CDOT: De-icer isn’t hurting environment |

CDOT: De-icer isn’t hurting environment

John Colson

As far as state highway officials are concerned, magnesium chloride does not pose a threat to Colorado’s roadside or aquatic environments.

And, its use is the best available method for keeping high mountain roads clear in winter weather.

That was the basic message from Colorado Department of Transportation officials at a press conference Wednesday in Glenwood Springs.

And their conclusions were backed, at least preliminarily, by the findings of a University of Colorado researcher who has been studying magnesium chloride’s effects on the environment for the past two years. Governments in the Roaring Fork Valley have backed away from using the de-icer on local roads until more is known about its environmental impact.

But CDOT officials could not directly respond to questions about magnesium chloride’s potential to harm human health if the stuff is inhaled when it forms a mist hanging over Highway 82.

And their only advice for motorists, angered over what magnesium chloride does to a windshield, was: Be sure the windshield washer reservoir in your car is always full.

The CU researcher, William Lewis, presented an “interim report” of his findings based on what he said was a thorough review of the available scientific literature on magnesium chloride as a de-icer, and on studies of its effects on certain selected aquatic species. Among them are the boreal toad, rainbow trout, a water flea called Ceriodaphnia and a form of algae called Selenastrum.

While all four species showed ill health effects or reproductive dysfunction when exposed to high levels of magnesium chloride, Lewis said, the concentrations that make it into Colorado’s streams are not high enough to produce the same results.

Lewis said the mag chloride spread on Colorado highways is diluted by snowmelt and roadside runoff to such an extent that its concentration is actually below the levels that occur in nature.

He also said that his study showed that the deicer can cause limited damage to vegetation within 100 feet of a roadway.

CDOT maintenance supervisor Ed Fink said his agency is continuing to monitor its shipments of magnesium chloride, which is extracted from ponds at the edge of the Great Salt Lake, for repeat appearances of unacceptably high levels of poisonous heavy metals such as those Lewis found in the first batch he tested.

But Lewis and Fink both said that those levels of lead, arsenic and cadmium have not shown up again.

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