June 21, 2009 in Idaho

Questions, answers about slag

By The Spokesman-Review
 

What is slag?

A byproduct of the smelting process, which extracts metals from ore. Molten slag is mixed with water, producing a black, glassy, sand-like material.

How much slag did Teck Resources discharge into the Columbia River?

Up to 145,000 tons each year until mid-1995, when the practice was stopped. That’s about 400 tons daily. The Environmental Protection Agency has estimated that at least 23 million tons of slag was dumped into the Columbia River. Teck Resources now sells the slag to the cement industry.

What does slag contain?

Twenty-five different compounds, including iron, zinc, aluminum, manganese, copper, chromium, cobalt, arsenic, nickel, lead, cadmium, silver and mercury.

What do past studies say about slag?

Two 1992 studies by the Canadian government found that slag was toxic to aquatic organisms. The toxicity was attributed to zinc and copper. In rainbow trout fingerlings, the sharpness of the slag damaged the fish’s gills, leading to their death. “Concentrations of copper and zinc … might also lead to mortality had fish survived the mechanical damage,” one of the studies said.

In the early 1990s, the Washington Department of Health said that slag posed negligible health risks to people. The department said a child could consume as much as four grams of slag per month, or about the same volume as four pennies, without experiencing adverse health effects. The primary source of slag data at the time was Teck Resources, the department noted.

In 2005, the Environmental Protection Agency tested 15 beaches on the Upper Columbia River for metals, pesticides and other pollutants. Based on the test results, the EPA said all of the beaches were safe for recreational use of two weeks per year.

What position does Teck Resources take?

“Slag is not designated as a hazardous waste or a Washington state dangerous waste,” said David Godlewski, Teck American’s vice president of environment and public affairs. “If you picked this material up, you could put it out with the municipal trash, or take it to the landfill.”

Teck Resources also questions whether slag is toxic to aquatic organisms, saying the way the 1992 studies were conducted may have produced erroneous conclusions.

What’s the Washington Department of Ecology’s position?

“Hazardous waste” and “Washington state dangerous waste” are narrowly defined terms used in managing waste disposal, said Jani Gilbert, Ecology spokeswoman.

Slag is “a hazardous substance because of its heavy metals content,” Gilbert said. “By its chemical nature, it has an impact on river ecology. We don’t want people to come into contact with it.”


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