Effectiveness of a Protocol to Reduce Children's Exposure to Particulate Matter and NO2 in Schools during Alert Days

Abstract

Reducing children's exposure to air pollutants should be considered a primary goal, especially for the most vulnerable subjects. The goal of this study was to test the effectiveness of applying a protocol in the event of alert days, i.e., days with forecasted PM₁₀ levels above the EU limit value (50 µg/m³). The test was conducted, before the onset of SARS-CoV-2 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 opening windows and doors, as well as the activation of an air purifier. Teachers and students were asked to apply the protocol only in the event of alert days, while no indications were provided for non-alert days. A monitoring system measuring PM₁, PM_2.5, PM₁₀, CO₂, and NO₂ was deployed in the 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 also remarkable for PM₁₀-the most critical air quality parameter in the study area (1.5 and 1.1 for non-alert and alert days, respectively). Indoor concentrations of PM₁₀-especially during non-alert days-were often higher than outdoors, showing a major contribution from resuspension due to the movement of people 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's exposure to air pollution during severe air pollution episodes. Considering the onset of COVID-19 and the airborne transmission of pathogens, this protocol now has more meaningful implications for children's welfare, and can be integrated with protocols designed as measures against the spread of SARS-CoV-2.

Keywords: indoor air quality; particulate matter; prevention; schools; severe air pollution episodes.

Figure 1

Location of the AQMesh measuring instrument in the classroom (a), support structure for AQMesh and air purifier (b), and location of the outdoor instrument with its solar panel (c).

Figure 2

Daily mean PM₁₀ concentration measured by the urban background station during the monitoring campaign. Red circles indicate alert days. The red line represents the EU daily limit value (50 µg/m³).

Figure 3

Mean trends of measured pollutants during school hours. The blue lines are the indoor concentrations, while the red lines are the outdoor concentrations, as measured by the AQMesh sensors.

Figure 4

Comparison of the indoor/outdoor ratios of the measured toxic pollutants during alert and non-alert days.