Chemicals trouble Delaware River tributaries

We have our work cut out for us.

A recent report from the scientists at the Delaware River Basin Commission indicates there is a significant presence of toxic chemicals in the tributaries that feed the Delaware River Estuary.

The presence of these chemicals, which stem from past and current use, is not exactly news in the urban section of the river from south of Trenton, N.J., to Wilmington, Del., but the report offers data not previously collected.

“It provides another set of data points,” said Diane Schrauth, policy director for water at New Jersey Future. She said that New Jersey is largely aware of pollution problems from petrochemicals and the chemical industry.

She noted that New Jersey is known as “a hot spot” for the class of “forever chemicals” known as PFAS, and added, “This data is important to understanding exactly what the problems are.”

We are already worried about what you might call the marquee toxins, like PFAS, and its many siblings, as well as PCBs in our water supply.

But there are, unfortunately, others.

The DRBC sampled surface water in 12 tributaries of the Delaware Estuary in the fall of 2023 for various hazardous substances, including per- and polyfluoroalkyl substances (PFAS), polychlorinated biphenyls (PCBs), dioxins and furans (DxF), organochlorine insecticides (OC), neonicotinoids, pyrazoles and polycyclic aromatic hydrocarbons (PAHs).

From the report, which was released in April: “Compounds from all pollutant groups analyzed were present in each tributary, albeit at varying concentrations. Exceedances of USEPA and/or DRBC Human Health Surface Water criteria were found for four different PAH compounds, eight OC compounds and for the total concentration of PCBs.”

Yes, that’s lots of science. If some of those multisyllabic compounds are of concern for you (and really, we should be concerned about all of them) have a read of the report, which you can find here: Enhanced Monitoring for Toxics and Emerging Contaminants in Delaware Estuary Tributaries.

The report was written by Jeremy Landon Conkle, Ph.D., Senior Chemist/Toxicologist at the Delaware River Basin Commission; with the assistance of Elaine Panuccio, Senior Water Resource Scientist; and Jacob Bransky, Senior Aquatic Biologist. Water Resource Scientist Matthew Amato, Ph.D., contributed to data processing and report writing.

Five tributaries stood out

In summary, all the chemicals were present in all the tested tributaries, and even those with low concentrations, the amounts “still exceed water quality criteria, particularly for PCBs.”

But five tributaries “stood out due to one or more compounds, classes of pollutants or trends in pollutants.”

They are:

• Frankford Creek in Pennsylvania, for its high presence of both currently used insecticides as well as chemicals that have been banned for more than 50 years.

• The Christina River in Delaware “is a hotspot for legacy pollution, including dioxins and furans, PCBs and PAHs, and also for the emerging contaminant PFAS.”

• Marcus Hook Creek in Pennsylvania “had the highest PCB concentration, high organochlorine insecticides and high PFAS concentration.”

• Mantua Creek in New Jersey “is dominated by high-density suburban sprawl followed by warehouses and petrochemical facilities near its mouth at the Delaware River,” and that is likely the reason this tributary has the highest PAH concentrations.

• Cooper River in New Jersey “is comprised of suburban neighborhoods and commercial properties, with a lower industrial presence than many of the other tributaries sampled. Upstream of the sampling location, the river features a large impoundment called Cooper River Lake (circa 1940), which likely traps sediment- and particulate-bound pollutants while increasing contact times that enhance sorption and degradation. This impoundment may explain why the Cooper River has a relatively higher concentration of legacy pollutants.”

‘Always playing defense’

It’s great to have the report, as Schrauth said, but it’s also important to note what the three states most concerned about these tributaries — Delaware, New Jersey and Pennsylvania — have to say. The toxins found in the tributaries come from land — and the land in the watershed is the purview of each state. Delaware Currents contacted each state department that oversees these issues. Comments from the states are in full at the bottom of this story.

It’s worrying that these toxins could make their way into our drinking water, so a major line of protection are the public and private facilities that treat the water we drink.

“We’re always playing defense,” Matthew Fritch, the watershed protection program manager for the Philadelphia Water Department, said in a recent interview.

And that’s because industry is always developing new chemicals and only time tells us if one of them poses a problem to human health. Then, if it does, more time passes as the Environmental Protection Agency develops regulations for water suppliers to follow.

But Fritch was quick to point out that, in the report, “right now, PWD is below the limits on all compounds regulated by EPA, DRBC or the PADEP.”

Of course, not all the compounds found in the tributaries have limits.

“There are some chemicals we don’t test for, like neonicotinoids,” which are unregulated, he said. “We can’t test for everything. We focus on those substances that are regulated.”

Also, many conventional treatments don’t typically prove effective at reducing concentrations of unwanted chemicals. He said there are advanced treatments that might work for some, like granulated activated carbon, but setting that up is a costly proposition.

For many public water suppliers costs are a major concern as residents can only afford to pay so much for their drinking water, and money from the state and federal governments is limited.

Fritch also pointed out that “the tributaries, being smaller bodies of water, will have much higher concentrations of problematic chemicals than the Delaware River. So, the amounts sampled here do not necessarily correlate to amounts in the river.”

Where are these chemicals coming from?

Many of these compounds are not from one single, possibly identifiable source, he said. They are omnipresent like the poster child, PFAS, which you can find in many consumer products like contact lenses, dental floss, etc.

If some water samples test high for substances regulated by the Safe Drinking Water Act, the department would report it to the PADEP, he said. And the PADEP would, in turn, issue a violation or a warning. “We haven’t been in that situation,” Fritch said.

The commissioner of the Department of Public Works in Wilmington, Del., Kelly Williams, had some important observations: “While the sample sites included the Christiana and Brandywine Rivers,” she wrote in an email, “it is important to note that the Brandywine sampling location was downstream from the dam used as Wilmington’s drinking water source. Therefore, it is not a representative sample of our drinking water source.”

She also brought us up to speed on the recent changes to EPA rules.

“In April 2024, the EPA announced final drinking water standards involving six different PFAS with an extended compliance deadline of 2029. Last month, the EPA — now headed by a different administration — announced its intentions to rescind the 2024 drinking water standards for four of the six PFAS. The drinking water standards for PFOA and PFOS were not changed, but the EPA extended the compliance date until 2031. Last month’s announcement can be found here.”

Patrick McDonnell, president & CEO of PennFuture, wrote, addressing both the report and our current state of affairs:

“This report confirms the presence of many harmful compounds, but it was not designed to identify sources that could help mitigate and control these issues, so follow up is needed. The reality, however, is that we probably won’t be getting it, which really underscores the immediate harm from impact of the Trump Administration’s cuts to the EPA and all related research and funding.”

Let’s drill deeper

So, armed with all this background information, let’s look more closely at the report, which does delve into details. It also offers an overview about specific chemicals that are easy to understand.

For example, PCBs (polychlorinated biphenyls) has its own heading in the report, which details their history (manufactured from 1929 until a ban in 1979).

“Due to their broad use and limited toxicological knowledge at the time, PCBs were mass-produced and frequently mishandled, resulting in widespread environmental releases,” the report said. “Because of their long-term stability and hydrophobicity, PCBs — banned for ~45 years — remain nearly ubiquitous in sediment and are found at low concentrations in water.”

Hydrophobic and its antonym — hydrophilic — describes the relationship of a molecule to water. If “phobic,” it is repelled by water; if “philic” it is attracted to water.

And it explains why some of these chemicals, like PCBs, are found in sediment. They are hydrophobic, while others float in the water. Being lodged in sediment also means they have the ability to remain in our water years after their manufacture and use ceased.

PCBs were found in all tributaries, with the three highest concentrations in Marcus Hook Creek in Pennsylvania; Brandywine Creek in both Pennsylvania and Delaware; and the Christina River in Delaware.

Finding ‘forever chemicals’

Another toxin that is increasingly causing concern and that has some pending EPA criteria (as noted above) is the big family of PFAs (Per and Polyfluoroalkyl Substances) — so-called forever chemicals.

“The first commercially produced PFAS compound, PTFE (Teflon), was accidentally discovered at the DuPont Chambers Works facility in Deepwater, N.J., on the banks of the Delaware River in 1938. Since then, the number of PFAS compounds has surged to nearly 15,000,” the report said.

PFAS were found in all tributaries, with the highest concentrations in the Christina River and Chester and Marcus Hook Creeks.

Studies of the PFAS family is ongoing with the DRBC’s approval in its recent business meeting of the analysis of microplastics and per- and polyfluoroalkyl substances (PFAS) in historic (2007-2012) and fresh sediment cores

On to some of the lesser-known problem chemicals.

For the purposes of this story, Conkle was able to link PAHs (Polycyclic Aromatic Hydrocarbons) with dioxins and furans since both result from industrial processes, and from incomplete combustion.

From the report: “In the Delaware River Basin, a few of the primary contributors (to PAHs) include fire, combustion engines and incinerators in the urbanized portion of the river. Therefore, it is expected that tributaries with a large industrial footprint, highly trafficked roads and refineries will have a higher prevalence of PAHs.”

Mantua Creek in New Jersey, had a significantly higher presence of PAH, almost a third higher than the total in the Christina River.

Dioxins, furans and insecticides and where they were found

Next up: dioxins and furans, which are “unwanted byproducts of chemical processes used to make chlorinated intermediates and the combustion of chlorinated materials. They can be released to the environment from various sources, including waste incineration, fuel combustion for heat and power generation, foundries, scrap metal melting, paper production and more.”

Lots of possible sources but the highest amounts were found in the Cooper River and, once again, in the Christina River.

Rounding out the list were two categories of insecticides.

The use of organochlorine insecticides “rapidly expanded after WWII to control mosquitoes and other insects in agriculture. Their broad application continued until the late 1960s when organochlorine effects on non-target organisms became evident. Organochlorines have not been produced since the early 1970s, yet their resistance to degradation allows them to persist in sediment and water, remaining detectable after more than 50 years since they were banned.”

The highest concentrations were found in the Frankfort and Marcus Hook Creeks in Pennsylvania.

The other category of insecticides was those in current use.

Neonicotinoids “…are among the most heavily used globally and are highly effective in controlling and preventing insect infestations. These chemicals can be applied prophylactically as seed coatings or directly to plants. Unlike most insecticides, neonicotinoids are water-soluble, which allows them to be absorbed by plants to control boring insects. Despite their effectiveness, neonicotinoids have low toxicity to vertebrates, making them relatively safe for human use. A major concern with neonicotinoids is their potential adverse impacts on non-target species, particularly pollinators, which remains an open area of research.”

They were really high concentrations in Frankford Creek. Other waterways had them but at much lower concentrations.

The other insecticide in current use are pyrazoles, one of them is Fipronil, which “is a pyrazole insecticide used to control pests on crops and golf courses as well as fleas on pets,” the report said. “Like neonicotinoids, it has high toxicity to insects but low toxicity to vertebrates. Fipronil, however, has a lower solubility than neonicotinoids, making it less mobile in the environment and, consequently, more persistent.”

To sum up all the science, let’s hear from Schrauth at New Jersey Future, “Data can’t drive change on its own, but it gives us information to make improvements.”

From the Delaware Department of Natural Resources and Environmental Control

From John Cargill, a hydrologist and environmental program manager at the department:

The April 2025 DRBC report titled ‘Enhanced Monitoring for Toxics and Emerging Contaminants in Delaware Estuary Tributaries is a great snapshot of regional water quality with regards to toxic contaminants. I say this as DNREC’s representative to the DRBC Toxics Advisory Committee and as co-manager of DNREC’s Watershed Approach to Toxics Assessment and Restoration (WATAR) program.

To begin, it’s important to state upfront that DRBC’s surface water data from the fall of 2023 simply confirms what DNREC has known and has been addressing for many years, including the presence of the emerging contaminant PFAS. Of note, PAHs, dioxins/furans, PCBs and PFAS were detected in the Christina River surface water at elevated concentrations when compared to other locations sampled during the regional study. DNREC has been tracking concentrations of these, and other, chemicals in fish tissue, surface water and sediment for quite some time (for several decades in the case of PCBs). DNREC’s data collection and evaluation has resulted in fish consumption advisories for both the Christina River and Brandywine River, the advisories driven by PCBs, dioxins/furans and dieldrin (a legacy organochlorine pesticide). 

More recently (since approximately 2020), DNREC has been conducting a sediment remediation feasibility study in the lower Christina and Brandywine Rivers as part of a Christina and Brandywine Rivers Remediation, Restoration and Resilience initiative, more familiarly CBR4 by the initiative’s acronym. The associated contaminant evaluation is focused on understanding the distribution and relationships of contaminants in the surface water, sediment and fish tissue within the project area, and developing a remediation plan to address sources of legacy contaminants in the sediments. While that study is being completed, DNREC programs are focused on removing and/or controlling the remaining known upland sources of the primary contaminants of concern.

From the New Jersey Department of Environmental Protection’s press office

As a member of the Delaware River Basin Commission and in its capacity on various technical committees and working groups, the DEP routinely collaborates with commission staff and partner states on scientific work to advance improvements to water quality in the Delaware River and its watershed. The DEP will use the valuable information provided in the Enhanced Monitoring for Toxics and Emerging Contaminants in Delaware Estuary Tributaries report as part of the department’s ongoing efforts to improve water quality both within the Delaware River Basin and across the state.

From the Pennsylvania Department of Environmental Protection

Within the Delaware River basin, emerging contaminant monitoring has increased significantly, which has provided additional information for permitting and restoration programs. The Pennsylvania Department of Environmental Protection (DEP) has led a Commonwealth-wide monitoring study, including pilot sampling for contaminates of emerging concern. This includes discrete and passive surface water sampling, sediment sampling, and fish tissue. Results from the Commonwealth study can be found at: Contaminants of Emerging Concern | Department of Environmental Protection | Commonwealth of Pennsylvania .

At the Environmental Protection Agency’s (EPA) request, Delaware River Basin Commission (DRBC) developed, and DEP follows, a Total Maximum Daily Load (TMDL) for Polychlorinated biphenyls (PCBs) in the tidal Delaware River and its tidal tributaries. The TMDL requires that when a discharger is identified to have PCBs present in their discharge, they must conduct ongoing monitoring for 209 PCB compounds. The dischargers must also prepare and implement a PCB Pollutant Minimization Plan (PMP) and conduct subsequent monitoring to determine if PCBs remain present in the discharge above ambient water quality criterion and to achieve the maximum practicable reduction of PCB in the discharge.

While there are not specific restoration requirements in place when it comes to priority organic compounds (POC) for Municipal Separate Storm Sewer (MS4) permittees, the present MS4 permit cycle does require MS4 permittees with drainage to waterways that have POCs present to implement pollution control measures (PCMs). These MS4 permittees must develop an inventory of suspected sources, create a map of their locations, and perform investigations. The permittee must report when sources of POCs are being discharged in stormwater from industrial sites into the permittee’s MS4 system.

From Wilmington Water Utility’s commissioner, Kelly Williams

In the fall of 2023, DRBC sampled 12 tributaries in the Delaware River Basin for a variety of chemicals.  While the sample sites included the Christiana and Brandywine Rivers, it is important to note that the Brandywine sampling location was downstream from the dam used as Wilmington’s drinking water source. Therefore, it is not a representative sample of our drinking water source.

It’s important to note the report does not reference drinking water standards; it references EPA’s Human Health Surface Water Criteria. As the report states ‘These criteria are not regulations, but they are guidelines for states to use when developing their own water quality standards. They are based on the latest scientific knowledge and do not consider economic or technological feasibility.’ (Economic and technological feasibility are key factors that the states and the federal government consider when setting drinking water standards.)

Regarding how this report’s potential impacts, this data set will be used by the state and DRBC to help them determine new water quality standards. 

Those standards may or may not require operational changes, but we simply don’t know at this early stage.  What can be said is that we have always met established drinking water standards and we will continue to do so.

Our utility has long had a source water protection plan, and we sample our drinking water in accordance with state and EPA regulations.  The source water protection plan can be found here:  https://wilmingtondewater.gov/218/Source-Water-Protection [wilmingtondewater.gov]

Our latest sampling results can be found in our Water Quality Report, which can be found here:  https://www.wilmingtondewater.gov/DocumentCenter/View/456/2024-Water-Quality-Report?bidId= [wilmingtondewater.gov]. 

A few educational notes regarding the EPA’s PFAS-related standards for treated drinking water. (The standards do not apply to untreated surface water.) 

In April 2024, the EPA announced final drinking water standards involving six different PFAS with an extended compliance deadline of 2029.

Last month, the EPA – now headed by a different administration – announced its intentions to rescind the 2024 drinking water standards for four of the six PFAS.  

The drinking water standards for PFOA and PFOS were not changed, but the EPA extended the compliance date until 2031.  Last month’s announcement can be found here:  https://www.epa.gov/newsreleases/epa-announces-it-will-keep-maximum-contaminant-levels-pfoa-pfos [epa.gov]