Human Hormones and Pharmaceuticals Contaminate Ponds in Residential Areas with Septic Systems

July 10, 2010

Research Area: 

Chemicals Detected May Harm Fish Reproduction—Human Health Risk Uncertain

Newton , MA – A new peer-reviewed study to be published online on July 10 in Environmental Toxicology and Chemistry shows that ponds located in residential areas where septic systems predominate are contaminated by a variety of pollutants that may be harmful to wildlife and pose unknown risks to human health. Water quality in these groundwater-fed ponds is an indicator of what’s in the surrounding aquifer, which is the sole source of drinking water.

Scientists from the Silent Spring Institute monitored pharmaceuticals and hormone-disrupting chemicals including natural estrogen in ponds on Cape Cod, Massachusetts, in areas with high septic system use. Human health effects of detected contaminants may include reproductive disorders and hormonal cancers, as well as effects such as antibiotic resistance. The two largest routes of exposure to the pollutants in the ponds may be drinking water and swimming in the ponds.

Because septic systems do not completely remove pharmaceuticals and other hormones, these contaminants make their way into groundwater, which is often used for drinking water, and into ponds. More than 85 percent of residential and commercial properties on Cape Cod are serviced by septic systems. The study tested six ponds; half of the study ponds were located in areas with a high density of residential septic systems and half in areas with few or no septic systems nearby.

Researchers detected both a greater number and higher concentrations of contaminants in samples from ponds in higher residential density areas. Contaminants most often detected were the steroidal hormones androstenedione, estrone, and progesterone, and the pharmaceuticals carbamazepine (antiepileptic), pentoxifylline (used to improve blood flow in patients with circulation problems), sulfamethoxazole (antibiotic), and trimethoprim (antibiotic). Of particular concern, estrogenic hormones were present at concentrations approaching those that induce physiological responses in fish.

The presence of hormone-disrupting chemicals and pharmaceuticals in rivers and streams has been associated with feminization of male fish and reductions in their ability to escape predators. Further research is needed to determine whether the concentrations typically observed in the environment produce adverse effects on humans. In laboratory studies of mammals, exposure to natural hormones and hormone-disrupting chemicals can result in cancer and adverse effects on reproduction, especially when given during critical prenatal and childhood reproductive development stages. While pharmaceuticals are considered to have benefits that outweigh the health risks in populations taking
these drugs, many questions remain unanswered as to the potential for adverse effects in the general population, even at much lower exposure levels.

Previous research on hormone disruptors and other organic wastewater contaminants has focused on surface waters receiving discharges from wastewater treatment plants. In contrast, this is the first study to document the presence of pharmaceuticals and hormone disruptors in ponds fed by wastewater-contaminated aquifers and at levels previously determined to change the reproductive physiology of fish.

With housing density leapfrogging construction of infrastructure such as centralized wastewater and drinking water services, there is an increased likelihood that wastewater from on-site septic systems will contaminate aquifers that feed drinking water wells and are interconnected with surface water bodies, such as ponds and lakes. The Silent Spring researchers also detected lower levels of a few of the chemicals in water collected from ponds that do not have nearby septic systems but are used for recreation, indicating that recreational use is another source of some of the chemicals.

Lead researcher for the Silent Spring study, Laurel Standley said, “It is worrisome that we are finding these contaminants in groundwater-fed ponds. Septic systems are not getting rid of pharmaceuticals and hormones, and these contaminants are getting into the groundwater that is used extensively for drinking water. For an area relying so heavily on commercial and residential septic systems, this is of great concern.” Many questions remain about effects of some of these chemicals, particularly when they are present as mixtures, as documented in these ponds.

Silent Spring’s findings support efforts by communities to consider more restrictive land use policies to protect water quality in aquifers that supply ponds and drinking water wells. Communities may also consider replacing on-site septic wastewater treatment systems with improved on-site technologies or centralized wastewater treatment plants tested specifically for their ability to remove pharmaceuticals and endocrine disrupting chemicals. Technologies to remove these contaminants from wastewater or drinking water treatment plants are under development, but little attention has been paid to developing on-site treatment technologies for the regions where septic systems dominate.

(617-332-4288, ext. 226), (Embargoed until 7/10, 12:01 a.m.)

The study, which was published online on July 10, 2008, also appears in the November 2008 print edition of Environmental Toxicology and Chemistry.