PDS 75: Microbiome, infections and respiratory effects, Johan Friso Foyer, Floor 1, August 27, 2019, 1:30 PM - 3:00 PM Background: The link between the external and internal microbiological communities on host health is an emerging area of scientific inquiry. Gut dysbiosis or the unequal balance of healthy and unhealthy microbes has been associated with numerous inflammatory, metabolic and immune disorders. Urban environments are thought to be less diverse than rural environments, but the health impacts of these differences are poorly understood. The aim of this study is to examine urban and rural factors predicting gut microbial diversity among a randomly selected population-based sample of adults. The geographically diverse sample includes unique opportunities to explore differences in both urban and rural communities in which air pollution and drinking water sources vary considerably. Methods: Participants included adults over the age of 18 from the 2016 Survey of the Health of Wisconsin (SHOW) and its ancillary microbiome study. SHOW is a general population-based health examination survey, collecting a wide range of health determinants including drinking water sources and filtration, as well as objective measurements of body habitus, and biological specimens. Residents can be linked to numerous extant data including downscaled air monitoring and drinking water source data. Data for this analysis came from participants who also submitted a stool sample and completed a microbiome survey questionnaire. Results: Using carefully adjusted models, among 466 participants, gut microbial α-diversity and richness were associated with higher income, older age, and urbanicity. Water filtration use was only associated with α-diversity among rural residents, 98% private-well users. Similarly, β-diversity was associated with water filter use for those with increasing income level. In contrast, low-level ambient-air pollution was not associated with an altered gut microbial composition in either context. Conclusion: Results suggest urban and rural sources of water and air pollution may contribute to differences in microbial diversity, additional research is needed to fully understand the health impacts.