Chemical Contamination

An osprey nests close to a chemical plant along the James River.

© Krista Schlyer/iLCP

Toxic Chemicals Harm Our Bay and Our Health

Chemical contaminants in water do not break down easily and persist in the environment for many years, impacting not just fish and birds, but humans as well.

What are Chemical Contaminants?

Chemical contamination occurs when chemicals are either found where they shouldn’t be or are present in amounts that are higher in concentration than is considered safe. Toxic chemicals are constantly entering the Chesapeake Bay and its rivers and streams via industrial sites, military bases, wastewater, stormwater, agriculture, and air pollution. These dangerous chemicals, including mercury and other metals, pesticides, PCBs (polychlorinated biphenyls), PAHs (polycyclic aromatic hydrocarbons), and PFAS (per- or poly-fluoroalkyl substances), do not break down easily, persisting in the environment for many years. You can’t see them, smell them, or taste them, but these contaminants are present, causing harm to the Bay, its fish, and wildlife—and many have also been linked to human health problems.

Types of Chemical Contaminants

There are many types of chemical contaminants in the waters of the Chesapeake Bay. According to the Chesapeake Bay Program, almost three-quarters of the Chesapeake Bay’s tidal waters are considered impaired by contaminants. Each contaminant has a unique and harmful impact on the fish, birds, and humans that depend on the Bay. Many bioaccumulate, or build up in the body, faster than they can be eliminated.

Learn about these contaminants and just how devastating they can be. It’s important to note that there is much we still don’t know about the effects of toxic contaminants on human and ecological health.  


Pesticides flow into the Chesapeake Bay primarily from surrounding farms, but also from private yards, via polluted stormwater runoff. Exposure to neurotoxic pesticides has been linked to lower birth weight, reduced IQ, delayed motor development, attention disorders, and more. 

One example is the herbicide atrazine. Used for agriculture and in lawn products, it is just one of many known to disrupt regular hormone function and cause several types of cancer. Though banned in much of the world, it is the second most commonly used herbicide in the United States. Hawaii and five U.S. territories have recently banned it.


This heavy metal, often released from the burning of coal, is a highly toxic chemical that pollutes waterways, taints fish, and subsequently can cause harm to humans that consume them. The chemical becomes more concentrated as it moves up the food chain as fish, wildlife, and people consume contaminated food. For example, the amount of mercury in fish tissue can be more than a million times higher than in surrounding water. Mercury is especially detrimental to the developing nervous system and can cause IQ deficits in children. For this reason, fetuses, infants, children, and women of childbearing age are at the greatest risk. In the Chesapeake region, governments have issued statewide fish-consumption advisories for mercury for all lakes and rivers in Pennsylvania and Maryland, and many rivers in Virginia.


Commonly referred to as “forever chemicals,” more than 9,000 PFAS, many of them toxic, are found in products we take for granted every day: nonstick cookware, flame retardants, water- and stain-resistant clothing and furniture, and fire-fighting foams used at airports and military bases. They spread easily in water, build up in organisms that ingest them, and stay in the body for long periods of time. In the Chesapeake region, they have been found in high levels in striped bass, blue crabs, and oysters. Lab studies suggest high levels of PFAS may be linked to a range of health problems, from liver and immune system damage to birth defects and an increased risk of cancer.


The EPA’s Chesapeake Bay Program has prioritized PAHs as among the most critical toxic contaminants to rivers, streams, and the Chesapeake Bay. These compounds make their way into our waters and our air through polluted runoff and air deposition. Sources include leaking motor oil, vehicle exhaust, the burning of fossil fuels, coal-tar pavement sealants, and more. They can harm people, birds, amphibians, fish, mammals, and plants. They are found to cause lesions, tumors, and developmental issues in fish and amphibians, and accumulate in mussels, clams, and oysters.

Pharmaceuticals and Personal Care Products (PPCPs)

Considered emerging contaminants of concern, PPCPs end up in our waters in a number of ways.  Antibiotics and medications, which pass through the body as waste (both human and animal), are found in wastewater. Personal use products, from hair color to shampoo to cosmetics, which contain a range of toxic chemicals and heavy metals, are washed off into drains. People also dispose of unwanted products and medications improperly, dumping them down the sewer or putting them into the trash. 


Although PCBs were banned in 1977, these highly toxic industrial compounds continue be widespread in the Bay watershed, entering our waters through accidental leaks, improper disposal, and legacy deposits that can remain in the environment for decades. Even low levels of PCBs are dangerous, as they accumulate in fish and animal tissue, traveling up the food chain. These compounds are known to cause a wide range of health problems in both wildlife and humans, ranging from cancer and birth defects to hormonal imbalances and an increased susceptibility to other diseases. 

How Chemicals Enter the Water

Chemical contaminants enter the water quietly, often without being seen or smelled. But by understanding their origins, we can devise ways to stop toxic chemicals from contaminating the waters of the Chesapeake Bay and causing harm to the water, fish, wildlife, and ultimately humans, as well. 

Industrial Facilities

Left unchecked, industrial facilities (like the old Sparrows Point Steel Mill in Baltimore) are notorious for violating pollution regulations for water, air, and toxic wastes that foul local waterways and impact communities. Toxic chemicals released by industrial facilities include benzene, chromium, lead, naphthalene, benzo(a)pyrene, and zinc, among others. These chemical pollutants can migrate beyond the facility and surrounding land, ending up in the water we drink and fish we eat, presenting a risk to human health and the environment. They contaminate groundwater and sediment, eventually seeping into local creeks, rivers, and ultimately the Bay.


Stormwater runoff or urban/suburban polluted runoff picks up oil, pesticides, fertilizer, and other chemicals as it flows across lawns, roads, driveways, and parking lots, contaminating nearby streams and storm drains. This polluted runoff is significant and challenging to control.


Pharmaceuticals and chemicals from personal care products end up in wastewater. They cannot be removed at wastewater treatment plants, so they find their way into our rivers and the Bay.

Coal-fired Power Plants

Coal-fired power plants are the largest single source of mercury emissions in the U.S. They also produce microscopic soot particles that spread by the wind over hundreds of miles. While renewable energy sources are replacing the need for many coal-fired power plants, those in the Chesapeake Bay airshed continue to affect our water and put human health at risk. In addition to toxic contaminants, one-third of the Bay’s nitrogen pollution comes from the air.

How CBF Is Helping to Stop Water Contamination

The best way we can reduce toxic contamination and reduce nitrogen, phosphorus, and sediment pollution are largely the same: Stop pollutants at their source. The work CBF and partners are doing to implement the Chesapeake Clean Water Blueprint tackles this critical objective. We’re working hard to control polluted runoff from urban and suburban areas as well as from farms. When we limit urban, suburban, and agricultural polluted runoff, less pollution of all kinds will end up in our waterways and food. The same goes for upgrading wastewater treatment technology and reducing the amount of waste we have to treat before putting it back into the environment.

How YOU Can Help Stop Water Contamination

Chemical contamination of our water can be curbed and even reversed, but we need to take action. Here are six things you can do as an individual and how you can put pressure on businesses and regulators to do their part:

  1. Dispose of pharmaceuticals responsibly. More and more pharmacies offer special disposal bins for medications.
  2. Be cautious when fertilizing your lawn and garden so that excess nitrogen and phosphorus don’t end up in stormwater and groundwater. What we do upstream on land ultimately ends up in the water and in us.  
  3. Use an environmentally friendly service or self-service location when performing work on or washing your car.
  4. Stand up for the Bay by signing our  pledge.
  5. Call Congress and tell your representative and senators to stand up for our Bay.
  6. Call your governor and/or local/state/federal representatives and tell them why protecting the Bay from chemical contamination matters to you. 


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