Yes it's often a perceived risk which people run with. In the early 80s I did some work with Consolidated Professor Mines which had a deposit on an island on Shoal Lake I believe. The deposit contained arsenic which was to be carted by barge or over ice to a smelter on the mainland - a safe distance from the water. Those opposed emphasised the possible effect on the Winnipeg water supply even though the currents flowed the opposite way. Also there was reputedly arsenic in the rocks in and around the lakes. I never heard the outcome of all this - but it emphasised to me at least the question of perceived versus real risk with environmental issues