* Study finds pollutants from oil sands widespread
* Northern Alberta lakes not yet damaged
* Supports 2010 Schindler study
CALGARY, Alberta, Jan 7 (Reuters) - Pollution from extraction plants in the oil sands of northern Alberta is spreading farther than previously thought, contaminating lakes up to 90 kilometers (55 miles) from the world's third largest crude reserve, a study published on Monday found.
Polycyclic aromatic hydrocarbons (PAHs) and other toxins associated with production of tar-like bitumen from the oil sands were found in lakebed sediments in the region, according to the study published in the Proceedings of the National Academy of Sciences of the United States of America.
"We have, in some ways, a smoking gun here," said John Smol, a biology professor at Queen's University and Canada Research Chair in Environmental Change, one of the study's authors. "We can show the amount of PAHs, only one of the many contaminants that are out there, are increasing in lockstep with the tar sands developments starting in the 1960s."
The findings run counter to arguments by some within the industry that many pollutants found in the lakes and rivers of northeastern Alberta are naturally occurring and leached from the bitumen deposits themselves.
The Canadian Association of Petroleum Producers, which lobbies for the country's largest oil producers, could not be immediately reached for comment.
The study also supports a landmark 2010 paper by University of Alberta ecologist David Schindler and others that concluded oil sands extraction operations were contaminating the Athabasca River watershed with such toxins as mercury, arsenic and lead.
That study forced Canada and Alberta to replace an industry-funded environmental monitoring organization that reported no ill effects from oil sands developments with government-run agencies.
While levels of PAHs and other toxins in the six lakes covered in the study are rising as development expands, Smol says they do not yet threaten the health of the lakes.
"They are not poisonous pools," he said. "They're at about the same level of PAHs that you'd find in a city lake, an urban lake."
However, with production from the region, the largest source of crude oil exports to the United States, set to more than double over the next decade, the waters of northeastern Alberta could be seriously threatened unless emissions from oil sands plants are further controlled.
"We might well be close to significantly higher levels and more dangerous levels very quickly," Smol said. "This is an early warning that we are not on the right trajectory."
Smol also said that the study does not contradict a paper released last year that found no contaminants from oil sands developments in lake bottoms 200 kilometers away from the most developed oil sands region.
"Our lakes are closer," he said. "Possibly somewhere between 200 and 90 kilometers (from the developments) the effect is lessened. They also worked on a riverine system ... we have much simpler systems, simple lakes that are like passive samplers."
The new study was funded by Environment Canada and the Natural Sciences and Engineering Research Council of Canada.
(Reporting by Scott Haggett; editing by Andrew Hay)