Effects of Road Salt Applications on Human and Ecological Health: A Risk Assessment and Risk Management for Prospective Policy Options
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Under many winter weather conditions, the use of de-icing chemicals is deemed necessary to maintain safe traveling conditions. Salt applications are used as the most effective method for treating ice and snow. Depending on the weather conditions, 10 to 20 million tons of de-icing salts are used in the United States each year. Although alternatives exist, the most commonly used material for de-icing is sodium chloride (NaCl). Chloride is extremely soluble in water and cannot be destroyed, only diluted; once applied to a road, it migrates easily through surface or ground water to tributaries, reservoirs, soils, and watersheds. Studies have shown that road salt leaches into the ground and changes soil composition, making it hard for plants to survive; damages vegetation and soils along the shoulders of roads, causing erosion; deteriorates buildings, bridges, and paved surfaces; clogs stormwater catch basins and streambeds, resulting in higher potential for flooding; and accumulates in drinking water reservoirs near highways and salt storage areas, where high levels of sodium contribute to cardiovascular, kidney, and liver diseases. These risks, along with countless others, cannot be mitigated without policy. This analysis characterizes the risks to human and ecological health by using the risk assessment and risk management paradigm. Exposure assessment data shows that groundwater and drinking water sources observe salt concentrations above the limits set by the Environmental Protection Agency (EPA). Laboratory conducted dose-response analyses were drawn on to show the effects of road salt on ecological settings including terrestrial wildlife, aquatic life, and vegetation. Dose-response data shows varying responses of species to different dosages of the contaminant ranging from acute survival to lethal dose. A separate human health risk assessment showed increased risks of car accidents and injury in addition to high economic costs if no deicer is used in dangerous weather conditions. The risk characterization illustrates all primary risks, pathways, and a wide range of secondary risks including invasive species, reduced biodiversity, reduction in recreational and market fishing, in addition to high economic costs resulting from primary and secondary risks. Policy options were developed that would mitigate risks by using less or no salt through human behavior changes, chemical alternatives, technological and mechanical applications, and research and development of new and existing methods. Policy options were analyzed based off of effectiveness at reducing risks, cost of implementation, technical feasibility, and degree of public acceptance. Not all possible policy options were found to be feasible. The use of alternative deicers and calibrated deicing equipment was shown to be effective and not cost inhibiting. Regional analyses to explore the effectiveness of policy options would result in the least data limitations and highest reduction of risks to human and ecological health.