Historically, some chemicals that have performed as originally intended also have caused unforeseen problems when released into the environment. Polychlorinated biphenyls (PCBs) and dichloro diphenyl trichloroethane (DDT) are two examples.
VIMS researchers have recently discovered that another chemical with detrimental environmental properties—a widely used class of fire retardants known as brominated diphenyl ethers (BDEs)—have become dispersed throughout the Roanoke and Dan rivers in south central Virginia.
The biological effects caused by BDEs are not immediately obvious to the eye, but interactions of these chemicals with cellular metabolism may lead to long-term damage to exposed organisms, including humans. Medical researchers suspect that BDEs may impair immune system responses, disrupt endocrine function, and delay intellectual and physical development.
BDEs are of mounting concern in Europe, where Swedish researchers have recently reported that concentrations of BDEs in human breast milk have been doubling every 5 years. Although overall levels remain low, the dramatic increase over time is alarming.
“Although we don’t yet know the full extent of their toxic effects, we do know that BDEs are persistent and that they can bioaccumulate to high levels,” says VIMS associate professor RobHale. “We’re finding that their environmental properties rival those of PCBs. BDEs persist in the field, accumulate in aquatic animals and exhibit similar modes of toxicity. They’re bad news—particularly since we continue to release them.”
PCBs were used as insulators or fire retardants in hydraulic fluids and electrical transformers. Although PCB manufacture was halted in the 1970s, the chemical persists in measurable quantities in soil and water, and in the bodies of many fish and animal species worldwide, even in areas far removed from their original point of manufacture. Implicated as a cause of liver cancer in lab animals, PCBs may cause eye, skin, and respiratory irritation in people in direct physical contact.
BDEs, on the other hand, continue to be widely used in the production of flame-resistant plastics, in the housings of personal computers, and as a constituent of foam padding in seat cushions. Because BDEs have only recently been identified as an environmental threat, their release to the biosphere is not explicitly regulated by the federal government or the states.
The BDEs were detected by VIMS in the course of a study supported by and in collaboration with Virginia’s Department of Environmental Quality (DEQ), examining the extent of contamination in edible fish from state tributaries. After the discovery of the BDEs, the Commonwealth formed a task force consisting of DEQ, the Virginia Health Department, VIMS, and several other state and federal agencies to further investigate the extent of pollution throughout the Dan and Roanoke river watersheds.
The source of the BDEs and their route of entry to the rivers is currently uncertain. However, the polyurethane foam production process may be key. VIMS research has already shown that BDEs can be released to the atmosphere from foam manufacturers’ exhaust stacks.
“Our data show that these BDEs have been widely released without anyone really noticing,” Hale says. “The BDEs detected to date are likely the top of the iceberg. Even if we found the source today and eliminated it, the chemicals already released will remain in the environment for years to come. And the longer they are used, the greater these levels will be.”