Scientists taking part in a study on mercury pollution near the oilsands say they’re seeing increasing levels of the toxin in a comparison of studies between 2009 and 2012.

But they add further research is needed to determine the source of the mercury, according to The Globe and Mail.

The findings are contained in a federal-provincial program called The Joint Oilsands Monitoring Program.

In 2009, and again last year, the program studied mercury levels in bird eggs from two sites in Northeastern Alberta, as well as eggs taken from a site in Southern Alberta far away from the oilsands.  That’s when the disparity in data — both in terms of years and locations — was discovered.

Mercury causes damage to human kidneys, spinal cords, brains, liver and developing fetuses.