There is evidence of chemical contaminants impacting fish throughout the Bay and its watershed. Just a few examples:

  • State figures show that 72 percent of the Bay's tidal waters have some level of toxics impairment, often based on contaminants in fish.
  • Male fish have been found with eggs in their testes in several areas of the Potomac and Susquehanna basins.
  • Tumors are frequently found in brown bullhead and other bottom dwellers in parts of the Bay.

"Toxic contaminants have adverse effects on fish and wildlife in the Chesapeake Bay and its watershed," flatly states a new report written by a team of federal scientists.

Toxic contaminants historically used in the watershed, such as organochlorine pesticides like DDT, had widespread impacts on the reproductive systems of fish and wildlife such as bald eagles, the report said. While some of those far-reaching and acute impacts of toxic contaminants have subsided, other widespread problems remain. Authorities issue fish consumption advisories in large portions of the Bay and its watershed, the report found, because of PCBs and mercury.

Meanwhile, concerns have risen more recently about new classes of chemical contaminants, such as pharmaceuticals and personal care products, which reach waterways through sewage systems, and their potential effect on fish and other aquatic life.

In the coming year, the state-federal Bay Program will determine whether concerns about chemical contaminants are great enough to put toxics back on its agenda.

"Given the findings of the report, there is an opportunity to apply the creative, collaborative resources of the Bay Program partnership to figure out how to lessen the impact of toxic contaminants," said Greg Allen, an environmental scientist with the EPA Bay Program Office and one of the report's authors.

Whether that will happen is uncertain. Once a major part of Chesapeake restoration efforts, toxic contaminants faded as a priority when the Bay Program increasingly focused on controlling nutrient and sediment pollution. Part of the rationale was that toxic contaminants were generally not seen as a widespread threat and — unlike nutrients — state and federal agencies had other programs to deal with the issue.

But the new report, which sought to characterize the extent and severity of 10 contaminant groups based on available research around the region, found that PCBs and mercury cause widespread problems in the Bay and the watershed.

Others, such as PAHs (polycyclic aromatic hydrocarbons) are widespread and known to cause localized problems, while some herbicides are widespread, although their impact on fish and wildlife is uncertain.

There was too little information available to characterize the extent and impact of half of the contaminant classes examined, though some — such as pharmaceuticals, hormones, personal care products and some herbicides —are suspected of contributing to problems in fish, such as impaired immune systems and the feminization of male fish.

"Some of these newer contaminant groups are used throughout the Bay watershed, which suggests that if you were to go out and monitor for them, they may have a widespread occurrence," said Scott Phillips, who oversees U.S. Geological Survey Chesapeake Bay activities and is a co-author of the report.

Further complicating efforts to fully characterize the impact of many contaminants, the report said, is that fish are often exposed to low levels of multiple contaminants at once, which may have a cumulative effect on them, so looking at a single chemical in isolation may not provide a full picture of its impact on fish health.

"The breadth of what you need to consider for toxic contaminants seems overwhelming at times," Phillips said. But, he added, "If the Bay Program goal is to make waters swimmable and fishable and wadeable, it can't just be about nutrients and sediment. The report findings suggest you have to also address the impacts of toxic contaminants."

Others agree that the report provides fresh reasons to heighten attention paid to toxic contaminants to achieve the overall Bay Program goal of protecting and enhancing the living resources of the Chesapeake.

In some cases, runoff-control efforts promoted to reduce nutrient and sediment runoff can also reduce pesticide runoff. In other cases, they could work at cross purposes — for instance, no-till farming can reduce sediment and phosphorus runoff, but it often requires the use of more herbicides to control weeds.

"On one hand you are reducing an important element of what's impacting the Bay, and on the other you are increasing another one," said Ruth Berlin, executive director of the Maryland Pesticide Network. "One could cancel out the other in terms of Bay health. It is important that we understand all of that and how we can create best management practices that reduce both nutrient and chemical runoff into the Bay."

The report concluded that the presence of some herbicides was widespread in the Bay and the watershed. Although it listed their impact as "uncertain," it cited several studies that suggested that low-level exposure to some widely used herbicides, such as atrazine, did harm fish.

The report was required by the federal Bay strategy developed in response to President Obama's 2009 Chesapeake Bay Executive Order. That strategy also called for new toxics reduction goals to be adopted in 2013, leading to new control strategies in 2015.

But the report said its findings would be used by the state-federal Bay Program partnership to "consider whether" to establish new goals for toxic contaminants.

Requirements from the executive order are not binding on the states, and many state officials have expressed little interest in adopting goals beyond their nutrient reduction obligations under the Chesapeake Bay Total Maximum Daily Load, or "pollution diet."

But states aren't the only ones who balk at putting toxics on the Bay Program's to-do list.

"I'm glad they did it," said Beth McGee, senior scientist with the Chesapeake Bay Foundation, and a toxicologist by training, of the report. "I think it was time for them to look at what new science was available, and certainly there are new chemicals of concern, and we have seen intersex fish in the Susquehanna and different parts of the Potomac."

Nonetheless, she said, toxics could detract from efforts to control nutrient and sediment pollution. "I recognize toxic chemicals are an issue, particularly in certain regions of the Bay," McGee said, "but I'm also reticent to recommend that scarce resources be devoted to that issue when I think we are on the right track in terms of addressing the nitrogen, sediment and phosphorus issues of the Bay."

The last major Bay Program effort to deal with chemical contaminants was the Toxics 2000 strategy adopted a dozen years ago. Most of its commitments went unfulfilled, including such lofty goals as eliminating all toxics-related fish consumption bans and advisories. Instead of stepping up toxic control efforts, the Bay Program ultimately disbanded its Toxics Subcommittee in 2007.

The new report did not attempt to make a quantitative evaluation of whether progress has been made since 2000, although it described the toxics impairment situation — as manifested in fish consumption advisories — as "stable" over the past decade. "Since the strategy was written, the conditions that existed remain," it said.

Improvement has been seen in some areas, including the Anacostia and Elizabeth rivers. In most, but not all, areas around the Bay, levels of pesticide-related contamination in birds has declined sharply.

Of the two compounds that were deemed to be both widespread and having severe impacts, PCBs may pose the greatest challenge — but also the greatest opportunity for Bay region efforts.

Much of the mercury problem, which is in freshwater areas of the watershed, is a byproduct of air pollution. The EPA recently adopted new regulations aimed at controlling mercury emissions that could eventually drive down contaminant levels in the watershed.

PCBs, a group of chemicals widely used as coolant fluids in electrical transformers and capacitors, have been banned since 1977 and remain a widespread problem. They are responsible for fish advisories in much of the Bay and parts of the watershed. PCB concentrations in the tissues of many species of wildlife has not declined since the ban.

The report said that in some places, they continue to persist in sediment and the water column. And, although they are banned, the chemical was so widely used that it continues to reach waterways from multiple sources.

"All of those sources are leaving us with a continued identification of impairments from PCBs in fish," Allen said. But he said identifying and reducing sources of PCB contamination was an area where the Bay Program could have an impact. "If we can do something that would reduce the inputs and begin to get improvements, that would be good for the fish, and good for the people who eat the fish."

"Technical Report on Toxics Contaminants in the Chesapeake Bay and its Watershed: Extent, Severity and Potential Biological Effects," will be posted on the Chesapeake Bay Executive Order website,

Toxics report at a glance

The report examined 10 broad groups of contaminants known or suspected of affecting the health of aquatic animals:

  • PCBs (polychlorinated biphenyls): A group of synthetic organochlorine chemicals widely used as coolant fluids in transformers and capacitors until being banned in 1977
  • Dioxins & Furans: A family of toxic substances produced as a byproduct of fossil fuel and wood combustion
  • PAHs (Polyaromatic hydrocarbons): A class of hundreds of chemicals derived from coal and petroleum and as a byproduct of fossil fuel combustion
  • Petroleum hydrocarbons: A group of several hundred chemicals derived from crude oil
  • Pesticides: herbicides, insecticides, fungicides
  • Pharmaceuticals: Chemicals used to treat conditions in humans or animals that enter waterways through human or animal wastes
  • Household & Personal Care Products: A group that includes cosmetics, detergents, soaps, food additives and other common products
  • PBDE (Polybrominated Diphenyl Ether): A group of chemicals widely used as fire retardants
  • Biogenic Hormones: Naturally occurring hormones originating from humans and livestock that enter waterways through waste
  • Metals & Metalloids: A range of substances, such as mercury, chromium, lead, zinc, aluminum and other compounds

The report sought to characterize the impact of contaminants by their extent and severity. Extent was based on available monitoring data, and severity was based on impairments to aquatic life stemming from fish consumption advisories, or impairments listed in state water quality assessments.


Widespread: PCBs, PAHs, some herbicides, mercury

Localized: dioxins, petroleum hydrocarbons, some pesticides, some metals

Uncertain: pharmaceuticals, personal care products, flame retardants, some pesticides, biogenic hormones


Widespread: PCBs, mercury

Localized: dioxins, PAHs, petroleum hydrocarbons, some pesticides, metals

Uncertain: pharmaceuticals, personal care products, flame retardants, herbicides, biogenic hormones