Classroom Carbon Dioxide Concentration, School Attendance, and Educational Attainment

BACKGROUND: We tested the hypothesis that classroom carbon dioxide (CO2) concentration is inversely related to child school attendance and educational attainment. METHODS: Concentrations of CO2 were measured over a 3-5 day period in 60 naturally ventilated classrooms of primary school children in Scotland. Concentrations of CO2 were related to the class average annual attendance and proportions attaining a national standard for reading, writing, and numeracy, adjusted for socioeconomic status and class size. RESULTS: The median (interquartile range, IQR) CO2 concentration averaged over the school day was 1086 ppm (922, 1310). In the model, Time Weighted Average CO2 concentrations were inversely associated with school attendance but not academic attainments. An increase of 100 ppm CO2 was associated with a reduced annual attendance of 0.2% (0.04, 0.4) roughly equivalent to 1 half day of school per annum, assuming schools are open on 190 days per year. Indoor temperature and relative humidity were not related to attendance or academic attainment. CONCLUSIONS: Inadequate classroom ventilation, as evidenced by CO2 concentration exceeding 1000 ppm, is not uncommon and may be associated with reduced school attendance. A relationship between inadequate classroom ventilation and adverse health outcomes in children may be present and this needs to be explored.