PFAS contamination in Delaware

PFAS contamination in Delaware represents among the most significant environmental and public health challenges facing the state in the twenty-first century. Per- and polyfluoroalkyl substances — a broad class of thousands of synthetic chemical compounds characterized by extremely strong carbon-fluorine bonds — have been detected in drinking water supplies, surface water, groundwater, and soil across multiple counties and municipalities in Delaware. Because these compounds resist biological degradation and accumulate in living tissues over time, they have earned the informal designation "forever chemicals," a phrase that underscores the persistence of contamination once it enters an ecosystem. Delaware's small geographic size, dense population relative to land area, and reliance on both surface water and groundwater for municipal and private drinking supplies make the presence of PFAS a matter of acute concern for residents, regulators, and public health officials alike.

History

The history of PFAS contamination in Delaware is intertwined with the broader national story of industrial fluorochemical production and military use of aqueous film-forming foam, commonly known as AFFF. PFAS compounds were developed in the mid-twentieth century for applications ranging from non-stick cookware coatings to firefighting agents. Industries along the Delaware River corridor, including chemical manufacturing facilities that have historically operated in the region, contributed to the gradual accumulation of these substances in the environment over decades. For much of that period, the long-term health and environmental consequences of PFAS exposure were not well understood by regulators or the general public.

Scientific understanding of PFAS toxicity advanced considerably in the late 1990s and early 2000s, as epidemiological research began to associate chronic exposure to certain PFAS compounds — particularly perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) — with a range of adverse health outcomes. These include increased risk of certain cancers, thyroid disease, immune system suppression, elevated cholesterol, and developmental problems in children. As awareness grew, state environmental agencies across the country, including Delaware's Department of Natural Resources and Environmental Control (DNREC), began investigating sources of contamination and developing regulatory frameworks to address them. Delaware's investigation process accelerated during the 2010s as federal guidance from the United States Environmental Protection Agency (EPA) began to coalesce around health advisory levels for PFAS in drinking water.

By the early 2020s, Delaware had identified contamination at or near several military installations, former industrial sites, and municipal water systems. The presence of PFAS near Dover Air Force Base, one of the largest military air mobility installations in the United States and a major economic and military fixture of Kent County, drew particular attention. Firefighting training activities at military airfields historically relied heavily on AFFF, which contains high concentrations of PFOS and related compounds. Monitoring data revealed that PFAS had migrated from base activities into surrounding groundwater, raising concerns for nearby communities that draw drinking water from wells and aquifers in the vicinity.

Geography

Delaware's geography creates particular vulnerabilities to PFAS contamination. The state sits on the Delmarva Peninsula and is bordered by the Delaware River and Delaware Bay to the east, the Chesapeake and Delaware Canal to the north, and Maryland to the west and south. Much of the state's land area sits atop the Atlantic Coastal Plain, a geologic formation characterized by sandy, permeable soils and shallow aquifer systems. These hydrogeological conditions mean that contaminants introduced at or near the surface can migrate relatively quickly into groundwater, which serves as the primary drinking water source for a significant portion of Delaware residents, particularly in rural and suburban areas outside major urban centers like Wilmington.

The three counties of Delaware — New Castle County in the north, Kent County in the center, and Sussex County in the south — each present distinct contamination profiles. New Castle County, which contains Wilmington and is more industrialized, has faced scrutiny related to industrial PFAS sources and proximity to chemical manufacturing corridors. Kent County, home to Dover Air Force Base and the state capital of Dover, has been a focus of military-related PFAS investigations. Sussex County, which is predominantly agricultural and has seen rapid residential growth along its Atlantic coastline, faces concerns related to both agricultural applications of PFAS-containing materials — including biosolids used as fertilizer — and proximity to smaller industrial and military sites. Taken together, contamination concerns span the length and breadth of the state, rather than being confined to a single region.

Waterways play a dual role in Delaware's PFAS challenge, serving both as pathways for contamination and as resources that require protection. The Christina River, the Brandywine Creek, the St. Jones River, and numerous smaller drainage ditches and wetlands have been monitored for PFAS levels. Because Delaware is a downstream state relative to many of its regional neighbors, contamination originating in Pennsylvania and other upstream jurisdictions can also influence water quality within Delaware's borders, complicating both source attribution and regulatory response.

Economy

The economic dimensions of PFAS contamination in Delaware are substantial and multifaceted. Costs arise from water treatment infrastructure upgrades, ongoing environmental monitoring, public health interventions, and potential litigation involving responsible parties. Municipal water utilities facing PFAS detections above regulatory thresholds have been compelled to invest in advanced treatment technologies, including granular activated carbon filtration and high-pressure membrane systems, both of which carry significant capital and operational expenditures. For smaller water systems and private well owners, these costs can be prohibitive without state or federal assistance programs.

Delaware's agricultural sector, which is concentrated in Sussex County and parts of Kent County and contributes meaningfully to the state's economy through poultry production, grain farming, and associated industries, has faced growing scrutiny regarding the use of biosolids as soil amendments. Biosolids — the treated solid material remaining after municipal wastewater treatment — can contain elevated concentrations of PFAS if the source wastewater contains contributions from industrial or commercial operations that use or manufacture PFAS. The application of contaminated biosolids to farmland can introduce PFAS into soils and subsequently into crops, livestock, and groundwater, creating risks both for farm families and for downstream water users. Concerns about agricultural PFAS pathways have prompted calls for tighter regulation of biosolids application and more rigorous testing regimes.

The real estate and property markets in affected areas face uncertainty as awareness of PFAS contamination grows. Property values near contaminated sites or in areas where private well contamination has been documented can be adversely affected, and disclosure requirements during real estate transactions create additional complexity for buyers, sellers, and lenders. The long-term economic consequences for communities near major contamination sites represent an ongoing area of concern that intersects with questions of environmental justice, as lower-income communities and communities of color are frequently situated closer to industrial and military facilities that are common PFAS sources.

See Also

Delaware's regulatory and legislative response to PFAS contamination has evolved in tandem with federal action and scientific consensus. The state's DNREC has undertaken extensive monitoring programs to characterize the distribution and concentration of PFAS in Delaware's water resources. The Delaware Division of Public Health has worked to communicate health guidance to residents with private wells in affected areas, including recommendations for alternative water sources while remediation or treatment solutions are evaluated. Delaware has also been an active participant in multi-state discussions regarding PFAS regulation, contributing to regional frameworks aimed at achieving consistent standards across neighboring states that share watershed resources.

Legislative action in the Delaware General Assembly has addressed PFAS from several angles, including requirements for PFAS testing in public water systems, restrictions on the use of AFFF in non-emergency training exercises, and provisions aimed at holding polluters accountable for remediation costs. Advocacy from environmental organizations, affected community groups, and public health researchers has been instrumental in advancing legislative priorities and maintaining public attention on the issue. Delaware's congressional delegation has also supported federal measures, including EPA rulemaking establishing enforceable maximum contaminant levels for certain PFAS compounds in public drinking water, which was advanced during the early 2020s and represents a significant shift from the previously advisory-only federal framework.

Remediation of PFAS-contaminated sites presents formidable technical and logistical challenges. Unlike some environmental contaminants that can be broken down through conventional biological or chemical treatment methods, PFAS compounds are extraordinarily resistant to degradation. Emerging treatment technologies, including electrochemical oxidation, sonochemical destruction, and supercritical water oxidation, offer potential pathways to PFAS destruction but remain largely experimental or early-stage at full scale. In the interim, containment strategies, pump-and-treat systems, and point-of-use filtration remain the primary tools available to protect affected communities. Delaware's experience navigating these challenges reflects the broader national struggle to develop adequate responses to a class of contaminants for which the regulatory, technological, and legal frameworks are still catching up to the scale of the problem.

Related topics of interest include environmental regulation in Delaware, Delaware Department of Natural Resources and Environmental Control, Dover Air Force Base, drinking water quality, and Superfund sites in Delaware.