School Children Exposure to Low Indoor Air Quality in Classrooms During Covid-19 Pandemic: Results of a Pilot Study

Abstract

Background: Indoor air quality (IAQ) in classrooms affects children's health and academic performance. The aim of this pilot study was to determine IAQ in elementary schools different in their internal and external characteristics, in settings of COVID-19 epidemics. Methods: IAQ parameters: fine particulate matter (PM 2,5 ) mass concentration, CO 2 concentration, temperature and relative humidity were measured in parallel in four elementary schools/classrooms during October (non-heating season) and four months (including holiday in January) of heating season. IAQ parameters were measured in settings of anti-epidemic restrictions (≤13 students in classroom, frequent ventilation). Results: During October, except in one school, PM 2,5 concentrations were below the upper recommended value (25μg/m³), but started rising in all schools in the heating season. The highest concentrations of PM 2,5 were registered in two schools with closed or shortly opened windows. CO 2 concentrations were mostly in the recommended range (up to 1000ppm) except in the school with constantly closed windows and in three schools in February when concentrations were higher. Except in one, the same school, and in January, both temperature and relative humidity were out of the recommended range (24,0-27,0°C in non-heating; 20,0-24,0°C in heating season; and 45-55%), with temperature mainly above and relative humidity mainly below it in three schools. The largest deviation in temperature and relative humidity were registered in urban schools. Registered differences may be explained by different internal and external characteristics.

Systematic Review of the Key Factors Influencing the Indoor Airborne Spread of SARS-CoV-2

“…Mechanical ventilation rules can be put in place and are already applied in various schools around Europe. By manually opening doors and windows and emptying classrooms during breaks, as previously discussed, CO 2 level can be kept below a certain level, thus efficiently mitigating the risk of infection during classes [ 44 , 46 , 50 , 58 , 63 , 64 ].…”

“…Indeed, it is unsurprising that infection and mortality numbers tend to be lower during summer periods [ 2 ], when higher temperatures, low RH, and abundant sunlight enhance the viral inactivation, and ventilation measures are well respected in order to keep indoor environments cool and breathable. Inversely, infection numbers peak during colder periods, when lower temperatures and higher RH favor the viral load survival rate, and people neglect proper ventilation procedures in order to keep warm [ 44 , 64 ]. This trend is also recognized in other respiratory viruses, such as SARS-CoV-1, influenza, and human respiratory syncytial virus (RSV), which show peak incidence rates during winter months [ 6 , 8 ].…”