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Maryland Department of the Environment

MDE releases report on sampling for PFAS in St. Mary’s River surface water and oysters


No levels of concern found within study area; pilot study conclusions will assist MDE’s development of a comprehensive approach to PFAS


BALTIMORE (October 5, 2020) – A new report shows that sampling of surface water and oysters in the St. Mary’s River for per- and polyfluoroalkyl substances, or PFAS, found no levels of concern.

The sampling, done under a Maryland Department of the Environment (MDE) pilot study, found very low concentrations of PFAS in surface water in the St. Mary’s River and its tributaries near Naval Air Station Patuxent River (NAS Pax River) and found no detections of PFAS in oysters in those waters, according to MDE’s report. The pilot study is integral to MDE’s development of a comprehensive plan for PFAS, which includes sampling, soon to begin, of finished water from more than 130 public drinking water treatment systems across Maryland.

“The Maryland Department of the Environment is committed to developing a comprehensive plan for understanding, communicating and reducing unacceptable risk related to PFAS,” said Maryland Environment Secretary Ben Grumbles. “The results from the St. Mary’s River pilot study provide valuable information as we move forward in future monitoring of PFAS to protect the environment and public health.”

PFAS compounds are contaminants of emerging concern. Used since the 1940s, PFAS can be found in common household products (non-stick cookware, water resistant clothing, and personal care products), firefighting foams, at fire-training facilities and on military installations.The widespread use of PFAS and their ability to remain intact in the environment means that over time PFAS levels from past and current uses can result in increasing levels of environmental contamination, which may bioaccumulate throughout the food chain. Further research on these compounds continues as scientists work to understand their toxicity and impacts on human and environmental health.

MDE is putting a priority on developing a comprehensive plan for understanding, communicating, and reducing risks related to PFAS. This includes identifying and inspecting areas with the highest potential exposure risks such as drinking water, surface water, and fish and shellfish.

MDE is working with the U.S. Department of Defense and the U.S. Environmental Protection Agency to assess, remediate and monitor Department of Defense sites in Maryland where PFAS are or were present. The St. Mary’s River Study piloted an approach for determining the presence of PFAS in surface waters and oysters in the vicinity of NAS Pax River and its Webster Field Annex, where potential sources of PFAS may be present due to the use of firefighting foam. MDE worked in partnership with the Maryland Department of Natural Resources (DNR) on the pilot study.

Because there are no national standards for PFAS values for recreational waters, fish or shellfish, the agencies developed an evaluation method approach for water samples that included: a comparison to PFAS concentrations from a reference site on the Eastern Shore with expected low levels due to no known direct PFAS sources; a comparison to Maryland risk-derived PFAS recreational surface water screening concentrations based on accidental ingestion; and a comparison to the EPA PFAS drinking water lifetime health advisory level. A similar approach was used for oysters.

MDE’s sampling was done under strict quality assurance and quality control procedures, which is particularly important when sampling for PFAS because of the relatively high risk of cross-contamination of samples and the fact that human health levels of concern in drinking water are at part-per-trillion levels. Samples were collected in July and August throughout the study area.

The results for PFAS in surface water within the St. Mary’s River study, including near Webster Field Annex, showed very low concentrations, with most samples near the lowest concentration that can be reliably measured. The results showed no detections of PFAS compounds in oysters in the St. Mary’s River study area. These results are similar to the reported findings of another more limited study conducted in the spring of 2020, also in the St. Mary’s River.

MDE intends to next analyze fish tissue samples for PFAS. Starting this year, MDE will begin to sample for PFAS in recreationally caught fish species in several locations across the state as part of its established fish tissue monitoring program.

The report, “St. Mary’s River Pilot Study of PFAS Occurrence in Surface Water and Oysters,” is available on MDE’s website.


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