Oligomerisation products of but-2-yne-1,4-diol and ethylene oxide

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Effect on fertility: via oral route

Endpoint conclusion:

no adverse effect observed

Effect on fertility: via inhalation route

Endpoint conclusion:

no study available

Effect on fertility: via dermal route

Endpoint conclusion:

no study available

Additional information

Toxicity to reproduction:

E.g. Article 13 of REACH is indicating, that “…information shall be generated whenever possible by means other than vertebrate animal tests, through the use of … or from information from structurally related substances”. On this basis a reliable read across wasperformed to evaluate the toxicity to reproduction of 2-butyne-1,4-diol, ethoxylated (>1 < 4.5 mol EO). The molecule is consisting of a core molecule (2-butyne-1,4-diol) in which the OH-side groups are ethoxylated to a varying degree (>1 < 4.5 mol EO, repeating unit). Therefore a reliable read-across can be made by validating the data for (1) the core molecule 2-butyne-1,4-diol (CasNo 110-65-6) and (2) the propoxylated structural analogue 2-propyn-1-ol, compound with methyloxirane (CasNo. 38172-91-7). All three molecules (relevant substance and read across substances) share a common functional group (tertiary unsaturated carbon bond). The relevant substance and 2-propyn-1-ol, compound with methyloxirane furthermore share acommon/similar precursor/core molecule (2-butyne-1,4-diol/ 2-propyn-1-ol) and a similar alkoxylated repeating unit (=1, >1 < 4.5 mol).By this, the read across is essentially justified by taking into account the toxicity of the core substance and that off similar repeating units (oxirane, methyloxirane). 

By using a structural analog with a low degree of alkoxylation sufficient bioavailability can be guaranteed. It can be anticipated that in case a low molecular weight molecule (core molecule with low degree of alkoxylation) has been proven to be non-toxic, these substance characteristic can be extrapolated to a high molecular weight molecule (core molecule with high degree of alkoxylation), due to a lower bioavailability. Furthermore alkoxylation of the hydroxyl group is increasing its logP value (e.g. by 0.24 units for methyloxirane). The combined effect of these changes is to significantly reduce the bioavailability and hence this approach is representing a worst case estimation of the possible influence of alkoxylation on the potential reproductive toxicity based on maximal systemic availability.

Generally aliphatic esters of propylene glycol, lactic acid and pyruvic acid are expected to be hydrolysed by carboxylesterases or esterases (predominating in hepatocytes) or pancreatic esterase (JECFA, 2002).

Here, neither the core substance nor the structural analogue which was identified to address the repeating unit (CasNo. 38172-91-7) indicated any sign of toxicity to reproduction, when tested to maternally toxic doses.

 

Toxicity to fertility:

For 2-butyne-1,4-diol toxicity to reproduction was investigated in a GLP one generation drinking water study (OECD 415 Guideline) using concentrations of 1, 7.6, and 40 mg/kg body weight/day (BASF AG, 1999). There were no indications from the clinical and pathological examinations that the administration had adverse effects on reproductive performance or fertility of the F0 parental animals of all substance-treated groups. Estrous cycle data, mating behavior, conception, gestation, parturition, lactation and weaning as well as sperm parameters, sexual organ weights, gross and histopathological findings of these organs revealed no substance-related adverse effects. Most of the F0 parental rats proved to be fertile.

For 2-propyn-1-ol, compound with methyloxirane (CasNo. 38172-91-7) toxicity to reproduction was tested in a GLP combined oral repeated dose toxicity study and reproduction/developmental toxicity screening test according to the OECD 422 guideline (TNO Triskelion, 2013). In this study male and female Wistar rats were daily administered test substance concentrations of 0, 5, 25 or 125 mg/kg by gavage. Test substance application was during a premating period of 2 weeks and during mating (1 week), up to a total of approximately 4 weeks for males and including gestation and lactation until postnatal day 4 (PN day 4) for females (up to a total of approximately 6 weeks). Systemic toxicity was e.g. characterized by a marked increase in absolute and relative kidney and liver weights males and females of the high dose group. In addition, relative liver weight was increased in males of the mid dose group. Slight increases in alanine aminotransferase activity, bilirubin levels and bile acids were noted in the high-dose group males. However, in absence of histopathological changes in the liver and kidneys, these effects were considered to be treatment-related, but not adverse. No treatment related findings were identified during daily clinical observations or neurobehavioural observations and motor activity assessment at the end of the study. Furthermore no treatment-related effects were observed in mean body weight, body weight changes and food consumption in exposed animals throughout the study. Regarding reproductive parameters no treatment-related effects were observed on mating index, male and female fertility indices, gestation index, duration of gestation, number of corpora lutea, implantation sites, lost implantations. No effects were observed on litter size, pup sex and weight and pup survival. 

Short description of key information:
Read across:
2-butyne-1,4-diol (CasNo 110-65-6) - one generation drinking water study (OECD 415 Guideline, BASF AG, 1999)
2-propyn-1-ol, compound with methyloxirane (CasNo. 38172-91-7) - OECD 422 (TNO Triskelion, 2013)

Effects on developmental toxicity

Description of key information

Read across: 
2-butyne-1,4-diol (CasNo 110-65-6) - OECD 414 (BG Chemie, 1995)
2-propyn-1-ol, compound with methyloxirane (CasNo. 38172-91-7) - OECD 422 (TNO Triskelion, 2013)

Effect on developmental toxicity: via oral route

Endpoint conclusion:

no adverse effect observed

Effect on developmental toxicity: via inhalation route

Endpoint conclusion:

no study available

Effect on developmental toxicity: via dermal route

Endpoint conclusion:

no study available

Additional information

See "effects on fertility" for read-across justification.

Developmental toxicity/teratogenicity:

Developmental toxicity of 2-Butyne-1,4-diol was assessed in a GLP, OECD 414 Guideline study using concentrations of 10, 40, and 80 mg/kg body weight/day (BG Chemie, 1995). Under the conditions of this full-scale prenatal toxicity study, 2-Butyne-1,4-diol caused overt signs of maternal toxicity at 80 mg/kg bodyweight/day substantiated by reduced food consumption, impaired body weight gains, the intercurrent death of one dam and some adverse clinical signs. 40 and 10 mg/kg body weight/day were tolerated by the dams without any substance-induced findings. Marginal signs of developmental toxicity were observed at the highest dose level (80 mg/kg body weight/day), substantiated by an increased number of affected fetuses/litter with accessory 14th rib(s), a skeletal variation. No substance-induced teratogenic effects, however, were observed up to and including the dose of 80 mg/kg body weight/day and there were no signs of embryo-/fetotoxicity at 40 mg/kg and 10 mg/kg bodyweight/day.

For 2-propyn-1-ol, compound with methyloxirane (CasNo. 38172-91-7) toxicity to reproduction was tested in a GLP combined oral repeated dose toxicity study and reproduction/developmental toxicity screening test according to the OECD 422 guideline (TNO Triskelion, 2013). Please see toxicity to fertility for details.