Possibly there's some concern there with sodium getting into ground water. I believe it is somewhat more effective as a de-icer than sodium chloride. It is also more deliquescent, and often used for road dust suppression there as well. 21 Aug 2000 About 15 million tons of road salt was used in the USA in 1999 for deicing and dust control . Most of this is sodium chloride, but a small fraction of the total is calcium chloride.
Calcium chloride is mixed with sodium chloride for melting ice and snow in low temperature regions.
It is also used for dust control on roads. I am not aware of any significant use of magnesium chloride because of the cost. The major health problem with these salts is when sodium chloride leaches into wells, lakes and ground water. Sodium is well known to cause and influence hypertension in humans, thus, doctors prescribe low sodium diets in persons that are susceptible to this problem. 23 Aug 2000 From my experience as the Highway and Bridge Maintenance Engineer for Long Island and New York City the main health effects, of which I am aware due to the use of sodium chloride on roads and bridges occurs from improper storage and previously used coloring agents, some of which contained cyanide, and or other heavy metals .