Traces of some toxic chemicals have persisted in animals and waterways such as the Back River in Baltimore County for decades after the U.S. government banned their use.
A study in the Back River soon could help explain why the chemicals continue to show up — and maybe provide insights into how to get rid of them.
Industrial chemicals known as polychlorinated biphenyls, or PCBs, were long used in electrical and hydraulic equipment and plastics. The cancer-causing chemicals were outlawed in 1979 but continue to be found throughout the environment, including in humans.
A study of 20 years of precipitation, pollution and water quality data has traced degradation of Baltimore's Gwynns Falls to frequent sewage leaks, and some environmental improvements to projects to clean up or reduce stormwater runoff.
As Baltimore City, Baltimore County and other jurisdictions around the state struggle with how to tackle the toxic pollution in the Chesapeake Bay, researchers at the U.S. Geological Survey and University of Maryland, Baltimore County, are focusing on the Back River to better understand the contamination. They plan to collect and analyze samples of PCBs that are embedded in muddy creek bottoms, flowing out of wastewater treatment plants and floating around in the water — and into fish gills.
Baltimore’s Board of Estimates approved city funding for the research Wednesday.
PCB pollution is often thought of as a contaminant found only in soils and sediments, a remnant of old factories and dirty industry. But the research aims to address a different reality regarding PCBs, said Upal Ghosh, a UMBC professor of chemical, biochemical and environmental engineering.
“What we are finding for our area, especially, and many other urban areas, is there are ongoing sources still,” he said. “We’re starting to figure out what these sources are.”
PCBs are known to cause cancer and impair reproductive and immune systems in animals, building up the most in those at the top of the food chain. Research published last week found the chemicals are threatening the future survival of killer whales.
As another surge of stormwater and pollution flows down the Susquehanna River, requiring Conowingo Dam floodgates to open for the second time in weeks, Chesapeake Bay scientists are concerned about the potential impact on oysters and still watching closely for other impacts.
Enough of the contamination has been found in fish tissue or sediments in Chesapeake waterways — including the Potomac, Severn, South, Rhode, Elk and Sassafras rivers, along with Back River — that they are classified as PCB-impaired by the Environmental Protection Agency.
Much like the state’s responsibilities to reduce nutrient and sediment pollution across the Chesapeake, the EPA requires jurisdictions that contain impaired waterways to address the pollution.
But given relatively poor understanding of the types and sources of PCBs, there is little those governments can do for now, said Emily Majcher, a USGS hydrologist collaborating with Ghosh and other researchers on the Back River study.
“Right now, there are a lot of unknowns,” she said. “It’s difficult to apply resources to mitigate anything at this point.”
There are 209 varieties of PCBs, and groups of them behave differently. But there is no data on which types are most prevalent in the bay, Majcher said.
The research aims to fix that. The scientists will collect and analyze samples not just long-embedded in the dirt but also potentially built up inside old sewer mains and slowly being released through the Back River Wastewater Treatment Plant, which processes sewage from across much of the Baltimore region.
The data used to classify Back River as PCB-impaired as recently as 2008 dated as far back as 2001, and it didn’t differentiate between different types of PCBs, known as congeners.
“I don’t want to say it’s meaningless, but it’s much more detailed and informative if you’re looking at the congener level,” Majcher said.
The researchers plan to collect samples from the Back River over the coming months, funded with about $200,000 — including the $75,000 Baltimore officials approved Wednesday, and other money from Baltimore County and the U.S. Department of the Interior.