ABSTRACT Poor indoor air quality is a public health concern, particularly in schools, where children spend a significant amount of time. This study aimed to assess the daily concentrations of bacteria and fungi in the indoor air of four primary schools in the Community of Madrid, and to correlate these data with environmental parameters and children's health. The study was conducted in four primary schools in Madrid, with two classrooms selected from each school. A total of 640 samples (128 outdoor and 512 indoor) were collected between April and December 2023. Indoor samples were taken at four different times of day. Bacteria and fungi were quantified in agar media using an active air sampler impactor. Environmental parameters were monitored and children's health data were collected through surveys. Mean indoor air bacteria concentrations ranged from 10 to 548 CFU/m 3 , and fungi concentrations ranged from 0.25 to 58.5 CFU/m 3 . Bacterial and fungal concentrations in indoor air met the UNE comfort criteria (< 600 CFU/m 3 for bacteria and < 200 CFU/m 3 for fungi) although there were sporadic bacterial peaks in December. Human occupation increased bacteria 7-fold and fungi 3-fold. Low air infiltration rate and higher relative humidity were associated with microbial peaks. The present study constitutes the first examination of the concentrations of bacteria and fungi in primary schools in Madrid. This study highlights the impact of human occupation on indoor air contamination by bacteria and fungi. Factors such as poor ventilation due to low air infiltration rates and humidity influenced microbial growth.
Cervera et al. (Mon,) studied this question.