About 300 million of the world's children live in areas with highly toxic air, the United Nations Children's Fund (UNICEF) says in a new report.
About 220 million of these children live in South Asia, in areas where air pollution is six times higher than international guidelines set by the World Health Organization, the October 31 report explains.
UNICEF executive director Anthony Lake said air pollution was a "major contributing factor in the deaths of around 600,000 children under five every year."
UNICEF called on governments, which will meet in Morocco next month for talks on global warming, to restrict use of fossil fuels to give twin benefits of improved health and slower climate change.
The UN agency also called on countries to minimize children's exposure by ensuring sources of pollution, including factories, are not located near schools and playgrounds.
"No society can afford to ignore air pollution," Lake said in a statement.