Mercury-contaminated fish in a Dryden-area river will remain a serious health problem for decades and beyond if the province doesn’t take the plunge and speed up “natural-recovery” processes, says a new report released Monday.

The report prepared for Grassy Narrows First Nations, warns mercury levels in the Wabigoon River remain extremely high.

“It is shocking that this river remains so highly contaminated after more than four decades,” University of Toronto environmental scientist Miriam Diamond said in reaction to the report.

“One meal of Clay Lake walleye contains up to 150 times the safe dose of mercury recommended by the U.S. Environmental Protection Agency,” Diamond added.

“That could cause serious lifelong harm to a fetus or child at a critical stage in their development.”

Report co-author John Rudd, a scientist based in British Columbia, said the province was warned in 1984 “that Grassy Narrows’ fish would remain contaminated for generations if the river was not cleaned up.”

Rudd added: “Our recommendations to clean the river were not followed and our troubling prediction has proven correct.”

The mercury, about 9,000 kilograms worth, leaked more than 40 years ago from a Dryden-area paper mill that used a chlor-alkali plant once common in the paper industry.

Generations of Grassy Narrows First Nation residents who ate fish caught in the river came down with mercury poisoning, suffering vision loss, imbalance and trembling, says the report.

The report recommends the province alleviate the mercury contamination by “capping” known hot spots in the upper Wabigoon River, and injecting clean clay to accelerate the natural rate at which mercury is buried in the river bed.

About four years ago, the province paid a portion of the $7-million cost of placing a thin layer of sand on top of a mercury-contaminated section of Marathon’s Peninsula Harbour. That mercury also came from a former chlor-alkali plant.

According to the Grassy Narrows report, “ the river has shown little to no improvement in the last 30 years.”

“To this day, mercury is continuing to spread downstream into the lower lakes of the river system.”

NDP MPP Sarah Campbell, whose riding includes the Dryden area, said the cap and clay-injection plan “seems completely feasible and it’s beyond me why the province hasn’t done it.”

The province didn’t say Monday that it will take a similar approach with the Wabigoon River, but said it would review the Grassy Narrows report.