Abstract
Indoor formaldehyde (CH2O) exceeding the recommended level is a severe threat to human health. Few studies have investigated its effect on indoor surface bacterial communities, affecting habitants' health. This study used 20-L glass containers to mimic the indoor environment with bacterial inputs from human oral respiration. The behavior of bacterial communities responding to CH2O varied among the different CH2O levels. The bacterial community structure significantly changed over time in the 0.054 mg·m−3 CH2O group, which varied from the 0.1 mg·m−3 and 0.25 mg·m−3 CH2O groups. The Chao1 and Shannon index significantly increased in the 0.054 mg·m−3 CH2O group at 6 week, while they remained unchanged in the 0.25 mg·m−3 CH2O group. At 12 week, the Chao1 significantly increased in the 0.25 mg·m−3 CH2O group, while it remained unchanged in the 0.054 mg·m−3 CH2O group. Only a few Operational Taxonomic Units (OTUs) significantly correlated with the CH2O concentration. CH2O-induced OTUs mainly belong to the Proteobacteria and Firmicutes. Furthermore, bacterial communities formed at 6 or 12 weeks differed significantly among different CH2O levels. Functional analysis of bacterial communities showed that inferred genes related to chemical degradation and diseases were the highest in the 0.25 mg·m−3 CH2O group at 12 weeks. The development of nematodes fed with bacteria collected at 12 weeks was applied to evaluate the bacterial community's hazards. This showed significantly impaired growth in the 0.1 mg·m−3 and 0.25 mg·m−3 CH2O groups. These findings confirmed that CH2O concentration and exposure time could affect the indoor bacterial community and formed bacterial communities with a possibly more significant hazard to human health after long-term exposure to high CH2O levels.
Highlights
Indoor formaldehyde (CH2O) exceeding the recommended level is a severe threat to human health
Principal coordinates analysis based on the Bray–Curtis distance of Operational Taxonomic Units (OTUs) matrix showed experiment time (PERMANOVA, R2 = 0.172, P = 0.045) and CH2O level (PERMANOVA, R2 = 0.176, P = 0.021) both significantly affected the bacterial community structure (Fig. 2)
The bacterial community of the 0.054 mg·m−3 CH2O group significantly changed at 6 (PERMANOVA based on Bray–Curtis distance, R 2 = 0.192, P = 0.029) and 12 weeks (PERMANOVA based on Bray–Curtis distance, R2 = 0.198, P = 0.026), but that of the 0.1 mg·m−3 group did not change at these periods and 0.25 mg·m−3 CH2O group obviously changed at 12 weeks (PERMANOVA based on Bray–Curtis distance, R2 = 0.156, P = 0.055)
Summary
Indoor formaldehyde (CH2O) exceeding the recommended level is a severe threat to human health. The development of nematodes fed with bacteria collected at 12 weeks was applied to evaluate the bacterial community’s hazards This showed significantly impaired growth in the 0.1 mg·m−3 and 0.25 mg·m−3 CH2O groups. These findings confirmed that CH2O concentration and exposure time could affect the indoor bacterial community and formed bacterial communities with a possibly more significant hazard to human health after long-term exposure to high CH2O levels. We mimicked the indoor environment using 20-L glass containers and human microbial inputs by occupants via oral respiration, which brings in a much higher number of taxa than via nasal respiration (700 vs 100 taxa)[20,21] (Fig. 1a) These containers were exposed to three CH2O levels and samples were taken at different times (Fig. 1b). This study is valuable for studying the interaction between various VOCs/VOCs complex and indoor bacterial communities
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