Chemical contaminants continue to afflict the Chesapeake Bay watershed, raising concern over water quality and the health of fish, wildlife and watershed residents.
Close to three-quarters of the Bay’s tidal waters are considered impaired by chemical contaminants, from the pesticides applied to farmland and lawns to repel weeds and insects to the household and personal-care products that enter the environment through our landfills and wastewater. But so-called “PCBs” and mercury are particularly problematic in the region, according to a report released last week by the U.S. Environmental Protection Agency (EPA), U.S. Geological Survey (USGS) and U.S. Fish and Wildlife Service (USFWS).
Both PCBs—short for “polychlorinated biphenyls”—and mercury are considered “widespread” in extent and severity, concentrating in sediment and in fish tissue and leading to fish-consumption advisories in a number of rivers and streams.
The District of Columbia, for instance, has issued such advisories for all of its water bodies, asking the public not to consume catfish, carp or eels, which are bottom-feeding fish that can accumulate chemicals in their bodies. While the District’s Anacostia and Potomac rivers raise the greatest concern in the watershed when it comes to fish tissue contamination, a November report confirmed that many Anacostia anglers are sharing and consuming potentially contaminated fish, sparking interest in reshaping public outreach to better address clean water, food security and human health in the area.
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”; mercury can find its way into the atmosphere through coal combustion, waste incineration and metal processing.
Exposure to both of these contaminants can affect the survival, growth and reproduction of fish and wildlife.
The Chesapeake Bay Program will use this report to consider whether reducing the input of toxic contaminants to the Bay should be one of its new goals.
The Bay Program Toxics Subcommittee has updated its list of Toxics of Concern, ranking the toxic organic chemicals in the Chesapeake Bay with the most potential for harm. PCBs topped the list, followed by PAHs and organophosphate pesticides. Organochlorine pesticides and five other organic toxics are also included in the list.
The original Toxics of Concern list, which was completed in 1991, identified and documented chemicals that were adversely impacting or had the potential to impact the Bay. The list was subsequently refined in 1996 and 2000 prior to this latest update.
The 2006 Toxics of Concern list is based on the same chemical ranking system used for the 1996 list, incorporating chemicals' source, fate and effects of exposure. Also, like the 2000 list, fish consumption advisories and 303(d) impairments were considered for the 2006 revision.
The Toxics of Concern list is used by the Bay Program Toxics Subcommittee to help develop strategies to address the most problematic toxic organics in the Bay and its tributaries. It is not a complete list of all chemicals that may impact the Bay or its watershed. Some organics could not be included due to data gaps. Also, metals, such as mercury, are not included in the list because assessment guidelines comparable to those used for organics are not currently available.
Although PCB manufacturing was banned in 1977, PCBs can build up in bottom sediments and persist for many years; therefore, historic discharges of PCBs can still affect the Bay today. Also, when old PCB-containing equipment that is still in use fails, PCBs can flow into the nearest stream or river via stormwater.
PAHs are formed when coal, gasoline and fuel oil are burned and are a major component of tar and asphalt. The most rapid increases of PAHs in river bottom sediments are found in watersheds with increasing development and motor vehicle traffic.
Organophosphate pesticides are mostly herbicides and insecticides used in agriculture. Organochlorine pesticides, such as DDT, are no longer widely used but persist in the environment.
In recent years, people have become increasingly concerned about the issue of toxic materials, like Polychlorinated Biphenyls (PCBs), contaminating fish and shellfish in water bodies around the world. In the Chesapeake Bay region, the Bay states have issued fish consumption advisories throughout the Bay and its rivers to protect the health of people who enjoy dining on the Bay's fish and shellfish.
One way that Bay scientists assess how toxic pollutants are affecting the animals and plants in the region, Bay Program partners have focused on PCB concentrations in local white perch. PCBs are persistent organic chemicals that were formerly used in industrial practices in the United States. They enter the environment and can impact the creatures living within it. Although PCBs are not the only contaminants in an area, PCB concentrations in white perch provide an indication whether other chemical contaminants are present in an area.
White perch are a good indicator of toxic contaminant concentrations in the Bay's waters because they are a resident species in the Bay; the majority of white perch remain in local waters throughout their lives. Considered an enjoyable fish to eat, white perch are a commercial and recreational fishery in the Bay. For scientists who are examining the effects of chemical contaminants on fish, as well as the impact on humans who eat PCB-contaminated fish, white perch are a logical species to study.
Data gathered from Maryland and Virginia suggests that PCB concentrations are higher among white perch in the upper Bay than they are in the lower Bay. Similarly, there is a trend in fish tissue where fish on the eastern shore have lower concentrations of PCBs than their counterparts on the western shore.
A common characteristic among the areas of the Bay where white perch have higher PCB concentrations is related to land development; the western shore of the Bay is more developed than the eastern shore of the Bay, and white perch from the Bay's western shore have higher PCB concentrations than their counterparts on the eastern shore. Additionally, white perch sampled from the Patapsco River had particularly high PCB concentrations, which can be attributed to the level and type of industrialization in the Baltimore area.
Many of the Bay's waters have active advisories for limiting the consumption of white perch. As is true with any fish, it is important for someone who plans to catch white perch in the Bay's waters to first check out the fish consumption advisories to see what the state recommends regarding consuming fish caught in the Bay and its rivers.
Without sufficient data to determine a trend in the PCB concentrations in white perch in the Bay, Bay scientists cannot say for sure what to expect regarding the future of those toxic contaminants in white perch in the Bay. However, PCBs were banned more than 25 years ago, so scientists expect to see a natural decrease in their concentration in white perch over time.
Chemical contaminants that get into the environment and harm the animals and plants around them are typically considered to be toxic pollution. Learn about toxic pollution in the Bay.