According to data submitted by Delaware, Maryland, Virginia and the District of Columbia to the U.S. Environmental Protection Agency in 2016, 82 percent of the Chesapeake Bay’s tidal segments are partially or fully impaired by toxic contaminants. Chesapeake Bay Program partners have set a goal to observe no such impairments. The latest listings of impaired waters under Section 303(d) of the Clean Water Act mark a continued increase in the observation of toxic contaminant impairments since 2010. An analysis to determine whether this observed increase is the result of a rise in the number of tidal segments analyzed or an actual decline in environmental conditions has not been conducted.
Toxic Impairments in the Tidal Chesapeake Bay (2010-2016)
Percentage of Tidal Segments in Delaware, Maryland, Virginia and the District of Columbia with Partial or Full Impairments Due to Chemical Contaminants
Toxic Impairments in the Tidal Chesapeake Bay (2016)
While chemical contamination is often characterized as a localized problem occurring in “hot spots” or “regions of concern,” pollutants like metals, polychlorinated biphenyls (PCBs) and priority organics exceed water quality criteria in at least part or all of the tidal tributaries that deliver water to the main stem of the Bay. Because toxic contaminants are present in the water column, persist in bottom sediment and build up in the tissue of fish and other organisms through a process known as bioaccumulation—impacting the health of fish and other ecological resources—management actions undertaken through state Total Maximum Daily Loads (TMDLs) are necessary to support long-term positive change in this indicator of environmental health.
A technical report shows PCBs and mercury are particularly problematic in the region, and are considered widespread in severity and extent. Polycyclic aromatic hydrocarbons (PAHs) and some herbicides are also considered widespread in extent, while dioxins, petroleum hydrocarbons, some chlorinated insecticides and some metals occur locally. Information is insufficient to determine the extent of biogenic hormones, household and personal care products, pharmaceuticals or flame retardants.
Toxic contaminants can harm human health and affect the survival, growth and reproduction of fish and wildlife. Increasing our understanding of toxic contaminants is critical to the drafting of policy and prevention approaches that will reduce their effects on living resources.