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Exposure to air pollution is ubiquitous and a major cause of global morbidity and mortality. This chapter provides a broad introduction to indoor and outdoor air pollution, beginning with a brief review of the emergence and recognition of air pollution as a major public health concern. The chapter then reviews general principles and concepts related to inhalation injury, exposure, and health outcomes. The health consequences of indoor and outdoor air pollution are covered separately, although this distinction is largely artificial, given the significant overlap in exposure between pollutants found in indoor and outdoor locations. While the emphasis of the chapter is on respiratory health effects, the extrapulmonary effects of air pollutants are briefly discussed. The chapter concludes with a discussion of susceptible populations and different control strategies, aimed both at public health and individual levels.


Air pollution is now considered the largest environmental cause of disease and premature death in the world, responsible for an estimated seven million deaths per year.1 Exposure to air pollution is a significant cause of cardiopulmonary disease and likely increases the risk of neurodevelopmental disorders, poor birth outcomes, metabolic disease, and malignancy. While a global problem, air pollution disproportionately affects the poor with the highest exposure levels occurring in low- and middle-income countries. Several of the principal air pollutants also act as greenhouse gases, contributing to global warming and the additional health risks associated with climate change.

The sources and concentration of pollutants have changed throughout history, as societies develop and as the climate warms. The use of fire for heating and cooking created exposure to smoke, a problem that persists for the billions of people who still use biomass fuels today. The rise of cities concentrated the emissions of pollutants from dwellings and manufacturing facilities within restricted locales. Industrialization introduced localized or point sources of pollution, such as power plants, which generate immense emissions of combustion byproducts in areas where people live and work. During the 20th century, mobile sources, including cars, trucks, and other fossil fuel–powered vehicles, created a new type of pollution: photochemical pollution, or “smog.” The unprecedented growth of some urban areas to form “megacities,” such as Mexico City, São Paulo, and Shanghai, has led to unrelenting air pollution from massive vehicle fleets, standstill traffic, polluting industries, and power plants.

Increasingly, there is recognition that the problem of air pollution extends into the indoor environment. In low- and middle-income countries, exposure to smoke from biomass fuel combustion for indoor cooking and heating is still widespread. In the more developed countries, indoor pollutants can be either generated by human activities or released from building and construction materials. Buildings designed to optimize energy conservation by reducing the exchange of indoor and outdoor air can seal pollutants within and result in unhealthy concentrations.

For centuries, people have recognized that air quality has health consequences. Classical writings ...

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