An investigation by two leading mining reform groups, Earthworks and MiningWatch Canada, found that mining companies are disposing more than 180 million tonnes of toxic waste into rivers, lakes, and oceans worldwide, threatening vital bodies of water with heavy metals and poisonous chemicals.

Mine processing wastes, or tailings, can contain as many as three dozen dangerous chemicals including arsenic, lead, mercury, and cyanide. The study found that the mining industry has left mountains of such waste from Alaska and Canada to Norway and Southeast Asia.

Although several nations including the US, Canada and Australia have restrictions on dumping mine tailings in natural bodies of water, the investigation found that these regulations are being weakened by amendments, exemptions, and loopholes.

For instance in the States although there is a law banning lake dumping, in 2009 the US Supreme Court allowed Coeur D’Alene Mines of Idaho to dump 7m tonnes of tailings from the Kensington Gold Mine in Alaska into Lower Slate Lake, filling the lake and destroying all life in it.

The report points out that there are safer methods of disposing of mine tailings, including returning the waste to the emptied mine, but in other places, dumping of any kind is too risky.

No feasible technology exists to remove and treat mine tailings from oceans – even partial clean-up of tailings dumped into rivers or lakes is prohibitively expensive.

MiningWatch Canada’s research coordinator Catherine Coumans says that some multi-national mining companies are guilty of a double standard.

“Some companies dump their mining wastes into the oceans of other countries, even though their home countries have bans or restrictions against it,” she said.

“We found that of the world’s largest mining companies, only one has policies against dumping in rivers and oceans, and none against dumping in lakes.”

Maxine Perella

Action inspires action. Stay ahead of the curve with sustainability and energy newsletters from edie