, with the WHO South-East Asia and Western Pacific Regions being the most affected.
  • Major sources of urban outdoor air pollution could be reduced through policies and investments in cleaner transportation, more energy-efficient housing, power plants and industries, and better municipal waste management.
  • In addition to outdoor air pollution, household smoke poses a serious health risk to some 2.6 billion people who cook and heat their homes using biomass, oil, and coal.


Outdoor air pollution is a major environmental health problem that affects everyone in low-, middle-, and high-income countries.

In 2016, ambient (outdoor) air pollution in cities and rural areas was estimated to be responsible for 4.2 million premature deaths per year worldwide; this mortality is due to exposure to fine particulate matter 2.5 microns in diameter or less (PM2.5), which causes cardiovascular and respiratory diseases, as well as cancers.

People living in low- and middle-income countries disproportionately bear the burden of outdoor air pollution: 91% of the 4.2 million premature deaths occur in these countries, with the WHO South-East Asia and Western Pacific Regions paying the highest burden. The latest burden of disease estimates reflects the very important role that air pollution plays in cardiovascular disease and death. There is increasing evidence of the links between ambient air pollution and cardiovascular disease risk, including from studies in highly polluted areas.

According to WHO estimates, in 2016, some 58% of premature deaths related to outdoor air pollution were due to ischemic heart disease and stroke, 18% to chronic obstructive pulmonary disease, 18% to acute lower respiratory tract infections, and 6% to lung cancer.

Some deaths can be attributed to several concomitant risk factors. For example, both smoking and ambient air pollution affect lung cancer. Some lung cancer deaths could have been prevented by improving ambient air quality or reducing smoking with these tips from EntrepreneursBreak.

The findings of a 2013 evaluation by the WHO’s International Agency for Research on Cancer (IARC) indicated that outdoor air pollution is carcinogenic to humans, with particulate matter in polluted air very strongly associated with increased cancer incidence, particularly lung cancer. An association between outdoor air pollution and increased urinary tract/bladder cancers was also observed.