| [Background]The air pollution in our country has been highly concerned.Since 2012,China has implemented a series of air pollution control measures and has achieved good results in improving air quality.From 2013 to 2018,the national average annual concentration of PM10 decreased from 118?g/m3 to 71 ?g/m3,and the annual average concentration of PM2.5 decreased from 72?g/m3 to 39?g/m3.However,the air pollution is still not optimistic.In 2018,The number of days with a concentration of PM2.5 higher than 100 ?g/m3 was more than 110 days in Beijing,accounting for 1/3 of the year.The health hazards of PM cannot be ignored.Epidemiological data show that PM10,PM2.5 and PM1 were closely related to the occurrence and development of various diseases.Schoolchildren were sensitive to air pollution.Their lungs were immature and their breathing rates were faster.They were more susceptible to PM than adults.Studies had confirmed that air pollutants,especially PM2.5,were strongly associated with childhood asthma,prolonged cough,pneumonia,bronchitis,rhinitis,upper respiratory tract infections,and lower respiratory tract infections.Elementary school students spend most of their time in the classroom.The classrooms were densely populated and the spaces were relatively closed.Air pollution was the main source of air pollution in the classroom.In addition to personnel activities,the individual exposure concentration of primary school students may be higher than the atmospheric pollution concentration when the air pollution is heavier.Elementary school students may suffer higher health risks than expected due to immature lung development.Because of air pollution cannot be completely resolved in short term,it was particularly important to take convenient,scientific and effective protective measures to reduce the health hazards of PM on schoolchildren.Air purifiers were one of the important measures.However,how to evaluate the protective effect of air purifiers,due to the complex influencing factors,has always been a challenge faced by scientific researchers,and it is also an important scientific problem that needs to be solved urgently in the health protection of air pollution.Therefore,it has great public health significance to discuss the harm of PM to the respiratory health of primary school students and the role of air purifiers in the health protection of primary school students.Through systematic review of the literature,it was found that in the study of atmospheric particulates on the health hazards of primary school students' respiratory system,student activities,family environment,diet,and so on had a greater impact on the research results,and it was necessary to effectively control confounding factors;most of the exposure assessments used monitoring station data,did not consider the impact of individual activity and microenvironment concentration on individual exposure concentration;the health effect indicators included in a single study are limited,and there were a lack of systematic evaluation;the evaluation of exposure levels and the effects on health effects of different teams are biased,and even different researches's conclusions were contradictory.In the limited research on the health protection evaluation of air purifiers,it often restricted the normal activities of the subjects,which were different from their real life,work or learning environment.In this study,a boarding elementary school was selected.The follow-up and cross-intervention study design was adopted to control confounding factors and accurately assess the exposure level under the normal learning and living conditions of the primary school students,and to study the harmful effects of PM on the respiratory health of primary school students and the health protection effect of the purifier on the schoolchildren.Through the harmful effects of PM on primary school students and the health protection effect of air purifiers on primary school students,the evaluation indicators are screened from both positive and negative aspects to comprehensively assess the health effects of atmospheric particulates on primary school students and the health protection effects of air purifiers.[Objective]This study aimed to strictly control confounding factors,selected a more accurate individual exposure assessment method,established a more complete evaluation index system,comprehensively and systematically studed the effect of atmospheric particulate matter(PM10,PM2.5,and PM10)on the respiratory health of schoolchildren,and at the same time evaluate the purification effects of air purifiers on atmospheric particulate matter(PM10,PM2.5 and PM1)and the protective effects of primary school students' respiratory system health,providing adequate scientific basis for the primary school student's respiratory system health protection under polluted weather.The research results can guide schools to use air purifiers reasonably,reduce health hazards,and provide a scientific basis for establishing personalized health protection measures for specific people in polluted weather.[Methods]This study intended to carry out a follow up study to study the health effects of PM2.5 on the respiratory system of schoolchildren,and a random cross-intervention design to evaluate the health protection of schoolchildren through the intervention of air purifiers.Grades 4-5 students in a full boarding school were selected according to strict inclusion and exclusion criteria.First,conduct follow up study two times,each time monitoring the outdoor and indoor PM10,PM2.5 and PM1 concentrations for 5 consecutive days(Monday to Friday),and use time activity patterns and microenvironmental concentrations to calculate the time-weighted individual exposure concentration.On the 5th day(Friday)Questionnaire survey were conducted to get the respiratory symptoms information(cough,sputum,stuffy nose,runny nose,sore throat,fever,headache)of schoolchildren during the survey period,detected FeNO of schoolchildren with FeNO detector,detected lung function with spirometer(VC.FVC,FEV1,FEV1/FVC,PEF,FEF25%,FEF50%,FEF75%,FEF25%-75%),used Rtube TM tube to collect EBC,collected clean mid-term morning urine,used pH meter to detect pH in EBC,ELISA method to detect 16 inflammatory and oxidative stress indicators in EBC(EBC 8-iso,EBC IL-1?,EBC IFN-?,EBC IFN-y,EBC TNF-?,EBC MCP-1,EBC IL-6,EBC IL-8,EBC IL-10,EBC IL-12p70,EBC IL-17A,EBC IL-18.EBC IL-23,EBC IL-33)and 2 indicators in urine(urine 8-OHdG and urine 4-HNE),performed GC-TOF-MS non-targeted metabolomics to detect EBC samples,using Wilcoxon signed rank sum test to analysis single factors,and multi-factors analysis were performed on Simca 4.1,screening out metabolites with FDR q<0.05 and VIP>1.0 in PLS-DA model(or OPLS-DA model).Logical mixed-effect model and linear mixed-effect model were used to analyze the correlation between PM and effect indicators(including differential metabolites),screen sensitive biomarkers,and explore the health effects of PM on schoolchildren.Secondly,an air purifiers cross-intervention study was conducted with a washout period of 1 month.Divided the students into two groups by class.In the first stage,one group used air purifiers with high-efficiency filters,and the other group used air purifiers without high-efficiency filters.After 5 days of intervention,the medical examination and sample collection were performed.One month later,air purifiers were exchanged,and the second stage of intervention was conducted.After intervention,the medical examination and samples were collected.In order to verify and compare the sensitive biomarkers screened by follow-up study,PM monitoring,questionnaire surveys,physical examinations and sample detection methods in this study were consistent with the follow-up study.Logical mixed effect model and linear mixed effect model were used to analyze the correlation between air purifier intervention and effect indexes.Finally,a comparative analysis of the relevant indicators of two studies was conducted to explore the health hazards of PM on schoolchildren and the health protection of air purifiers.[Results](1)Follow up study included 123 and 118 subjects,respectively,and the average exposure weighted individual exposures of PM1o were 19.44?g/m3 and 51.76?g/m3,PM2.5 were 14.86?g/m3 and 41.37?g/m3,PM41 were 6.27?g/m3 and 22.33?g/m3.Comparison of the two samples found that cough,expectoration,runny nose,VC,FVC,FEV1/FVC,FEF25%,FEF75%-EBC pH,FeNO,EBC 8-iso,EBC IL-33,EBC IL-1?,EBC IFN-?,EBC TNF-?,EBC MCP-1.EBC IL-8,EBC IL-18.urine 8-OHdG and urine 4-HNE has significant differences.EBC metabolomics analysis found 26 differential metabolites with FDR q<0.05 and VIP>1.0 in PLS-DA model.Correlation analysis found that the rise of PM10,adjusted PM2.5,adjusted PM1 were associated with the increase of runny nose,EBC pH,FeNO,EBC 8-iso,EBC IL-1?,EBC IL-6,EBC IL-8,EBC IL-33,4-HNE and 8-OHdG,Among them,FeNO had a largest increase,every increase of PM10,PM2.5 and PM1 by 10?g/m3 can cause FeNO increased by 10.17%(95%CI:6.63%-13.7%)?12.54%(95%CI:8.12%-16.95%)and 22.17%(95%CI:14.3%-30.04%)respeactivly;Were associated with decrease of FVC,FEV1,FEV1/FVC and FEF 25%,FEV1 had a largest decrease,every increase of PM10,PM2.5 and PM1 by 10?g/m3 can cause FEV-decreased by 3.25%(95%CI:1.95%-4.56%),3.93%(95%CI:0.24%-7.62%)and 6.43%(95%CI:3.86%-9.00%),respectively.Among the differential metabolites,it was found that acute exposure to PM can cause an increase in 14 metabolites and decrease in 9 metabolites.Among them,EBC NA,EBC CBE,EBC MU,EBC PA 16:1N-7 and EBC OA were related to inflammatory response,EBC PA and EBC UD were related to oxidative stress,and EBC FA was related to immune regulation.At the same time,the study found that PM had immediate and lagging effects,with the strongest lagging effect in lag 1-2 day.The impact on boys was stronger than girls.(2)In the cross-intervention study of air purifiers,124 and 116 subjects were included in the intervention group and the non-intervention group.respectively.The average time-weighted individual exposure concentrations of PM10 in the two groups were 48.5±0.76?g/m3 and 71.08±0.21?g/m3.respectively,PM2.5 in the two groups were 53.79 ?g/m3 and 30.77 ?g/m3.respectively.PM1 in the two groups were 28.06±0.79?g/m3 and 39.08±2.91?g/m3.The study found that the air purifier can effectively reduce the indoor PM10,PM2.5 and PM 1 concentration,and had a strongest purification rate for PM2 5,when the outdoor PM2 5 concentration were between 110?g/m3 to 150?g/m3,the average purification rate of air purifiers was 52.83%(50.26%.56.13%).Comparison of the two groups found that the incidence of runny nose.FeNO,EBC IFN-?,EBC MCP-1 and urine 8-OHdG in the intervention group were lower than those in the non-intervention group(P<0.05).EBC non-targeted metabolomics screened out 16 potential differential metabolites.Correlation analysis found that the air purifier intervention can effectively reduce the concentration of FeNO,EBC IL-1?,EBC IL-6 and urine 8-OHdG,After the intervention of the air purifier,the reduction of PM10.PM2.5 and PM1 was associated with the reduction of runny nose.FeNO.IL-1?,MCP-1,IL-6 and urine 8-OHdG,of which EBC MCP-1 decreased the most.After adjusting the influence of PM10,for every 10?g/m3 decrease in PM2.5 and PM1,EBC MCP-1 decreased by 5.47%(95%CI:0.65%-10.29%)and 13.56%(95%CI:3.43%-23.7%).Air purifier intervention reduced 7 differential metabolites in EBC and increased 3 metabolites,of which EBC L-Ser and EBC LLA were related to inflammation and oxidative stress,EBC MU was related to inflammation,EBC PUT was related to oxidative stress related.Comparison of the two studies found that runny nose,FeNO,EBC IL-1?,EBC IL-6,urine 8-OHdG and EBC MU are all related to PM(PM10,PM2.5 and PM1)and air purifier intervention.There were differences changes in boys and girls,PEF,FEF25%,FeNO,EBC IL-1?,EBC IL-8 and urine 8-OHdG were changed more in boys,FEV1,FEV1/FVC,FeNO,EBC IL-6 and EBC MU were changed more in girls.[Conclusions](1)The acute exposure of PM was associated with respiratory inflammation and oxidative stress in primary school students,and it had an adverse effect on respiratory symptoms and lung function in healthy primary school students.The smaller the PM particle size,the greater the health impact,and the larger particle size has a certain interference effect on the health effect of the smaller particle size.When considering the health effects of PM with different particle sizes,if the impact was not deducted,it may lead to overestimation of the health effect of the particulate matter.(2)PM has lagging effect,its maximum effect was at 1-2 days after exposure,and its effect could last for many days.When a pollution occurs,people not only need to wear masks,close doors and windows when they go out.and conditionally turn on air purifiers and other protective measures indoors,and pay attention to personal protection for a period of time after pollution occurs.(3)The air purifier can effectively reduce the indoor PM concentration.The outdoor PM2.5 has the maximum purification efficiency at 115?g/m3-150?g/m3.At the same time,after intervention.respiratory inflammation and oxidative stress were observed in primary school students,the indicators change accordingly,suggesting that when polluting weather occurs,even during the normal learning process,properly turning on air purifiers can also have an important protective effect on the health of the respiratory system of schoolchildren.(4)Boys are more susceptible to PM than girls.In the future research and population health protection,the influence of gender should be considered.(5)A comprehensive analysis of the two studies found that FeNO,EBC IL-1?,and urine 8-OHdG,supplemented with EBC MU,were sensitive indicators to assess the impact of PM10 on the respiratory health of schoolchildren.FeNO,EBC IL-1?,EBC IL-6,urine 8-OHdG,supplemented by runny nose and EBC MU were sensitive indicators to assess the health effects of PM2.5 and PM1 and the health protection effects of air purifiers on primary school students.(6)When evaluating the health effects of boys,we should focus on the changes of runny nose,PEF,FEF25%,FeNO,EBC IL-1?,EBC IL-8,and urine 8-OHdG.When evaluating the health effects of girls,we should focus on the changes of FEV1,FEV1/FVC,FeNO,EBC IL-6 and EBC MU.(7)This study evaluated the health protection effects of PM on the health hazards of the respiratory system of primary school students and the intervention of air purifiers from both positive and negative aspects.It screened and established a relatively complete evaluation index system,which can be used for normal life,study or work in the future.Under the circumstances,carrying out the assessment of the health effects of PM pollution and the effect of air purifiers intervention on health protection provides technical methods,and can also provide a scientific basis for the personalized health protection of specific people in polluted weather. |
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