Association Of Respiratory Infections With Indoor Air Quality And Ventilation In School Classrooms

Classrooms in elementary schools are important places for pupils to study and stay.The indoor air quality in classrooms has great influence on students’health and learning efficiency.In China,students spend a long time in classrooms.The density in classrooms is large,and classrooms are naturally ventilated through infiltration and opening windows.What’s more,students are more susceptible to poor indoor air quality compared to adults.These all make respiratory infectious diseases easily spread in school classrooms.This study focuses on the association of respiratory infections with indoor air quality and ventilation in school classrooms.This study was carried out from November 2018 to January 2020.It was conducted in 47 classes of ten elementary school in urban,suburban and rural area of Tianjin.The subjects of the study were second and fifth grade students,involving a total of 2020 people.Field monitoring was divided into two parts,classroom environment monitoring and student health monitoring.The classroom environment monitoring can be divided into two parts:quarterly on-site testing and long-term online monitoring.Quarterly on-site testing measured concentrations of formaldehyde,TVOC,benzene,toluene,xylene and ultrafine particulate matter.Long-term online monitoring of environmental parameters were PM_2.5concentration,indoor air temperature,relative humidity,CO₂concentration,and the ventilation rate was calculated based on the CO₂concentration.The teacher in charge of the class reported the absence of students due to respiratory infections every day.Results showed that in the quarterly on-site testing,TVOC concentration in some classes exceeded the Chinese national standard.In the long-term online monitoring,CO₂concentration and ventilation rate exceeded the standard severely.Only 15%of the samples with CO₂concentration were under the standard of 1000ppm,while only4%of the samples with ventilation rate per person met the national standard of 5.56L/s per person.We used zero-expansion negative binomial models to analyze the association between various environmental parameters and the number of absenteeism caused by respiratory infections.It showed that PM_2.5concentration,temperature,relative humidity,and ventilation had significant effects on absenteeism caused by respiratory infections per day.Specifically,when PM_2.5concentration increased by10μg/m³,the number of absences increased by 1.05～1.15 times;When the temperature increased 1℃,or relative humidity increase 1%,absenteeism the number of absenteeism decreased to 0.78～0.92 times and 0.93～0.95 times;When air change rate increase 0.1h^-1,or ventilation rate per person increase 1L/s per person,the number of absenteeism decreased to 0.98 times and 0.87～0.91 times.In addition,we used the Well-Riley model to predict the minimum ventilation rate,which could ensure a healthy classroom environment to prevent airborne transmission of respiratory infections.Meanwhile,we established a risk assessment model of respiratory infection in classroom and calculated the probability of infection with and without prevention measures.It predicted that when effective prevention measures were taken,the probability of infection was reduced by an average of 81%.Through this study,we obtained information on indoor air quality,ventilation rates in classrooms in elementary schools,and students’respiratory infection rates among pupils.Based on the association of respiratory infections with indoor air quality and ventilation in school classrooms,ventilation and indoor air quality control strategies was put forward,which will benefit the formulating of air quality standards for school environment.