Impacts of compound weather events on indoor mold and respiratory health issues in indoor environments

Hurricanes can cause long periods of moisture entering residential buildings, which can lower indoor air quality and lead to respiratory health problems such as asthma and allergy. Previous studies have mostly focused on the immediate effects of flooding, but less attention has been given to the role of compound weather hazards such as rainfall and wind after a hurricane event. This study examined how total rainfall and wind speed can exacerbate the impacts of hurricanes on indoor air quality in terms of mold respiratory outcomes. We used a database from 60 buildings affected by Hurricanes Ida and Ian, collected during the winters of 2021 and 2022. The database was based on survey questionnaires, laboratory analyses, field inspections, ground measurements and flood hindcasts. Among these building, 25 were located in Louisiana (New Orleans and Baton Rouge), eight in the northeastern United States (New York and Philadelphia), and 27 in central and southern Florida (Fort Myers, Orlando, and Miami). The dataset included inspection data, laboratory measurements of indoor and outdoor mold spore in terms of several species, respiratory health issues (new symptoms), hindcasted flood depths, rainfall, wind speed. The weather data were processed into various mold-influencing variables, including total rainfall depth, number of rainy days, rainfall intensity, and wind characteristics. To explore the relationships, L1-regularized (LASSO) logistic regression was used to model (1) whether residents reported post-hurricane respiratory symptoms and (2) whether they reported any level of symptom severity. Although no strong statistically significant relationships were found using traditional regression methods, the LASSO analysis showed modest and consistent associations between cumulative post-hurricane rainfall and the time since hurricane landfall with both respiratory outcomes. These results suggest that post-hurricane rainfall events contribute to respiratory health effects, but it is not the main controlling factor; indoor mold indicators were more strongly related to maximum flood depth during the hurricanes. Overall, the findings suggest that longer exposure to moisture after a hurricane may play a role in respiratory health problems. Our results showed the importance of considering compound weather conditions rather than a single extreme event like hurricanes when evaluating respiratory health risks and planning for indoor resilience after natural disasters.