Chemical Contaminants

Chemical contaminants are chemicals or compounds that can potentially harm the heath of humans, wildlife and aquatic life. Toxic chemicals are constantly entering the Chesapeake Bay and its tributaries via wastewater, agriculture, 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.

What Types of Chemical Contaminants Can Be Found in the Chesapeake Bay?

There are two broad categories of chemical contaminants that can be found in the Chesapeake 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 (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 (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 (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 the Potomac River and other Chesapeake Bay tributaries. Evidence suggests that low doses of exposure to some human-produced chemicals may disrupt endocrine (reproductive) 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.

Where Do Chemical Contaminants Come From?

There are four general sources of chemical contaminants to the Chesapeake Bay and its tributaries:

• Wastewater that is discharged from industrial facilities and wastewater treatment plants directly into local waterways.
• Runoff from farmland.
• Stormwater runoff from cities, towns and suburbs. Stormwater picks up oil, pesticides and other chemicals as it flows across lawns, roads and parking lots and into nearby streams and storm drains. This type of pollution is significant and difficult to control.
• Air pollution from factories, power plants, auto emissions, gas-powered lawn tools and other emitting sources.

How Are Chemical Contaminants a Pressure on the Chesapeake Bay?

Many chemical contaminants, including mercury, PCBs and PAHs, do not break down easily; instead, they bind to sediments and persist in the environment for many years. The Chesapeake Bay's wildlife and aquatic life are affected when toxic chemicals move through the food web in a process called bioaccumulation:

• Small, bottom-dwelling aquatic organisms take up contaminants while feeding or through skin contact.
• Larger fish accumulate toxins in their tissues when they eat contaminated organisms.
• In turn, birds and other wildlife eat the contaminated fish.

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

What Parts of the Chesapeake Bay Are Most Affected by Chemical Contaminants?

While there are streams and rivers throughout the Chesapeake Bay 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