Air pollution

Air pollution is the contamination of Earth’s atmosphere with gases or particulates that are toxic or environmentally disruptive.

Quotes

Outdoor air pollution is a major global public health issue (Cohen et al., 2017), leading to 4.14 million non-accidental premature deaths in both urban and rural areas worldwide in 2019 alone (Global Burden of Disease, 2019). In 2016, 54 % of the world's population lived in urban areas (United Nations, 2018), where ground-level ozone (O₃), particles with an aerodynamic diameter lower than 2.5 μm (PM_2.5), and nitrogen dioxide (NO₂) are the most harmful air pollutants for human health (Pascal et al., 2013; McDuffie et al., 2021; Anenberg et al., 2022). By 2050, 70 % of the world's population will reside urban areas (United Nations, 2018), and outdoor air pollution would lead to about 6.6 million premature deaths (Lelieveld et al., 2015). Air pollution also adversely affects biodiversity, ecosystems, and ecosystem services, such as nutrient cycling (Agathokleous et al., 2020; Hu et al., 2022; Perring et al., 2022).
- Pierre Sicard, Evgenios Agathokleous, Susan C. Anenberg, Alessandra De Marco, Elena Paoletti, and Vicent Calatayud, (February 2023)"Trends in urban air pollution over the last two decades: A global perspective". Science of The Total Environment 858, Part 2. DOI:10.1016/j.scitotenv.2022.160064.

There are numerous ways to approach air pollution. Biologists may think of how contaminants in the air affect living things. Within biology, the subdisciplines vary in their interests. Ecologists are often interested in how exposure to air pollutants affect biodiversity and overall ecosystem health. Biomedical scientists are concerned about the diseases associated with various air contaminants. ...
Epidemiologists are interested in how the exposure and effects of air pollutants differ in time and space. They may observe a cluster of diseases and associate this with a source of air pollution. Or, they may observe a change in disease occurrence over time that tracks with changes in the type and amount of pollution released in an area.
- Daniel A. Vallero, Fundamentals of Air Pollution (5th ed.). Academic Press. 2014. p. 43. ISBN 9780124046023. (1st edition 1973; 6th edition 2025)

The global response to the COVID-19 pandemic has resulted in unprecedented reductions in economic activity. We find that, after accounting for meteorological variations, lockdown events have reduced the population-weighted concentration of nitrogen dioxide and particulate matter levels by about 60% and 31% in 34 countries, with mixed effects on ozone. Reductions in transportation sector emissions are largely responsible for the NO₂ anomalies.
- Zander S. Venter, Kristin Aunan, Sourangsu Chowdhury, and Jos Lelieveld, (2020). "COVID-19 lockdowns cause global air pollution declines". Proceedings of the National Academy of Sciences 117 (32): 18984-18990. DOI:10.1073/pnas.2006853117.

Fine particulate matter (PM_2.5) air pollution has recently been recognized as a risk factor for dementia. ... Fine particulate matter may affect cognitive function via neuroinflammation as a result of systemic inflammation or oxidative stress following lung irritation. ... It has also been proposed that the smallest particles, often coated with neurotoxic chemicals, ... can enter the brain through the olfactory bulb or cross the blood-brain barrier. ... Unlike many other common risk factors for dementia (eg, hypertension, stroke, and diabetes), exposures to air pollution can be modified at the population level, making it a prime target for large-scale prevention efforts.
- Boya Zhang, Jennifer Weuve, Kenneth M. Langa, Jennifer D’Souza, Adam Szpiro, Jessica Faul, Carlos Mendes de Leon, J. Gao, J. D. Kaufman, L. Sheppard, and J. Lee, (2023). "Comparison of particulate air pollution from different emission sources and incident dementia in the US". JAMA Internal Medicine (10): 1080-1089.