Hydrogen cyanide

PBT assessment

Assessed Substance

Assessed substance:

substance itself

Results of detailed PBT / vPvB assessment

Persistence

Evidence of non-P / non-vP properties

Screening criteria

Not P and not vP based on: readily biodegradable

Remark:

Cyanide can be metabolised by a wide variety of organisms including bacteria, fungi, arthropods and plants using a number of different pathways. Non-toxic concentrations of cyanide can be readily biodegraded, both aerobically and anaerobically. Aerobic degradation yields CO2 and ammonia (that may be further converted to nitrate or nitrite); anaerobic biodegradation yields ammonia and methane. Degradation of cyanides in sewage treatment plants depends on the availability of adapted (micro-)organisms. Sudden high levels of cyanide in these sewage plants may lead to a loss of viability, while fully adapted sludge may tolerate and degrade concentrations up to 100 to 150 mg CN-/l with a high degree of efficiency. Vegetation is also able to remove cyanide from water or soil. Initial data indicate that cyanide-tolerant plants may be used for the remediation of cyanide-contaminated soil.

Criteria based on Annex XIII of REACH

Conclusion

Conclusion on P / vP properties:

not P/vP

Bioaccumulation

Evidence of non-B / non-vB properties

Screening criteria

Not B and not vB based on: Log Kow ≤ 4.5

Remark:

Based on its physico-chemical properties (log Kow = -0.25), HCN is not expected to bioaccumulate in aquatic organisms. HCN is either quickly metabolised or the organism dies.

Criteria based on Annex XIII of REACH

Conclusion

Conclusion on B / vB properties:

not B/vB

Toxicity

Evidence of non-T properties

Criteria based on Annex XIII of REACH

Evidence of T properties

Screening criteria: L(E)C50 < 0.01 mg/L

Remark:

The acute aquatic LC50 in fish (Onchorhynchus mykiss or, for saltwater, Menidia menidia) is 57-59 micrograms of CN-/L. The acute LC50 in invertebrates in saltwater (Cancer irroratus), is 5 microgram/L. The acute aquatic EC50 in algae (Chlorococcales sp. or, in saltwater, Nitzschia closterium) is 45-57 microgram CN-/L).
The chronic LC50 for freshwater fish (Lepomis macrochirus) is estimated at 1 microgram CN-/L. The chronic LC50 for invertebrates (Gammarus pseudolimnaeus or, in saltwater, Mytilus galloprovincialis) is 3.2-3.9 microgram/L. The chronic EC50 for algae for saltwater (Champia parvula) is 3.9 microgram CN-/L.
The combined freshwater and saltwater value, based on 16 NOEC's, is 1.1 microgram CN-/L (JACC 53, 2007).
The substance is classified according to Regulation EC No. 1272/2008, for acute and chronic aquatic toxicity, Category 1, H400 and H410.

Conclusion

Conclusion on T properties:

T

Remark:

HCN does not display properties of environmental persistence or bioaccumulation, although it is highly toxic to aquatic organisms. It does not meet the criteria for classification as PBT.