Sodium thiocyanate

Endpoint summary

Additional information

A wide range of microorganisms degrade thiocyanates utilizing these compounds as energy, nitrogen or sulfur source. Due to the action of microorganisms, the required pass levels are achieved in prescribed tests for thiocyanate to allow a ready biodegradability classification. Ready biodegradable compounds can be treated in biological systems as demonstrated and will be degraded very rapidly in ecosystems. Environmental concentrations of thiocyanate are therefore significantly reduced by biodegradation.

Sodium, ammonium and potassium thiocyanate are salts that readily dissolve in water, and completely dissociate into their separate ions at all pH values (1 -14), and thus will have no tendency to hydrolyze. Degradation of the thiocyanates through hydrolysis is therefore not considered.

Direct photolysis of the three thiocyanates inair/water/soil will not occur, because they do not absorb UV radiation above 290 nm. Photo transformation in air/water/soil is therefore assumed to be negligible.

All the three thiocyanate compounds have negative log Kow values. Using the thiocyanic acid (HSCN) as a worst case scenario, the estimated log Kow value of 0.58 still falls short of the cut-off value of 3, thus no further data requirement for thiocyanates with respect to bioaccumulation are necessary.

Ammonium thiocyanate as a representative member of the category is readily biodegradable according to the results of an OECD 301D test. The thiocyanates in this category all have estimated log Kow values less than zero, indicating a low potential for adsorption. However, SCN- can adsorb to soils with a large anion exchange capacity (Fe, Al and Mn oxides, clay minerals), especially at high temperatures. The surfaces of most soil particles have low anion exchange capacity, thus this mechanism would be of minor relevance.