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The biodegradation of cyanides in environmental media was comprehensively evaluated by the ECETOC Task Force in Cyanides of Hydrogen, Sodium and Potassium, and Acetone Cyanohydrin (CAS No. 74 -90 -8. 143 -33 -9, 151 -50 -8 and 75 -86 -5), Volume I, JACC No. 53, September 2007), Section 4.3.5, pp. 106 -117. The ECETOC Task Force stated that "cyanide can be metabolised by a wide variety of organisms, including bacteria, fungi, arthropods and plants, following a number of different pathways", and focused on biodegradation by micro-organisms and terrestrial plants. Evidence for biodegradation was presented for aerobic and anaerobic wastewater treatment sludges, as well as the water and soil compartments.

Potassium cyanide and sodium cyanide can be considered as a chemical category, along with hydrogen cyanide (HCN) and acetone cyanohydrin (ACH, also known as 2-hydroxy-2-methylpropanenitrile), based on structural similarity, similar physico-chemical properties and common breakdown/metabolic products in physical and biological systems. Particular attention is paid to the dissociation constant of HCN. In the vast majority of environmental and physiologic conditions, the cyanide salts will dissolve in water to form hydrogen cyanide. The physico-chemical hazards and toxicity result from the activity of this common proximal toxicant, HCN. Support for this category approach is provided in examination of acute and chronic toxicity by oral, dermal, ocular and intraperitoneal administration of various forms of cyanide and in aquatic and terrestrial compartments of the environment, which provide consistent and comparable values when expressed as mmol/kg bw.  An ECETOC Task Force, in the 2007 ECETOC Joint Assessment of Commodity Chemicals ( JACC ) Report No. 53, “Cyanides of Hydrogen, Sodium and Potassium, and Acetone Cyanohydrin (CAS No. 74-90-8, 143-33-9, 151-50-8 and 75-86-5)” supports the development of this chemical category. Hydrogen cyanide (Index No.006-006-00-X) and salts of hydrogen cyanides (Index No.006-007-00-5) are both listed in Annex VI,Table 3.1 of Regulation (EC) No. 1272/2008, entry 006-007-00-5, and are restricted in comparable ways taking into account physical characteristics. Thus, the assignment of potassium cyanide and sodium cyanide to a chemical category does not result in a less protective regulatory status.