In 2006, Silent Spring Institute researchers discovered that natural and synthetic hormones, as well as many pharmaceuticals, were in test wells down-gradient from a septic system plume on Cape Cod. The researchers then wanted to know if the chemicals travel in groundwater into ponds.
Silent Spring Institute researchers conducted a study of six Cape Cod ponds to determine whether hormone-disrupting and cancer-inducing chemicals have found their way from septic systems into the water. Ponds studied included three that were located in higher residential density areas (Lewis [Barnstable], Oyster [Falmouth], and Schoolhouse [Brewster]) and three located in lower residential density areas (Joshua [Barnstable], Flax [Dennis], and Flax [Brewster]).
The study found that Cape Cod ponds located near residential septic systems are contaminated by pollutants including human hormones and pharmaceuticals. Levels of estrogenic hormones approached those found to induce physiological changes in male fish. This is the first study to document the presence of pharmaceuticals and hormone disruptors in ponds fed by wastewater contaminated aquifers.