| Air pollution is one leading environmental risk factor in world health,each year about 3.5 million people die from exposure to household air pollution caused by global combustion of solid fuels.Due to the widespread use of traditional solid fuels,causing serious indoor and outdoor air pollution and resident health risk in rural China,however,the problem is often overlooked with few quantitative researches and lacking of controls and protection policies.To study the level of pollutants emitted in rural areas,focusing on the characteristics of typical?carcinogenicity,teratogenicity and mutagenesis?polycyclic aromatic hydrocarbons?PAHs?pollution,analyzing the human health risks caused by PAHs,and providing data support for the government to formulate relevant policies and protect the health of residents.In this study,we focused on indoor and outdoor household air pollution,24-hour average indoor and outdoor air samples were simultaneously collected and analyzed from burning wood and coal homes in rural Enshi.Emission factor?EF?,stove combustion efficiency?MCE?,feature ratio and correlation of EF,also,indoor/outdoor levels,I/O,composition spectrum,feature ratio and size distributions of?PAH28 were key to study and compared between homes burning coals and wood.Health risks due to inhalation exposure to PAHs were evaluated by calculating increment lifetime cancer risk?ILCR?.The result show that homes of using improved wood?2.06?0.88 mg/kg1513.38?59.64 g/kg?were much higher than using improved coals?0.21?0.13mg/kg1280.55?112.77 g/kg?of pollutant emission factors?except SO2?in Enshi.EC/OC is 0.5 in homes burning wood air sample,and in homes burning coal air sample EC/OC is 0.02,and EC/OC of the Enshi improved stove air samples are smaller than EC/OC of traditional stove air samples in the literature.The MCE of improving wood homes is 96?4%,in homes burning coals MCE is 98?3%,there is no significant difference between the MCE.In the correlation of pollution emission factors of the two stoves,MCE and CO2 are significant positive correlation,and they are significant negative related to CO and SO2,they are no significant related to OC and TSP.CO is significant positive correlation to SO2,significant negative related to CO2,and has no significant correlation with EC,OC,and TSP.The gaseous PAHs are no significant correlation with PM10,PM2.5 and EC.The particulate PAHs on PM10 are independent of EC and OC.However,in wood stoves,MCE and EC are significant positive correlation,and coal stoves are no significant correlation;in wood fired boilers,OC are significant negative related to gaseous PAHs,coal stoves are no significant correlation;in wood fired boilers,PM10 particles on the PAHs are significant negative related to PM10,coal stoves are no significant correlation;in wood fired,PM2.5 particles on the PAHs have significant positively related to PM2.5,coal stoves are irrelevant.There is no correlation between particulate PAHs on PM2.5and EC in wood stoves,and the coal are significant positive correlation.In wood stoves,the PAHs on PM2.5.5 are no significantly related to OC,and the coal stove is significantly positive correlation.In homes burning coal,the total concentration of 28 PAHs(?PAH28)was507?449 and 120?18 ng/m3 in indoor and outdoor air,respectively,while in homes burning woods,the?PAH288 was 849?421 and 268?44 ng/m3,respectively.Due to existence of indoor sources,indoor burning were much higher than outdoor,with the indoor-outdoor ratio of?PAH288 ranging from 2 to 13.The PAHs composition profiles were generally similar between indoor and outdoor air with the dominated compounds of low and intermediate molecular weight PAHs,but there were subtle differences.In homes burning coals,there were much higher molecular weight PAHs compared to that in homes burning wood.Feature ratio of PAHs is 0.7,0.6,0.5,0.4,0.5 and 0.2 in firewood families;and coal burning families is 0.5,0.6,0.3,0.5,0.5 and 0.1.Most Particles PAHs,especially those high molecular weight were enriched in fine particulate matter.Mass fraction of particulate PAHs in fine PM1.0 was about 5080%of the particulate?PAH28.The calculated median ILCR for the population burning coals was 1.8×10-5(1.2×10-53.1×10-5 as the inter-quartile range),while for the population burning wood the median ILCR was 7.1×10-5(6.5×10-57.8×10-5).In both groups,the ILCR was much higher than the acceptance level of 10-6,indicating high health risks due to severe air pollution by PAHs in the study area. |
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