PCBs, which are responsible for most fish consumption advisories in the Chesapeake region, and PAHs, which have been linked to fish tumors, top the latest version of the Bay Program’s latest “toxics of concern” list.

It was the first revision to the list since 1999, and is intended to identify the organic toxic contaminants of greatest concern based on their potential to affect fish and other Bay resources.

In the analysis, polychlorinated biphenyls (PCBs) topped the list, followed by polycyclic aromatic hydrocarbons (PAHs), organophosphate pesticides and organochlorine pesticides, with five substances that did not fit into any of those groups rounding out the list.

It was the third full update since the first toxics of concern list was developed in 1991, and was the first time the list ranked toxics by their relative threat to the Bay’s resources and to humans by way of fish consumption. The rankings were made by a panel of scientists based on a variety of factors, such as a chemical’s prevalence in the Bay, its persistence, ability to bioaccumulate in fish and wildlife, its contribution to fish advisories, and other factors.

“It was a lot of data to pull together,” said Greg Allen, toxics coordinator with the EPA’s Bay Program Office. “It blends the best available information we have about the substances. And it blends in information about ecological and human health effects.”

Still, the list is not comprehensive. It does not include metals, such as copper, cadmium and chromium, which were on earlier lists because part of the ranking methodology—which used an EPA formula that factored in persistence and bioaccumulative effects of chemicals—could not be used for metals. That’s mainly because many metals, other than mercury, do not bioaccumulate. Allen said a ranking for metals would be done after the EPA completes a new methodology for metals.

Also not included are endocrine disrupters, which affect hormones in fish, and some contaminants of growing concern, such as flame-retardant chemicals, because of a lack of enough information.

Other chemicals were not included because of a lack of monitoring. For instance, the widely used pesticide atrazine—which has been the target of increased concern nationally—was not included because there is no loading estimate for the amount that enters the Bay. “We were really limited by the number of compounds that we had a load estimate for,” Allen said.

Because toxic chemicals already fall under the regulatory jurisdiction of the EPA and the states, the list is not a regulatory tool. Rather, it is used by the Bay Program and its Toxics Subcommittee to direct its efforts, which may include encouraging voluntary programs that go beyond regulatory requirements.

“We are going to try to develop some sort of regional cooperative efforts over this next year for the two top hitters, PCBs and PAHs,” Allen said. “We are trying to figure out how the Bay Program can form partnerships that will reduce loads to the Bay.”

For example, while production of PCBs is banned, the chemicals are still in use in power transformers. Some regions of the country have launched efforts to accelerate the phase-out of those still in use. Allen said such an effort could be considered in this region as well.

Likewise, PAHs—a group of chemicals created as a byproduct of fossil fuel combustion—often enter the environment when applied as sealants for roads and driveways. They have been linked to high rates of tumors found in bullhead catfish in both the Anacostia River in the District of Columbia and the South River outside Annapolis.

Some sealants are asphalt-based, others are made with coal tar. The asphalt sealants have far fewer PAHs, and Allen said educational campaigns could be used to encourage homeowners, highway agencies and other sealant users to purchase the less harmful variety.

Some of the pesticides on the list might be targeted in voluntary agreements between the Bay Program and the lawn care industry. This year, the Chesapeake Executive Council signed an agreement with the lawn care industry calling for a 50 percent reduction in phosphorus in lawn fertilizers. The agreement called for future reductions in nitrogen and a “dialogue” to recommend changes in pesticide use in 2008.

“We are trying to figure out how the Bay Program can form partnerships that will reduce loads to the Bay,” Allen said.

Toxics of Concern

The toxics are ranked by chemical groups, and by individual chemicals within that group.


PCBs (1)
PCBs (2)






Endosulfan, alpha & Endosulfan, beta
Endrin aldehyde