The Characteristics Of Household PM_2.5 Pollution And Human Health Risk Evaluation In Rural Hunan Province

With the development of society and the urgent need of environmental protection,the household energy structure in rural China is transforming from solid fuel to clean energy.However,solid fuel is still the major energy in China’s rural households.Due to low combustion efficiency of rural household stove,incomplete combustion of solid fuels emitted large quantities of air pollutants,including PM_2.5（particles with aerodynamics diameter less than 2.5μm）,resulted in severe household air pollution.PM_2.5 exposure can trigger cardiovascular diseases,such as hypertension,and pose serious health risk to rural residents.However,researches related to household air pollution are always focused on northern China,limited researched are conducted in southern China.Furthermore,the influence of PM_2.5 exposure on blood pressure is unclear,which lead to considerable uncertainty for the evaluation of household air pollution and its health effect on rural residents.In this study,field measurements were conducted in rural areas of Hunan province,southern China,to measure household PM_2.5 concentrations and blood pressure of rural residents in both winter and summer in 2020.Personal information,household information and time in different microenvironments were recorded through questionnaires.Based on the field measured data,the pollution levels and characteristics of household PM_2.5 and personal PM_2.5 exposure were analyzed.The impact of fuel type,population size,opening window hours and other influencing factors on personal PM_2.5 exposure and blood pressure and quantitative relationship between PM_2.5 exposure and blood pressure were analyzed in generalized linear model.Furthermore,the variations of household PM_2.5 pollution,personal PM_2.5 exposure and blood pressure under the influence of the Chinese Spring Festival and different seasons were discussed.The major findings of this study were showed as below:（1）The average daily concentrations of household PM_2.5 in kitchen,living room and outdoor areas in rural Hunan were 149±84,122±62 and 93±14μg/m~3,respectively,in winter,which were 50.8±24.1,47.1±20.3 and 38.9±12.2μg/m~3 in summer,indicating more serious household PM_2.5 pollution in winter.The ratio of PM_2.5concentration in kitchen to that in outdoor（K/O）and PM_2.5 concentration in kitchen in living room to that in outdoor（L/O）were 1.6±0.9 and 1.4±0.8 in winter,which were1.3±0.8 and 1.4±0.9 in summer,respectively,indicating that indoor emission source was the main factor of indoor PM_2.5 in rural areas.（2）Cooking and heating activities can significantly increase indoor PM_2.5concentrations,and the elevated concentrations were affected by fuel types.In comparison with clean fuels,the usage of solid fuels can result in higher indoor PM_2.5concentrations,peak values and indoor to outdoor ratios in both winter and summer.As a unique human activity in summer,mosquito coil combustion can result in higher PM_2.5 concentrations in living room.Furthermore,mosquito coil combustion had similar PM_2.5 peak values with fuel wood burning,but longer burning time,which lead to higher contributions to indoor PM_2.5.（3）Personal PM_2.5 exposure of rural residents in winter and summer were 120±49 and 49.3±20.6μg/m~3,respectively.Population size and fuel types can significant influence personal PM_2.5 exposure in winter,with the higher PM_2.5 exposure in larger population size and solid fuels usage.While the significant influencing factor of personal PM_2.5 exposure was mosquito coil combustion.The systolic blood pressure（SBP）and diastolic blood pressure（DBP）in winter were 132±19 and 79±12 mm Hg,respectively,which were 122±18.2 and 76.2±11.2 mm Hg in summer.The personal PM_2.5 exposure was significantly correlated with SBP in winter,with the increase of 10μg/m~3,the SBP would increase 0.36 mm Hg（95%confidence interval:0.05～0.77mm Hg）.However,personal PM_2.5 exposure had minor effect on both SBP and DBP in summer.（4）During the Chinese Spring Festival,the population size and the household PM_2.5 concentrations in rural households increased.In addition,rural residents spent longer times in indoors during the Chinese Spring Festival,resulting in significantly higher personal PM_2.5 exposure than that before the Chinese Spring Festival.The seasonal variations of household PM_2.5 concentrations and personal PM_2.5exposure showed higher levels in winter and lower levels in summer.This is attributed to the transition of household energy to cleaner fuels and better ventilation conditions in summer.While the increased temperature and the reduction of PM_2.5 exposure were the main reasons for lower residents’blood pressure in summer.