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Chemical Contaminants


Almost three-quarters of the Chesapeake Bay’s tidal waters are considered impaired by chemical contaminants. These contaminants include pesticides, pharmaceuticals, metals and more, and can harm the health of both humans and wildlife. From the insecticides that are put on farm fields to the cleaners we use to disinfect our homes, contaminants can enter the Bay and its tributaries in several different ways. While production bans have lowered the presence of some contaminants in the watershed, others are still widely used today.

What kind of chemical contaminants can be found in the Chesapeake Bay?

Two kinds of chemical contaminants can be found in the Chesapeake Bay: metals and organics.

The most common metal found in the watershed is mercury. A 2010 report from the U.S. Environmental Protection Agency (EPA) found the extent and severity of mercury contamination to be widespread in the watershed. Contamination with metals like aluminum, chromium or iron, on the other hand, is more often localized.

Common organic chemical contaminants include PCBs, PAHs and pesticides:

  • PCBs, or polychlorinated biphenyls, act as a flame retardant in electrical equipment and have also been used in the production of inks, adhesives, sealants and caulk. 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.” Data indicates the extent of PCB contamination in the watershed is widespread.
  • PAHs, or polycyclic aromatic hydrocarbons, form when gas, coal and oil are burned. PAHs are detected at varying concentrations across the watershed, with the highest reported in or near Baltimore Harbor and the Anacostia and Elizabeth rivers.
  • Pesticides are applied to the land to prevent, destroy, repel or reduce pests. While agriculture accounts for about 75 percent of all pesticide use, 85 percent of U.S. households store at least one pesticide at home (and more than half of U.S. households store between one and five).

Pharmaceuticals and personal care products are an emerging concern in the region. These contaminants can appear in our landfills and our wastewater, and have been linked to behavior changes and reproductive disruptions in fish and other species.

Where do chemical contaminants come from?

There are four general sources that push chemical contaminants into the Chesapeake Bay and its tributaries:

How do chemical contaminants harm Chesapeake Bay wildlife? 

Some of the most common chemical contaminants in the Chesapeake Bay watershed can persist in the environment for a long time. These contaminants bind to sediment or build up in the tissues of fish and other organisms, moving through the food web in a process called bioaccumulation. During bioaccumulation:

  • Small, bottom-dwelling organisms take up contaminants through skin contact or while feeding
  • Larger fish eat contaminated organisms and accumulate toxins in their tissues
  • Birds, mammals and other wildlife eat contaminated fish

Because the consumption of contaminated fish and shellfish can cause health problems in humans, cities and states issue fish consumption advisories in areas where chemical contaminants are a concern. The District of Columbia, for instance, has issued advisories for all of its water bodies, asking the public not to consume bottom-feeding fish like catfish, carp or eels.

Different chemical contaminants can affect the survival, growth and reproduction of fish and wildlife in different ways. Exposure to PAHs, for instance, has been linked to the development of liver tumors in brown bullhead catfish; exposure to pesticides has been linked to eggshell thinning in wild birds; and several studies have shown that PCB concentrations in bald eagle eggs can contribute to their failure to hatch.

What parts of the Chesapeake Bay are most affected by chemical contaminants?

Almost three-quarters of the Chesapeake Bay’s tidal waters are considered impaired by chemical contaminants. But the EPA has identified three “regions of concern” that show significant problems:

  • The Baltimore Harbor
  • The Anacostia River
  • The Elizabeth River

Current restoration goals

As part of the 2014 Chesapeake Bay Watershed Agreement, Chesapeake Bay Program partners committed to the goal of ensuring that the Bay and its rivers are free of effects of toxic contaminants on living resources and human health. This goal includes two parts: to continually increase our understanding of the impacts and mitigation options for toxic contaminants, and to continually improve practices and controls that reduce and prevent the effects of toxic contaminants below levels that harm aquatic systems and humans.

Take Action

For Chesapeake Bay restoration to be a success, we all must do our part. Our everyday actions can have a big impact on the Bay. By making simple changes in our lives, each one of us can take part in restoring the Bay and its rivers for future generations to enjoy.

To lower chemical contaminants in the Bay watershed, consider using non-toxic pesticides or chemical-free cleaning and personal-care products. You can also follow safe and legal disposal methods for paint, motor oil and other household chemicals, and keep pharmaceuticals out of our waterways by returning unused medicine to a consumer drug return location or fouling it with coffee grounds or cat litter before putting it in the trash.



Chesapeake Bay News

In The Headlines

Chemical Contaminants

Based on the list of impaired and threatened waters that states submitted to the U.S. Environmental Protection Agency in 2012, 74 percent of the 92 tidal segments analyzed in the Chesapeake Bay were partially or fully impaired by chemical contaminants.

Bay 101: Intersex Fish

November 20, 2014

Fish biologist Vicki Blazer with the U.S. Geological Survey (USGS) brings her team to the Shenandoah River in Front Royal, Va., to collect and study smallmouth bass, a species in which intersex characteristics have been linked to chemical contaminants in the Chesapeake Bay region.

Intersex conditions occur when exposure to chemicals disrupts the hormonal systems of an animal, leading to the presence of both male and female characteristics in an animal that should exhibit the characteristics of just one sex in its lifetime. In the case of smallmouth bass, male intersex fish are found with immature eggs in their testes, which indicates exposure to estrogenic and anti-androgenic chemicals.

“The sources of estrogenic chemicals are most likely complex mixtures from both agricultural sources, such as animal wastes, pesticides and herbicides, and human sources from waste water treatment plant effluent and other sewage discharges,” says Blazer, who first discovered intersex characteristics in fish while studying fish kills in the South Branch of the Potomac River and the Shenandoah River.


Chemical & Toxicological Characterization of Tidal Freshwater Areas in the James river, VA from Jamestown Island to Jordan Point

Publication date: July 01, 2002 | Type of document: Report | Download: Electronic Version

This report represents the coordinated effort of a team of scientists from various institutes, who continue a long series of studies aimed at toxicological and chemical characterization of the Chesapeake Bay.

Ambient Toxicity and Chemical Characterization of Four Bayside Creeks of the Eastern Shore

Publication date: January 01, 2001 | Type of document: Report

An assessment of ambient toxicity of Delaware public peninsula creeks where agriculture is the dominant land use. The assessment evaluates potential persistent impacts and potential intermittent or pulsed impacts. Three watershed…

Toxics 2000 Strategy: A Chesapeake Bay Watershed Strategy for Chemical Contamination Reduction, Prevention and Assessment

Publication date: December 01, 2000 | Type of document: Agreement | Download: Electronic Version

This strategy commits to voluntary efforts that build on the successes of the state and federal regulatory programs and go beyond compliance /existing regulatory point and nonpoint source programs to preclude the need for costly regulations…

Appendix A: Chesapeake Bay Watershed Chemicals of Concern as of September 26, 2000

Publication date: December 01, 2000 | Type of document: Fact Sheet | Download: Electronic Version

Chemicals of concern include chemical contaminants identified in the 1999 Toxics Characterization that are at levels that may cause toxic impact, chemical contaminants responsible for listing waterbodies as impaired or threatened, and…

Contaminants in Chesapeake Bay Sediments 1984-1991

Publication date: May 01, 1996 | Type of document: Report

The primary objectives of this report are to describe the spatial patterns in the distribution of sediment chemical contaminants in Chesapeake Bay and to compare sediment chemical contaminant concentrations in Chesapeake Bay to sediment…

Chesapeake Bay Chemical Contaminant Geographic Targeting Protocol-Chesapeake Bay Basinwide Toxics Reduction and Prevention Strategy-commitment Report

Publication date: March 01, 1995 | Type of document: Report

The purpose of this document is to present a geographical targeting approach for focusing chemical contaminant remediation, reduction, prevention, protection, and assessment actions within the Chesapeake Bay basin.

Chesapeake Bay Groundwater Toxics Loading Workshop Proceedings

Publication date: July 01, 1993 | Type of document: Report | Download: Electronic Version

The Chesapeake Bay Groundwater Toxics Loading Workshop was held April 15-16, 1992, at the U.S. EPA Chesapeake Bay Program Office. Workshop participants reviewed and discussed available information on results from groundwater studies and…

Chesapeake Bay Contaminated Sediments Critical Issue Forum Proceedings-Basinwide Toxics Reduction Strategy Reevaluation Report

Publication date: February 01, 1993 | Type of document: Report

The Chesapeake Bay Contaminated Sediment Critical Issue Forum was structured to seek a technical consensus on a series of questions related to the magnitude and extent of contaminated sediments within the Bay; and how that affects the…

From Around the Web

Bay FAQs

  • What are chemical contaminants?
  • What are the most common chemical contaminants found in the Chesapeake Bay?
  • What are endocrine disruptors?
  • What is a fish consumption advisory?


Bay Terms

  • Bioaccumulation
  • Chemical contaminants
  • Pesticides
  • Pharmaceuticals
  • Pollution
  • Polychlorinated biphenyls (PCBs)


Bay-Friendly Tips

  • Fix Car Leaks
  • Fix car leaks so engine fluids like oil and antifreeze don't drip onto the ground and run off into local waterways.
  • Reduce Polluted Runoff
  • Wash your car on grass or gravel rather than pavement so soapy, grimy wash water won't run off your property.
  • Use Pesticides Properly
  • Never use more pesticides than you need. Take care to store chemicals properly so containers do not leak.
  • Dispose of Chemicals Properly
  • Follow safe (and legal) disposal methods for household chemicals like paint or motor oil.
  • Dispose of Medicine Properly
  • To keep medicine out of our waterways, don't pour expired or leftover drugs down the sink or flush them down the toilet. Instead, return unused medicine to a consumer drug return location or foul your medication with coffee grounds or cat litter and put it in the trash.
  • Reduce Pesticide Use
  • Make your own garden insect repellents using common household items like garlic, vinegar and cooking oil.
  • Use Safer Pesticides
  • Use weed and insect-control products that contain plant-derived, non-toxic ingredients.


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