Air pollution is a problem for much of the developing world and is believed to kill more people worldwide than AIDS, malaria, breast cancer, or tuberculosis. Airborne particulate matter (PM) is especially detrimental to health, and has previously been estimated to cause between 3 and 7 million deaths every year, primarily by creating or worsening cardiorespiratory disease. Particulate sources include electric power plants, industrial facilities, automobiles, biomass burning, and fossil fuels used in homes and factories for heating. In China, air pollution was previously estimated to contribute to 1.2 to 2 million deaths annually.