Effectiveness of a protocol to reduce children exposure to par-2 ticulate matter and NO2 in schools during alert days

Reduction of children exposure to air pollutants should be considered a primary goal, especially for the most vulnerable subjects. The goal of the study consisted in testing the effectiveness of applying a protocol in case of alert days, i.e. days with forecasted PM10 levels above the EU limit value (50 g/m3). The test was conducted, before the onset of SARS-Cov2 restrictions, in a classroom of a primary school in Parma (Italy), a highly polluted area in Northern Italy. The protocol included indications for the frequency of windows and door opening, and the activation of an air purifier. Teachers and students were asked to apply the protocol only in case of alert days while no indications were provided for no alert days. A monitoring system measuring PM1, PM2.5, PM10, CO2 and NO2 was deployed in a classroom. Measurements of the same parameters were also performed outdoors near the school. The application of the protocol reduced the Indoor/Outdoor (I/O) ratio for all toxic pollutants. The reduction was remarkable also for PM10, the most critical air quality parameter in the study area (1.5 and 1.1 for no alert and alert days, respectively). Indoor concentrations of PM10 especially during no alert days were often higher than outdoors showing a major contribution from resuspension due to people movement and personal cloud. The protocol did not cause any increase in indoor CO2 levels. Our findings showed that the application of a ventilation protocol together with the contribution of an air purifier may represent an effective way to reduce children exposure to air pollution during severe air pollution episodes. Considering the onset of COVID-19 and air transmission of pathogens, this protocol has now a more meaningful impact on children welfare and can be integrated with protocols designed as measures against SARS-Cov2 spread.