Relative Toxicity of NaCl and Road Deicing Salt to Developing Amphibians

Recently, increases in both road deicing salt use and impervious cover have caused salinity to increase in urban aquatic environments. Road deicing salts consist of salt, abrasives, metals, and anticaking agents, all of which can be transferred to surrounding aquatic environments through runoff. Few studies have attempted to identify the relative toxicity of road deicing salt ingredients. To investigate the relative toxicity of NaCl and road deicing salt to amphibians, we exposed embryonic Rana (=Lithobates) clamitans and larval Eurycea bistineata to NaCl and road deicing salt solutions with comparable NaCl concentrations in laboratory microcosms. Chemical analysis indicated the road deicing salt used was similar in chemical make up to other road deicing salt and was predominately (98.2%) NaCl. For both species we found little difference in survival between road deicing salt exposures and NaCl exposures. Our results suggest toxicity of road deicing salt is likely related to loss of osmoregulatory control as a result of NaCl exposure.