Octylphosphonic acid

Endpoint summary

Additional information

OPA has been evaluated for genotoxicity using a range of in vitro and in vivo assays covering endpoints of gene mutation, chromosomal damage and DNA repair.

In vitro,OPA consistently gave negative results in the Ames test in S typhimurium strains TA 1535, TA 1538, TA98, TA 100 and E Coli strains WP2P, WP2Puvr A and WP2 uvr A, both in the presence and absence of S9. In two out of five studies, Salmonella strain TA 1537, small increases in revertant colonies were seen on some occasions only in the presence of S9. In the mammalian cell mutation assay in L5178Y cells, small increases in mutant frequency were seen with one sample of OPA, but only in the absence of S9. A second sample showed no such increases. In an in vitro cytogenetic assay in human lymphocytes, OPA gave a negative response in both the presence and absence of S9. The weak nature of the increases seen in the Ames and L5178Y assays, the lack of reproducibility with samples, lack of consistency regarding requirements for S9 and lack of rationalisation against the chemical structures of the components of OPA lead to the conclusion that they do not indicate a significant genotoxic hazard for OPA.

In vivo,OPA has been shown to be negative in the mouse bone marrow micronucleus assay for clastogenicity and in the rat liver UDS assay for general DNA damage/DNA repair. These two in vivo assays, using dose levels up to and including the maximum tolerated dose levels, confirm that OPA is not genotoxic in the entire animal.

It is concluded that OPA has no significant genotoxic potential and does not pose a genotoxic hazard for animals or man.

Justification for selection of genetic toxicity endpoint
No study was selected, since OPA has been evaluated for genotoxicity using a range of in vitro and in vivo assays.

Short description of key information:
Octylphosphonic acid (OPA) has been evaluated for genotoxicity using a range of in vitro and in vivo assays, all evaluated as Reliability 1 and 2.
in vitro:
- Bacterial mutagenicity (Ames test): negative in 3 studies (Thompson, 1994, 1997; muller, 1988) but weakly positive only in S.typhimurium TA 1537 with activation in 2 studies (Callendar, 1997a, 1997b)
- Mutagenicity in mammalian cells: weakly positive without activation only in one L5178Y TK (+/-) Assay (Clay, 1997a) but negative in a repeat of the same assay using a different batch of test substance (Clay, 1997b).
- Clastogenicity/Aneugenicity in mammalian cells: negative in a chromosome aberration test in human lymphocytes (Fox, 1997a).
in vivo:.
- Clastogenicity/Aneugenicity: negative in a mouse bone marrow micronucleus test (Fox, 1997b).
- DNA damage/repair: negative in the UDS assay in rat liver (Fox, 1997c).

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

Based on absence of mutagenicity in the UDS study in vivo and absence of clastogenicity in a mouse micronucleus study in vivo, it is concluded that the OPA is not genotoxic. Therefore no classification is required according to the EU criteria.