Air pollution has emerged as the deadliest form of pollutant, causing 5.5 million premature deaths globally in 2013 – four times the toll from HIV/AIDS and six times the lives lost to malaria. The data comes from a joint study by the World Bank and the Institute for Health Metrics and Evaluation, published Thursday. Young children and the elderly are hardest hit, with tiny airborne dust-like particulates doing the most damage, the study finds. Indoor air pollution comes from burning solid fuels like coal, wood or dung for cooking and heating, and it is also taking a steady toll. Outdoor air pollution from vehicles, industry and other sources has gotten worse since 1990. The economic cost in lost wages alone was $225 billion, with an overall impact many times higher. Air pollution is estimated to cut eight-tenths of a percent of GDP in South Asia, and six-tenths of a percent in sub-Saharan Africa. Losses in East Asia and the Pacific were lower but still significant. The report’s authors say quantifying the death toll and financial losses strengthens the case for using scarce resources to cut pollution. They urge "more ambitious action” and say health officials should take air pollution as seriously as they take deadly diseases. The study says about 87 percent of the world’s population lives in areas affected by air pollution.