Indoor Air Pollution due to Yak Dung Combustion in Nam Co, Tibet

Yak dung is widely used for cooking and heating in Tibet. This study monitored black carbon (BC) and fine particulate matter with an aerodynamic diameter of 2.5μm or less (PM_2.5) concentrations in six households with different living conditions and stove types in Nam Co, Tibet. Our survey results indicate that most residents are aware of adverse health impacts due to indoor yak dung combustion and approximately 2/3 of residents have already installed chimney stoves in hopes of mitigating indoor air pollution. However, our measurements reveal that installing chimneys may not always reduce indoor air pollutant concentrations. Peak concentrations in households using chimney stoves are similar to those using simple stoves without chimneys. The 6-h average PM_2.5 concentration in a stone house using a chimney stove (872.6±1573 μg/m³) was comparable with that in a traditional tent without a chimney (1243±2318 μg/m³). Similarly, the 6-h average BC concentration in a stone house using a chimney (24.48±70.16 μg/m³) was higher than in a tent without a chimney (13.34±13.07 μg/m³). We further find evidence of a dilemma in reducing both BC and PM_2.5 concentrations simultaneously. Combustion efficiency and fuel moisture content appear to play essential roles on pollutant emissions, and ventilation of residences is a critical factor for indoor air pollutant concentrations.