air pollution

Air pollution is the contamination of the air we breathe with harmful gases and particles. Unlike a workplace exposure that ends at the factory gate, ambient air pollution surrounds entire populations day and night, so even modest concentrations can add up to a large public-health burden across millions of lungs.

The major components include particulate matter (fine particles graded by size, such as PM2.5 and PM10), ground-level ozone, nitrogen dioxide and sulphur dioxide from traffic and combustion, and indoor pollutants such as biomass smoke. Particles small enough to reach the alveoli, and reactive gases, inflame the airways, increase oxidative stress, and over time impair lung growth in children and accelerate decline in adults.

Health effects span the acute and the chronic. Short-term spikes trigger asthma and COPD exacerbations, respiratory infections and hospital admissions; long-term exposure contributes to the development of asthma, COPD, reduced lung function and lung cancer, and is now recognized as a leading environmental cause of death worldwide. Risk is graded — there is no clearly safe threshold — so reductions in pollution yield measurable health gains at the population level.