The use of road salt to melt existing snow and ice buildup as well as prevent additional accumulation is becoming more common throughout the northern United States. Estimates of road salt use in the U.S. range as high as 20 million tons per year. Deicing and anti-icing compounds are known to be elevated in soils adjacent to treated roadways and, along with runoff from melting snow, can significantly raise salt concentrations in nearby wetlands. To determine the relative toxicity of commercial deicer and anti-icer products, as well as their primary active ingredients (MgCl₂ and NaCl), short-term laboratory toxicity studies were conducted using various species of anurans, including Bufo americanus, Rana pipiens and Rana sphenocephala. Tests were conducted for seven days beginning with early-stage tadpoles (i.e., Gosner stage 19-21). Survival was monitored as was growth using snout-vent length and body width.

Results/Conclusions

Both survival and growth were affected in all test species at deicer concentrations of 1% or less of what is applied to roads during normal winter treatment operations. These data indicate that, even at high dilution rates that may occur with snow melt or spring rains, deicer salt concentrations may be high enough to cause significant negative effects to amphibian populations in wetlands adjacent to highways.  Even distal wetlands may be affected if local streams and waterways channel nonpoint source water directly to lakes and ponds. Elevated salt concentrations may also cause more subtle effects, including changes in growth patterns and malformations.