"Protecting children from air pollution not only benefits children", Lake added.
The crisis saw large swathes of north India and parts of neighbouring Pakistan blanketed in acrid air - an annual phenomenon as cooler air traps particles near the ground, cause pollution levels to spike.
The United Nations report had also stated that it is South Asia which has the largest percentage of babies that are living in areas where the pollution in air is at least around six times higher than the set global limits which happens to be ten micro grams for one cubic metre.
Another 4.3 million babies in the East Asia and Pacific region live in areas with pollution levels at least six times higher than the global recommendation.
"Not only do pollutants harm babies' developing lungs, they can permanently damage their developing brains and, thus, their futures", said UNICEF executive director, Anthony Lake. Air pollution has known links to asthma, pneumonia, bronchitis and other respiratory infections.
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The report highlights the relationship between pollution and brain functions " like memory and verbal IQ and non-verbal, test results, lower scores among schoolchildren, as well as other neurological problems ".
The World Health Organization describes air pollution as a "major environmental risk to health". "But this growing body of research does provide an indication of the scale of harm", said the UNICEF. Babies are also more susceptible to the effects of air pollution because they breathe more rapidly and their immune defenses are not fully developed.
The author of the "Danger In The Air" report, Nicholas Rees, told AFP that toxic pollution is "impacting children's learning, their memories, linguistic and motor skills".
California was found to have the most polluted air in the country, with Los Angeles ranking highest for ozone pollution and Visalia the top city for year-round particle pollution.
It called for a greater use of masks, air filtration systems and for children to avoid travelling when pollution levels are at their highest.