Washington, Jan 16 (IANS): Burning of Yak dung is leading to pollution of indoor air in Tibetan households, filling the atmosphere inside with dangerous levels of fine particulate matter including black carbon, a new study finds.

"In a cold place like Tibet, the impact on individuals could be even greater because they spend so much time indoors and try to keep their homes as air-tight as possible," said Eri Saikawa, assistant professor in the department of environmental sciences at the Georgia-based Emory University in the US.

In 2013, team member Qingyang Xiao, a graduate student at the Emory University's Rollins School of Public Health, travelled to the Nam Co region in Tibet to gather the data.

About 4,500 residents live in the region located at an altitude of 4,730 metres.

Xiao used battery-powered aerosol monitors to measure indoor concentrations of fine particulate matter, which consists mainly of black carbon and organic carbon.

She recorded the measurements in six households with different living conditions and stove types.

Yak dung was the main fuel for cooking and the only fuel for heating.

The results showed that the average concentrations for black carbon and fine particulate matter were nearly double those reported by some similar studies of households in areas located at lower altitudes and consequent warmer climates such as India and Mexico.

The moisture content of the yak dung is a key factor in the emission levels.

"After rain or snowfall, the piles of uncovered dung are moist, leading to incomplete combustion and more emissions of fine particulate matter," Saikawa added.

She hopes to work with Georgia Tech engineer Jonathan Colton to develop gasifier cooking stoves that would burn yak dung in a more efficient matter, thereby producing fewer emissions.

The findings were detailed in the journal Atmospheric Environment.