Pre-contamination of new, wood-based building materials: fungal diversity and susceptibility under different moisture scenarios

Indoor fungal contamination may pose health risks and cause superficial deterioration of building materials. This study investigated the fungal susceptibility of new, commonly used wood-based materials (planed wood, plywood, oriented strand board (OSB), particleboard, medium-density fibreboard (MDF), and gypsum board). The surface cleaned or disinfected samples were subjected to three moisture scenarios: 1) prolonged high relative humidity (RH), 2) undiscovered water leakage, and 3) flooding with subsiding water. All materials were prone to fungal growth under favourable conditions, regardless of type, treatment, or retailer, though wood was the most resistant. Surface disinfection was ineffective in preventing growth, indicating that spores are embedded within materials. Quick drying after water exposure could prevent fungal establishment. A diverse array of fungal species was identified, with the most frequent being Aspergillus pseudoglaucus, Asp. hiratsukae, Purpureocillium lilacinum, Ascotricha chartarum, Aspergillus section Nigri, Aspergillus spp., Penicillium spp., and Pen. corylophilum. Associations were observed between material types and fungal taxa, with wood composites being particularly vulnerable to contamination, likely due to the use of carbohydrate-enriched adhesives, which serve as a food source for fungi. Moisture response varied by material, moisture scenario, and exposure duration. Plywood and MDF showed the highest and fastest sorption and desorption capacities, whereas OSB and particleboard showed slower responses. Gypsum board had the lowest initial free water content and was the least hygroscopic under high RH, but with the highest liquid water absorption capacity relative to its initial water content. Planned wood demonstrated moderate sorption potential from air humidity, the lowest from liquid water, and the lowest fungal load and diversity.