​Contaminants of Emerging Concern (CECs)

​​Preface

DEP’s Division of Water Quality has studied contaminants of emerging concern (CECs) in streams and rivers throughout the Commonwealth, from as early as 2006. CECs are any contaminants that are new to the environment, have been present in the environment for some time but only recently brought to the forefront of attention, or are only recently able to be studied due to advances in laboratory techniques. In addition, CECs often do not have associated water quality criteria, which makes limiting these contaminants difficult. One of the first studies of CECs was completed in cooperation with the U.S. Geological Survey from 2006−2009, as reported in: Occurrence of Pharmaceuticals, Hormones, and Organic Wastewater Compounds in Pennsylvania Waters, 2006−09.

DEP uses different collection protocols to study and characterize the distribution of CECs across Pennsylvania. Since many of these compounds occur at very low levels that could still impact protected uses, passive water samplers were deployed 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 collected on filters or membranes within the passive samplers are then analyzed in a lab. Leaving these submerged for a long period of time allows for the detection of low-level contaminants. Passive samplers can also capture brief periods of higher concentrations that may otherwise be missed in a discrete sample. Analyses of passive sampler data from 2013−2017 are summarized in a Story Map and interactive mapping document located at: Passive Sampler Story Map. An in-depth document of the same 2013−2017 analyses is located at: Passive Sampler Analyses 2013−2017. Data from the study is located at: Passive Sampler Data 2013−2017. Other collection methods have included sediment sampling and filtering large volumes of lotic (flowing) surface waters.

Additional information on the CECs that DEP has focused on through the present day is provided below for the following:

• Contaminants in Sediment
• Endocrine Disrupting Compounds (EDCs)
• Microplastics
• Neonicotinoid Insecticides
• Per- and Polyfluorinated Alkyl Substances (PFAS)

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 2014−2016 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 2013−2017 are summarized in a Story Map and interactive mapping document located here: Sediment Story Map. An in-depth document of the same 2013−2017 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. In addition to surface water, estrogenic compounds could be present in springs and groundwater.

A 2019−2020 pilot study of the concentrations of total estrogenicity in Pennsylvania springs was conducted. Results were reported in: Total Estrogenicity in Springs Across Pennsylvania (2019-2020). 

Microplastics

Microplastics (MPs) have been found in every type of environment throughout the world, and research has found them to pose risks to aquatic life and human health. MPs are solid, synthetic polymeric particles ranging from 20 µm-5 mm and are categorized as primary or secondary. Primary MPs are manufactured to be small, such as nurdles and microbeads, and secondary MPs are products of weathering or degradation from larger plastic items, such as fragments from plastic bags. Aquatic life can mistake MPs as food, which (upon ingestion) replace nutrient-rich foods and can deliver adsorbed toxic chemicals to the animal. The extent to which MPs are harmful to human health is not yet well understood, but through ingestion of food and beverages or through inhalation, MPs may cause unwanted immune and stress responses and reproductive and developmental toxicity.

In 2025, DEP collected MPs from lotic surface waters through a case-study type sampling plan. This study was the initial step in developing MP data collection protocols and in gaining a better understanding of the breadth of MPs present in streams throughout the Commonwealth. Results of this study were described in: Microplastics 2025 Data Collection Protocol Development and Pilot Study in Lotic Surface Waters: Report.

Neonicotinoid Insecticides

A 2016−2017 pilot study examined the occurrence of neonicotinoid pesticides in surface waters. 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 conducted the 2016-2017 pilot study in agricultural streams of southcentral Pennsylvania: Neonicotinoid & Sulfoximine Insecticides in Flowing Surface Water Pilot Study.

Per- and Polyfluorinated Alkyl 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). To this day, DEP and its partners continue to collect PFAS data, which will be used to assess and protect water quality.

The 2019 sampling effort was analyzed in different ways and two publications were produced. The first one focuses on sample results and possible land use relationships, which are described in: Per- and Polyfluorinated Alkyl Substances (PFAS) in Pennsylvania Surface Waters: A Statewide Assessment, Associated Sources, and Landuse Relations. The second publication delves deeper into the anthropogenic and environmental variables affecting PFAS contamination through machine learning models and is reported here: Predicted Potential for Aquatic Exposure Effects of Per- and Polyfluorinated Alkyl Substances (PFAS) in Pennsylvania’s Statewide Network of Streams.