This presentation addresses Sustainability Goal 6: to ensure access to water and sanitation for all. Specifically, this presentation will discuss public and environmental health implications of sea level rise for onsite wastewater treatment systems (commonly called septic systems). Billions of people worldwide rely on septic systems to collect and treat household waste. Yet recent data from the United Nation finds that many septic systems are not adequately treating pathogens and other contaminants. The proportion of inadequately functioning septic systems is expected to increase under sea level rise scenarios. One reason for this is that sea level rise will cause groundwater rise in many coastal and low-lying areas. This groundwater rise will reduce the zone of unsaturated soil under septic systems and diminish the soil’s ability to transform and remove pollutants, including wastewater-borne pathogens. This presentation provides brief background on how septic systems remove pathogens and how their functioning is being impaired by climate change, and then presents results on new research that combines sea level rise projection data with septic system distribution data for Small Island Developing States worldwide. The results show high vulnerability to public and environmental health threats for numerous locations, especially small islands in the Pacific and Caribbean.