As firefighters expand their fight against wildfires, fire retardant’s impact on infrastructure becomes a larger issue.

According to a study funded by the Iowa Department of Transportation, researchers found that, “In our experiments, the magnesium component of deicer salts proved to be the most deleterious, (compared with sodium chloride and calcium chloride)” and they concluded their report saying, “Magnesium solutions are especially damaging and … decreases service life of concrete.”

A similar study from the Michigan Tech Transportation Institute conducted for the South Dakota Department of Transportation to determine the impact of deicer on cement roads found that magnesium chloride interacts with cement paste in concrete, resulting in “expansive cracking, increased permeability, and a significant loss in compressive strength.”

In addition to being used as a deicer, magnesium chloride is sometimes used on dirt roads to control dust. The magnesium chloride from these applications enters domestic water systems through aquifers and public water systems, and once it is in household water it is highly corrosive to copper and stainless steel. “It rapidly corrodes the copper lines, fixtures, and stainless steel found in most appliances,” according to Paul Hurlburt with Professional Water Systems, Inc.