Some 300 million children are exposed to heavily toxic outdoor air, while two billion live in areas where pollution exceeds minimum air quality guidelines set by the World Health Organization.
Every year some 600,000 children under the age of five die globally due to air pollution, a UNICEF report released on Monday 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," said Anthony Lake, executive director of UNICEF.
"Pollutants don't only harm children's developing lungs. They can actually cross the blood-brain barrier and permanently damage their developing brains and, thus, their futures. No society can afford to ignore air pollution," he explained.
The report titled "Clear the Air for Children" is released a week ahead of the annual UN climate-change talks being hosted by Morocco on November 7-18.
With the help of satellite imagery, the report says that some 300 million of the world's children – almost one in seven – are exposed to heavily toxic outdoor air while two billion live in areas where pollution exceeds minimum air quality guidelines set by the World Health Organization (WHO).
South Asia has the largest number of children living in such areas, around 620 million, followed by Africa with 520 million and the East Asia and Pacific region with 450 million.
The air is poisoned by vehicle emissions, fossil fuels, dust, burning waste and other airborne pollutants, the report says.
The study also looked at indoor air pollution, typically caused by burning coal and wood for cooking and heating.
The UNICEF report urged world leaders to take the following four urgent steps in their countries to protect children from air pollution:
Reduce pollution: All countries should work to meet WHO global air quality guidelines to enhance the safety and well being of children. To achieve this, governments should adopt measures such as cutting back on fossil fuel combustion and investing in energy efficiency and renewable energy sources.
Increase children's access to healthcare: Investing in children's overall healthcare – including with immunisation campaigns and by improving knowledge, community management and numbers seeking care for pneumonia (a leading killer of children under five) – will improve their resilience to air pollution and their ability to recover from diseases and conditions linked to it.
Minimise children's exposure: Sources of pollution such as factories should not be located within the vicinity of schools and playgrounds. Better waste management can reduce the amount of waste that is burned within communities. Cleaner cooking stoves can help improve air quality within homes. Reducing air pollution overall can help lower children's exposure.
Monitor air pollution: Better monitoring has been proven to help children, youth, families and communities to reduce their exposure to air pollution, become more informed about its causes, and advocate for changes that make the air safer to breathe.
"We protect our children when we protect the quality of our air. Both are central to our future," Lake said.