Registration Dossier

Administrative data

Endpoint:
toxicity to microorganisms
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Experimental data were reviewed by the ECETOC Task Force, author of the 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)”, 2007. The report is a weight of evidence approach to an extensive body of literature, much of which was undertaken prior to development of guidelines. The report was peer reviewed by the scientific non-governmental organization (NGO), which judged the data to be reliable with restrictions.

Data source

Reference
Reference Type:
review article or handbook
Title:
Unnamed
Year:
2007

Materials and methods

Principles of method if other than guideline:
A search of the available literature on cyanides identified an extensive database of valid studies on microbial toxicology. The literature was reviewed and the appropriate studies were identified for the evaluation of cyanide effects on each of four groups of micro-organisms: bacteria and cyanobacteria; protozoa; fungi; and activated sludge.
GLP compliance:
not specified

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent

Test organisms

Test organisms (species):
other: cross-section of micro-organisms in four groups, including bacteria and cyanobacteria; protozoa; fungi; and activated sludge.

Test conditions

Details on test conditions:
The ECETOC Task Force reviewed each study, and judged each to be valid and informative for the evaluation of the endpoint.

Results and discussion

Effect concentrationsopen allclose all
Dose descriptor:
NOEC
Effect conc.:
0.007 mg/L
Nominal / measured:
not specified
Conc. based on:
other: CN- ion
Basis for effect:
growth inhibition
Remarks on result:
other: Tetrahymena pyriformis (protozoa) NOEC of 0.007 mg/l converted from NOEC of 0.013 mg/l for NaCN (test material)
Duration:
72 h
Dose descriptor:
other: EC5
Effect conc.:
1.8 mg/L
Nominal / measured:
not specified
Conc. based on:
other: CN- ion
Basis for effect:
growth inhibition
Remarks on result:
other: Entosiphon sulcatum (protozoa)
Duration:
6 h
Dose descriptor:
EC50
Effect conc.:
4.9 mg/L
Nominal / measured:
not specified
Conc. based on:
other: CN- ion
Basis for effect:
other: turbidometric
Remarks on result:
other: activated sludge EC50 of 4.9 mg/l represents average of 17 laboratories in a ring test; range is 2.0 mg/l to 9.2 mg/l.
Details on results:
The two NOEC values from protozoans represent the lowest NOEC (0.007 mg CN-/l in Tetrahymena pyriformis) and highest NOEC (1.8 mg CN-/l in Entosiphon sulcatum) reported from a range of assays on six protozoan species.

The EC50 for activated sludge (4.9 mg CN-/l) represents the average of values from results from 17 laboratories in an international ring test, with a range of EC50 values from 2.0 mg CN-/l to 9.2 mg CN-/l.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Remarks:
The ECETOC Task Force evaluated each study and found to be valid.
Conclusions:
A review of the available literature revealed an extensive database on the microbial toxicity of cyanides. These studies were categorized for each of four organism groups: bacteria and cyanobacteria; protozoa; fungi; and activated sludge. Taking into account the substantial metabolic differences between bacterial species, the significant influence of the culture conditions upon cyanide toxicity, the variety of endpoints tested and the small number of published toxicity results, the relevance of of those test data for environmental exposure of bacteria were unclear. The results for fungi were not determined to be approriate , since the tests on fungal species were either conducted according to non-standard protocols, were not performed by a methodology in which the cyanide concentrations in the test agar could be determined, or from which the relevance of the data (from a study of the effects of airborne HCN to fungi) to the general sensitivity of fungi could not be determined.

The results for two for two of the groups (protozoa and activated sludge) were determined to be relevant for the evaluation of environmental exposures. The range of threshold toxicity concentrations reported for protozoans ranged from a NOEC of 0.007 mg CN-/l for Tetrahymena pyriformis, to an EC5 of 1.8 mg CN-/l for Entosiphon sulcatum. The mean EC50 for activated sludge was 4.9 mg CN-/l, from an international ring test of 17 laboratories performing a 72 h growth inhibition assay; the range of EC50 values from the 17 laboratories was 2.0 mg CN-/l to 9.2 mg CN-/l.