Variability in indoor PM2.5 from homes using different heating energies and impacts of clean heating in rural northern China
Indoor combustion of low-quality coal chunks significantly contributes to wintertime haze episodes and directly affects indoor air quality,posing high risks to human health.Besides electricity or gaseous fuels,clean coals and pelletized biofuels have been proposed as alternative fuels to reduce pollutant emissions associated with raw coal burning in some policies and pilot projects.However,there is still a lack of quantitative evaluation on real-world indoor air quality from homes using different heating fuels.This limits a comprehensive understanding of the environmental and health co-benefits of clean heating policy.In this study,indoor fine particulate matter(PM2.5)was measured from 1600 households located in rural north China.The aim was to assess indoor PM2.5 variations within and between different homes and attribute the pollution differences to heating types.The study found that the average indoor PM2.5 during the heating period was 102 μg/m3,but it varied greatly from 19 to 497 μg/m3.In the home burning traditional coals and biomass fuels,the indoor PM2.5 concentrations were as high as 162 μg/m3 and 144 μg/m3,respectively,while in the home using clean coals or biomass pellets,the indoor PM2.5 levels were significantly lower,at about 84 μg/m3,although this still exceeded the national standard(50 μg/m3)during more than 56％of the entire monitoring period.The lowest indoor PM2.5 levels were observed in the home using clean modern energies like electricity or gas for heating.Due to distinct human activity intensities and meteorological conditions,the indoor PM2.5 also varied greatly from day to day.The coefficient of variation(COV)in indoor PM2.5 from different days was approximately 76％in the home using solid fuels,while it averaged 53％in the home using clean energies.Internal combustion sources contributed to about 60％of indoor PM2.5 in the home burning traditional solid fuels.When switching to cleaner household energies,internal combustion emission contributions declined obviously.To lower indoor PM2.5 levels,low-quality dirty coals should be suspended and replaced by cleaner energies like pelletized biofuels or clean coals,and the most significant reduction would be achieved by switching from coals to electricity.The present study provides empirical evidence from first-hand observational data to enhance the understanding of indoor air pollution variability.It supports a comprehensive scientific evaluation of clean heating policy in terms of air pollution mitigation and human health protection.
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