Risk assessment of historical soil contamination with cyanides; origin, potential human exposure and evaluation of Intervention Values

Knowledge on ecotoxicological effects of CN species in soils is insufficient to derive Intervention Values. Consequently these have to be based on human exposure. Consumption of crops is the major contributing factor to the current soil Intervention Values. Recent plant physiological studies indicate that soil contamination will not lead to CN concentration in crops which effect human health. Critical human exposure can occur via inhalation of free CN in ambient air, or after a one time peak ingestion by children of soil contaminated with complex CN. Therefore provisionally 25 ug/m3 HCN in soil air or in ambient air is suggested as a possible soil Intervention Value, equal to the Tolerable Concentration in Air.

Further research is indicated to obtain a sound base for CN Intervention Values for soil. Consumption of untreated groundwater contaminated with ferrohexacyanide or thiocyanate can lead to critical exposure. For thiocyanate the Tolerable Daily Intake for children will be reached with 75 ug total CN per dm3, which may be proposed as an Intervention Value for groundwater.