Butanoic acid, 3a,4,5,6,7,7a-hexahydro-4,7-methano-1H-indenyl ester

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

The NOAEL is based on read across from Cyclacet which was tested in an OECD 421, GLP, oral gavage. The systemic NOAEL was determined to be 1000 mg/kg bw/day based on the absence of treatment-related toxicologically relevant effects. The fertility NOAEL is considered to be >= 1000 mg/kg bw/day based on the absence of treatment-related reproductive effects

Effect on fertility: via oral route

Endpoint conclusion:

no adverse effect observed

Quality of whole database:

The fertility information is retreived from an OECD TG 421 of an analogue and from repeated dose toxicity information of the same analogue. This information is considered to be sufficiently adequate to cover this endpoint.

Additional information

No study was available with test substance Cyclobutanate, however, a reproscreening study (OECD TG 421) with structural similar substance Cyclacet can be used for read across. Cyclobutanate has a similar tricyclodecenyl fused ring-backbone compared to Cyclacet. Cyclobutanate, however, has a butyl ester attached to this backbone, while Cyclacet has an acetic (ethyl) ester here (see for a documentation of the read across document the end of this section). The additional propyl group in Cyclobutanate is considered minimally relevant for the toxicity to reproduction/developmental toxicity. In addition, no effects on gonads were seen in the repeated dose toxicity study of 90 days with Cyclacet and the 28 day study with Cyclobutanate further supporting the absence of fertility effects.

The study with Cyclacet complies with the recommendations of the OECD Guidelines for Testing of Chemicals No. 421 “Reproduction/Developmental Toxicity Screening Test” (adopted 27 July 1995), and potential adverse effects of Cyclacet on reproduction including offspring development were assessed.

The test material was administered by gavage to three groups, each of ten male and ten female Wistar rats, for up to forty-six consecutive days (including a two week maturation phase, pairing, gestation and early lactation for females), at dose levels of 100, 300 and 1000 mg/kg/day. A control group of ten males and ten females was dosed with vehicle alone (Arachis oil BP).

Clinical signs, bodyweight change, dietary intake and water consumption were monitored during the study. Pairing of animals within each dose group was undertaken on a one male: one female basis within each treatment group on Day 15 of the study, with females subsequently being allowed to litter and rear their offspring to Day 5 of lactation. During the lactation phase, daily clinical observations were performed on all surviving offspring, together with litter size and offspring weights and assessment of surface righting reflex.

Adult males were terminated on Day 43, and all females and surviving offspring on Day 5post partum. All animals were subjected to a gross necropsy examination and histopathological evaluation of reproductive tissues was performed.

The oral administration of Cyclacet to rats by gavage, for a period of up to forty six consecutive days at dose levels of 100, 300 and 1000 mg/kg/day did not result in any treatment-related reproductive effects. The ‘No Observed Adverse Effect Level’ (NOAEL) for reproductive toxicity was therefore considered to be >=1000 mg/kg/day. Based on this result, the read-across NOAEL for Cyclobutanate was also established to be >=1000 mg/kg bw/day.

 

Effects on developmental toxicity

Description of key information

The NOAEL is based on read across from Cyclacet which was tested in an OECD 421, GLP, oral gavage. The systemic NOAEL was determined to be 1000 mg/kg bw/day based on the absence of treatment-related toxicologically relevant effects. The developmental NOAEL is considered to be >= 1000 mg/kg bw/day based on the absence of treatment-related developmental effects.

Effect on developmental toxicity: via oral route

Endpoint conclusion:

no adverse effect observed

Additional information

For Cyclobutanate fertility information is available from the OECD TG 407 subacute study but fertility information on other than gonads and developmental toxicity is missing. For the assessing these endpoints an OECD TG 421 study from the structurally, kinetically and toxicologically related Cyclacet is used. The read across justification is presented below after presenting the summary of the Cyclacet OECD TG 421 study.

Cyclacet – OECD TG 421 Reproductive toxicity screening test

The study complies with the recommendations of the OECD Guidelines for Testing of Chemicals No. 421 “Reproduction/Developmental Toxicity Screening Test” (adopted 27 July 1995), and potential adverse effects of Cyclacet on reproduction including offspring development were assessed.

The test material was administered by gavage to three groups, each of ten male and ten female Wistar rats, for up to forty-six consecutive days (including a two week maturation phase, pairing, gestation and early lactation for females), at dose levels of 100, 300 and 1000 mg/kg/day. A control group of ten males and ten females was dosed with vehicle alone (Arachis oil BP).

Clinical signs, bodyweight change, dietary intake and water consumption were monitored during the study. Pairing of animals within each dose group was undertaken on a one male: one female basis within each treatment group on Day 15 of the study, with females subsequently being allowed to litter and rear their offspring to Day 5 of lactation. During the lactation phase, daily clinical observations were performed on all surviving offspring, together with litter size and offspring weights and assessment of surface righting reflex. Adult males were terminated on Day 43, and all females and surviving offspring on Day 5 post partum. All animals were subjected to a gross necropsy examination and histopathological evaluation of reproductive tissues was performed.

The oral administration of Cyclacet to rats by gavage, for a period of up to forty six consecutive days at dose levels of 100, 300 and 1000 mg/kg/day did not result in any treatment-related developmental effects. The ‘No Observed Adverse Effect Level’ (NOAEL) for developmental toxicity was therefore considered to be 1000 mg/kg/day.

The assessment of reproductive toxicity (including fertility and developmental toxicity of Cyclobutanate using read across from Cyclacet

Introduction and hypothesis for the analogue approach

Cyclobutanate is a butylester attached to a tricyclodecenyl fused ring structure. For this substance no reproductive toxicity (i.e. fertility and developmental toxicity) data are available. In accordance with Article 13 of REACH, lacking 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. For assessing the fertility and developmental toxicity of Cyclobutanate the analogue approach is selected because for one closely related analogue reliable fertility and developmental toxicity information is available from a Reproscreen OECD 421 study.

Hypothesis: Cyclobutanate has similar reproductive toxicity compared to Cyclacet resulting in a similar NOAEL because the analogue Cyclacet based on structure, kinetic and toxicological similarity.

Available experimental information: For Cyclobutanate a 28-day repeated dosed toxicity study (OECD TG 407 under GLP) is available in which no effects were seen on male and female reproductive organs up to 1000 mg/kg bw with a reliability of 1. The source substance Cyclacet has been tested in a well conducted Reproscreen study (OECD TG 421 under GLP) up to 1000 mg/kg bw and the test result receives a reliability of 1.

Target chemical and source chemical(s)

Chemical structures of the target chemical and the source chemical are shown below. These two Cycla-esters have a tricyclodecenyl fused ring structure with on the left ring an ester bond with an alkyl chain an unsaturated bond in the right ring. Physico-chemical properties and toxicological information, thought relevant for reproductive and developmental toxicity of the two substances, are listed in the data matrix below.

Purity / Impurities

The constituents and impurities of the source and target chemicals indicate a similar reproductive toxic potential. The impurities are all below < 10%.

Analogue approach justification

According to Annex XI 1.5 read across can be used to replace testing when the similarity can be based on a common backbone and a common functional group. This read across is presented with reliable and adequate documentation and can be applied for C&L and/or risk assessment.

Structural similarities and differences: The target and the source chemical, have a tricyclodecenyl fused ring structure with an unsaturated bond in the right ring. The alkyl chain attached to the ester of Cyclobutanate (C4) is two methyl groups longer than of Cyclacet (C2). These differences between the target and source chemical are not expected to behave differently compared to the target organs because the alkyl side chains (butyl versus acetyl) are not expected to influence significantly the reproductive toxicity of these chemicals.

Toxico-kinetic considering absorption, distribution and excretion via all exposure routes Cyclobutanate (target) and Cyclacet (source) have similar toxico-kinetic behaviour:  the molecular weights are 220 and 198, respectively; both are both liquids and; vapour pressures are similar. The t the water solubility and log Kow are somewhat lower and higher for Cyclobutanate and Cyclacet respectively because of the longer alkyl chain of Cyclobutanate.

For metabolisation the target and the source chemical will both be metabolised into the Cycla-alcohol (3385-61-3) by carboxylesterases and butyl and acetic acid for Cyclobutanate and Cyclacet, respectively. This metabolisation of the Cycla-ester is further outlined and illustrated in the toxico-kinetic section.

Similarities in results for toxicological endpoints between the target and the source chemical(s):

In the data matrix a summary of the other toxicological data is presented to show that there are hardly toxicological differences between the target and the source chemical and a similar C&L is derived. The acute oral and dermal toxicity data show limited acute toxicity for the source and the target chemical. The repeated dose toxicity in both are >=1000 mg/kg bw.  Cyclobutanate and Cyclacet also show negative results in the available genotoxicity tests (e.g. Ames) and therefore reproductive toxicity resulting from genotoxicity is not expected.

Uncertainty of the prediction: The prediction of the NOAEL of >=1000 mg/kg bw for the target chemical for reproductive toxicity (both fertility and developmental toxicity) has a high certainty because of close similarity between the target and the source chemical. The two methyl groups difference in the alkyl chain will not have an impact on the reproductive toxicity. The available information from the source chemical is a high quality Reproscreen test (Reliability 1). Furthermore, for the target chemical itself no effects up to the limit dose of 1000 mg/kg bw on gonads were found in a 28 day repeated dose toxicity study.

Data matrix

The relevant information on physico-chemical properties and toxicological characteristics are presented in the Data Matrix.

Conclusions on reproductive toxicity

For Cyclobutanate limited effects on fertility and no information on developmental toxicity is available, while such information is present on a closely related analogue Cyclacet, which can be used for read across. When using read across the result derived should be applicable for C&L and/or risk assessment and is presented with adequate and reliable documentation.

For Cyclacet (acetyl side chain) a well conducted Reproscreen test is available (Reliability 1) with a NOAEL of >=1000 mg/kg bw for fertility, developmental toxicity and systemic toxicity. Based on the read-across applied it can be concluded that Cyclobutanate also has a NOAEL of >=1000 mg/kg bw for reproductive toxicity.

Final conclusion: Cyclobutanate has a NOAEL of >=1000 mg/kg bw for fertility and developmental toxicity.

Data matrix for the read across to Cyclobutanate from Cyclacet for reproductive toxicity

Common names	Cyclobutanate Target	Cyclacet Source
Chemical structures
CAS no	113889-23-9 (generic)	54830-99-8 (generic)
Empirical formula	C14H20O2	C12H16O2
441-420-8	441-420-8	911-369-0
REACH registered	Yes	Yes
Molecular weight	220	192
Physico-chemical data
Physical state	liquid	liquid
Melting point ^oC	< -20	< -20
Boiling point ^oC	275	249
Vapour pressure Pa	11.2	2.1
Water solubility mg/l	11.5	186
Log Kow	4.48	3.9
Human health endpoints
Acute oral tox in mg/kg bw	>5000 (OECD TG 423)	2750 (OECD TG 401)
Acute dermal tox in mg/kg bw	>2000 (OECD TG 402)	>5000 (OECD TG 402)
Genotoxicity – Ames test	Negative (OECD TG 471)	Negative (OECD TG 471)
Repeated dose toxicity (mg/kg bw/day)	NOAEL >=1000  (OECD TG 407)	NOAEL >=1000 in 90-day study (OECD TG 408) and in a Reproscreen (OECD TG 421)
Reproductive toxicity Fertility       Developmental toxicity	In repeated dose no effects on gonads were seen in 28-day study up to 1000 mg/kg bw Read across	NOAEL >=1000 for fertility in a 90-day study (OECD TG 408) and in a Reproscreen study (OECD TG 421)   No developmental toxicity effects seen in the Reproscreen study.

 

 

Justification for classification or non-classification

Based on the results of the available Repeated dose and Reproductive toxicity studies the substance does not have to be classified for reproductive toxicity (fertility and developmental toxicity) according to EU CLP (EC 1272/2008 and its amendments).