Approximately 2.7 billion people burn biomass (wood, animal dung, crop waste) around the world (WHO, 2007). Compared with results reported by some studies in households without chimneys in other areas, we find that the air pollutant concentrations in Tibetan households are higher. For households using a simple stove, the average PM2.5 concentration during our entire study period was 956 mg/m3. Mukhopadhyay et al. (2012) conducted measurements in five rural households using biomass as fuel in Haryana, India, and found the 24-h mean PM2.5 concentrations to be 468 mg/m3.
Balakrishnan et al. (2004) reported that the 24-h average concentrations of respirable particulates based on 83 households using dung as fuel in India were 732 ± 88 mg/m3. In Mexico, PM2.5 concentrations in a kitchen using biomass as fuel were 554.7 ± 492.9 mg/m3