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Key value for chemical safety assessment

Additional information

A number of in vitro genetic toxicity tests (i.e., gene mutation studies in bacteria; cytogenicity studies in mammalian cells; and gene mutation studies in mammalian cells) were identified for linear alpha olefins. Additionally, an in vivo mouse bone marrow micronucleus assay was identified. All studies showed negative results.

A read-across reverse gene mutation assays in bacteria was identified from octadec-1-ene and dodec-1-ene, in which five strains of Salmonella typhimurium (TA98, TA100, TA1535, TA1537, and TA1538) and 2 strains of Escherichia coli (WP2and WP2uvrA) were exposed to alpha C18 (octadec-1-ene) or C12 (dodec-1-ene) product in acetone at concentrations of 0, 0.2, 2, 20, 200, or 2000 µg/plate in the presence and absence of mammalian metabolic activation using the plate-incorporation method (Dean, 1980). No increase in reverse mutation rate was noted in either assay in the presence or absence of metabolic activation for either test material. A preliminary study to assess bacterial cytotoxicity to determine appropriate doses was not performed.

In a read-across mammalian cell chromosome aberration studies from octadec-1-ene and dodec-1-ene, monolayer slide cultures of rat liver cells (RL1) were exposed to either alpha C18 product (octadec-1-ene) or alpha C12 product (dodec-1-ene) in acetone at concentrations of 0, 125, 250, 500µg/mL for 24 hours (Dean, 1980). Alpha C18 product was tested up to cytotoxic concentrations (500µg/mL). The positive control (DMBA) induced the appropriate response. There was no evidence of consistent increase in the frequency of chromosomal damage (chromatid gaps, chromatid breaks, or total chromosomal aberrations) induced over background for either test material.

A read-across study from hex-1-ene performed with mammalian cells was identified (Adams et al., 1990). Hex-1-ene, diluted in DMSO, was examined in a mouse lymphoma thymidine kinase assay using L5178Y (TK+/-) cells. Prior to the main mutation study, a preliminary study was conducted with the test chemical to determine its potential to cause cytotoxicity and also to determine an appropriate range for the main mutation study. Study protocols for both the preliminary and main study were similar with minor modification made in the main study. Based on experimental results, the study authors concluded that 1-hexene was cytotoxic at doses = 300 µg/ml while, itwas not mutagenic either in the presence or absence of S9 at concentrations =300 µg/mL.

 

A read-across in vitro mammalian gene mutation study from C12 -14 alpha olefins (i.e., a linear alpha olefin) was identified, in which CHO-K1 cells were treated with Gulftene 12-16 to study its potential to induce point mutations in the HGPRT gene in the CHO-K1 cell line in the absence and presence of metabolic activation (±S9) (Papciak and Harnois, 1983). Concentrations of 4, 8, 16, 32, 64, 128, 512, 1024, and 2048 ug/mL Gulftene 12-16 (vehicle-F68 Pluronic®Polyol) were used for the range finding. Cytotoxicity was observed at 2048 ug/mL in the absence of metabolic activation and =64 ug/mL in the presence of metabolic activation; however, the cytotoxicity was clearly not dose-dependent. Mutagenicity was evaluated at 4, 16, 128, 512, 1024, and 2048 ug/mL Gulftene 12-16 (±S9); however, results were only provided for concentrations =128 ug/mL.  In the absence of S9, there were an insufficient number of cells to sub-culture 1 million cells per dish at the 1024 and 2048 ug/mL test concentrations and cell counts for these concentrations were also reduced with metabolic activation (+S9). In addition, the cloning efficiency was depressed at 1024 and 2048 ug/mL, indicating that the immediate toxic effect also delayed growth of surviving cells.  There was no increase in the frequency of mutant colonies at any test concentration with or without metabolic activation (±S9). The vehicle control was well within the <90% toxicity level, while the two positive control groups (ethyl methane sulfonate & benzo(a)pyrene) exhibited a positive response indicating that the assay was functional. Based on these results, the study authors concluded that there was no increase in the frequency of mutant colonies in cells treated with Gulftene C12-16 when compared to the controls.

A read-across in vivo mouse bone marrow micronucleus assay from hex-1-ene was identified, in which 5 mice/sex/dose were treated (whole body inhalation exposure) with Gulftene 6 at doses of 0; 1000; 10,000; or 25,000 parts per million for a period of 2 hours on two consecutive days (Harnois, 1983). Bone marrow cells were harvested post sacrifice on either day 3 or 4 of the study period. Lethargy and rapid respiration were observed in animals treated at 10,000 and 25,000 parts per million but these clinical effects were reversible post-exposure. 50 percent of the female mice exhibited statistically lower mean body weights on days 1 and 3. However, mean body weights of the remaining female mice were observed to be normal when compared to corresponding control animals. No significant increase in the frequency of micronucleated polychromatic erythrocytes in the bone marrow was noted after treatment at any dose level. Male and female animals induced with cyclophosphamide exhibited a statistically higher frequency of micronucleated polychromatic erythrocytes in the bone marrow when compared with negative controls.

In the read-across study from alkenes C20 -24 (i.e., anisomerised olefin; alpha, internal, linear and branched – multiple carbon numbers),the test material was administered to seven male Crl:CD-1TM(1CR)BR mice intraperitoneally at 500, 1000, or 2000 mg/kg body weight (Dunward, 1998). A vehicle control group (arachis oil, seven male mice) and a positive control group (cyclophosphamide, five male mice) were also utilized in the study. There were no signs of clinical toxicity or mortality in male mice dosed with 500, 1000, or 2000 mg/kg in the micronucleus assay. No statistically significant increases in the number of PCEs or decreases in the PCE/NCE (normochromatic erythrocytes) ratio were observed in male mice at any treatment level.Intraperitoneal administration of C20-C24 alkenes, branched and linear, did not result in an increase in the frequency of PCEs. The test material was reported to be non-genotoxicunder the conditions of the test.

Justification for Read Across:

Several criteria justify the use of the read across approach to fill data gaps for linear alpha olefin substances using multiple carbon number isomerised olefin analogues.  Studies indicate that changing the carbon number, the location of the double bond, or adding branching to olefins does not measurably alter their respective toxicological effects on mammalian health endpoints. Multiple carbon number isomerised olefins are considered to have minimal acute toxicity potential. Genotoxicity studies indicate that these substances are not mutagenic. No adverse systemic toxicity was observed in a 90-day repeated oral dose study in which rats were exposed to alkenes, C20-24, a multiple carbon number isomerised olefin. The toxicological profile for multiple carbon number isomerised olefins, outlined above, indicates a low hazard potential for human health. There do not appear to be any significant toxicological differences between multiple carbon number isomerised olefins and linear alpha olefins. Therefore, read across between these two categories is justified.


Short description of key information:
Read across from octadec-1-ene and dodec-1-ene was used for bacterial (OECD 471) and chromosome aberration assays (OECD 473). Read-across studies, including a gene mutation assay performed on the mouse lymphoma TK locus (OECD 476) and an in vivo mouse bone marrow micronucleus assay (OECD 474), from hex-1-ene were identified. Two read-across studies (OECD 474) for in vivo gene mutation were identified, one from 1-hexene and another from alkenes, C20-24. All studies showed negative results.

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

All read-across in vitro genetic toxicity studies (i. e., gene mutation studies in bacteria; cytogenicity studies in mammalian cells; and gene mutation studies in mammalian cells) from linear alpha olefins (i.e., octadec-1-ene, dodec-1-ene, hex-1-ene, and C12 -14 alpha olefins) showed negative results. Read-across in vivo mouse micronucleus studies from hex-1-ene and alkenes, C20-24 also produced no evidence of mutagenic effects. 

Consequently, icos-1 -ene is unlikely to be mutagenic and does not meet the criteria for classification and labelling as described in EU Dangerous Substances Directive 67/548/EEC or CLP EU Regulation 1272/2008.