Deicing of roads making city streams toxic

MILWAUKEE, Sept. 1 (UPI) -- Using salt to deice city pavements can make city streams toxic to aquatic life, a government study of winter runoff in northern U.S. cities says.

A U.S. Geological Survey study focusing on eastern Wisconsin and the Milwaukee area found more than half the Milwaukee streams had potentially toxic chloride levels in winter, with effects that lingered into summer in some streams, a USGS release said Wednesday.

Nationally, samples from 13 northern cities found 55 percent of studies streams were potentially toxic.

"While winter driving and walking safety are the priority in treating pavements, this study suggests the need for advancements that will reduce salt loads to surface waters without compromising safety," Matthew C. Larsen, USGS Associate Director for Water, said.

While municipal road deicing accounts for a significant portion of salt applications, salt is also used by many public and private organizations and individuals to deice parking lots, walkways and driveways, the study found.

"We expected to see elevated chloride levels in streams near northern cities during the winter months," Steve Corsi of the USGS Wisconsin Water Science Center said.

"The surprise was the number of streams exceeding toxic levels and how high the concentrations were," Corsi, who led the study, said.