Study On Personal PM_2.5 Exposure Levels And Influencing Factors Of Pupils Under Air Purification Intervention

Objective In order to investigate the effects of multi-scenario air purification interventions and determinants affecting personal PM_2.5 exposure,and to provide a theoretical basis for precise protection of vulnerable populations and intervention strategies.Method A randomized,double-blind,crossover intervention trial（RCT）on 2classes of 105 elementary school students in Mengzhou,Jiaozuo City,Henan Province,China,from April 2021 to December 2021.2 High efficiency particleair filter（HEPA）air purifiers and 1 fresh air unit were installed in each classroom,and 1 air HEPA purifiers were installed in the students’household living rooms.During the study period,4 visit investigations were conducted on April 11 to April 15,June 28 to July 1,September 22 to September 25,December 9 to December 12,2021.The light scattering method and the gravimetric method were used for parallel monitoring to collect PM_2.5 exposure data from each microenvironment;and 24h time activity pattern questionnaires,student questionnaires and parent questionnaires were collected.The PM_2.5 exposure data obtained by the gravimetric method was used to calibrate the light scattering data.The method of microenvironment monitoring and time activity model was used to calculate the concentrations of personal daily PM_2.5 exposure.The mixed-effects models were used to evaluate the potential determinants of personal daily PM_2.5 exposure.Result After calibration,the slope of the fit of the light scattering method and the gravimetric method monitoring results improved and the ratio of the two converged to 1.During the intervention period,the purification efficiency of living rooms and classrooms air purification devices ranged from 32.5%to 54.8%and 81.6%to 92.4%,respectively.The average personal daily PM_2.5 exposure concentrations were significantly lower in the intervention group compared to the control group.Air purification devices intervention,outdoor PM_2.5,indoor humidity,indoor temperature,absolute value of indoor and outdoor temperature difference and environmental tobacco smoke（ETS）exposure were identified as important determinants of personal PM_2.5 exposure.The intervention of air purification in living rooms and classrooms resulted in 42.31%[95%confidence interval（CI）:45.28%～39.17%]and 21.34%（95%CI:24.89%～17.61%）reduction of personal PM_2.5daily exposure,respectively.Conclusion Household and classroom air purification interventions are effective in reducing personal PM_2.5 exposure levels.In single-scenario interventions,household interventions were the best interventions.