MUMBAI, India — About 300 million children in the world breathe highly toxic air, the United Nations Children’s Fund said in a report on Monday that used satellite imagery to illustrate the magnitude of the problem.
The vast majority of these children, about 220 million, live in South Asia, in places where air pollution is at least six times the level that the World Health Organization considers safe, Unicef said.
The agency said the children faced serious health risks as a result.
“Children are uniquely vulnerable because their lungs are still developing,” said Nicholas Rees, the author of the report.
“Early exposure to toxic air has lifelong consequences for them,” he said.
Among the most dangerous pollutants are air particles known as PM2.5, which are a small fraction of the width of a human hair.
They can be released from fossil fuel combustion and industry, and include natural sources like dust.
The ultrafine particles enter the bloodstream through the lungs, worsening cardiac disease and increasing the risk of stroke and heart failure, in addition to causing severe respiratory problems, like asthmaand pneumonia.
Early studies also suggest a possible link between pollution and children’s cognitive function, the Unicef report noted.
It also cited numerous studies connecting chronic exposure to high pollution with an increased risk of miscarriage and early labor in pregnant women, and low birth weight.
Globally, about seven million deaths are linked to air pollution, 600,000 of them children under 5, the Unicef report said, citing World Health Organization studies in 2012 and 2015.
Air pollution is linked to one in 10 deaths of children under 5, the W.H.O. has reported.
But in its report, Unicef also argued that the effects of toxic air go well beyond early mortality, in particular for children, on whom the lifelong effects are only now being understood.
Beyond the children living in the most toxic air, about two billion children in the world, constituting the vast majority, live in places where air pollution exceeds the level that the W.H.O. considers unhealthy, the report said.
And Unicef warned that children’s health could be increasingly at risk in the ensuing decades as the most populous countries rapidly industrialize, a factor that historically has been accompanied by rising rates of air pollution.
But the future doesn’t have to be that way, Ramanan Laxminarayan, a senior research scholar at the Princeton Environment Institute, argued in an interview.
He noted that China, where air pollution soared during industrialization, has radically changed course.
“China is investing significantly in clean-air technology on a scale unprecedented,” Mr. Laxminarayan said.
Air pollution is about as severe in India, he said, but the causes are in some ways more easily correctable, like the burning of paddy straw by northern Indian farmers after they harvest it.
“This is just gross stupidity,” Mr. Laxminarayan said, and alternative ways of disposing of the crop can easily be found without compromising India’s economic future.
Industry isn’t yet as big a source of air pollution in India, where development so far has come from less-polluting industries like pharmaceuticals, giving India a choice of whether to take a different route to future development, Mr. Laxminarayan said.
India has taken some steps toward charting a cleaner road to development but needs to be much bolder if it is to protect its children’s health, he said.
“India could have been a country to get rich without China’s type of industrial pollution,” he said. “It is throwing away that opportunity.”