Can Green Infrastructure Decrease Gastrointestinal and Mosquito Borne Illnesses in Areas Surrounding Combined Sewer Overflows?

Combined sewer systems (CSS) are used by over 750 cities in the United States. They collect storm and sewer water into the same pipes for transport to a wastewater treatment plant. Combined sewer overflows (CSOs) occur during large storm events, when increased volume and flowrate of stormwater runoff cause CSS pipes to exceed capacity. CSOs pose a health risk because they can expose the public to untreated sewage. Numerous pathogens that may cause gastrointestinal illnesses including Ecoli, cryptosporidium, and giardia have been identified in CSOs and/or waterbodies downstream. In addition, waterbodies affected by CSOs are organically rich and lack oxygen and predators making them favorable breeding environments for mosquitoes. Mosquitoes are vectors for illnesses such as West Nile and Zika. Green Infrastructure (GI) is traditionally used for low-impact stormwater management and may mitigate the health effects of CSO by decreasing the flow rate and volume of stormwater runoff that flows into CSS pipes. This could decrease CSO volume and frequency. GI may also mitigate health effects of CSO via filtration and bioremediation, thereby improving the runoff water quality. I research whether GI can decrease gastrointestinal and mosquito borne illness hospital admissions in areas with CSO outfalls within Washington DC. Twenty different types of 16,184 total GI sites specific to Washington DC will be analyzed in this study. The health outcomes will be studied based on proximity to the 53 CSO outfall locations and catchment waterbodies. Socio-demographic confounders including race, income, education, sex, and age will be considered and interaction variables will be introduced with the assessment of effect modifiers. Wet/dry weather and land characteristics such as impervious surface and water cover will also be factored into the models. This study will be the first to quantify the mitigation impacts of GI on aliments related to CSOs. Findings from this study can inform policy makers of whether GI can be implemented to help combat gastrointestinal and mosquito borne diseases in areas with CSOs.