United Nations Children's Fund, UNICEF has said, about 300 million children live with polluted outdoor air and it can cause serious physical damage, including harming their developing brains. In a study published, it said, nearly one child in seven around the globe breathes outdoor air that is at least six times dirtier than international guidelines.<br/><br/>The study said, air pollution is a leading factor in child mortality. Executive Director of UNICEF, Anthony Lake, has said, air pollution is a major contributing factor in the deaths of around 600,000 children under five every year, and it threatens the lives and futures of millions more every day. He said, pollutants do not only harm children's developing lungs but can actually cross the blood brain barrier and permanently damage their developing brains.<br/><br/>South Asia has the largest number of children living in such areas at about 620 million, followed by Africa with 520 million and the East Asia and Pacific region with 450 million. The report said, the air is poisoned by vehicle emissions, fossil fuels, dust, burning waste and other airborne pollutants.