WASHINGTON/ NEW DELHI-Some 300 million children live with outdoor air so polluted it can cause serious physical damage, including harming their developing brains, the United Nations said in a study released Monday.

Nearly one child in seven around the globe breathes outdoor air that is at least six times dirtier than international guidelines, according to the study by the UN Children’s Fund, which called air pollution a leading factor in child mortality.

UNICEF published the study a week before the annual UN climate-change talks, with the upcoming round to be hosted by Morocco on November 7-18.

The agency, which promotes the rights and well-being of children, is pushing for world leaders to take urgent action to reduce air pollution in their countries.

“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,” Lake said.

UNICEF points to satellite imagery which it says confirms that about two billion children live in areas where outdoor air pollution exceeds minimum air-quality guidelines set by the World Health Organization. The air is poisoned by vehicle emissions, fossil fuels, dust, burning waste and other airborne pollutants, it said. 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 study also looked at indoor air pollution, typically caused by burning coal and wood for cooking and heating.

Together, outdoor and indoor air pollution are directly linked to pneumonia and other respiratory diseases that account for almost one death in 10 in children under the age of five, making air pollution a leading danger to children’s health, UNICEF said.

The agency noted that children are more susceptible than adults to indoor and outdoor air pollution because their lungs, brains and immune systems are still developing and their respiratory tracts are more permeable.

The most vulnerable to illnesses caused by air pollution are children living in poverty, who tend to have poorer health and little access to health services.

UNICEF is calling for more robust measures to reduce pollution, increase children’s access to healthcare and to monitor and minimize children’s exposure to polluted air.

Meanwhile, New Delhi was shrouded in a thick blanket of toxic smog Monday after millions of Indians lit firecrackers to mark the Diwali festival, with authorities reporting record levels of pollution in parts of the capital.

The reading for pollutants in the atmosphere breached the 1,000 microgram mark for the first time in one neighbourhood in south Delhi - 10 times the World Health Organization’s recommended level.

It came on the same day that another United Nations body reported how some 300 million children live with outdoor air so polluted it can cause serious physical damage, with the situation most acute in South Asia.

Gufran Beig, chief scientist at India’s state-run System of Air Quality Weather Forecasting and Research (SAFAR), said needles on monitors in the RK Puram neighbourhood had flickered briefly past the 1,000 level late on Sunday night at the finale of a frenzy of fireworks.

The levels had subsided through the night but were still running at more than 500 in several districts across the capital by afternoon.

“Almost 60-70 percent of the smoke came from the firecrackers,” said Beig, who said the situation had been widely expected given that Diwali is always one of the worst periods for pollution.

“It was already predicted that the levels would increase several notches,” he told AFP. In a health advisory on its website, SAFAR said there was a “serious risk” of respiratory problems for people living in Delhi and all outdoor physical activity should be avoided. People with heart or lung disease, older adults and children should stay indoors and keep activity levels low, it added.

Levels of pollution traditionally surge over Diwali but the situation this year had been worsened by high levels of moisture in the air and the burning of agricultural residue by farmers on the outskirts of the capital or in neighbouring states, Beig added.

New Delhi’s air quality has steadily worsened over the years, a consequence of rapid urbanisation that brings pollution from diesel engines, coal-fired power plants and industrial emissions.

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It also suffers from atmospheric dust, burning of crop stubble in farms around the city and pollution from open fires lit by the urban poor to keep warm in winter or to cook food.

Delhi authorities have responded with a series of measures, including driving restrictions earlier this year that took around a million cars off the roads for two weeks and a ban on old trucks from entering the city.

Last week the city government also announced plans to install air purifiers and a mist-making device at major intersections to curb choking pollution.

But expert Anumita Roychowdhury said more needs to be done to tackle Delhi’s post-Diwali air, which is already saturated with the onset of winter as cooler temperatures trap pollutants.

“Diwali’s effect will stay for a while now thanks to all the firecrackers’ chemicals and heavy metals released into the already-aggravated air,” Roychowdhury, from the Delhi-based Centre for Science and Environment, told AFP.

“There’s been a decline in the use of firecrackers and there have been measures to cut (smog) down, but the change is not big enough. We need to do a lot more,” she said, suggesting a strict licensing policy on sales and a gradual phase-out of firecrackers.

A new study by the UN’s children’s fund UNICEF reported Monday that nearly one in seven children around the globe breathes outdoor air at least six times dirtier than international guidelines.

“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,” said Anthony Lake, executive director of UNICEF.

“No society can afford to ignore air pollution.”