Alberta Health has issued a health warning about eggs from two northern lakes downstream from the oilsands after they were found to contain dangerous levels of mercury.
James Talbot, chief medical health officer, has advised people to restrict consumption of gull and tern eggs from Lake Athabasca and Mamawi Lake in the Peace-Athabasca delta. Children and pregnant women are at higher risk from mercury, a potent neurotoxin that accumulates in the body as more contaminated food is consumed.
"The developing brain is the one that's most at risk from mercury," Talbot said.
He added that the Nunee Health Authority in Fort Chipewyan has been informed of the advisory. A previous mercury advisory which been issued for fish in the area remains in place.
Mercury levels rising
Concerns about mercury in the environment downstream from the oilsands date back to at least 2010, when an Environment Canada study found that levels of the element in the eggs of water birds downstream from oilsands development seemed to have increased by nearly 50 per cent over the previous three decades.
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Last September, Environment Canada researchers monitoring the environmental impact of the oilsands published a study expanding on that research, sampling eggs from several species in 2009, 2011 and 2012.
All species showed increases in mercury over those years, with some showing increases of up to 139 per cent. In at least one species, mercury levels were high enough to start harming the birds.
Talbot acknowledged that not enough is known about what's happening with other traditional foods, such as duck or goose eggs, or with larger animals, such as moose or deer. He said he has asked the monitoring program to put more emphasis on health issues.
"Anything that's part of the traditional diet, it's worth assuring people that it's safe to eat," said Talbot.
"Given the mandate for the monitoring agency, a health perspective on what's there could result in timely information."
Talbot said surveys suggest that gull and tern eggs aren't commonly eaten. But he acknowledged that information may be incomplete.
"Those studies may be flawed if they missed people who are living a more traditional lifestyle and not available to answer
More study needed
The amount of mercury in the eggs is still low enough so pregnant women can eat three eggs a week from Lake Athabasca and five from Mamawi, although Talbot points out that gull and tern eggs are much smaller than chicken eggs.
Mercury can drift into the environment from such sources as forest fires or coal-fired power plants.
But the study ruled out those sources in the bird eggs, pointing out that mercury in eggs from the same species in southern Alberta has actually declined. It also ruled out dietary changes as the cause of the increase.
"Obviously, there is the possibility that changes in oilsands-related sources of (mercury) could be responsible for the
egg (mercury) trends described here," it says.
It concludes more study is needed to definitively pin the increasing toxic load on industry.
"Increasing (mercury) levels in eggs of multiple species nesting downstream of the oilsands region of northern Alberta warrant continued monitoring and research to further evaluate (mercury) trends and to conclusively identify sources."