Sodium cyanide

Long-term toxicity to fish

Description of key information

Data from a range of multiple long-term toxicity studies for a range of freshwater and marine  fish, invertebrate, algal and vascular plant species were pooled into a species sensitivity distribution (SSD).  The SSD for the combination of freshwater and marine fish, invertebrate, algal and vascular plant species resulted in a chronic HC5 of 2.0 µg/l (90% confidence interval from 0.9 to 3.3 µg/l).  The chronic HC5 value is based on free cyanide. 

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

2 µg/L

Marine water fish

Marine water fish

Effect concentration:

2 µg/L

Additional information

The species sensitivity distribution (SSD) for chronic aquatic toxicity developed by Hommen (2011) is similar to the SSD derived by the ECETOC Joint Assessment of Commodity Chemicals (2007).  The SSD by Hommen includes more recent guideline studies on chronic aquatic toxicity selected after a re-assessment of the data base.  The chronic HC5 reported by Hommen for all aquatic species (2.0 ug/L) is higher than the chronic toxicity HC5 of 1.1 ug/L for all aquatic species as estimated by ECETOC (2007).

The chronic HC5 value of 2.0 ug/L value served as the point of departure for the derivation of the chronic PNECaquatic for both freshwater and saltwater species.

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 cyanide (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.