Polychlorinated biphenyls (PCBs), a group of likely carcinogenic chemicals, were banned in the U.S. in 1979. Yet because the chemicals were so widely used, and linger in the environment for so long, PCBs continue to be a major source of fish consumption advisories in Maryland and surrounding states. 

A recent study by Professor Upal Ghosh, in the Department of Chemical, Biochemical, and Environmental Engineering, demonstrates the "unfinished work" of ridding our waters of PCB pollutants, the researchers write. The study was highlighted in a story in the Bay Journal.

The researchers, led by Ghosh and Research Assistant Professor Nathalie Lombard, analyzed PCB concentrations in fish that had been collected across 323 monitoring stations in Maryland over three decades. They identified five watersheds as highly impacted by PCBs, including the Upper Chesapeake Bay. Most impacted waterways have seen gradual, yet steady improvements over the years, with the exception of the Gunpowder-Patapsco near Baltimore, which showed no decrease in PCB pollution concentration levels in fish since 1996. 

Overall, the study showed that the ban on PCBs and pollution remediation efforts implemented across Maryland and surrounding states have helped waterways recover, the researchers say, but more efforts are still needed.