Causal inference between indoor dampness and adverse health effects

Abstract

Indoor dampness can promote the establishment of microbes in indoor environments, and as such, controlling dampness is important for maintaining a healthy indoor environment. Here, an index is proposed for evaluating indoor dampness based on checking for visible condensation, mold in living rooms and bedrooms, and moldy odors indoors. In this evaluation method, eight items related to visible condensation, presence of mold, and moldy odors are assigned a maximum score of 3 points; the total score (a maximum of 24 points) is then used as an index for the degree of dampness. We classified the total score into four rankings based on quartiles. Rank 4 represents the lowest rank and was assigned to houses that had the most severe levels of indoor dampness. We hypothesized that the lower the rank, the higher the incidence of sick housing syndrome (SHS) would be among young children. To clarify whether there was an association between child SHS and indoor dampness, we conducted an Internet-based cross-sectional survey on children aged 4–12 years. This study first identified potential confounding variables for exposure to indoor dampness using a directed acyclic graph. The results indicated that the higher the degree of dampness, the higher the health risk was for ocular, nasal, and throat symptoms. Dose-response relationships between indoor dampness and SHS were presented using the dampness index proposed in this study.