Trioctylphosphine oxide

Endpoint summary

Additional information

In vitro

A study was conducted to evaluate the mutagenicity of the test substance using bacterial reverse mutation assay, in accordance with OECD Guideline 471 and EU method B.13/14, and in compliance with GLP. In the dose range finding study, concentrations of up to 5,000 μg/plate in the strains TA100 of Salmonellatyphimurium and WP2uvrA of Escherichia coli in the direct plate assay were used. In the first mutation experiment, the substance was tested up to concentrations of 1,600 μg/plate in the strains TA1535, TA1537 and TA98 and in the second experiment, up to concentrations of 1,600 μg/plate in the strains TA1535, TA1537, TA98, TA100 and WP2uvrA. Toxicity was observed in the strains TA1535, TA1537 and TA100 in the absence of S9-mix and in TA100 in the presence of S9-mix. The negative control values were within the laboratory historical control data ranges, except for TA100 in the absence of S9-mix (second experiment). However, since this value was just outside the limit of the range, the validity of the test was not considered to be affected. The strain-specific positive control values were at least three times the concurrent vehicle control group mean, indicating that the test conditions were adequate and that the metabolic activation system functioned properly. The test substance did not induce a significant dose-related increase in the number of revertant colonies in each of the tester strains both in the absence and presence of S9-metabolic activation. These results were confirmed in a follow-up experiment. Under the study conditions, the test substance was not mutagenic in the Salmonella typhimurium and Escherichia coli reverse mutation assay (Verspeek-Rip CM, 2014).

A study was conducted to evaluate the mutagenicity of the read across substance ‘A mixture of: hexyldioctylphosphineoxide; dihexyloctylphosphineoxide; trioctylphosphineoxide’ using a method similar to OECD Guideline 471, in compliance with GLP. The test substance was subjected to a preliminary toxicity screen at dose levels of 100, 333, 1,000, 3,333 and 10,000 µg/plate. Based upon the findings, the top dose selected for the plate incorporation mutation assay was 3,000 µg/plate. Test substance was evaluated in strains TA1535, TA1537, TA1538, TA98 and TA100 of Salmonella typhimurium with and without metabolic activation preparation at doses of 30, 100, 300, 1,000 and 3,000 µg/plate. The results were negative in all groups. All positive and solvent controls used in the evaluation of the test substance induced mean mutant frequency values which were within the acceptable range of mean historical data. Under the study conditions, the read across substance was considered non-mutagenic in thisSalmonella typhimuriumreverse mutation assay (Barfknecht TR, 1985).

A study was conducted to evaluate the mutagenicity of the read across substance ‘A mixture of: hexyldioctylphosphineoxide; dihexyloctylphosphineoxide; trioctylphosphineoxide’ using a method similar to the OECD Guideline 471, in compliance with GLP. The test substance was subjected to a preliminary dose-range finding study at dose levels of 10, 33, 67, 100, 333, 667, 1,000, 3,333, 6,667 and 10,000 µg/plate. Based on the findings, the top dose selected for the plate incorporation mutation assay was 10,000 µg/plate. Test substance was evaluated in strains TA1535, TA1537, TA1538, TA98 and TA100 of Salmonella typhimurium with and without metabolic activation preparation at doses of 667, 1,000, 3,333, 6,667 and 10,000 µg/plate. No evidence of mutagenicity was observed in any of the tested strains in the presence and absence of metabolic activation. All positive and solvent controls used in the evaluation of the substance induced mean mutant frequency values which were within the acceptable range of mean historical data. Under the study conditions, the read across substance was considered non-mutagenic in this Salmonella typhimurium reverse mutation assay (Lawlor TE, 1987).

A study was performed to assess the ability of the read substance ‘A mixture of: hexyldioctylphosphineoxide; dihexyloctylphosphineoxide; trioctylphosphineoxide’ to induce chromosomal aberrations in human lymphocytes culturedin vitro,according to OECD guideline 473. Human lymphocytes, in whole blood culture, were stimulated to divide by addition of phytohaemagglutinin, and exposed to the test substance both in the presence and absence of S-9 mix derived from rat livers. Solvent and positive control cultures were also prepared. After the appropriate incubation time, cell division was arrested using colcemide, the cells harvested and slides prepared, so that metaphase figures could be examined for chromosomal damage. In order to assess the toxicity of the test substance to cultured human lymphocytes, the mitotic index was calculated for all cultures treated with the test substance and the solvent control. On the basis of these data, the appropriate concentrations were selected for metaphase analysis. In both absence and presence of S-9 mix, the read across substance did not cause a statistically significant increase in the proportion of metaphase figures containing chromosomal aberrations, when compared with the solvent control. All positive control substances caused large, statistically significant increases in the proportion of aberrant cells. Under the study conditions, the read across substance did not show evidence of clastogenicity in thisin vitrocytogenetic test system (Akhurst LC, 1995).

In vivo

An OECD Guideline (474) comparable study was conducted to assess the genotoxicity of the read across substance ‘A mixture of: hexyldioctylphosphineoxide; dihexyloctylphosphineoxide; trioctylphosphineoxide’ using a micronucleus cytogenetic assay in mice. The test substance-vehicle mixture and the vehicle alone were administered by intraperitoneal (IP) injection in two equal volumes of 10 mL/kg bw/d which were given 24 h apart. Positive control was injected through IP route at a dose level of 0.15 mg/kg bw. At the sacrifice (6 h following second dose), femurs were exposed, cut just above the knee and the bone marrow was aspirated into a syringe containing FBS. Using oil immersion, 1,000 polychromatic erythrocytes were scored for the presence of micronuclei. The proportion of polychromatic erythrocytes to total erythrocytes and the number of micronucleated normocytes in the field of 1,000 polychromatic erythrocytes were also enumerated. There was no significant difference in the ratio of polychromatic erythrocytes to total erythrocytes between treatment groups per sacrifice time. The number of micronucleated polychromatic erythrocytes per 1,000 PCE was not significantly increased in the test substance-treated groups, regardless of sex or sacrifice time point. TEM induced a significant increase in micronucleated polychromatic erythrocytes in male and female mice relative to the vehicle control. Under the study conditions, the read across substance did not increase the frequency of micronuclei in mice (Putman DL, 1986).

Justification for selection of genetic toxicity endpoint
The data is available on read across substance. All data contribute to the overall endpoint conclusion.

Short description of key information:
The test substance was not mutagenic in an Ames test. Also, the read across substance was negative in Ames tests, an in vitro chromosomal aberration assay and in vivo micronucleus assay. Based on this data, the substance is not considered to have any genotoxic potential.

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

The test substance was evaluated for its mutagenicity potential in an Ames test. The read across substance was evaluated in several in vitro as well as in vivo studies. No evidence of genotoxicity was observed in any of the above assays; hence the test substance does not require classification for genotoxicity according to CLP (EC 1272/2008).