• 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).

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).