PFAS in Delaware

DNREC and the DHSS Division of Public Health are working with federal agencies to protect the environment and public health in Delaware from the effects of a group of synthetic chemicals known as PFAS.

Contact Us

DNREC Division of Waste and Hazardous Substances
Todd Keyser

DNREC Division of Water
Doug Rambo

DNREC Division of Watershed Stewardship
John Cargill

DHSS Office of Drinking Water
Steve Mann

Per- and polyfluoroalkyl substances (PFAS) include thousands of synthetic chemicals including PFOA, PFOS, and GenX. They have been used throughout the world in manufacturing, firefighting, and consumer products since the 1940s.

The state maintains a list of sites being investigated by DNREC for per- and polyfluoroalkyl substances (PFAS) in drinking water, groundwater or surface water in Delaware.

About PFAS

PFAS do not readily break down in the environment and can accumulate in living things. Some toxicological studies have found that exposure to these substances can cause serious health effects.

PFAS are considered “emerging contaminants” by federal environmental and public health regulators. A group of state and federal agencies are investigating PFAS, their sources, and their presence in the environment. This group includes DNREC, the Delaware Department of Health and Social Services (DHSS), the US Environmental Protection Agency (EPA), the US Geological Survey (USGS) and the CDC’s National Center for Environmental Health/Agency for Toxic Substances and Disease Registry.

In 2018, the DNREC Division of Waste and Hazardous Substances adopted a policy to define where sampling for PFAS may occur in groundwater and surface water within the state. In 2023, this policy was updated to include other media and add select PFAS as hazardous substances regulated under the Hazardous Substance Cleanup Act (HSCA), pertinent aspects of the addition, as well as expectations related to sampling and characterization of these emerging contaminants. (Learn more about the update)

In April of 2024, the EPA adopted a rule to designate PFOA and PFOS as hazardous substances under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) known as Superfund. The designation allows the EPA to investigate and clean up releases of these substances into the environment. A companion policy also directs the EPA to focus on parties that have manufactured PFAS or used PFAS in their manufacturing process. Learn more about the EPA final PFAS Cleanup rule.

DNREC also lists PFOA and PFOS as hazardous substances as well as six other PFAS compounds including:

  • Perfluorononanoic acid (PFNA)
  • Perfluorohexanoic acid (PFHxA)
  • Perfluorohexane sulfonic acid (PFHxS)
  • Perfluorobutanoic acid (PFBA)
  • Perfluorobutane sulfonic acid (PFBS)
  • Hexafluoropropylene oxide dimer acid (HFPO-DA, or GenX chemicals)

PFAS and Drinking Water

The federal Safe Drinking Water Act governs the quality and testing of all public drinking water supplied by water systems in the United States. The EPA works with states, localities and water suppliers to implement drinking water regulations. Drinking water supplied by public water systems (PWS) in Delaware is regulated by the DHSS Division of Public Health to ensure compliance with the National Primary Drinking Water Regulations.

The National Primary Drinking Water Regulations are legally enforceable standards and treatment techniques that include maximum contaminant levels (MCLs) for regulated contaminants.

EPA Proposes Drinking Water Regulations

Researchers continued to develop new and more effective methods to understand the possible health effects of PFAS. In April 2024, the EPA adopted Maximum Contaminant Levels (MCLs) for five PFAS compounds in Public Drinking Water Systems (PWS):

  • Perfluorooctanoic acid (PFOA) at 4 ppt
  • Perfluorooctane sulfonic acid (PFOS) at 4 ppt
  • Perfluorononanoic acid (PFNA) at 10 ppt
  • Perfluorohexane sulfonic acid (PFHxS) at 10 ppt
  • Hexafluoropropylene oxide dimer acid (HFPO-DA, or GenX chemicals) at 10 ppt

A Hazard Index (HI) of 1 has also been established for any sample containing a mixture of two or more of the PFAS compounds PFNA, PFHxS, HFPO-DA and PFBS (perfluorobutane sulfonic acid).

As of April 2024, the EPA has finalized Maximum Contaminant Levels (MCLs) in regulated Drinking Water for several PFAS. The details and timeframe are included in the Delaware PFAS Action Plan from the DHSS Office of Drinking Water.

Community water systems are required to report PFAS monitoring results in their annual Consumer Confidence Reports (CCR), beginning with the 2027 report.

Public drinking water systems must also start notifying the public of any PFAS monitoring or testing exceeding values.

Starting in 2029, public drinking water systems will have to comply with all MCLs and notify the public of all PFAS MCL violations.

Learn more on the EPA website.

Water systems that need assistance implementing the PFAS maximum contaminant levels can find information on options and potential financial assistance from the Department of Health and Social Services, Delaware Drinking Water State Revolving Fund (DWSRF). 

Learn more about how to apply for DWSRF funds.

Statewide Survey

DNREC and partners conducted statewide groundwater sampling groundwater through existing public potable wells based on a sampling plan that details the dynamic sampling approach and protocols used to conduct the survey.

The result of that sampling is a Persistent Pollutants Sampling Report that details the actions taken, significant detections and overall distribution of select PFAS compounds across Delaware.

Private Wells

Delawareans who do not have public drinking water generally get their water from private wells. Groundwater (water stored in aquifers below the surface of the earth), directly supplies all private wells. The Safe Drinking Water Act does not apply to drinking water from private wells.

Currently, when PFAS are detected in private drinking water in Delaware at concentrations above the EPA’s PWS established Maximum Contaminant Level (4 parts per trillion), DNREC and DHSS implement a response plan, which may include monitoring and studies to determine alternate sources of water and/or water treatment, to ensure that water supplies are safe to consume. These values have been used by DNREC and DHSS since the values were proposed by EPA in March 2023.

If you own a private well, the EPA recommends learning more about how to protect and maintain your well for all contaminants of concern.

Learn more about private wells, ground water and drinking water from the EPA.

Find information about private well classes and other water well owner resources.

PFAS Testing for Private Wells

Sampling for PFAS is best done by a professional. DNREC recommends using environmental consulting firms certified to perform work in Delaware under the Hazardous Substance Cleanup Act (HSCA), as well as DNREC-approved laboratories.

Laboratory analysis for PFOS and PFOA by EPA Drinking Water Method 537 may cost $400 or more. This does not include the cost of collecting the sample by the environmental consulting firm.

In-home Water Filtration Systems

Water contaminated with PFAS can be treated with carbon filters and reverse osmosis. The American National Standards Institute (ANSI) publishes standards (NSF/ANSI 53 and 58) related to the removal of PFAS through these systems.

The National Sanitation Foundation lists products it has certified to reduce PFOA/PFOS in drinking water.

PFAS and Surface Water

Surface water is withdrawn from a few rivers, streams and/or ponds in Delaware for purposes of public drinking water supply. The remainder of domestic water supply in the state comes from groundwater. Irrigation wells for agriculture extract significant quantities of groundwater during the growing season in certain parts of the state, as well.

Based on the generally sandy nature of the soils in the coastal plain of Delaware, shallow groundwater readily discharges to surface water, especially during seasonally high groundwater elevations in the winter and early spring when evapotranspiration is at a minimum. Baseflow in local streams and rivers is derived from shallow groundwater discharge.

As a consequence, any contaminants that may be present in groundwater (including PFAS) can be released to surface water through groundwater to surface water discharge.

PFAS and other toxic contaminants can also enter surface water through overland flow (i.e., stormwater runoff), through industrial discharges, and through atmospheric deposition.

Once in the surface water, contaminants can contribute to direct toxicity to fish and other aquatic life. Depending on several factors, some contaminants can also be taken up by local fish and other aquatic life in the process of bioaccumulation. This not only increases the body burden of the chemicals in the biota themselves, potentially causing impacts, but it also creates an exposure pathway to higher life forms like piscivorous birds (e.g., kingfishers, great blue heron, osprey, bald eagles), aquatic mammals (e.g., otters), and humans through the consumption of contaminated fish.

DNREC’s Watershed Approach to Toxics Assessment and Restoration (WATAR) team conducted a comprehensive statewide PFAS surface water study in the fall of 2022. Find more information about the study on the WATAR web page.

PFAS and Wastewater

Project Design and Sampling Plan Documents

Septic Pumpouts

Nationwide studies since the early 2000s indicate that PFAS exist in influent, effluent and residuals (biosolids) of wastewater treatment plants (Bogdan, D. 2021). Some of the most frequently detected PFAS were PFAAs (persistent perfluoroalkyl acids). This makes wastewater treatment plants important in managing and mitigating the environmental spread of PFAAs and a key participant in protecting both human and environmental health.

In Delaware, various wastewater streams (domestic, industrial and municipal) are treated and discharged into surface water bodies (NPDES discharges) as well as onto the ground surface, where it infiltrates the soil and ultimately enters groundwater (on-site wastewater discharges). Biosolids are land applied at numerous sites across the state.

DNREC’s Water Resource Protection team has started a statewide study of PFAS in wastewater.

Biosolids were selected to be examined first under a Biosolids Project Design and Sampling Plan. In December 2022, samples of biosolids (before being land applied), soils (from a selected land application site) and groundwater (from the monitoring wells installed at the selected site) were collected.

A Project Design and Sampling Plan for wastewater influent, effluent and discharge receival media (soil and groundwater) has been completed. Field sampling was expected to start in the summer of 2023. 

In addition, samples of septages from individual septic systems will also be collected and evaluated, under a Project Design and Sampling Plan for septages.