Mix of toxins keeps streets clear of ice
New information from the Colorado Department of Transportation shows that the popular road de-icer known as magnesium chloride contains concentrations of heavy metals and toxic compounds.
Aspen City Council members were told Monday that the widely used de-icer contains concentrations of copper, lead, zinc, arsenic and cadmium – 14 to 2,270 times higher than “the accepted standard.”
According to a memo from Aspen Environmental Health Director Lee Cassin, the state has ordered its mag chloride suppliers to reduce the amount of toxic substances used in their products, but it remains unclear when or if the less poisonous version of the de-icer will be available for use in town.
The use of mag chloride has increased rapidly over the last five years. CDOT expects to use more than four million gallons on state highways this year, according to a department spokesman.
Aspen has used it on city streets since 1994, although it has cut the amount it uses each winter by more than a third, from about 30,000 gallons to 18,400 gallons, according to Streets Superintendent Jack Reid. The streets department now limits its use of mag chloride to Main Street, bus routes, and major intersections, he said. Elsewhere, street crews either use sand to improve traction, or simply plow the snow to the side of the road.
Magnesium chloride is a form of salt that comes from evaporating sea water, according to University of Colorado chemistry professor Arlan Norman. Like its cousin, sodium chloride, or table salt, magnesium chloride lowers the melting point of ice.
In Aspen, Reid said, it has been effective in melting ice at temperatures as low as 6 degrees Fahrenheit.
Unlike sodium chloride, which has been used in crystalline form on roads throughout the Midwest and Northeast for several decades, magnesium chloride can be spread in a liquid form over a road surface, which allows for more even distribution and fewer icy spots.
CDOT recently completed the second phase of a three-phase study on the environmental effects of magnesium chloride. The City Council was presented with the preliminary results at yesterday’s noon work session.
Cassin’s memo outlined several other causes for worry, including a finding that “negative effects, including the death of some organisms, were found at about the concentration CDOT expects in runoff as it leaves the roadway.”
De-icing chemicals mixed in with mag chloride, according to the memo, “contained 200 to 800 times more organic compounds than stream water.”
And, noted Cassin, “From early 1994 through the end of 1997, chloride levels increased more below town and in the middle of town than they did above town where [magnesium chloride] is not heavily used.”
Cassin made it clear in her presentation that the city’s tests were not scientifically sound, because no baseline data on the level of chloride or other compounds and metals in the Roaring Fork River, was gathered before the city started using mag chloride.
She also pointed out that nobody is studying the long-term effects of magnesium chloride.
While many on the City Council struggled over how to deal with the new information, Councilman Terry Paulson said that for environmental reasons he favors discontinuing use of the de-icer altogether.
Mayor John Bennett and Councilwoman Rachel Richards were less willing to rule out its use. Both said pedestrian safety is their paramount concern.
But Paulson, siding with two people in the audience, wondered whether Aspen has the courage to ban the substance and find other ways to protect pedestrians.
“I really have trouble with our use of magnesium chloride,” he said. “Why does it seem our environmental conscience is moving downvalley, where Basalt can ban this stuff on their streets and Aspen can’t?”
The Basalt Town Council banned use of magnesium chloride on town streets late last year over environmental concerns about the chemicals that manufacturers add to limit corrosion and increase its effectiveness as a de-icer.
The Aspen City Council is planning to more closely review the city’s use of mag chloride at a study session later this winter.
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