1.4 million children die of pneumonia and diarrhea each year, the overwhelming majority of whom live in lower and middle-income countries, a UN report said on Friday.

About half of all childhood pneumonia deaths are linked to air pollution, the UNICEF report of One is Too Many: Ending Child Deaths from Pneumonia and Diarrhea reads.

"We have seen clearly that air pollution linked to climate change is damaging the health and development of children by causing pneumonia and other respiratory infections," said UNICEF Deputy Executive Director Fatoumata Ndiaye. These childhood deaths occur despite large-scale prevention through straightforward and cost effective solutions.

Two billion children live in areas where outdoor air pollution exceeds international guidelines, with many falling ill and dying as a result. Around 80 per cent of childhood deaths linked to pneumonia and 70 per cent of those linked to diarrhea occur during the first two years of life. Nearly 34 million children have died from pneumonia and diarrhea since 2000.

The UN report shows low- and lower-middle income countries are home to 62 per cent of the world's under 5 population, but account for more than 90 per cent of child pneumonia and diarrhea deaths globally.

UNICEF estimates that 24 million more children will die from pneumonia and diarrhea by 2030 if no further investment in key prevention and treatment measures is made.