Background
Climate change may increase flooding and relative humidity, promoting fungal growth and toxin production. These processes pose health risks when individuals are exposed to airborne fungi indoors. This study investigated the effect of relative humidity during cultivation on Aspergillus niger, focusing on ochratoxin A release, particle concentrations and size distribution, and the viability and culturability of airborne fungi.
Methods
Relative humidity levels of 30%, 60%, and 90% were tested. A. niger was dispersed using an Automated Fungal Particle Aerosolizer (AFPA). Air samples were collected with NIOSH two-stage cyclone bioaerosol samplers for microbial analysis, while particle concentrations and size distributions were measured using an Electrical Low-Pressure Impactor (ELPI).
Results
Fungal particle concentrations and ochratoxin A levels increased as relative humidity decreased. Most fungal particles were larger than 1 μm. Ochratoxin A was not detected in the fragment size range (<1 μm), indicating that toxins were mainly associated with spores. Relative humidity did not significantly affect fungal viability or culturability.
Conclusions
These findings suggest that higher relative humidity may not greatly increase exposure to airborne fungal particles or toxins. However, as elevated humidity facilitates fungal growth, disturbance in fungi-contaminated environments should be minimized to reduce health risks.