A newly published study has cast doubt on past findings that mercury levels are increasing in fish near Alberta's oilsands but concludes that better monitoring is needed to understand the true impact of the massive industry.

"There is no evidence to support the contention that mercury concentrations are increasing in fish as a result of expanding oilsands development," says the study, which was published last week in the Journal of Environmental Monitoring.

The Environment Canada scientists who wrote the report acknowledge their conclusions are softened by the quality of the data they had to work with.

"An improved monitoring system is required to reach more definitive conclusions," they wrote.

Follow-up to 2009 study that pointed to oilsands

The review by Marlene Evans and André Talbot was done following a published 2009 study that suggested that, while still low, levels of the potent neurotoxin in fish from the lower Athabasca River had increased by more than one-quarter between 1975 and 2005.

That study, by independent biologist Kevin Timoney and Peter Lee with Global Forest Watch attributed the increase to increased oilsands development.

But Evans and Talbot felt there were problems with both the study and its conclusion. Sampling techniques were inconsistent. Sometimes whole fish were tested; sometimes fillets. And the results weren't adjusted to compensate for the age or size of the fish, which were taken from different stretches of the Athabasca.

Finally, the study only had three years' worth of more complete and consistent data.

Evans and Talbot collected data from all available sources, some of which weren't available to Timoney and Lee. Although the data had been collected for different reasons, at different times of year and using different methods, Talbot said they did their best to standardize it.

They found no evidence of increasing mercury. There were indications that levels were actually declining in some fish.

Other studies, however, have found levels of mercury and other toxic pollutants that exceed provincial guidelines in parts of the Athabasca that are downstream from oilsands developments.

Erin Kelly and David Schindler of the University of Alberta Mercury found that thallium and other pollutants accumulated in higher concentrations in snowpacks and waterways near and downstream from oilsands development than in more remote areas. Their results were published last year in he Proceedings of the National Academy of Sciences.

Levels fluctuating but no overall trend

Talbot acknowledges industry figures show increasing amounts of mercury are entering the environment around the oilsands. He's also aware of research that finds mercury is among the contaminants being pumped from smokestacks and falling as rain or snow.

As well, other research has suggested mercury levels in bird eggs on the Athabasca Delta are rising.

But when it comes to the river and lakes — and the fish within them — Talbot said mercury levels are low and stable.

'It's difficult to attribute the cause of mercury levels to any one industry.'— Andre Talbot, Environment Canada scientist

"Although they're fluctuating quite a bit from site to site and from year to year, there's no time trend," he said. "We limit ourselves to that conclusion.

"It should be some level of comfort to the people eating fish along the river."

The Athabasca ecosystem is affected by many other factors besides oilsands development —from climate change to improving emissions standards in other industries, Talbot said.

"There's a very large number of factors that influence mercury levels," he said. "It's difficult to attribute the cause of mercury levels to any one industry. In fact, it's quite impossible. The cause-and-effect data is non-existent."

Environment Canada is working on ways to "fingerprint" environmental contaminants, which would allow scientists to definitively name their source. But Talbot said that technology is a few years off.

Data limited

Timoney welcomed the Environment Canada study.

'It is dangerous to confuse failure to find an effect with lack of an effect.'— Kevin Timoney, biologist

"We are pleased that our earlier study spurred further research and that a more comprehensive analysis has been published," he said in an email.

"The lack of evidence for an increasing trend in fish mercury concentrations is encouraging but should not be generalized beyond the limitations of the data ... It is dangerous to confuse failure to find an effect with lack of an effect."

The Evans and Talbot study will be used in ongoing federal-provincial efforts to implement more rigorous and informative monitoring for the environmental effects of the oilsands.

"This research will help build a comprehensive, scientifically grounded understanding of baseline environmental conditions in the oilsands region in order to properly assess changes over time," said federal Environment Minister Peter Kent.