Air pollution is estimated to cause 2.4 million premature deaths per year and increases the risk of lung disease, heart disease, preterm birth, and developmental problems in children. The body of evidence is so strong that researchers regard air pollution as a public health problem as serious as smoking.
Air pollution is one of the greatest health risks in the world. According to estimates from the World Health Organization, approximately 2.4 million people die prematurely from air pollution every year. Researchers now compare its public health burden to that of smoking and advocate for equally strict policy (PMID 22726103, 38888169).
The harmful effects are wide-ranging and well documented. Exposure to fine particulate matter (PM2.5, tiny particles that penetrate deep into the lungs) and ozone increases the risk of death and disease from both short-term and long-term exposure. This holds true in Europe, North America, and East Asia alike, demonstrating that the problem is not regional (PMID 38321318). Concretely, this includes serious lung diseases such as COPD (chronic obstructive pulmonary disease) and asthma, as well as heart attacks. Biologically, measurable abnormalities in lung tissue, the cardiovascular system, and even DNA are already detectable at an early stage, before a person has any symptoms (PMID 29177959).
Pregnant women and their unborn children are particularly vulnerable. For every increase of 10 micrograms per cubic metre of fine particulate matter (PM10), birth weight falls by approximately half a percent and gestational duration decreases slightly, while the risk of low birth weight rises by 22% and the risk of preterm birth by 16%. The damage is greatest in the third trimester and among mothers with lower levels of education, which underscores the inequality in health risks (PMID 35001469). After birth the risk continues: exposure in early life is associated with more respiratory complaints, allergies, a delay in brain development, and reduced growth (PMID 37169689).
There is good news on the policy front. There is evidence that targeted measures, such as stricter standards for diesel engines and government policies for cleaner air, can genuinely reduce the number of premature deaths (PMID 22726103, 33671274). More urban greenery also helps: a measurable increase in vegetation within a city is associated with approximately 3% less mortality from cardiovascular disease, likely because greenery counteracts air pollution, noise nuisance, and heat (PMID 39688058).
An important caveat: most associations have been established through population studies (associational research), which means we observe strong correlations but cannot always fully prove a direct cause-and-effect relationship. The effects on pregnant women and birth weight are, however, considered likely causal by researchers. The total harm is also difficult to measure precisely, because air pollution consists of many different substances that are present simultaneously.
Nine claims based on seven PMIDs, including large international studies and a meta-analysis on prenatal effects. Strength of evidence is strong for mortality and chronic disease, moderate for early biological damage and infant outcomes. Most studies are observational in nature.