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​Contaminants of Emerging Concern (CECs)


DEP has initiated a study to examine contaminants of emerging concern (CECs) in streams and rivers of the state. CECs are any contaminants that are new to the environment or have been around for a long time but are just now able to be studied due to advances in laboratory techniques. In addition, they are not likely to have any associated water quality criteria, which makes controlling these contaminants difficult. 

Some of the first work on CECs was initiated with a study in cooperation with United States Geological Survey (USGS) in 2006-2009: Occurrence of Pharmaceuticals, Hormones, and Organic Wastewater Compounds in Pennsylvania Waters, 2006-09. In 2012, DEP began sampling streams and rivers for a variety of CECs.

Click below to view a summary of work conducted by DEP from 2012 through 2016:

Emerging Contaminant Sampling in the Susquehanna River Basin – Sediment & Passive Water Sampling

Per- and Polyfluoroalkyl Substances (PFAS)

In 2019, DEP and USGS coordinated on a sampling effort of PFAS at each surface water quality network (WQN) station. Sampling continued in 2020 – 2023 at a subset of stations, and a summary of the data collected was completed: Surface Water PFAS Summary (2019 - 2023). Data collected in the study are located here: USGS PFAS Data (2019) and WQN PFAS Data (2020 – 2023).

Passive Samplers

To characterize the distribution of CECs across Pennsylvania, the DEP began sampling many different groups of compounds in a variety of ways. Since many of these compounds occur at very low levels that could still impact protected uses, passive water samplers were used to collect many of the samples. Passive samplers are placed in the water column for a length of time, typically about a month, and then retrieved. Contaminants collect on filters or membranes and are then analyzed in a lab. Leaving these out for a long period of time allows low-level contamination to be detected. Passive samplers can also capture any brief periods of higher concentrations that may be otherwise missed with a discrete sample. 

Analyses of passive sampler data from 2013 through 2017 are summarized in a Story Map and interactive mapping document located here: Passive Sampler Story Map. An in-depth document of the same 2013 through 2017 analyses is located at: Passive Sampler Analyses 2013 - 2017. Data from the study is located at: Passive Sampler Data 2013 – 2017.

Contaminants in Sediment

Some compounds have the potential to accumulate in streambed sediments and could affect macroinvertebrates or fish that live close to or on sediment. In addition, during storm or high flow events, sediments can be lifted into the water column and affect organisms, as well as travel downstream. Because of this, sediment was also tested for a variety of compounds. A pilot study of polycyclic aromatic hydrocarbons (PAHs) was conducted on sediment in Conodoguinet Creek, Cumberland County: Polycyclic Aromatic Hydrocarbons (PAHs) Pilot Study in Conodoguinet Creek, Southcentral Pennsylvania.

Analyses of sediment data from 2013 through 2017 are summarized in a Story Map and interactive mapping document located here: Sediment Story Map. An in-depth document of the same 2013 through 2017 analyses is located at: Sediment Analyses 2013 - 2017. Data from the study is located at: Sediment Data 2013 – 2017.

Endocrine Disrupting Compounds (EDCs)

Some CECs are also endocrine disrupting compounds (EDCs). EDCs are compounds that impact an organism’s endocrine system by either promoting or inhibiting processes to occur. This can cause a multitude of problems, the most famous example being male fish growing egg precursors in a phenomenon known as intersex.

Total estrogenicity of samples shows the concentration of all compounds that could affect estrogen receptors and, therefore, be EDCs, as described above. It is not possible to determine what compounds compose the results unless additional sampling is conducted, but it is a very good way to characterize a site. Total estrogenicity has been tested using both passive and grab water samples. 

Neonicotinoid Insecticides

In addition to the above work, pilot studies are completed when specific needs arise. One such study examined the occurrence of neonicotinoid pesticides in surface water. Neonicotinoid pesticides are used in a wide variety of ways, commonly applied to seeds and soil to protect seedlings and sprayed directly on leaves to protect mature plants. They are applied to nearly all corn seeds in North America and are commonly used by homeowners. As with any insecticide, concern exists over its effects to non-target organisms. Sub-lethel effects on vertebrates and non-target invertebrates, particularly bees, have been seen. In addition, aquatic macroinvertebrates have been shown to be sensitive to neonicotinoids at low concentrations. Macroinvertebrate samples are used by DEP to help determine water quality and are very important. As a result, DEP decided to conduct a pilot study examining the occurrence and concentrations of neonicotinoids in agricultural streams of southcentral Pennsylvania: Neonicotinoid & Sulfoximine Insecticides in Flowing Surface Water Pilot Study.