Salt Lake County ranks second in the nation as a depository for the most materials containing toxic substances.

According to the Environmental Protection Agency's annual report of the top 20 counties in the country that have these deposits, 120.3 million pounds of materials containing toxic substances were deposited in Salt Lake County in 2007.

That puts Salt Lake County behind Alaska's Northwest Arctic County, with 615.3 million pounds of materials deposited, but ahead of Humboldt County, Nev., which had 84.6 million pounds of materials deposited — and 17 other counties with smaller numbers.

Ostensibly, Salt Lake County's numbers are so high because Kennecott Utah Copper, one of the world's largest copper mines, is located in the county.

However, that figure is not as dreadful as it sounds, since it mainly accounts for the waste rock generated by Kennecott in which toxic substances are found only at trace levels.

Rick Sprott, executive director of the Utah Department of Environmental Quality, said the huge number reported to the EPA "tends to overwhelm other releases that could be far more dangerous to public health. The risk to the public from Kennecott's impounded tailings is so low, I would be a lot more worried about diesel fumes along the highways or even automobile painting in neighborhoods. They don't rise to the level of the Kennecott landfill."

Sprott said he understands Utah, which is always high on the list because of the huge amount of material dug up by Kennecott each year, is actually reporting about 11 percent lower numbers this year. "States that have large surface mining operations move to the top of the list."

Kyle Bennett, a spokesman for Kennecott Utah Copper, said the company mines an average of about 150,000 tons of copper ore and 270,000 tons of overburden each day, so the trace amounts add up over a year's time. "For every one ton of ore, we'll get two ounces of lead and five ounces of zinc, which shows how small some of the amounts can be."

Sprott said although the listing for Salt Lake County might be misleading to someone who doesn't carefully read it, he is glad the EPA keeps track of such contaminants because it lets people know what manufacturing and mining companies are doing in their areas. "It's an important report, and people ought to look at it and if they have questions, they should call our office."