ULAN BATOR, Feb. 23 (Xinhua) -- A joint report warns of a rising financial burden for treating child diseases if no actions are taken to reduce the air pollution in Mongolia's capital Ulan Bator.

The Mongolian National Center for Public Health and the UN Children's Fund (UNICEF) issued such a warning in the report entitled "Mongolia's air pollution crisis: A call to action to protect children's health," which was released on Thursday.

Without concrete and urgent actions, financial cost for treating child's diseases due to air smog will increase by 33 percent by 2025, costing circa two million U.S. dollars every year to the country's public health system from 2025, said the report.

Ulan Bator, home to nearly half of the country's child population, suffers one of the world's highest air pollution in winter months. The city's air pollution on Jan. 30th exceeded 133 times above the safety level set by the World Health Organization.

Pneumonia is now the second leading cause for the deaths of kids under the age of five in the country. Also, children living in a highly polluted district of central Ulan Bator are found to have 40 percent lower lung function than those from rural areas.

More than 800,000 residents, over half of Ulan Bator's population, live in slums, also known as ger districts. They have to rely on burning raw coal and other flammable materials such as plastics, old tires to stay warm and cook meals during the six-month-long winter season.

It is estimated that 80 percent of air pollution in Ulan Bator is caused by ger stoves. The rest is caused by transportation, thermal power plants, and solid wastes.

Since the early 2000s, the Mongolian government, international donors and development organizations, including the World Bank and the Asian Development Bank, have spent millions of dollars combating air pollution in Ulan Bator.