Concentrations exceeding these soil levels have been reported within about 30 m from the edges of highways in Canada and in patrol yards, and concentrations exceeding these tissue concentrations have been reported within about 100 m from the edges of Canadian highways. A number of field studies have documented damage to vegetation and shifts in plant community structure near roadways resulting from the use of road salts. Behavioural and toxicological impacts have been associated with exposure of mammalian and avian wildlife to road salts. Road salt increases the vulnerability of birds to car strike and may poison some birds directly. Road salt may also affect wildlife through its impact on habitat, with reduction in plant cover or community shifts that could affect wildlife dependent on these plants for food or shelter.
Ferrocyanides are very persistent but are of low toxicity.
However, in solution and in presence of light, they can dissociate and form cyanide. The ultimate effects of ferrocyanides therefore depend on the complex balance between photolysis and volatilization, which in turn depend on environmental factors. Modelling studies undertaken in support of this assessment, indicate that there is some potential for certain aquatic organisms to be affected by cyanide in areas of high use of road salts, although the likelihood that sensitive organisms would actually be exposed for extended periods in roadside habitats is uncertain. Based on the available data, it is considered that road salts are entering the environment in a quantity or concentration or under conditions that have or may have an immediate or long-term harmful effect on the environment or its biological diversity, and that constitute or may constitute a danger to the environment on which life depends. Future management should focus on key sources in areas where the assessment has indicated concerns.