Portuguese primary schools: dust filter samples, a simple tool for assessing bacterial contamination indoors?

Pena, Pedro; Cervantes, Renata; Viegas, Carla

http://hdl.handle.net/10400.21/22111

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Authors

Pena, Pedro

Cervantes, Renata

Viegas, Carla

Abstract(s)

This study aimed to assess seasonal variations in bacterial contamination across school settings (canteen, classroom, gymnasium, library, and toilet) with dust filter samples, to identify high-risk areas and inform targeted hygiene practices and public health strategies in educational environments. Dust filter samples were collected in 10 schools within the Metropolitan Lisbon Area. Sterilized coffee filters were placed inside the disinfected vacuum tube for sampling. Samples were collected in the warm (N=33) and cold seasons (N=34), from canteens (N=14), classrooms (N=33), gymnasium (N=9), library (N=9), and toilets (N=2). Settled dust was collected from shelves, plinths, and floors around students' desks and near the door in all sampled rooms. After extraction with NaCl+Tween 80 solution, samples were inoculated onto Tryptic Soy Agar (TSA), Violet Red Bile Agar (VRBA), and MacConkey Agar (MAC). Results from the cold season indicate that gymnasiums (TSA = 1.8×10⁴ CFU/m²) and libraries (VRBA = 1.4×10⁴ CFU/m²) were contamination hotspots, although libraries showed lower contamination on TSA (1.8×10³ CFU/m²). Canteens (2.3×10³ CFU/m²) exhibited elevated Gram-negative bacteria, while classrooms had the lowest contamination on VRBA (5.0×10² CFU/m²). For the warm season, canteens showed higher contamination on TSA (6.5×10³ CFU/m²), while classrooms showed higher contamination on VRBA (4.5×10³ CFU/m²). For MAC results, gymnasiums showed higher contamination (2.0×10³ CFU/m²). Seasonal and spatial differences significantly influence microbial air contamination in schools. Gymnasiums and classrooms are potentially critical hotspots, particularly for MAC and TSA contamination results. TSA contamination results showed high variability (e.g., SD = 23,645 in canteens), suggesting fluctuating total bacterial contamination, likely tied to occupancy or cleaning schedules. These findings emphasize the need for seasonally adaptive hygiene protocols and focused monitoring in high-traffic areas to mitigate exposure risks.

Description

H&TRC authors gratefully acknowledge FCT/MCTES UIDP/05608/2020, and UIDB/05608/2020. This work is also supported by national funds through FCT/MCTES/FSE/UE, 2023.01366.BD; and Instituto Politécnico de Lisboa, national support through IPL/2022/InChildhealth/BI/12M; and for funding the projects IPL/IDI&CA2024/WWTPSValor_ESTeSL and IPL/IDI&CA2024/MycoSOS_ESTeSL. This project was partly funded by an EU Horizon 2021 grant no. 101056883 and co-funding from the author’s organizations and/or Ministries. Funding from Swiss SERI grant 22.00324, UKRI grant 10040524, and NHMRC grant APP2017786 and APP2008813. Views expressed are of the author(s) and do not necessarily reflect those of EU, Swiss SERI, UKRI, or NHMRC.

Keywords

Occupational health Indoor contamination Exposure contamination Elementary school Children Portugal FCT_UIDP/05608/2020 FCT_UIDB/05608/2020 IPL/2022/InChildhealth/BI/12M IPL/IDI&CA2024/WWTPSValor_ESTeSL IPL/IDI&CA2024/MycoSOS_ESTeSL

URI

http://hdl.handle.net/10400.21/22111

Citation

Pena P, Cervantes R, Viegas C. Portuguese primary schools: dust filter samples, a simple tool for assessing bacterial contamination indoors? In: AIRMON 2025 – 11th International Symposium on Modern Principles for Air Monitoring and Biomonitoring, Loen (Norway), June 15-19, 2025.