Environmental groups have long called the tailings lakes in the Alberta oilsands Canada's toxic secret, but companies operating there will soon be required to disclose exactly what pollutants are there.

In April, a Federal Court ordered Ottawa to make the mining industry release a complete inventory of what material they release into the environment. Now companies in the oilsands will also have to comply, CBC News has learned.

"It'll be the first time that Canadians have actually known what is in these tailings facilities and the extent of the pollution that these companies are producing," said Justin Duncan, a lawyer for the environmental groups that took the federal government to court on the issue and won.

Environment Canada has confirmed the lakes of sludge produced in the Alberta oilsands also fall under the ruling.

The pollution data will be ammunition for critics like David Schindler, a professor of ecology at the University of Alberta.

"The magnitude of the numbers is going to really shock people," Schindler said. "It's huge compared to any other mining development anywhere on the planet."

The contents of tailings lakes have not been kept secret, insists Alberta Environment Minister Rob Renner.

"It certainly will improve transparency, and anything that can improve transparency is fine with me," Renner said Wednesday.

The court ruling forces mining companies to provide pollution data going back to 2006. By law, the information must be stored in an online database that the public will be able to see simply by typing in a postal code. For example, people living in Fort Chipewyan, in northern Alberta, will be able to type in their postal code and learn what kinds of pollutants are in their area.

There is no timeline for when the information will be available online, but it is expected to be in the next few months, Duncan said.

The Mining Association of Canada is concerned about how the new pollution numbers will be interpreted by the public, Justyna Laurie-Lean, vice-president environment and health, said Wednesday.

But the association maintains it is working with the government to comply with the court ruling.