While environmental exposures are known to play a significant role in human disease, these effects are understudied compared to genomic and molecular components of disease. One example is the effect of chronic, low-level exposures to cyanobacteria toxins on health outcomes. Here we perform a retrospective analysis on real-world data in the National Clinical Cohort Collaborative (N3C) COVID Enclave, examining the possible impact of chronic exposure to cyanobacteria toxin on the severity of COVID-19 outcomes in patients from Colorado. We combined data from N3C, satellite data from the USEPA CyAN project, and field observations from the Colorado Department of Public Health & Environment (CDPHE). Our results show that COVID-19 patients living near recurring cyanobacteria blooms had 2.75 times higher odds of experiencing severe outcomes (hospitalization or death) than individuals who do not. In addition, living in a county with low to middle levels of poverty had protective effects. Further work is needed to understand the precise mechanism of action and fully understand the long-term risk of chronic exposures to low-level cyanobacteria toxins on health outcomes. International Committee of Medical Journal Editors (ICMJE) Statement: Authorship was determined using ICMJE recommendations. IRB: 24-2680 DUR ID: DUR-15EB88A.