The Halifax Regional Municipality is warning people not to enter the water or consume fish from Barry's Run in Dartmouth, N.S., due to arsenic contamination from historical gold mining.
Barry's Run is located between Lake Charles and Highway 107, just a few hundred metres downstream from Montague Gold Mines, the site of extensive gold mining dating back to the 1860s.
The municipality says a recent environmental site assessment at Barry's Run found high levels of arsenic in the stream's mud.
There may be health risks associated with exposure to or ingestion of the sediment, the HRM said in a statement.
"The primary concern with arsenic-contaminated sediment (mud) is from ingestion, such as drinking water with suspended/dissolved arsenic, and through prolonged contact with the skin," according to information posted by the municipality.
"In some cases, fish can also accumulate arsenic and mercury in their flesh, which may be a concern for local anglers who regularly catch and eat fish from the area."
The former mining site at Montague Gold Mines is now owned by the province, which is beginning the process of trying to clean it up. Part of that process will include identifying potential health risks from mine tailings, the materials left over after gold is extracted from rock.
Arsenic does occur naturally in rocks, but gold mining can disturb and mobilize it in the environment.
Saint Mary's University professor Linda Campbell studies contamination at historical gold mine sites, including at Montague Gold Mines.
She said she's glad the province is warning of potential risks at Barry's Run.
"I'm very happy that different levels of government are finally starting to explore this issue," she said. "That's good news for all of us. We need better quantification of the risks. What's out there? It's a big gap in the information."
But she said there are other gold mine tailings sites worthy of further examination.
"We do need to have the conversation about where are there other contaminated tailings. That is not well-quantified.… What about the other tailings sites out there that could be impacting freshwater systems as we speak?"
Campbell said it's difficult to assess the potential human health impacts of contaminated sediment, but disturbing it could negatively affect the ecosystem, including invertebrates, plants and overall biodiversity.
The municipality commissioned the study of contamination at Barry's Run because adjacent land was being considered for residential development.
The study notes that development could increase stormwater flow to the body of water and remobilize the tailings.
But tailings may already be getting remobilized.
The report mentions an Acadia University study of sediments in Barry's Run that suggests some near-surface sediments have arsenic concentrations similar to old tailing deposits, providing evidence a nearby fen is acting as a sink for tailings that are then mobilized into Barry's Run.
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