Federal scientists have uncovered evidence that contaminants wafting out Alberta’s oilsands operations are collecting on the bottom of remote lakes up to 100 kilometres away.

The chemical “legacy” in the lake sediments indicates that oilsands pollution is travelling further than expected and has been for decades.

“The footprint of the deposition is potentially larger than we might have anticipated,” says Derek Muir, a senior Environment Canada scientist, who will present the findings Wednesday at an international toxicology conference in the U.S. where the oilsands are a hot topic.

A team led by federal scientist Jane Kirk, also of Environment Canada, will report that snow within 50 kilometres of oilsands operations is contaminated with a long list of “priority pollutants” including a neurotoxin that “bioaccumulates” in food webs.

Kirk’s colleague Joanne Parrott will report that melt water from snow collected near oilsand plants is toxic to newly hatched minnows in the lab.

But perhaps the most dramatic findings is that pollutants called polycyclic aromatic hydrocarbons, or PAHs, are building up in lake sediments up to 100 kilometres from the oilsands operations.

“That means the footprint is four times bigger than we found,” says David Schindler, an aquatic scientist at the University of Alberta. He and his colleague Erin Kelly made headlines in 2010 when they reported that airborne heavy metals and other pollutants from oilsands operations were contaminating the landscape up to 50 kilometres away.

Their findings have been criticized by oilsands proponents, but the Environment Canada scientists report they have not only “confirmed” the Schindler-Kelly findings but found evidence PAHs can travel even farther.

Muir, a world authority on chemical contaminants, teamed up with Queen’s University researchers to look at the sediments that have been collecting for a century on the bottom of six remote lakes, five of them within 35 kilometres of the oilsands and the sixth lake 100 kilometres away. The lakes are undisturbed and received only atmospheric inputs, the scientists say.

They found that PAHs in the sediments “increased precipitously beginning at the early 1970s” and have climbed 2.5 to 23 times over pre-1960 levels.

“It is quite distinct in all the lakes,” Muir said in a telephone interview from California where he will present the findings at the annual meeting of the North American Society of Environmental Toxicology and Chemistry.

He says the rising levels of PAHs in the sediments “seem to parallel the development of the oilsands industry.”

In four of the five shallow lakes located within 35 kilometres of oilsands operations the highest PAHs levels observed are from the most recent sediments collected in 2009-2010.

PAHs also turned up in sediments Namur Lake, located in a remote provincial park and known for Lake Trout, Arctic Grayling, and Northern Pike. Muir said samples taken about 100 kilometres northwest of the main oilsands operations show PAHs levels have more than tripled in Namur Lake’s sediments since the 1960s.

“To see something outside the 50-kilometre zone was a bit of a surprise,” Muir said. “Having said that I have to caution it was only one lake.”

He said the PAHs increasing in the lake sediments have a different signature – or “fingerprint” – than PAHs generated by forest fires and other natural processes.

In the 1970s and 1980s the PAHs shifted to a more “petrogenic, in other words petroleum oriented, and more combustion source,” Muir said, noting that the chemicals could be from both upgraders, which convert oilsands bitumen into crude oil, and oilsands mining operations that release petroleum-based hydrocarbons into the atmosphere.

The PAHs levels in the sediments, with the exception of the lake closest to the oil sands operation, were lower than “guideline limits,” says Muir.

“So overall we don’t think that the PAHs have yet reached a level in the sediments of these lakes where they are going to be toxic to aquatic life,” said Muir. He notes that contamination levels are comparable to those around urban areas.

But he said “there is definitely a concern about it.” And more work in underway to sample sediments in other remote lakes in the region.

His colleague Jane Kirk built on Schindler and Kelly’s work by testing for heavy metals and other contaminants in snow at 90 sites located up to 200 kilometres from the oilsands plants. She reports that the “aerial loadings” of 13 “priority pollutants” were 1.5 to 13 times higher at sites within 50 kilometres of the upgraders and highest within 10 kilometres.

Muir says the elevated levels of methyl mercury is “probably the highest concern” because it is a neurotoxin that accumulates in food webs.

“We don’t really know the fate of the various metals including mercury as they go from snow, to melt water to run-off and then into the aquatic environment,” Muir said.

The Environment Canada work is part of the Joint Canada-Alberta Implementation Plan for Oilsands Monitoring. The federal and Alberta governments have billed it as a “transparent and accountable” system designed to improve understanding of the long-term cumulative effects of oilsands development.

Environment Canada earlier this month said scientists were not available to comment on their findings of contamination around the oilsands. The department’s media office arranged this week’s interviews with Muir and Parrott after Postmedia News obtained details of the reports the scientists will present at the U.S. conference on Wednesday.

Parrott and her colleagues in an Environment Canada lab have been exposing fathead minnows, which she describes as the “lab rat of the fish world”, to melt water from snow collected three to four kilometers from oilsands upgraders and mining operations. The snow was collected in 2011 and 2012 along the Athabasca River, which has several species of fish that have long been a dietary staple for aboriginal people in the region.

“The larval fish didn’t do very well in that snow at all,” says Parrott, who will report at the conference that melt water was “toxic to larval fathead minnows at 25 to 100 per cent.”

Once the melt water was diluted with water in the Athabasca River, Parrott says it was not longer toxic to the minnows.

She and her colleagues are expanding the testing to look at how young fish fare in the spring freshet and tributaries feeding into the Athabasca River.

Schindler says water in tributaries where young fish hatch in the spring can be largely melt water.

“My big concern is that slowly because of mortalities at spring melt, that this will erode the fishery, killing off the embryos,” says Schindler.

Parrott’s findings may explain why fish numbers the Muskeg River, a tributary of the Athabasca, have plummeted in recent decades, he said.

Schindler also says they may also explain why deformed fish are turning up in Lake Athabasca. “I think what could happen is that the few embryos that manage to survive, deformed as they are, struggle down to Lake Athabasca,” he said. While the deformed fish may not have a high load of contaminants, he said the fish look “so horrible” people won’t eat them. “I think that’s fair enough, they wouldn’t sell in Safeway,” says Schindler.

He says the Environment Canada scientists should not just present their findings at scientific conferences but also at the Joint Review Panel reviewing Shell’s proposed Jackpine oilsands mine expansion, 70 kilometres north of Fort McMurray.

Schindler would like the expansion delayed until the environmental impacts of existing oil sands operations are better understood.

“They should say: ‘Hey wait a minute, maybe we should get the monitoring system in place and see what the real state of the system is now,’ before this approval is made,” says Schindler.