Septic systems, but not sanitary sewer lines, are associated with elevated estradiol in male frog metamorphs from suburban ponds.

Suburban neighborhoods are a dominant type of human land use. Many housing regions globally rely on septic systems, rather than sanitary sewers, for wastewater management. There is evidence that septic systems may contaminate waterbodies more than sewer lines. There is also mounting evidence that human activities contaminate waterways with endocrine-disrupting chemicals (EDCs), which alter wildlife sexual development. While endocrine disruption is often associated with intense activities such as agriculture or wastewater treatment plant discharges, recent evidence indicates that endocrine disruption is pervasive in frogs from suburban neighborhoods. In conjunction with other putative EDC sources, one hypothesis is that wastewater is contaminating suburban waterways with EDCs derived from pharmaceuticals or personal care products. Here, we measure estradiol (E2) in metamorphosing green frogs (Rana clamitans) from forested ponds and suburban ponds adjacent to either septic tanks or sanitary sewers. We show that E2 is highest in male frogs from septic neighborhoods and that E2 concentrations are significantly lower in male frogs from forested ponds and from ponds near sewers. These results indicate that septic tanks may be contaminating aquatic ecosystems differently than sewer lines. This pattern contrasts prior work showing no difference in EDC contamination or morphological endocrine disruption between septic and sewer neighborhoods, implying that suburbanization may have varying effects at multiple biological scales like physiology and anatomy.