Overshadowed By ‘Forever Chemicals,’ PCBs Remain A Toxic Threat To Chesapeake Waters

Before the public learned about PFAS, so-called “forever chemicals,” there were other toxic chemicals in the environment arguably worthy of the same nickname.

Polychlorinated biphenyls, or PCBs, haven’t been produced since 1979, after studies found that exposure to them could cause a variety of harmful health effects, including cancer. But they were so widely used before then and so long-lasting that they still impair water quality in much of the tidal Chesapeake Bay and its tributaries.

PCBs differ from PFAS (per- and polyfluoroalkyl substances) in key respects. PFAS dissolve readily in water, which has made them a major threat in drinking water. PCBs are not as mobile, tending to accumulate in the sediment of rivers and streams.

But both chemical groups bioaccumulate, meaning they build up in the blood or fat of animals that ingest them. And like PFAS, PCBs have proven stubbornly resistant to efforts aimed at removing them from the Bay’s water and sediment.

Contamination has slowly declined in many parts of the Bay watershed through “natural attenuation,” as cleaner new sediment settles on the PCB-laden bottom. But PCBs remain a leading cause of fish consumption advisories throughout the six-state watershed. And there has been little to no progress in a handful of Bay tributaries, a recently published study notes — particularly the Gunpowder, Patapsco and Anacostia rivers.

“The frustrating part is that some of these watersheds … are not recovering,” said Upal Ghosh, one of the study’s co-authors. An environmental engineering professor at the University of Maryland Baltimore County, he has been studying PCBs and their remediation for more than three decades.

It’s not for lack of trying. Federal and state regulators have spent decades tracking down and cleaning up contaminated hotspots. But PCBs were manufactured in the U.S. for 50 years before being banned, and records of where they may have leaked, or been buried or dumped, are incomplete.

The Maryland Department of the Environment has developed total maximum daily loads or “pollution diets” for more than 30 waterways, addressing PCB contamination in fish tissue or bottom sediments, according to spokesman Jay Apperson. It is still working on plans for the Susquehanna River above and below the Conowingo Dam and for Middle River east of Baltimore.

In the last decade, Apperson said, MDE has issued 77 PCB fish consumption advisories, cautioning anglers to limit the number of meals they eat of locally caught fish or, in some cases, to avoid eating them at all.

There has been some progress: MDE has found six water bodies no longer impaired by PCBs, Apperson said. It has also revised 52 fish consumption advisories, telling recreational anglers they could safely consume more locally caught fish because PCB levels in them have declined.

Similarly, in Virginia, PCBs are responsible for two-thirds of the 94 fish consumption advisories listed on the Department of Health’s website. They are impairing water quality in most of Virginia’s portion of the Bay, plus more than 1,000 miles of rivers, according to a 2023 Chesapeake Bay Program presentation.

To date, Virginia’s Department of Environmental Quality has developed PCB cleanup plans for six water bodies, including the state’s portion of the Potomac River watershed and tributaries of the Rappahannock and Shenandoah rivers. DEQ also has been developing cleanup plans in stages for the entire James River and several of its tributaries.

The District of Columbia’s Department of Energy and Environment also has been working for years on a plan for reducing PCB contamination from past industrial pollution of a 9-mile portion of the Anacostia River flowing through the nation’s capital. DOEE is preparing to dredge or cap and treat contaminated bottom sediments at “11 hot spots,” at a cost of more than $30 million.

But that cleanup may be less effective and take longer than expected, Ghosh warns, because PCBs continue to flowinto the District from a tributary upriver, Lower Beaverdam Creek in Maryland.

One source of the continuing contamination has been identified and is being dealt with: a metal scrap and recycling business in Capitol Heights. A second source farther upstream has eluded investigators, though.

In the Baltimore area, progress has been perhaps even more complicated. There have been some spot cleanups launched, including the dredging and treatment several years ago of PCB-laden sediment in tributaries of Middle River. And the U.S. Environmental Protection Agency has proposed dredging and capping Bear Creek off Baltimore harbor to deal with PCBs and other contaminants deposited there — from more than a century of steelmaking at Sparrows Point.

But elsewhere, the sources are either uncertain or deemed beyond state control. In 2016, Maryland regulators concluded only natural attenuation could sufficiently reduce the PCBs responsible for fish consumption advisories in the Gunpowder and Bird rivers, which might take 49 to 93 years.

Sampling by Ghosh’s lab also identified Baltimore city’s Back River wastewater treatment plant as a major source of PCBs affecting that Bay tributary. The plant itself is not producing PCBs; they are in the wastewater piped into the facility. And while treatment removes more than 90%, some still are discharged into the river. Ghosh said he suspects legacy sediments in the sewer lines are the source, meaning the remedy isn’t as simple as excavating contaminated soil somewhere upstream.

In other parts of the Bay, if PCB levels keep declining as they have been, fish consumption advisories could be lifted in the next five or six years. But with no discernible trend in the Baltimore area, the University of Maryland study sees no future when fish caught there could be completely safe to eat.

Dealing with toxic contaminants, particularly PCBs and mercury, was one of multiple areas where the state-federal Chesapeake Bay Program failed to achieve its goals under the 2014 Bay Watershed Agreement. The revised 2025 agreement that leaders adopted in December renews their commitment while also expanding the list of targeted contaminants to include PFAS.

“We’re not getting away from PCBs,” said Greg Allen, who until early 2025 was the toxic contaminants coordinator in the EPA’s Bay Program office. “We’re just adding PFAS … a challenge that’s as big or maybe even bigger than PCBs ever were.”

So far, there aren’t as many PFAS-related fish consumption advisories in the Bay watershed as there are for PCBs. But PFAS are “emerging contaminants” that scientists and regulators are scrambling to understand. And while a few PFAS have been taken out of production, many more are still in widespread use in commerce — providing multiple pathways for them to spread and accumulate in animals, plants and people.

For those reasons, Ghosh agrees PFAS could well pose a much bigger problem. But he argues it’s important not to get sidetracked.

“While much of the nation’s attention has been diverted over the years to new and emerging pollutants, largely to prevent future environmental impacts,” the study’s authors concluded, “… this paper shows how much remains to be done for a critical legacy pollutant that has been impacting human health and the environment for decades.”