BROOKSVILLE, Maine — Researchers studying fish near Callahan Mine, a federally designated Superfund site on Blue Hill Peninsula, said Tuesday that elevated levels of heavy metals are not having obvious effects on the health or population of those fish.
But questions remain about whether metals leaching from the mine site are affecting the fish at the genetic level and whether that contamination is passing up the food chain.
A team of researchers from Mount Desert Island Biological Laboratory and several universities have been studying two types of fish — killifish and silversides — to determine how they are affected by high levels of copper, lead, zinc and cadmium coming from Callahan Mine.
The research is being conducted as part of the first phase of cleanup of the mine, where an estimated 800,000 tons of rock containing copper, zinc, lead and silver were extracted from the ground by Callahan Mining Co. in the late 1960s and early 1970s.
Celia Chen, a Dartmouth College professor who works on Superfund sites, told about two dozen Brooksville-area residents on Tuesday that her team found lead levels in fish in Goose Cove that were 300 times higher than those at nearby Horseshoe Cove.
But despite the high levels, the saltwater marsh in Goose Cove looks fairly typical in terms of vegetation and fish abundance, although Chen said the diversity of fish is lower in Goose Cove. The heavy metals do not appear to be affecting fish populations, however.
“They are living and thriving in there,” Chen said. “They just are carrying a lot of these metals in their tissues.”
Ed Hathaway, project manager for the U.S. Environmental Protection Agency, said the preliminary research shows that contamination from the mine is affecting the ecosystem. But more research is needed to find out how far the contamination goes and what, if anything, it would mean to human health.
“There are fish there,” said Hathaway, whose agency is overseeing the site cleanup and organized Tuesday’s meeting. “The question is are they passing along the contamination to other things that eat them.”
Unlike heavy metals such as mercury, most of the metals found at the site do not accumulate in intensity in tissues as you move up the food chain.
Charlie Wray of MDI Biological Lab and Chris Petersen of the College of the Atlantic said killifish near the mine are not exhibiting higher numbers of parasites — a possible sign of biological stress — or other ecological changes when compared with a “clean” site elsewhere on the peninsula.
Research is continuing at the site, however.
Joe Shaw, an Indiana University researcher, said his team has collected genetic data from fish at the mine site and at the clean reference site. The task now will be to crunch those 25 million data points to determine whether the fish near the mine are exhibiting genetic differences and if so how those differences could show up in the fish.
The EPA began the first phase of the Callahan Mine cleanup project this past spring, and activity on the site is expected to continue into the fall.
Soils contaminated with polychlorinated biphenyls — an industrial compound known as PCBs — have been excavated and stockpiled for removal. Cleanup of contamination at a handful of residential properties should be complete this week, Hathaway said.