Effects of propagule size and filter material on microbial recovery and viability in bioaerosol filtration

This study aimed to assess how propagule size and filter material affect the recovery and viability of airborne microorganisms. Five airborne fungal species with spore volumes ranging from 28.1 to 325.2 μm3 were filtered through four membrane filters. Analysis of variance revealed that a 30-min vacuuming process (i.e., air filtration) significantly reduced spore recovery and viability (p<0.05), with recovery ratios decreasing by 39.6% (ranging from 0.96 – 0.58) and viability ratios decreasing by 23.1% (0.91 – 0.70). Spore size affected recovery (p<0.05), while filter material had no effect. Before filtration, no exponential-rise-to-maximum pattern was observed between spore size and recovery for any filter (p<0.05). After filtration, a clear exponential-rise-to-maximum relationship was evident across all filters (R2 ≥ 0.58, p<0.05), suggesting that larger propagules (> 60 μm3) are less likely to become embedded within the filter matrix. Similarly, detachment efficiency followed an exponential- rise-to-maximum relationship (R2 = 0.65) with spore size when analyzed collectively. Spore viability was not affected by spore size or filter material. Propagule size exerts a critical impact on recovery, with larger propagules being more effectively recovered. These findings emphasize the need to optimize filtration and recovery methods to minimize sampling biases and enhance the accuracy of microbial analyses.