Particulate matter (PM2.5, PM10)

General

• PM2.5 largest sources are agriculture and wildfires followed by road traffic, nonroad traffic, burning coal for energy and industry, and windblown dust (NIH, 2023)
• Climate change will add to air pollution - 3°C increase could double ozone formation and PM2.5 could increase 40% (James Dinneen, 2024)
• Black carbon (BC) from fossil fuels used in commuting and is a major component of PM2.5, coming from partially combustible sources (ex: wood burning and fossil fuels). 40% fossil fuel, 40% biomass burning, 20% biofuel from household cooking (Dilip Kumar Mahato et al., 2024).
• Ambient PM2.5 stabilizing or reducing in many regions (State of Global Air, 2024)
• Fine particle air pollution (aka PM2.5) measures less than 2.5 micrometers in diameter. From vehicles, residential fuel use, coal-burning power plants, agriculture and industry, waste burning, wildfires, and more (human and natural) (State of Global Air, 2024)
• PM2.5 pollution leads to higher likelihood of developing breast cancer, as there is a statistically significant 28% increase in risk of breast cancer when fine-particle air pollution increased by 10 ug/m3 (aka 0.01 ppm) (Jamie DePolo, 2023)
• Particulate matter leading contributor of global disease burden in 2021 (Michael Brauer, Gregory A Roth, 2024)
• PM2.5 with rheumatoid arthritis, connective tissue diseases, and inflammatory bowel diseases (Harry Cockburn, 2022)
• PM2.5 sources in the UK: 29% construction and industry, 20% road transport, 20% wood burning, 14% waste, 5% agriculture, 5% non-road transport, 7% other (Healthy Air Coalition, 2025)
• Particulate Matter is considered to be one of the most harmful types of air pollution for our health, with long-term exposure associated with an increased risk of a wide range of health conditions (Coles, 2026).
• Laboratory studies suggest that when brain cells are directly exposed to fine particulate pollution, they incur damage that impairs their function and triggers cell death (Jain, 2026).
• Fine particulate pollution can interfere with a key component of the body's stress-response system, known as the hypothalamic-pituitary-adrenal axis (Jain, 2026).
• WHO's 2021 Global Air Quality Guidelines set the recommended annual mean limit at 5 µg/m³ for PM2.5 and 15 µg/m³ for PM10 — the PM2.5 figure was halved from the 2005 guideline of 10 µg/m³ (WHO, 2021)
• The US EPA's Integrated Science Assessment concluded there is a causal relationship between long- and short-term PM2.5 exposure and both cardiovascular effects and premature mortality (US EPA, PM ISA, 2019)
• In the landmark American Cancer Society cohort of ~1.2 million adults, each 10 µg/m³ rise in long-term PM2.5 was associated with roughly a 4%, 6% and 8% higher risk of all-cause, cardiopulmonary and lung-cancer death respectively (Pope et al., JAMA, 2002)
• The Harvard Six Cities study was the first major cohort to link long-term fine-particle exposure to higher mortality, and its extended follow-up showed that as PM2.5 fell, death rates fell with it (Dockery et al., NEJM, 1993; Laden et al., 2006)
• A detailed UK assessment found a large share of PM2.5 is secondary — formed in the air from precursor gases such as ammonia and nitrogen oxides — alongside directly emitted particles (AQEG, 2012)
• Ammonia from agriculture is a major precursor of secondary particulate matter, making farming an important UK source of PM2.5 (AQEG, 2018)
• Modelling for the UK indicates that reducing ammonia emissions can be one of the most cost-effective ways to lower population exposure to PM2.5 (AQEG, 2015)

India

• In 2023, for instance, India’s average fine particulate pollution, called PM2.5, was about 41 micrograms per cubic meter, which is more than eight times the level the World Health Organization has deemed safe (Jain, 2026).

United States

• In a December 2025 analysis of health records from 23.7 million older adults in the United States, long-term exposure to PM2.5 was associated with a higher risk of late-life depression. (Jain, 2026).