Associations between Illness-Related Absences and Ventilation and Indoor Pm2.5 in Elementary Schools of the Midwestern United States

Abstract

This study monitored indoor environmental data in 144 classrooms in 31 schools in the Midwestern United States for two consecutive days in fall, winter and spring during a two-year-long period; 3,105 pupils attended classrooms where the measurements were conducted.All classrooms were ventilated with the mechanical systems that had recirculation; there were no operable exterior windows or doors. The daily absence rate at the student level and demographic data at the classroom level were collected. The overall mean ventilation rate with outdoor air was 5.5 L/s per person (the rates were <12 L/s per person and corresponding mean carbon dioxide concentrations <2,000 ppm) and the mean indoor PM2.5 was 3.6 μg/m3 (the mean PM2.5 levels were <10 ug/m3). The annual illness-related absence rate at the classroom level was extracted from the student-level absence data and regressed on measured indoor environmental parameters. Significant associations were found. Each 1 L/s per person increase in ventilation rate decreased the annual absence rate by 4.6 days, corresponding to a 0.12% increase in average daily attendance rate, while each additional 1 μg/m3 of indoor PM2.5 was associated with an increased annual absence rate of 1.9 days, corresponding to a 0.05% increase in average daily attendance rate. No other relationships were significant. Present results confirm the previously demonstrated benefits of reduced absence rates when classroom ventilation is improved and provide new evidence on the benefits of reducing indoor inhalable particles. Reduced absence rates are expected to provide overall benefits for academic achievements and socioeconomic benefits, while higher ventilation rates and reduced particle levels will also contribute to reduced health risks also those related to airborne respiratory pathogens.

Keywords: Classroom, Indoor air quality, Pupils, Attendance, Particulate matter, Ventilation