Octabenzone

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

The substance is not mutagenic in the Ames test and does not cause chromosome aberrations in vitro. The methylated analogue did not cause gene mutations in mammalian cells in vitro (Seyfried, 2006).

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Genetic toxicity in vivo

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Ames Test

The key study for bacterial mutagenicity was performed according to OECD Guideline 471 and GLP (1991). Doses were 625, 1250, 2500, and 5000 µg/plate and DMSO was used as vehicle. No independent repeat experiment, but a separate toxicity test with two strains is reported. Strains S. typhimurium TA 1535, TA 1537, TA 98 and TA 100 and E. coli WP2 uvr A were tested both in the presence and absence of liver S9 mix prepared from Arochlor-induced rats. No significant toxicity and no increase in mutant frequency were observed. Positive and negative control experiments confirmed the validity of the results.

Results of a GLP-compliant Ames test (OECD 471) have been made public by MHLW (Japan). Applied doses were 313, 6235, 1250, 2500 and 5000 μg/plate in the presence and absence of metabolic activation. No indication of mutagenicity was observed. A third Ames assay was performed using tester strains TA98 and TA 100 (Nakajima, 2006). In this assay, octabenzone did not cause a two-fold increase in mutant frequency, which is the threshold for identification as a mutagen.

Chromosomal Aberration

Reliable data on clastogenicity in mammalian cells in vitro is available from two OECD 473 guideline and GLP compliant study in human lymphocytes (2001) and in Chinese hamster lung fibroblasts (MHLW Japan). The substance was found to be non clastogenic.

Mouse Lymphoma Assay

Reliable data on mutagenicity in mammalian cells in vitro is available for the short-chain analogue oxybenzone (2-hydroxy-4 (methoxy)phenyl](phenyl)methanone). It is of better solubility in water and of lower molecular weight because it carries a methyl group instead of a non-branched C8-alkyl chain. As an unbranched alkyl chain is not a structural alert for genotoxicity, it is acceptable to conclude on the outcome of the in-vitro mutagenicity study. The toxicokinetic investigation showed that octabenzone is metabolized via glucuronidation at the phenolic hydroxy group (Patel, 1968). In contrast to sulfonatiation or epoxidation, glucuronidation is not known to create reactive (genotoxic) metabolites. For oxybenzone, no mutagenicity was observed in the mouse-lymphoma assay (OECD 476). Tested doses were 22, 29, 37, 45 and 52 µg/mL (without S9) and 18, 24, 31, 37, 44 and 50 µg/mL (with S9) using DMSO as vehicle. A less than 3-fold increase occurred at highly toxic concentrations in the presence of metabolic activation. Therefore, the substance is not considered to be genotoxic in this assay.

Other tests

Absence of genotoxicity in vitro was reported in two non-standard tests (Nakajima, 2006). One of the non-standard tests was the umu test for DNA damage and the other an in-vitro cell transformation assay. The umu assay detects genetic damage using the expression of the genes involved in SOS repair that follows the damage. In this assay, lumineseent and light absorption Umu-tests were performed. The luminescent umu-test was performed using the Salmonella typhimurium TL210 strain. The light absorption umu-lest used the S. typhimurium TA1535/pSK1002 strain, with chlorophenolred-ß-D-galactopyranoside (CPRG) as the substrate. Octabenzone did not cause signs of genetic damage in the either umu assay.

The promotion activity was examined by the Bhas assay, a method that uses Bhas 42 cells for the formation of transformation foci. Bhas 42 cells were derived from BALB/3T3 cells. A phorbol ester (TPA) was used as a positive control. It caused a tenfold increase in the number of foci at a concentration of 50 ng/ml. Octabenzone caused no increase in foci formation at concentrations up to 10 μg/ml which was the hightest concentration that could be tested.

Justification for classification or non-classification

The available experimental test data are reliable and suitable for classification purposes under Regulation 1272/2008. As a result the substance is not considered to be classified for genotoxicity under Regulation (EC) No. 1272/2008, as amended for the eighth time in Regulation (EU) No 2016/218.