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Indoor & Outdoor Air Pollution

    Smog in Beijing.
    (Smog in Beijing - Dr. Edwin P. Ewing, Jr.)

    Both indoor and outdoor air pollution pose hazards, and together are estimated to be responsible for nearly 5% of the global burden of disease. Nearly 2 million children younger than 5 years of age die every year from acute respiratory infections--the primary killer of young children—and the World Health Organization estimates that about 40% of lower respiratory infections in developing countries are related to environmental conditions. In addition to acute respiratory infections, air quality is related to the incidence and severity of asthma, heart and lung diseases, allergies, and several types of cancers.

    Indoor air pollution is a major factor of respiratory infections in both rural and urban areas of developing countries. Indoor air is most affected by pollutants caused by biomass burning for cooking and heating, which releases particulates and carbon monoxide, and by tobacco use, outdoor air quality, mold, rodents, and insects. Indoor air pollution has its largest impact on very young children, women, and the infirm, because these groups spend much of their time indoors.

    Outdoor air problems largely involve point sources such as factories and forest fires, and fossil fuel burning for transportation and energy production. Some of the pollutants of concern include particulates, carbon dioxide, sulfur oxides, and lead. Further, the greenhouse gases released by combustion of fossil fuels are a primary cause of global warming. Around the world, both local and global air quality are being shaped by rapid population growth, urbanization, industrialization, and deforestation. The cross-border transport of pollutants such as ozone, as well as the gases and aerosols created from biomass burning, will increase in importance as total emissions rise. Such pollutant transport can raise “background” pollution levels over large regions of the globe.

    Several challenges exist to improve air quality in developing countries. Many countries lack the infrastructure needed to monitor air quality and emissions. And often existing air quality regulations in developing countries are unenforced. Finally, air quality improvements often conflict with international economic trends (such as industrialization and an increase in international transport) and with individual lifestyles (such as cooking with biomass fuels indoors and using gasoline-powered vehicles outdoors).


    NCEH/ATSDR is studying the effect of air pollution on children’s asthma and has tracked the human health effects of air pollution from forest fires in Asia. Other focal areas include carbon monoxide poisoning and the impact of mold exposure on health.

    Click here for a list of current NCEH/ATSDR projects related to this topic.