Chemical Contaminants

Chemical contaminants, or toxics, are chemicals or compounds that can potentially cause harm to organisms. Toxic chemicals are constantly entering the Bay and its tributaries through wastewater, stormwater and air pollution. While chemicals such as DDT and PCBs have been banned from production for years, many chemical contaminants are still widely used or persist in the environment, causing harm to both humans and wildlife.

What types of chemical contaminants can be found in the Bay?

There are two broad categories of chemical contaminants that can be found in the Bay and its tributaries: metals and organics. Mercury is the most common metal found in the Bay watershed. Common organic chemical contaminants include:

• Polychlorinated biphenyls, or PCBs, which act as a flame retardant in electrical equipment. Though their production has been banned since 1977, PCBs still pose a risk to humans and wildlife because they persist in the environment.
• Polycyclic aromatic hydrocarbons, or PAHs, which form when gas, coal and oil are burned. PAHs are common in areas with high rates of development and motor vehicle traffic.
• Organophosphate pesticides, or OPs, which are mostly herbicides and insecticides used in agriculture. OPs can affect functioning of the nervous system.
• Organochlorine pesticides, such as DDT, chlordane and chlorothalonil, which persist in the environment.

Endocrine disruptors are another group of contaminants that have caused concern since recent discoveries of intersex fish in several Bay tributaries. Evidence suggests that low doses of exposure to some human-produced chemicals may disrupt endocrine systems in fish and other species. Because the endocrine systems of fish are similar to those of humans, endocrine disruption in fish is an indication that these chemicals may also pose a risk to humans.

Compounds that may cause endocrine disruption in fish include:

• Human and veterinary pharmaceuticals that mimic, suppress or cause the body to over- or under-produce hormones.
• Some pesticides and industrial chemicals, including PCBs and PAHs.
• Personal care products, including sunscreens and antimicrobial soaps.

Where do chemical contaminants come from?

There are three general sources of chemical contaminants to the Bay and its tributaries.

• Point sources, such as industries and wastewater treatment plants that discharge wastewater directly into local waterways.
• Stormwater runoff from urban and suburban areas, which is a significant source of chemical contaminants. Stormwater carries residue from roadways, agricultural lands and other contaminated areas to local streams and storm drains. This type of pollution is difficult to control.
• Air pollution from factories, power plants, auto emissions, gas-powered lawn tools and other sources.

How are chemical contaminants a pressure on the Bay?

Many chemical contaminants, including mercury, PCBs and PAHs, do not break down easily in the environment; instead, they attach to sediment and persist in the Bay and its tributaries for many years. Small, bottom-dwelling organisms take up contaminants while feeding or through skin contact. Larger fish accumulate toxics in their tissues when they eat contaminated organisms. In turn, birds and other wildlife eat the contaminated fish, and toxics continue to move up the food web.

Chemical contaminants do not just impact wildlife. Humans can also experience negative health effects from eating contaminated fish. The six Bay states and the District of Columbia issue fish consumption advisories to prevent people from unknowingly eating fish that could be contaminated.

What parts of the Bay watershed are most impacted by chemical contaminants?

While there are streams and rivers throughout the watershed that have shown some evidence of chemical contaminants, three specific Regions of Concern have been identified as having significant problems:

• The Patapsco River, part of Baltimore's Inner Harbor.
• The Anacostia River, which flows through Washington, D.C.
• The Elizabeth River in Hampton Roads, Virginia.