2025 Theses Doctoral

Mold in a Changing Climate – Implications for Fungal Exposures and Asthma Morbidity in New York City Public Housing

Flores, Nina M.

Asthma is one of the most prevalent chronic conditions in the United States. More notable than asthma’s pervasiveness are its associated disparities. Nationally and in New York City (NYC), salient differences exist in asthma prevalence, morbidity, and mortality across racial, ethnic, and socioeconomic groups. Substandard, and often hazardous, conditions faced by lower-income families living in rented or public housing partially drive these asthma disparities by increasing exposure to indoor asthma triggers such as fungal exposure (mold). Mold has been causally implicated in both the development and exacerbation of asthma.

Disparities in mold exposures are exacerbated by climate change as more frequent extreme precipitation events, like Hurricane Sandy, disproportionately impact areas with higher risk of flooding and extreme precipitation and limited adaptation and resilience planning capacities. Despite the known adverse health impacts of mold, proprietors have little incentive to perform remediation. Mold remediations, especially those that are climate-resilient, targeting the root causes of water damage and mold growth, may be costly, often requiring replacement of pipe, roof, or ventilation systems.

Thus, the repairs needed to combat mold issues often go unaddressed. Residents of the NYC Housing Authority (NYCHA)—the largest public housing authority in North America, housing over 300,000 NYC residents —have long endured unabated, excessive mold exposures in their homes. These exposures likely contribute to their high rates of asthma morbidity. However, in 2019, under court order and federal oversight, NYCHA implemented ‘Mold Busters’—a comprehensive program aimed to remove mold in NYCHA developments. Some small-scale (n < 200) mold interventions suggest ‘Mold Busters’ could effectively reduce asthma morbidity.

This dissertation advances our understanding of intervening on mold on a large-scale to reduce asthma burden, particularly in the face of climate change. In Chapter 1, I discuss mold and its relevance to asthma in a changing climate. This includes an overview of the history of NYCHA, its mold and asthma burden, the ‘Mold Busters’ intervention, and the state of the evidence for intervening on mold to improve health.

In Chapter 2, we use Department of Health and Mental Hygiene (DOHMH) emergency department (ED) visit data to investigate the impacts of the ‘Mold Busters’ intervention by assessing: (a) the pre-intervention association between the rates of mold reports and asthma-related ED visits, (b) the impact of the intervention on mold reports, while considering neighborhood and development characteristics, and (c) the pre- and post-intervention rates of asthma ED visits in NYCHA compared to low-income, non-NYCHA controls. Prior to the ‘Mold Busters’ intervention (2016-2018), we found a positive association between the building-level rates of mold reports per 100 households and asthma-related ED visits per 100 residents (RR for 10-unit increase in mold reports per 100: 1.02, 95% CI: 1.00, 1.03), with the strongest relationship among older (40+) adults (any report: 1.03, 95% CI: 1.01, 1.05, repeat report: 1.05, 95% CI: 1.00, 1.10). Using latent class growth analysis (LCGA) we identified five subgroups in founded mold reports from 2019-2023 with groups A and C consistently experiencing highest rates of founded mold reports, groups B and D experiencing the largest decreases in mold rate with time, and group E consistently experiencing the lowest founded mold rates. Compared to groups B and D, group A and C buildings tended to be larger, older, more likely to lack mechanical ventilation, more likely to have flooding risks, and more likely located in higher poverty neighborhoods.

Using a doubly robust differences-in-differences approach, we found that the ‘Mold Busters’ intervention was associated with a significant decrease in asthma-related emergency department visits (average annual reduction of 8.6 per 1,000), again with the strongest effects among older adults and building groups that have been more amenable to mold reductions (groups B and D). These findings demonstrate strides towards reducing NYCHA’s mold burden with ‘Mold Busters.’ However, the LCGA group stratified analyses highlight that ensuring the benefits of the intervention reach all buildings may require further, targeted intervention for the poorest performing buildings. More effectively reducing these exposure disparities could lead to further improvements in asthma morbidity.

In Chapter 3, we investigated the impacts of extreme precipitation on ‘Mold Busters’ progress, while considering neighborhood, development, and building characteristics. In time-series analyses adjusting for weekly, seasonal, and long-term temporal trends, development and building correlation, and spatial confounding, we found an increased rate of founded mold reports in the week following extreme precipitation (RR 1.08, 95% CI: 1.03, 1.13) but same week and lagged (weeks 3- 4) decreases in founded mold reports. When considering only years 2022 and 2023—a time when reports already had substantially decreased and when post-COVID noise was reduced—we observed increases in mold reports 1-4 weeks following extreme precipitation events. Stratifying by LCGA groups revealed that extreme precipitation had the strongest effects on group A, which had the greatest overall burden and group D which had a large reduction in reports post intervention. We also identified increased reports when considering first-time reports only. These findings demonstrate a repetitive mold burden from extreme precipitation-related water intrusion, even from more common, less extreme (non-Hurricane or Superstorm caliber) storms, and suggest that, beyond exacerbating existing household mold issues, climate change is contributing to increased issues among new locations across NYCHA. This represents a threat to ‘Mold Busters’ progress.

In Chapter 4, we investigated fungal changes and their persistence from a single extreme precipitation event, Superstorm Sandy, among homes with mildly asthmatic NYC children. Comparing (n = 59) homes with damage to (n = 68) homes without damage, Sandy-damaged homes had lower fungal diversity (Shannon index) and higher total and allergenic fungal concentrations. In subsequent measures among damaged homes, fungal diversity increased (but remained lower than in non-damaged homes), and allergenic concentrations decreased over the following year. These findings demonstrate the lasting (> 2 year) persistence of asthma-relevant household fungal changes following extreme precipitation-related water intrusion.

In conclusion, from 2021-2023, the 2019, NYCHA-wide mold intervention, ‘Mold Busters,’ demonstrated decreases in mold reports and asthma burden across the NYCHA portfolio with health benefits driven primarily by older adults and buildings with the largest mold reductions. Climate change and its anticipated increases in water intrusion through extreme precipitation events could threaten the intervention’s progress. Ensuring the benefits of the ‘Mold Busters’ intervention reach all buildings may require further targeted, climate-focused intervention and continued collaboration between NYCHA and DOHMH.