Emerging Contaminants in Cape Cod Private Drinking Wells

In February 2011, Silent Spring Institute tested 20 private drinking water wells in 7 towns on Cape Cod for emerging contaminants to learn more about the effect of septic systems and other sources of groundwater pollution on water quality on the Cape.

Emerging contaminants include chemicals such as pharmaceuticals and consumer product chemicals that may have health effects but are not currently regulated or routinely studied in drinking water. This study is a follow-up to our 2010 study of emerging contaminants in Cape Cod public wells. We tested for 121 chemicals including pharmaceuticals, hormones, personal care products, perfluorinated chemicals, flame retardants and alkylphenols. Many of the target compounds have been found in other U.S. drinking water supplies and some are thought to be endocrine disrupting chemicals, which can mimic or interfere with the behavior of natural hormones.

A majority (85%) of samples contained emerging contaminants at parts per trillion levels. As in our public well study, these results show that chemicals in household and commercial wastewater can seep from septic systems into groundwater and make their way into drinking water. In general, results were similar in public and in private wells. Many of the same chemicals were detected in both studies, and maximum concentrations of these chemicals were generally similar. In both private and public Cape Cod drinking water wells, we found some compounds present at levels as high or higher than reported elsewhere in the US.

Our results demonstrate widespread impact of wastewater, primarily from septic systems, on Cape groundwater and drinking water. While there are no enforceable drinking water standards for emerging contaminants, health-based guideline values have been developed for four of the detected chemicals; levels in all samples were below guideline values. However, guideline values are not available for most of the chemicals we detected, and health effects of exposure to low levels of these types of chemicals, especially in complex mixtures, are not yet known.