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Bay Blog: toxics


By the Numbers: 8 ounces

In the rivers and streams of Pennsylvania, you can find channel catfish, small and largemouth bass, white perch and rainbow trout. But the persistence of toxic contaminants in the Delaware, Ohio and Susquehanna river basins has limited the amount of fish you can consume from the Commonwealth’s waters.

Anglers fish for hickory shad on the Susquehanna River.

Mercury, polychlorinated biphenyls (PCBs) and other toxic contaminants pose risks across the United States. Toxics enter the environment through air pollution, agricultural and urban runoff, and wastewater discharged from industrial and municipal treatment plants. Toxics bind to sediment, build up in the tissues of fish and move through the food web through a process called bioaccumulation. Because of the health risks associated with the frequent consumption of fish affected by toxics—birth defects and cancer among them—Pennsylvania has advised people to consume no more than eight ounces of locally caught sport fish in a given week.

Pennsylvania isn’t the only state in the watershed coping with contaminants. According to data from the U.S. Environmental Protection Agency (EPA), 74 percent of the tidal Chesapeake Bay is partially or fully impaired by toxics. And all states in the watershed have issued fish consumption advisories as a result.

Image courtesy Sergey Ryzhov/Shutterstock.

Of course, most fish consumption advisories aren’t meant to stop the consumption of all locally caught fish, unless Do Not Eat is shown in an advisory listing. Some people are more at-risk (pregnant and breast-feeding women, women of childbearing age, and children), and some fish are safer to eat (smaller, younger fish and those species that are not as fatty as their catfish, carp or eel counterparts). For most, the benefits of eating fish can be gained as long as you choose a safe place to fish, pick a safe species to eat, trim and cook your catch correctly, and follow recommended meal frequencies.

Through the Chesapeake Bay Watershed Agreement, the Chesapeake Bay Program has committed to reviewing the latest research on toxic contaminants and improving the practices and controls that would reduce their effects. Learn more about our efforts to further toxic contaminants research and policy and prevention.

Catherine Krikstan's avatar
About Catherine Krikstan - Catherine Krikstan is a web writer at the Chesapeake Bay Program. She began writing about the watershed as a reporter in Annapolis, Md., where she covered algae blooms and climate change and interviewed hog farmers and watermen. She lives in Washington, D.C.


Photo Essay: Microplastics in the Chesapeake Bay

If you’ve ever watched a solitary ant explore your countertop, you might have marveled at its tiny size. You also might have questioned how something seemingly insignificant can be such a nuisance in your aspiringly sterile kitchen. Then you remember what your tiny pioneer heralds — the impending arrival of thousands of her sisters — and she suddenly seems like a more formidable adversary.

Microplastics from the Magothy River are pictured at the laboratory of Dr. Lance Yonkos in the Department of Environmental Science & Technology at the University of Maryland in College Park, Md., on Feb. 6, 2015. The National Oceanic and Atmospheric Association Marine Debris Program collected sixty samples in 2011 in four tributaries feeding into the Chesapeake Bay, and microplastics were found in all but one.

At a few millimeters short of a typical carpenter ant, microplastics are another case of both extreme smallness and overwhelming magnitude. Microplastics are the fragments, pellets, sheets, fibers, microbeads and polystyrene that begin as improperly discarded plastic bottles and trash that get washed into our waterways. At less than five millimeters in length, they are nearly imperceptible. But plastic doesn’t degrade like most organic material, meaning the total amount of plastic in the environment doesn’t really change as it breaks down, allowing microplastics to persist in most surface waters around the globe, including the Chesapeake Bay.

A sample from the Patapsco River.

University of Maryland Professor Dr. Lance Yonkos is the primary author on a study of microplastics collected from four tributaries of the Chesapeake Bay — the Patapsco, Magothy, Rhode, and Corsica Rivers. Of the 60 samples taken by the National Oceanic and Atmospheric Association (NOAA) Marine Debris Program, all but one contained microplastics.

To Yonkos, it’s not really a surprise there are microplastics in the Bay.

“We have many of the prime sources for creating and introducing microplastics to aquatic environments,” Yonkos said. Roads are a main contributor because they promote physical degradation of plastics and provide easy transport via storm drains to Bay tributaries. Yonkos listed wastewater treatment plant effluent and substantial shipping traffic.

A piece of polystyrene from the Patapsco River. Types of microplastics also include small and large fragments, pellets, fibers, sheets, and other objects smaller than five millimeters.

As plastic fragments become smaller, a greater number of animals are able to swallow them—as exemplified by the recent case of a whale killed by a shard from a DVD case. When these materials break down enough reach the level of microplastics, even filter feeders like oysters can consume them.

Smaller pieces also mean more surface area, Yonkos said, which could mean more leaching, either of chemicals from the plastic itself or of the environmental contaminants that cling to its surface.

Assistant Professor Lance Yonkos poses in his laboratory workspace at the University of Maryland in College Park, Md., on Feb. 6, 2015.

“In this way, microplastics might serve as a vehicle for introducing bioaccumulative contaminants to the food chain,” Yonkos said. The concentration of such toxic contaminants can become magnified at higher levels of the food web.

But, the science isn’t clear yet on whether microplastics represent a serious environmental or human health concern.

“Since we don’t really know yet, it is a little disconcerting to think that most of the plastics we have created over the past 70 years are still in the environment,” Yonkos said.

And microplastics are here to stay. With no feasible method for removing microplastics that are already in the environment, measures like improved recycling and decreased use of offending products — like those that include microbeads, which would be banned by the state of Maryland according to legislation passed recently — could improve the situation going forward.

“The take home message is prevention,” Yonkos said. “If we want to reduce microplastics in the oceans we need to limit their release at the source.”

A large fragment from a Patapsco River sample.

A spherical piece of microplastic from the Patapsco River.

Fibers peel from a larger piece collected in the Patapsco River.

Pellets are formed from lengths of plastic chopped into small sections for various uses.

A sample from the Patapsco River.

A sample from the Rhode River.

A sample from the Patapsco River contains a large amount of foil.

A sample from the Corsica River.

A colorful sheet from the Patapsco River.

A small fragment from the Patapsco River.

A sheet from the Rhode River.

An almost-perfectly round piece from the Patapsco River.

A translucent pellet from the Patapsco River.

To view more photos, visit the Chesapeake Bay Program's Flickr page.

Will Parson's avatar
About Will Parson - Will is the Multimedia Specialist for the Chesapeake Bay Program. A native of Bakersfield, California, he acquired an interest in photojournalism while studying ecology and evolution at University of California, San Diego. He pursued stories about water and culture as a graduate student at Ohio University's School of Visual Communication, and as an intern at several newspapers in New England before landing in Maryland.


Chemical contaminants persist across Chesapeake Bay watershed

Chemical contaminants continue to afflict the Chesapeake Bay watershed, raising concern over water quality and the health of fish, wildlife and watershed residents.

Close to three-quarters of the Bay’s tidal waters are considered impaired by chemical contaminants, from the pesticides applied to farmland and lawns to repel weeds and insects to the household and personal-care products that enter the environment through our landfills and wastewater. But so-called “PCBs” and mercury are particularly problematic in the region, according to a report released last week by the U.S. Environmental Protection Agency (EPA), U.S. Geological Survey (USGS) and U.S. Fish and Wildlife Service (USFWS).

Both PCBs—short for “polychlorinated biphenyls”—and mercury are considered “widespread” in extent and severity, concentrating in sediment and in fish tissue and leading to fish-consumption advisories in a number of rivers and streams.

The District of Columbia, for instance, has issued such advisories for all of its water bodies, asking the public not to consume catfish, carp or eels, which are bottom-feeding fish that can accumulate chemicals in their bodies. While the District’s Anacostia and Potomac rivers raise the greatest concern in the watershed when it comes to fish tissue contamination, a November report confirmed that many Anacostia anglers are sharing and consuming potentially contaminated fish, sparking interest in reshaping public outreach to better address clean water, food security and human health in the area.

While PCBs have not been produced in the United States since a 1977 ban, the chemicals continue to enter the environment through accidental leaks, improper disposal and “legacy deposits”; mercury can find its way into the atmosphere through coal combustion, waste incineration and metal processing.

Exposure to both of these contaminants can affect the survival, growth and reproduction of fish and wildlife.

The Chesapeake Bay Program will use this report to consider whether reducing the input of toxic contaminants to the Bay should be one of its new goals.

Read more about the extent and severity of toxic contaminants in the Bay and its watershed.


New study shows Anacostia fishermen are sharing, consuming contaminated fish

A yearlong survey of anglers along the Anacostia River has confirmed that many fishermen are catching, sharing and consuming contaminated fish.

While fishing advisories in Maryland and Washington, D.C., have been in place for more than two decades, these warnings are often not seen, understood or listened to—and as many as 17,000 residents could be consuming fish caught in the Anacostia.

Image courtesy Len Matthews/Flickr

Located less than one mile from the nation’s capital, the Anacostia River has long suffered environmental degradation. Polluted runoff from urban streets and hazardous waste sites has caused toxic chemicals to build up in the water and in the bodies of fish, which could cause disease or development disorders in those who consume them.

According to the results of a survey that studied the social behavior of Anacostia anglers, a complex set of factors is driving the sharing and consuming of locally caught and potentially contaminated fish: past experience and present beliefs, a lack of awareness of the health risks involved and an overriding desire to share their catch with those who might otherwise go hungry.

Image courtesy LilySusie/Flickr

Research conducted through hundreds of interviews along fishing “hotspots” and a community survey that canvassed the lower Anacostia watershed found that 40 percent of fishermen had never heard that fish from the Anacostia could make them sick. Some anglers thought visual cues—like obvious lesions, cloudiness in the eyes or the color of a fish’s blood—would help them determine the health of a fish, or that related illnesses would soon be apparent rather than chronic or long-term. If a fisherman had not fallen ill from a meal of fish before, then he might perceive the fish to be healthy or think that his preparation methods made it clean.

Research also found that current advisories do not resonate among diverse anglers. Just 11 percent of fishermen had seen a sign or poster, and even fewer had received warning material with a fishing license or reviewed related information online. And English-only outreach is not effective among a population in which one-quarter speaks a language other than English at home.

Image courtesy 35millipead/Flickr

But how can Anacostia anglers be reached?

"The answer to this problem will be far more complex than simply telling anglers not to share their catch,” said Steve Raabe, principal of the Maryland-based research firm that conducted the survey.

The Anacostia Watershed Society, among the partners behind the survey, agrees. While the non-profit’s director of public policy acknowledged this study is not a “silver bullet solution,” he hopes it will bring about positive change.

“We are hoping [the study] will be the catalyst to engage all stakeholders—federal and local governments, food security and hunger organizations, environmental and health organizations, as well as residents—to come up with answers,” Brent Bolin said.

“Through this research effort, we have already begun identifying potential solutions,” Bolin continued, from directing better messaging to affected populations to expanding urban gardens, farmers markets and other programs that will address the long-term challenges of clean water, food security and human health.


Pesticide Runoff Can Pose Risk to Humans, Wildlife in Chesapeake Bay Region

Pesticides used by farmers, residents and business owners pose a significant risk to Chesapeake Bay wildlife and human health, according to a recent report released by the Maryland Pesticide Network.

Pesticides and the Maryland Chesapeake Bay Watershed lists the major types and sources of pesticides in the Bay region and explains how pesticides can affect the fish we eat and the water we drink. Toxic chemicals in pesticides can move up the food web when larger fish and birds eat smaller, contaminated organisms. Humans can also be affected if they catch contaminated fish or drink contaminated water.

According to the report, pesticides are a threat to the region’s environmental health because they can be toxic to aquatic life, wildlife and humans, even though those species are not being targeted by the pesticide applier. Even at low levels, toxic effects of pesticides can put additional stress on fish, plants, microscopic animals and other species. A 2007 report by the U.S. Geological Survey found that synthetic organic pesticides were widely detected at low levels throughout the Bay watershed.

One type of pesticide discussed in Pesticides and the Maryland Chesapeake Bay Watershed is atrazine, the most commonly used herbicide in the United States. Atrazine, which is used in both agriculture and on lawns, has been linked to sexual abnormalities in frogs and is a suspected endocrine disruptor: a substance that mimics hormones and can cause reproductive anomalies.

Pesticides get into our local waterways and the Chesapeake Bay when we apply them to the ground and rain washes them into nearby streams and storm drains. The largest source of pesticides in the Bay watershed is from agriculture, but commercial, residential and government properties also contribute measurable amounts of pesticides to local waterways and groundwater supplies. Pesticides used in our homes, such as the antimicrobial ingredient triclosan in soaps and personal care products, can also find their way into the Bay through treated wastewater.

Fortunately, there are many ways people can help reduce the flow of pesticides to the Chesapeake Bay and its rivers, from using effective pesticide alternatives to taking preventative measures rather than resorting to pesticides. The report’s conclusion outlines several recommendations for consumers, regulators and policymakers, including:

  • Educating residents about mosquito breeding habits to reduce the need for spraying.
  • Planting forest buffers along the edges of farm field to reduce polluted runoff into local waterways.
  • Promoting the use of Integrated Pest Management (IPM), a strategy that uses mostly non-chemical prevention techniques on farms and in residential gardens.
  • Supporting research on the effects of pesticides – from endocrine-disrupting chemicals to the interaction of multiple pesticides in the water – on wildlife, aquatic life and human health.

For more information, read the full Pesticides and the Maryland Chesapeake Bay Watershed report.

Keywords: toxics

Bay Program Updates Toxics of Concern List

The Bay Program Toxics Subcommittee has updated its list of Toxics of Concern, ranking the toxic organic chemicals in the Chesapeake Bay with the most potential for harm. PCBs topped the list, followed by PAHs and organophosphate pesticides. Organochlorine pesticides and five other organic toxics are also included in the list.

The 2006 Toxics of Concern list prioritizes organic chemicals based on:

  • Estimates of loads to the Bay
  • Presence in the Bay
  • Eco-toxicological properties
  • Any fish advisories or Clean Water Act 303(d) impairment designations in the Bay and its tidal tributaries due to these chemicals

The original Toxics of Concern list, which was completed in 1991, identified and documented chemicals that were adversely impacting or had the potential to impact the Bay. The list was subsequently refined in 1996 and 2000 prior to this latest update.

The 2006 Toxics of Concern list is based on the same chemical ranking system used for the 1996 list, incorporating chemicals' source, fate and effects of exposure. Also, like the 2000 list, fish consumption advisories and 303(d) impairments were considered for the 2006 revision.

Improvements in the 2006 chemical ranking system include:

  • Persistence, bioaccumulation and toxicity (PBT) adjusted loadings estimates.
  • Frequency of detection in the Bay's tidal rivers.
  • State management outcomes, including fish advisories and 303(d) impairments.

The Toxics of Concern list is used by the Bay Program Toxics Subcommittee to help develop strategies to address the most problematic toxic organics in the Bay and its tributaries. It is not a complete list of all chemicals that may impact the Bay or its watershed. Some organics could not be included due to data gaps. Also, metals, such as mercury, are not included in the list because assessment guidelines comparable to those used for organics are not currently available.


Although PCB manufacturing was banned in 1977, PCBs can build up in bottom sediments and persist for many years; therefore, historic discharges of PCBs can still affect the Bay today. Also, when old PCB-containing equipment that is still in use fails, PCBs can flow into the nearest stream or river via stormwater.


PAHs are formed when coal, gasoline and fuel oil are burned and are a major component of tar and asphalt. The most rapid increases of PAHs in river bottom sediments are found in watersheds with increasing development and motor vehicle traffic.

Organophosphate Pesticides, Organochlorine Pesticides

Organophosphate pesticides are mostly herbicides and insecticides used in agriculture. Organochlorine pesticides, such as DDT, are no longer widely used but persist in the environment.


White Perch in the Bay and its Rivers

In recent years, people have become increasingly concerned about the issue of toxic materials, like Polychlorinated Biphenyls (PCBs), contaminating fish and shellfish in water bodies around the world. In the Chesapeake Bay region, the Bay states have issued fish consumption advisories throughout the Bay and its rivers to protect the health of people who enjoy dining on the Bay's fish and shellfish.

One way that Bay scientists assess how toxic pollutants are affecting the animals and plants in the region, Bay Program partners have focused on PCB concentrations in local white perch. PCBs are persistent organic chemicals that were formerly used in industrial practices in the United States. They enter the environment and can impact the creatures living within it. Although PCBs are not the only contaminants in an area, PCB concentrations in white perch provide an indication whether other chemical contaminants are present in an area.

Why did the scientists select white perch?

White perch are a good indicator of toxic contaminant concentrations in the Bay's waters because they are a resident species in the Bay; the majority of white perch remain in local waters throughout their lives. Considered an enjoyable fish to eat, white perch are a commercial and recreational fishery in the Bay. For scientists who are examining the effects of chemical contaminants on fish, as well as the impact on humans who eat PCB-contaminated fish, white perch are a logical species to study.

What does the research show?

Data gathered from Maryland and Virginia suggests that PCB concentrations are higher among white perch in the upper Bay than they are in the lower Bay. Similarly, there is a trend in fish tissue where fish on the eastern shore have lower concentrations of PCBs than their counterparts on the western shore.

A common characteristic among the areas of the Bay where white perch have higher PCB concentrations is related to land development; the western shore of the Bay is more developed than the eastern shore of the Bay, and white perch from the Bay's western shore have higher PCB concentrations than their counterparts on the eastern shore. Additionally, white perch sampled from the Patapsco River had particularly high PCB concentrations, which can be attributed to the level and type of industrialization in the Baltimore area.

What does this mean for someone fishing for white perch in the Bay?

Many of the Bay's waters have active advisories for limiting the consumption of white perch. As is true with any fish, it is important for someone who plans to catch white perch in the Bay's waters to first check out the fish consumption advisories to see what the state recommends regarding consuming fish caught in the Bay and its rivers.

What is the future of PCBs in the Bay?

Without sufficient data to determine a trend in the PCB concentrations in white perch in the Bay, Bay scientists cannot say for sure what to expect regarding the future of those toxic contaminants in white perch in the Bay. However, PCBs were banned more than 25 years ago, so scientists expect to see a natural decrease in their concentration in white perch over time.

What is toxic pollution and how does it impact the Bay?

Chemical contaminants that get into the environment and harm the animals and plants around them are typically considered to be toxic pollution. Learn about toxic pollution in the Bay.

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