"...a catastrophic risk to the Athabasca River system."
The companies also released huge amounts of pollutants into the air last year, including 70,658 tonnes of volatile organic compounds, which can damage the function of human organs and nervous systems, and 111,661 tonnes of sulphur dioxide, a key contributor to acid rain.
The numbers are contained in Environment Canada's national pollutant release inventory, which details the dangerous compounds generated by industrial Canada. New numbers published this weekend track 85 mining facilities that generate tailings and waste rock. Of those, the oil sands produce just under 50,000 tonnes of reportable substances in tailings, or 10 per cent of the total.
Oil sands operations, however, produced the overwhelming bulk of several dangerous substances: for example, bitumen mines generated nearly all of the Canadian total of acenaphthene, one of a bevy of polycyclic aromatic hydrocarbons released around Fort McMurray. Such substances can cause tumours of the lung, skin and bladder, and some are carcinogens. And their volumes are growing in north-eastern Alberta: companies generated 42 per cent more acenaphthene in 2009 than they did in 2006.
Last year, oil sands mines also produced 322 tonnes of arsenic, 651 tonnes of lead and measurable volumes of mercury, chromium, vanadium, hydrogen sulphide and cadmium.
The numbers "are just ridiculously huge," said Justin Duncan, a staff lawyer with Ecojustice who helped prosecute the 2007 court case that forced Environment Canada to release the data.
"You're talking hundreds of thousands of kilograms of heavy metals going into some of these tailings ponds. If one of these things bursts, it's a catastrophic risk to the Athabasca River system."