Indoor Air Pollution And The Interventions In Rural Residences Of Tibet

Indoor air pollution caused by domestic use of solid biomass fuels (SBFs) has strong associations with pulmonary and cardiovascular diseases. In Tibet China, as the development is relatively slow, the pollution exposure pattern of the residents is unique and typical. However, studies on indoor air pollution in Tibet and its health effects are inadequate.In order to discover the pollution exposure sources, assess the contribution of combustion to public pollution exposure, estimate the health effects and social-economic effects of pollution exposure interventions, this study focused on the pollution characteristics caused by cow dung cake combustion, the indoor air pollution in the agricultural and pasturing areas in Tibet, and the public particulate matter (PM) exposure in rural Tibet. Result shows that indoor dung cake combustion is the dominant factor to the pollution exposure of rural residents in Tibet, which contributes at 47.0% to 99.7% to total PM exposure.The fuel parameter and composition test showed that the ash content of dung cake was higher while the heating value was lower than common SBFs such as agricultural straw and wood. These asked more consumption of dung cake for everyday use than other fuels, which would cause heavier indoor pollution. Research also showed that the contents of trace metal elements were low which indicated the low potential of trace elements toxicity to the residents. To increase the air supply and to minish the fuel size would make a better mix of oxygen and dung, and this would increase combustion efficiency and reduce CO emission. The PM emission from dung cake combustion was dominant by the sub-micron particles, especially those with aerodynamics diameter of 0.03-0.40μm.Field monitoring was carried out in both the agricultural (in Qushui, Zhanang, and Jiangzi Countries) and pasturing (in Dangxiong Country) areas of Tibet, while questionnaire survey was also performed. Sampling was taken in kitchens, bedrooms, living-rooms, tents, and the outdoor environment. The result showed that the daily average indoor CO pollution from dung cake combustion was under control, however, the peak concentration during cooking time was high enough to cause adverse health effects to the population involved in cooking. The size distribution showed the high comcentration of indoor PM appeared at diameters of 0.65-1.1μm and >9.0μm. Daily average PM₁₀ concentration exceeded the national standard of 0.15mg/m³ at1.1 to 28.8 times. The indoor PM₁₀ concentration in the tents with dung cake burning as open fire was as high as 3.02mg/m³, which is 12.6 times to those used stoves with chimney in the tents.Inorganic component analysis of indoor PM showed that the water soluble content was dominant by Cl, K, and Ca, while there was a low concentration of Cu, Fe, Mn, and Zn, and elements like As, Cr, Ni and other heavy metals were under detection limit. Organic component analysis showed the indoor polycyclic aromatic hydrocarbons (PAHs) were at a high risk. It was found that the PAHs were concentrated in PM with diameter less than 2.1μm. The primary source of the indoor PAHs was the combustion of dung cake. Among the detected PAHs, compounds with high cancer risk, such as BaP and BbkF, showed high concentration, for example, the concentration of BaP exceeded the national standard for 80 times. The total cancer risk of Tibetan indoor PM was 6.41×10^-3, which indicated the environmental health status was serious.If the improved stoves were equiped to those tent used throughourthe year, the morbidity of acute respiratory infections (ARI) and acute lower respiratory infections (ALRI) would reduce to about 60%. For people who live in tent only in summer in the pasturing area, to separate kitchens from living area would reduce the long-term mortality, chronic bronchitis, acute bronchitis, and asthma attack by 5% to more than 15%. For people live in the agricultural area, these interventions would result in more than 20% reduction of the health endpoint above by separating rooms, and more than 25% by methane use. And these would save the medical cost by more than 12 million yuan/year for the whole population in Tibet. The improvement of health would also contribute to the increase of local GDP at 419 million yuan/year for separating rooms, and at 542 million yuan/year for methane use, which equals to 1.98% and 2.56% of the Tibetan local GDP respectively.