Almost three-quarters of the Chesapeake Bay’s tidal waters are considered impaired by toxic 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:

  • Air pollution created by factories, power plants, cars, trucks, gas-powered lawn tools and other sources
  • Agricultural runoff
  • Stormwater runoff
  • Wastewater discharged from industrial facilities and wastewater treatment plants into rivers and streams

While production bans have lowered the presence of some contaminants in the watershed, others are still widely used. Two kinds of toxic contaminants can be found in the Bay: metals and organics. The most common metal found in the watershed is mercury. While the extent and severity of mercury contamination is widespread in the watershed, contamination with metals like aluminum, chromium or iron 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.