Phenyl isocyanate

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Several Ames tests with phenyl isocyanate are available. In the reliable studies including the key study (guideline study) the test showed a clear negative result.

Link to relevant study records

Reference

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: scientific acceptable and well documented - only 4 strains tested

Principles of method if other than guideline:

The mutagenic potential of phenyl isocyanate was examined in the Salmonella/microsome test. Bacteria of four histidine auxotrophic Salmonella typhimurium LT2 mutant strains (TA 98, TA 100, TA 1535, and TA 1537) were exposed to doses up to 12500 µg per plate.

GLP compliance:

not specified

Type of assay:

bacterial reverse mutation assay

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98 and TA 100

Additional strain / cell type characteristics:

other: Firstly, they are deep rough since certain lipopolysaccharide side chains are missing in the bacterial cell wall. Secondly, their reduced ability to repair damage from UV light (e.g. thymidine dimers) allows the phenotypic detection of mutation events

Metabolic activation:

with and without

Metabolic activation system:

S9 mix

Test concentrations with justification for top dose:

0, 20, 100. 500, 2500, 12500 µg/plate

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

not specified

Positive controls:

yes

Positive control substance:

other: Endoxan, Trypaflavin

Details on test system and experimental conditions:

Ames test

Key result

Species / strain:

S. typhimurium TA 1535, TA 1537, TA 98 and TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Remarks:

up to 2500 µg/plate

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Doses up to 2500 µg per plate did not cause any bacteriotoxic effects: Total bacteria counts remained unchanged and no growth inhibition was observed. Substance precipitation occurred at the dose of 2500 µg per plate and above.

Conclusions:

Interpretation of results: negative

Executive summary:

The mutagenic potential of phenyl isocyanate was examined in the Salmonella/microsome test. Bacteria of four histidine auxotrophic Salmonella typhimurium LT2 mutant strains (TA 98, TA 100, TA 1535, and TA 1537) were exposed to doses up to 12500 µg per plate.

There was no evidence for mutagenic effects of phenyl isocyanate with and without S9 mix. A biologically relevant increase of revertant colony numbers over control levels was not observed. Therefore, phenyl isocyanate was considered to be non-mutagenic in the Salmonella/microsome test.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Genetic toxicity in vivo

Description of key information

Two micronucleus tests in the mouse are available.

Link to relevant study records

Reference

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)

Principles of method if other than guideline:

The micronucleus test was employed to investigate phenyl isocyanate in male and female mice for a possible clastogenic effect on the chromosomes of bone-marrow erythroblasts. The known clastogen and cytostatic agent, cyclophosphamide, served as positive control. The treated animals received a single intraperitoneal administration of either phenyl isocyanate or cyclophosphamide.
The femoral marrow of groups treated with phenyl isocyanate was prepared 24, 48 and 72 hours after administration. All negative and positive control animals were sacrificed after 24 hours. The doses of phenyl isocyanate and the positive control, cyclophosphamide, were 30 and 20 mg/kg body weight, respectively.

GLP compliance:

yes

Type of assay:

micronucleus assay

Species:

mouse

Strain:

NMRI

Sex:

male/female

Route of administration:

intraperitoneal

Duration of treatment / exposure:

The femoral marrow of groups treated with phenyl isocyanate was prepared 24, 48 and 72 hours after administration.

Frequency of treatment:

single intraperitoneal administration

Post exposure period:

Animals were sacrificed 24, 48 and 72 hours after the administration, and the femoral marrow was prepared

Dose / conc.:

0 mg/kg bw/day

Dose / conc.:

30 mg/kg bw/day

No. of animals per sex per dose:

5 male and 5 female mice/dose

Control animals:

yes, concurrent vehicle

Tissues and cell types examined:

Femoral marrow

Sex:

male/female

Genotoxicity:

negative

Toxicity:

yes

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

The animals treated with phenyl isocyanate showed lasting symptoms of toxicity after administration. One of forty animals died before the end of the test due to the acute intraperitoneal toxicity of 30 mg/kg phenyl isocyanate. There was an altered ratio between polychromatic and normochromatic erythrocytes.

No indications of a relevant clastogenic effect of phenyl isocyanate were found after a single intraperitoneal treatment with 30 mg/kg.

Cyclophosphamide, the positive control, had a clear clastogenic effect, as is shown by the biologically relevant increase in polychromatic erythrocytes with micronuclei. The ratio of polychromatic to normochromatic erythrocytes was not altered.

Conclusions:

Interpretation of results: negative

Executive summary:

The micronucleus test was employed to investigate phenyl isocyanate in male and female mice for a possible clastogenic effect on the chromosomes of bone-marrow erythroblasts. The known clastogen and cytostatic agent, cyclophosphamide, served as positive control.

The treated animals received a single intraperitoneal administration of either phenyl isocyanate or cyclophosphamide. The femoral marrow of groups treated with phenyl isocyanate was prepared 24, 48 and 72 hours after administration. All negative and positive control animals were sacrificed after 24 hours. The doses of phenyl isocyanate and the positive control, cyclophosphamide, were 30 and 20 mg/kg body weight, respectively.

The animals treated with phenyl isocyanate showed lasting symptoms of toxicity after administration. One of forty animals died before the end of the test due to the acute intraperitoneal toxicity of 30 mg/kg phenyl isocyanate.

There was an altered ratio between polychromatic and normochromatic erythrocytes. No indications of a relevant clastogenic effect of phenyl isocyanate were found after a single intraperitoneal treatment with 30 mg/kg.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Additional information

Several Ames tests with phenyl isocyanate are available. In the reliable studies including the key study (guideline study) the test showed a clear negative result.

In other Ames tests with Salmonella typhimurium or Streptomyces the test had an ambiguous or positive result. Due to methodological deficiencies and limited documentation these results are not assignable. By a weight-of-evidence consideration, phenyl isocyanate is regarded as negative in the Ames test.

No chromosome aberration or mammalian cell gene mutation assay in vitro are available.

Two micronucleus tests in the mouse were negative.

Justification for classification or non-classification

Several Ames tests with phenyl isocyanate are available. In the reliable studies including the key study (guideline study) the test showed a clear negative result, however only 4 stains ( S. typhimurium TA 1535, TA 1537, TA 98 and TA 100). Phenyl isocyanate has no oxidising properties, is no cross-linking agent and no hydrazine derivative: Therefore testing in S. typhimurium TA 102 seems unnecessary.

Additionally 2 reliable chromosome aberration tests in the mouse are available. Both in vivo tests are negative.

According to CLP classification criteria (Regulation (EC) No 1272/2008) a classification is not justified.