[(methylethylene)bis(oxy)]dipropanol

Endpoint summary

Additional information

In vitro studies

One gene mutation study in bacteria, conducted in accordance with Japanese Guidelines for Screening Mutagenicity Testing of Chemicals and with GLP, was conducted by the Ministry of Health and Welfare of Japan (MHW, 1993). Although the study has been requested, only its abstract in English could be recovered. Nevertheless, as the study was conducted within the HPV/SIDS framework and considered to be reliable by OECD SIDS (1994), it is considered to be acceptable for assessment. Mutagenicity of tripropylene glycol was studied in S. typhimurium strains TA 1535, TA 1537, TA 98 and TA 100 and E.coli WP2 uvr A strain, with and without metabolic activation, at concentration levels 0, 312.5, 625, 1250, 2500 and 5000 µg/plate, using water as a vehicle. No cytotoxicity was observed at the highest dose tested (which corresponds to the limit dose established by OECD guideline 471) and no increase in mutation frequency was found, indicating that the substance is not mutagenic in the Ames test.

Another study of the Ministry of Health and Welfare of Japan (MHW, 1993), of which also only the abstract in English could be recovered, studied the ability of tripropylene glycol to induce chromosome aberrations in vitro, using Chinese hamster lung (CHL/IU) cells, with and without metabolic activation. The testing concentrations were 0, 0.48, 0.95 and 1.90 mg/mL in the long-term treatment; in the short term treatment, the concentration was set to 3.5 mg/mL because it was equivalent to ca. 10 mM as required in test guidelines. No structural or numeric chromosomal aberrations were observed up to a maximum concentration of 3.5 mg/mL under conditions of both continuous treatment and short-term treatment with or without an exogeneous metabolic activation system.

No studies on the ability of tripropylene glycol to induce gene mutations in mammalian cells were available for assessment. However, the ability of a structural homologue of tripropylene glycol and its metabolite, dipropylene glycol, to induce gene mutations in mammalian cells was evaluated in a GLP-compliant mouse lymphoma assay (SITEK Research Laboratories, 1988). No increase in the mutation frequency was evidenced both with and without metabolic activation, when the substance was tested at concentration levels of 50, 100, 300, 500, 750, 1000, 2500 and 5000 µg/ml. No evidence of cytotoxicity was evidenced up to the highest dose level, which corresponds to the limit dose level suggested by modern guidelines.

In vivo studies

No in vivo studies on genotoxicity of tripropylene glycol were available for assessment. However, according to Article 13 of the REACH legislation states that, in case no appropriate animal studies are available for assessment, information should be generated whenever possible by means other than vertebrate animal tests,i.e.applying alternative methods such as in vitro tests, QSARs, grouping and read-across. In vivo genotoxicity studies of two structural analogues and metabolites of tripropylene glycol, mono- and dipropylene glycol, were available for assessment.

The study of Litton Bionetics, Inc., 1974, reported the results of a micronucleous test with rats and a dominant lethal assay with rats treated with monopropylene glycol. In the first experiment, groups of 5 male rats were administered by gastric intubation either a single dose of monopropylene glycol at dose levels of 30, 2500 and 5000 mg/kg bw (acute study), or 5 times the same doses 24 hours apart (subacute study). In the acute study animals were killed 6, 24 and 48 hours post-administration, in the subacute study 6 hours after the last dose. In the second study, male rats were administered the test substance at the same dose levels by oral gavage either once (acute study), or for 5 days (1 dose/day, subacute study). Following the treatment, the males were sequentially mated to 2 females per week for 8 weeks (7 weeks in subacute study). Females were killed at 14 days after separating from the male, and at necropsy the uterus was examined for early deaths, late fetal deaths and total implantations. In both cases no evidence of genotoxic effect was observed. Also negative results were reported in the mouse micronucleus test by Hayashi et al., 1988, who administered propylene glycol by single intraperitoneal injection at dose levels of 0, 2500, 5000, 10000 and 15000 mg/kg bw to groups of 6 male mice. Animals were killed 18 hr post-administration and femoral bone marrow cells were scored for the number of micronucleated polychromatic erythrocytes. Three of six mice from the top dose group died during the course of the study. There was no statistically significant increase or trend in mononucleated polychromatic erythrocytes numbers. The percentage of polychromated erythrocytes in the top dose group appeared decreased relative to controls (31% versus 54%) suggesting that the test substance had reached the bone marrow.  

Cytogenicity of dipropylene glycol in vivo was evaluated in a mouse bone marrow micronucleus assay, performed in accordance with OECD Guideline 478 (Dow Chemical Company, 1999). Mice (6 males/dose) were administered single doses of 0, 500, 1000 and 2000 mg/kg bw dipropylene glycol by oral gavage for two consecutive days. All treated animals were sacrificed at 24 hours after the last administered dose for the collection of bone marrow sample. No clinical signs were observed in the study and no statistically significant differences were observed between the frequencies of micronucleated polychromatic erythrocytes (MN-PCE), % polychromatic erythrocytes (% PCE), and body weight in mice treated with the vehicle (negative control) and the test material.

Overall, based on the evidence from the available in vitro studies on tripropylene glycol and in vivo studies on its structural homologues and metabolites mono- and dipropylene glycol, it can be concluded that tripropylene glycol is not genotoxic in vitro and in vivo.

A full justification for read across within the propylene glycol series is contained in a separate document attached to chapter 13 of the lead registrants IUCLID dossier.

Justification for selection of genetic toxicity endpoint
Multiple studies are required for this end point.

Short description of key information:
Tripropylene glycol did not induce increased mutation frequency in Salmonella typhimurium strains TA98, TA100, TA1535 and TA1537, and E. coli WP2 uvr A, with and without metabolic activation, at concentrations up to 5000 µg/plate. It was also negative in the in vitro chromosome aberration assay with Chinese hamster lung cells at dose levels up to 1.9 mg/ml. The gene mutation study in mouse lymphoma cell culture with a structural analogue and metabolite of tripropylene glycol, dipropylene glycol, was negative up to dose levels of 5000 µg/ml, both in the presence and absence of metabolic activation. No in vivo studies with tripropylene glycol were recovered; however, negative in vivo studies with its metabolites mono- and dipropylene glycol were available for assessment. Based on these results, tripropylene glycol is considered to be non genotoxic.

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

Based on the negative results of available in vitro genotoxicity studies and negative results of in vivo genotoxicity studies with two metabolites of tripropylene glycol, mono- and dipropylene glycol, tripropylene glycol does not have to be classified for genotoxicity in accordance with Directive 67/548/EEC and EU Classification, Labeling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008.