Emerging contaminants and groundwater

A new study by the U.S. Geological Survey of 118 groundwater wells in Minnesota found contaminants of emerging concern in over a third of water samples.  Roughly half of North Carolinians get our water from groundwater, and this study has interesting lessons for our state.
Based on data collected between 2009 and 2012, the USGS study found 35 different emerging contaminants out of a field of 125 for which the agency tested, ranging from steroidal hormones to pharmaceuticals to human and animal antibiotics.  The study explains: "Examples of CEC chemical classes include prescription and over-the-counter pharmaceuticals, fire retardants, pesticides, personal-care products, hormones, and detergents."  These contaminants have been associated with human and animal health impacts, including feminization of male fish. 

Some interesting take aways from the study include:

• Only 28 of the 125 tested-for chemicals have health-based water quality standards. Of the 35 detected, only 14 have standards; the others don't.  Four of the six most commonly-detected chemicals do not have standards.  As a practical matter, this means that federal and state regulatory programs intended to protect drinking water or surface water quality simply won't address this contamination.

• As the USGS study notes, groundwater provides the base flow for surface streams, rivers, and reservoirs.  So, contaminants in groundwater now can be expected to show up in surface water in the future as well.

• Some of the wells sampled for the study draw from surficial aquifers in highly porous glacial sediments; others draw from groundwater in cracks in bedrock.  In North Carolina, wells in the coastal plain tend to draw from porous sands; in the Piedmont and mountains, from cracks in bedrock. Contamination showed up in both kinds of wells in Minnesota.

• The antibiotic sulfamethoxazole was the most frequently detected contaminant, and was found disproportionately in wells near active septic systems. But, in general, wells in deep bedrock, and in areas with sewer service, had a higher percentage of detections of contaminants, suggesting leakage from sewer pipes or infiltrating stormwater.

Minnesota Public Radio's coverage is here.  It would be a good idea for North Carolina's environmental managers to pursue a similar study of wells and surface waters here, and to begin thinking about the health implications of having these emerging contaminants so broadly present in our water supplies.