Indoor air bacterial and fungal burden in the environment of an atopic child: implications for elevated urine mycotoxin levels.

Here we present a case of an atopic boy from Zagreb, Croatia, whose elevated urine mycotoxin levels prompted us investigate whether they were associated with microbial indoor air burden in the child's primary and music school and family home. The music school had been water-damaged / mould-infested but had been repaired by the time of our measurements. We also measured urine mycotoxin in one healthy child who attended the same elementary school and in all household members of the atopic boy. The results showed no microbial contamination at any of the measurement locations, with bacterial concentrations ranging from 172 to over 570 CFU/m3 of air and fungal concentrations between 67 and 82 CFU/m3, all determined only in the music school classroom. The dominant species isolated in the music school were Aspergillus fumigatus (55 CFU/m3) and Penicillium verrucosum (24 CFU/m3), both potential mycotoxin producers. Considering that only the atopic boy had elevated urine mycotoxin levels, we believe that mould in the music school cannot be ruled out as the source of exposure. In fact, we believe our case illustrates that safety thresholds for mould exposure can vary and may be much lower for immunocompromised or sensitive individuals.