Tests find new contaminants in Cape Cod’s drinking water supply, septic systems are likely the main source of the pollution

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Tests of 20 wells and two distributions systems supplying drinking water on Cape Cod found that 75 percent of the wells and both distribution systems had detectable levels of emerging contaminants such as pharmaceuticals and consumer product chemicals, primarily coming from septic systems. Nine water districts on Cape Cod voluntarily participated in the study. The study provides some of the first information in the U.S. about impacts of septic systems on groundwater used for drinking water.

Septic systems are the most likely source for most of the 18 chemicals detected, which include nine pharmaceuticals, an insect repellent, halogenated organophosphate flame retardants and highly fluorinated chemicals. The two most frequently detected chemicals were sulfamethoxazole, an antibiotic commonly used to treat urinary tract infections and pneumonia, and PFOS, used in stain-resistant and nonstick coatings, as well as fire-fighting foams. Levels of these compounds were among the highest reported in US drinking water, except in a few cases of industrial contamination. The widespread presence of antibiotics has raised the possibility of promoting development of antibiotic-resistant pathogens. PFOS and the related compound PFOA, which was also detected in this study, are hormone disrupting compounds that have been associated at higher exposure levels with effects on the thyroid, mammary gland, cholesterol metabolism, immune system, cancer, and growth and development.

“We found many contaminants in Cape Cod’s drinking water supply, indicating that current policies are not adequate to prevent emerging contaminants from getting into drinking water. Septic systems are the main source,” said Laurel Schaider, Ph.D., a research scientist at Silent Spring Institute. “Water suppliers who participated in this study are very forward-looking in their approach to protecting water quality for the future.” Monitoring for the test chemicals is not required and there are no regulatory standards for them.

The wells that had higher levels and more frequent detections of contaminants are located in more highly developed areas that have more septic systems, the primary source of the contamination. The test results provide evidence to support efforts by Cape Cod communities to protect “Zone I” and “Zone II” areas surrounding public wells by limiting development, buying up land, enforcing zoning restrictions and replacing septic systems with sewers.

While septic systems are likely the main source of the contaminants, some detected chemicals may have commercial sources. Two highly fluorinated chemicals, PFOS and PFOA, used in fire-fighting foams and aviation hydraulic fluids were found at relatively high levels in Hyannis Water System wells downgradient of the Barnstable Municipal Airport. Additional testing is required to pinpoint the sources.

A different study published recently by scientists at Boston University reported elevated breast cancer risk for women in the 1980s and early 1990s in Hyannis compared with other Upper Cape areas and associates this increase with contaminants in the Hyannis Water System supply.

None of the chemicals detected are federally regulated, nor do the vast majority have health guidelines set by the government to recommend maximum exposure levels. For compounds found in the water supply that do have voluntary health guidelines, including PFOS, PFOA, and a flame retardant, the detected levels did not exceed the guidelines at the time the study was conducted.* Overall, chemical concentrations detected in this study – which were in the range of 1-100 nanograms per liter – were lower than drinking water standards for other regulated chemicals, which are typically above 1000 ng/L. Pharmaceutical levels were also much lower than typical prescribed doses, which are generally above 100,000,000 ng/day (a typical individual drinks about 1-2 liters water/day). However, pharmaceuticals can be very potent and are not intended for the general population, and health-based guidelines and standards do not account for the impact of being exposed to multiple chemicals simultaneously or the impacts on more sensitive people (children, pregnant women, the elderly and those with health problems).

“The tests found contaminants in a well that supplies drinking water to my house. I’m concerned and hope our community will do more to protect our water,” said Farley Lewis, a Hyannis Port resident.

“While people may be tempted to drink bottled water, it’s not as thoroughly regulated as public drinking water, and there is evidence that chemicals in plastic bottles can leach into the water. A well-maintained carbon filter can reduce levels of many of the contaminants that were found in the water,” said Dr. Schaider.

Concerned Cape residents can support their local government’s actions to protect the land surrounding public wells. Individuals can also reduce contamination and their own exposure by properly disposing of unused medications and hazardous substances and by purchasing household products without chemical additives, such as stain-resistant coatings, flame retardants, antibacterial agents or fragrances.

The samples from the wells were taken in October of 2009, and a second phase of study will start in the fall, when Silent Spring Institute plans to begin testing for these same chemicals in private wells, which are likely to be more vulnerable to contamination by septic systems. “We know that the levels of nitrate – an indicator of septic system influences – are higher in many private wells than in the public wells. Since we found that levels of contaminants were higher in public wells with higher nitrate levels, we expect to find more contaminants in the private wells,” said Dr. Schaider. Public wells in the current study were selected to test locations expected to have contamination, based on nitrate measurements and land use in recharge areas, and to include some more pristine areas for comparison.

Funding for the study came from the Massachusetts Environmental Trust and the U.S. Centers for Disease Control and Prevention.

* Update: In May 2016, the Environmental Protection Agency (EPA) lowered its drinking water health advisory levels for PFOA and PFOS. As a result, the new levels—70 parts per trillion (ppt) for both chemicals, individually and combined—put one of the wells in the study above EPA's new guidelines.