Forty percent of U.S. residents rely on groundwater for their drinking water. However, groundwater, especially unconfined sand and gravel aquifers, is vulnerable to contamination.
child with glass under faucet

In recent years, traces of pharmaceuticals and other contaminants have been found in drinking water supplies throughout the country. Contaminants in wastewater make their way into drinking water supplies when discharges from septic systems and wastewater treatment plants are released into groundwater, rivers and lakes. Some of the chemicals found in drinking water are endocrine disrupting compounds (EDCs), chemicals that can mimic the behavior of estrogens and other hormones in the body. There are concerns about the potential impact of these chemicals on human health. While some assessments conclude that health effects are unlikely at current exposure levels, there is growing evidence that some EDCs can produce effects at low levels of exposure that are not apparent at higher levels.

In a landmark study conducted in 2009, Silent Spring Institute collaborated with nine public water suppliers on Cape Cod to learn more about how septic systems and other sources of groundwater contamination affect water quality. Drinking water for Cape Cod residents comes from a sole-source aquifer. Because the Cape has a shallow water table and sandy, porous soil, the aquifer is particularly vulnerable to land use activity. Our water testing results revealed pharmaceuticals, hormones, personal care products, herbicides, alkylphenols, flame retardants and highly fluorinated chemicals present in Cape drinking water. The study provided some of the first information in the U.S. on the impacts of septic systems on groundwater used for drinking water. 

Through our work tracking contaminants in public water supplies, Silent Spring researchers are providing new information about contamination of by septic systems and other pollution sources. The goal is to inform drinking water regulations and wastewater management decisions in order to protect drinking water quality and ecosystem health, now and for future generations.

News & Updates


Study reveals efforts to address widespread PFAS contamination affecting millions of Americans


Researchers trace possible sources to fire training areas, airports, industrial sites, and wastewater treatment plants.


Study is among the first to examine the impact of septic systems on groundwater used for drinking supplies