Air Quality and Pollution
Air quality and pollution is the environmental-health area concerned with the presence of harmful substances in the air people breathe and the resulting effects on health. It spans the gases and particles emitted by combustion, industry, traffic and household fuels, the conditions under which they accumulate, and the burden of disease they impose worldwide.
Definition
Air pollution is the contamination of indoor or outdoor air by chemical, physical or biological agents that modify the natural characteristics of the atmosphere and are capable of harming human health. Air quality describes the degree to which ambient air is free of such pollutants, typically assessed against concentration thresholds for key pollutants.
Scope
This area orients the reader to outdoor (ambient) and indoor air pollution, the major pollutant classes (particulate matter and the principal gaseous pollutants), how exposure is measured and regulated, and the body of evidence linking poor air quality to respiratory, cardiovascular and other health outcomes. It is a reference overview; the constituent topics carry the detailed material.
Sub-topics
Key concepts
- Ambient versus indoor air pollution
- Particulate matter (PM2.5, PM10)
- Gaseous pollutants (ozone, nitrogen dioxide, sulfur dioxide, carbon monoxide)
- Exposure assessment and air-quality monitoring
- Concentration-response relationship
- Air-quality guidelines and standards
- Attributable burden of disease
Mechanisms
Inhaled pollutants act through several converging pathways: fine and ultrafine particles deposit deep in the airways and alveoli, triggering local and systemic inflammation and oxidative stress; reactive gases such as ozone and nitrogen dioxide irritate and injure airway epithelium; and some constituents enter the circulation, contributing to endothelial dysfunction and cardiovascular effects. The detailed mechanisms differ by pollutant and are developed in the topic entries.
Clinical relevance
Air quality is a major modifiable determinant of population health, and patterns of pollution-related disease shape public-health priorities and clinical case-mix, particularly for respiratory and cardiovascular conditions. This area describes how exposures relate to health at the population level and is not a basis for individual diagnosis or treatment.
Epidemiology
Ambient air pollution is among the leading environmental risk factors for death and disability globally; the Global Burden of Disease analyses attribute millions of deaths each year to ambient particulate matter and ozone, with the largest burden falling on low- and middle-income countries, and household air pollution adding a further substantial toll.
Evidence & guidelines
Decades of cohort and time-series epidemiology, synthesised in reviews and burden-of-disease analyses, support associations between air pollutants and adverse health outcomes. The World Health Organization's global air quality guidelines (2021) set recommended concentration levels for the principal pollutants, and national standards translate this evidence into regulatory limits.
Related topics
Seminal works
- cohen-2017
- brunekreef-2002
- who-aqg-2021
Frequently asked questions
- What is the difference between ambient and indoor air pollution?
- Ambient (outdoor) air pollution refers to contaminants in the open atmosphere, largely from traffic, industry and energy production, whereas indoor or household air pollution arises within enclosed spaces, often from cooking and heating with solid fuels.
- Which air pollutants matter most for health?
- Fine particulate matter (PM2.5) carries the largest documented health burden, alongside ground-level ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide, which are the pollutants addressed in the WHO air quality guidelines.