4-(1-methoxy-1-methylethyl)-1-methylcyclohexene

Endpoint summary

Key value for chemical safety assessment

Repeated dose toxicity: inhalation - systemic effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Reliability 2 is assigned because the information is based on read across

Justification for type of information:

Executive summary
Orange Flower Ether has no adverse effects after repeated exposure because Terpineol-multi has no adverse effects in a 90-day repeated dose inhalation toxicity study. The methyl ether bond versus the alcohol group is not expected to influence the long term repeated dose systemic effects. Structural similarities and differences: Orange Flower Ether is metabolized into Terpineol (multi) and therefore this Terpineol can be used for read across. In the case that some non-metabolised substance enters the system via the dermal or inhalatation route it can be seen that structurally both substances are very similar. The only difference is that the Orange Flower Ether contains a methyl ether while Terpineol-multi has an alcohol group at this position. These groups have similar low reactivity and are not anticipated to present differences in repeaed dose toxicity.
Toxico-kinetic similarities and differences: Absorption: Orange Flower Ether and Terpineol-multi both have physic-chemical properties that present full oral absorption and significant dermal and inhalation absorption. Though Orange Flower Ether has lower water solubility and a higher log Kow the values are still in the range of high absorption. The difference in vapour pressure may be due to a volatile impurity (see Data matrix.
Metabolism: Orange Flower Ether metabolises into Terpineol (multi) by demethylation of the ether CH3 group, resulting in Terpineol-alpha.
Toxico-dynamic aspect: Reactivity: For systemic toxicity (after metabolism) the starting substance will be Terpineol-alpha, which data will be used for the read across.
Experimental data similarity and difference: For systemic toxicity (after metabolism) the starting substance will be Terpineol (multi), which data will be used for the read across. Except acute toxicity there are no endpoints with which the repeated dose toxicity really can be compared with. For systemic toxicity the starting material is Terpineol-alpha (after metabolisation) and therefor the 90-day inhalation toxicity information can be directly used for Orange Flower Ether.
Uncertainty of the prediction: There is no remaining uncertainty, in view of a 90-day repeated dose toxicity information compared to the required 28-day study in an Annex VIII), the similarities in structure and Orange Flower Ether being metabolized into Terpineol (multi) , the read across is justified.

Reason / purpose for cross-reference:

read-across source

Key result

Remarks on result:

not determinable due to absence of adverse toxic effects

Key result

Critical effects observed:

no

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Study duration:

subchronic

Species:

rat

Quality of whole database:

The subchronic inhalation study is sufficiently reliable (based on read across) and therefore adequate to cover this endpoint.

Repeated dose toxicity: inhalation - local effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Reliability 2 is assigned because the information is based on read across

Justification for type of information:

Executive summary
Orange Flower Ether has no adverse effects after repeated exposure because Terpineol-multi has no adverse effects in a 90-day repeated dose inhalation toxicity study. The methyl ether bond versus the alcohol group is not expected to influence the long term repeated dose systemic effects. Structural similarities and differences: Orange Flower Ether is metabolized into Terpineol (multi) and therefore this Terpineol can be used for read across. In the case that some non-metabolised substance enters the system via the dermal or inhalatation route it can be seen that structurally both substances are very similar. The only difference is that the Orange Flower Ether contains a methyl ether while Terpineol-multi has an alcohol group at this position. These groups have similar low reactivity and are not anticipated to present differences in repeaed dose toxicity.
Toxico-kinetic similarities and differences: Absorption: Orange Flower Ether and Terpineol-multi both have physic-chemical properties that present full oral absorption and significant dermal and inhalation absorption. Though Orange Flower Ether has lower water solubility and a higher log Kow the values are still in the range of high absorption. The difference in vapour pressure may be due to a volatile impurity (see Data matrix.
Metabolism: Orange Flower Ether metabolises into Terpineol (multi) by demethylation of the ether CH3 group, resulting in Terpineol-alpha.
Toxico-dynamic aspect: Reactivity: For systemic toxicity (after metabolism) the starting substance will be Terpineol-alpha, which data will be used for the read across.
Experimental data similarity and difference: For systemic toxicity (after metabolism) the starting substance will be Terpineol (multi), which data will be used for the read across. Except acute toxicity there are no endpoints with which the repeated dose toxicity really can be compared with. For systemic toxicity the starting material is Terpineol-alpha (after metabolisation) and therefor the 90-day inhalation toxicity information can be directly used for Orange Flower Ether.
Uncertainty of the prediction: There is no remaining uncertainty, in view of a 90-day repeated dose toxicity information compared to the required 28-day study in an Annex VIII), the similarities in structure and Orange Flower Ether being metabolized into Terpineol (multi) , the read across is justified.

Reason / purpose for cross-reference:

read-across source

Key result

Remarks on result:

not determinable due to absence of adverse toxic effects

Key result

Critical effects observed:

no

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Study duration:

subchronic

Species:

rat

Quality of whole database:

The 90-day inhalation study may be used for assessing local inhalation toxicity. It should be noted that for local effects the extrapolation from rat to human is generally not justified (CLP, 2015)the repeated dose toxicity.

Additional information

Introduction

No repeated dose toxicity studies are available for Orange Flower Ether (CAS #14576-08-0). Therefore the 90 -day inhalation toxicity study available for Terpineol multi (CAS #8000-41-7) is used to assess the repeated dose toxicity for Orange Flower Ether. The NOAEC in this study is > 2230 mg/m3. This concentration is above the saturated vapour pressure (SVP) of Terpineol-multi and of Orange Flower Ether (411 and 685 mg/m3, respectively) and therefore this is considered the maximum achievable dose at which no adverse effects are anticipated (see for calculation of the SVP the acute toxicity Endpoint summary for acute toxicity-inhalation).

Selection of available information from Terpineol-multi for Orange Flower Ether

For Terpineol-multi also some other repeated dose toxicity information is available (OECD TG 422, 90 -day dietary study on males only and OECD TG 414). These studies are either of a shorter duration or limited to one sex (males) and therefore the 90 -day inhalation study is the key study for repeated dose.

Relevance of effects in the Terpineol-multi studies. In the 90 -day inhalation study no adverse effects were see at >=2230 mg/m3. In the oral gavage OECD TG 422 some sperm effects were seen at 750 mg/kg bw considered to be due to bolus dosing. This was supported with a 90 -day dietary study in males showing absence of effect at ca 800 mg/kg dw. In the oral gavage OECD TG 414 study no maternal effects were noted at 600 mg/kg bw. Therefore the key study is the 90 -day inhalation toxicity study for assessing repeated dose effects.

Conversion of inhalation data towards mg/kg bw data: The conversion of the NOAEC of the 90 -day inhalation study to derive an oral and dermal mg/kg bw results in a NOAEL of >=300 mg/kg bw (2230 mg/m3*0.38m3/kg d (respiratory volume rat)*6h/24h (exposure time in the test versus 24h)*5d/7d exposure time in a week)*100/50% (inhalation absorption versus oral absorption).

Conclusion on repeated dose effects vial all routes: In view of the absence of effects in all repeated dose studies at similar doses as presented above the conclusion is that no adverse effects observed via the inhalation and oral gavage and dietary routes. In view of Terpineol-multi being tested at the maximum achievable dosages this means that the final conclusion is that there are 'no hazards identified' vial all routes during 90 -days.

Further information: For the repeated dose toxicity studies other than the 90 -day inhalation and the oral gavage OECD TG 414 the REACH Dossier of Terpineol-multi can be explored.

Repeated dose toxicity: Summary of the inhalation of Terpineol-multi

In a repeated dose toxicity study conducted according to OECD Guideline 413 and in compliance with GLP, terpineol multiconstituent was administered by inhalation-aerosol to groups of Crl:CD(SD) rats (10 rats/sex/ group) by snout-only inhalation exposure at target exposure levels of 0.2, 0.6 and 2 mg/L for 6 hours per day, 5 days per week for 13 weeks. Control animals received air only. Recovery animals were similarly treated for 13 weeks followed by a 4 week off dose period. Control and high dose recovery groups were included (10/sex/group). During the study, clinical condition, body weight, food consumption, ophthalmoscopy, haematology (peripheral blood), blood chemistry, organ weight, macropathology and histopathology investigations were undertaken.

Verification of tested concentrations: The achieved levels were 101, 95 and 112% of the target concentrations of 0.2, 0.6 and 2 mg/L, respectively (achieved concentrations 0.202, 0.572 and 2.23 mg/L). MMAD: <0.52, 0.7 and 1.6 µm for achieved concentrations of 0.202, 0.572 and 2.23 mg/L, respectively. GSD: 2.99 and 1.75 for achieved concentrations of 0.572 and 2.23 mg/L, respectively. MMAD showed a general increase with increasing aerosol concentration. The MMAD for Group 2 could not be calculated, as virtually all the measurable test material was captured on the final filter stage, and the value presented is based on the cut point of the penultimate impactor stage. The Group 3 particle size distribution values showed a bi-modal distribution with an average of 49% of the captured droplet having a MMAD below 0.52 µm. The MMAD value for Group 4 was within the ideal range (1 to 3 µm), indicating that the terpineol multiconstituent aerosol was respirable to the rats. The MMADs for Groups 2 and 3 were below the ideal range of 1 to 3 µm. However, since the delivered aerosol was a liquid, it is likely that those inhaled droplets with an aerodynamic diameter below 1 µm would still have impacted on airway surfaces and not been exhaled.

Clinical sign: There were no treatment related deaths or effects on food consumption, blood chemistry, ophthalmoscopy, organ weights or macropathology findings. Group mean body weight gains were lower than control for males exposed to 0.202 mg/L and for both sexes exposed to 0.572 and 2.23 mg/L. In both sexes, no relationship between exposure concentration and body weight gain was observed but the decrease in mean body weight gain was statistically significant for males exposed to 2.23 mg/L. Body weights showed full recovery for animals previously exposed to 2.23 mg/L.

Clinical pathology: Measurements following 13 weeks of exposure revealed statistically significantly lower group mean reticulocyte percentages and absolute counts for males exposed to 0.572 or 2.23 mg/L, compared to control (as low as 0.82X control). A similar effect was observed for females exposed to 2.23 mg/L (as low as 0.87X control) but this did not attain statistical significance. During Recovery Week 4, values for both sexes previously exposed to 2.23 mg/L were similar to controls. Histopathological changes related to treatment were observed in the nasal turbinates for the majority of animals given terpineol multiconstituent and nasal pharynx for a limited number of animals given 0.572 or 2.23 mg/L.

Local effects: The nasal cavity was identified as a target organ for local effects. Changes related to treatment with terpineol multiconstituent were reported in the nasal turbinates and nasal pharynx in both males and females. In the nasal pharynx, minimal hyperplasia of the mucous cells was also seen in the respiratory epithelium in a small number of animals exposed to 0.572 mg/L or 2.23 mg/L. The changes in the nasal pharynx were also not associated with an inflammatory cell infiltrate or degenerative changes. Examination of recovery phase animals showed no changes in the nasal pharynx respiratory epithelium, suggesting complete recovery after 4 weeks which is therefore not considered adverse. In the nasal turbinate, mucous cell hyperplasia was present at all exposure levels and did not exhibit a clear dose response in terms of incidence or severity in males, although there were slightly higher incidences in females at 0.572 mg/L or 2.23 mg/L compared with females exposed to 0.202 mg/L. Following a 4 week recovery period, similar incidences of mucous cell hyperplasia in the respiratory epithelium were observed in animals exposed to 2.23 mg/L compared to those at the end of the main study phase, although most were of minimal severity. Mucous cell hyperplasia is considered to be an adaptive change in the epithelium in response to chronic irritation (Renne et al 2009). This may correlate with clinical signs of salivation and chin rubbing that were observed on consecutive days (from Day 23 onwards) and displayed a dose related response in terms of the number of animals affected. Given that the histopathology changes were of minimal or slight severity and were generally not associated with inflammatory or degenerative changes in the respiratory epithelium, particularly at lower exposure levels, it would be expected that these changes would reverse following a suitable recovery period. Therefore, mucous cell hyperplasia in the nasal turbinates is also not considered adverse. Therefore, the No Observed Adverse Effect Concentration (NOAEC) was considered to be >=2.23 mg/L (>=2230 mg/m3) for both local and systemic effects.

Conversion ot Orange Flower Ether: This means that also for Orange Flower Ether the NOAEC is >=2230 mg/m3. A correction factor for molecular weight differences between Orange Flower Ether and Terpineol-multi is not needed because the value of Terpineol-multi is conservative and the systemic exposure for both substances will be via Terpineol (multi).

Repeated dose toxicity of Orange Flower Ether(CAS #14576-08-0) using read across from Terpineol-multi (CAS #8000-41-7)

Introduction and hypothesis for the analogue approach

Orange Flower Ether is an ether attached to a cyclohexyl ring with one double bond with a methyl-group attached at the para-position. For this substance no repeated dose toxicity data are available. In accordance with Article 13 of REACH, lacking information should be generated whenever possible by mean other than vertebrate animals test, i.e. applying alternative methods such as in vitro tests, QSARs, grouping and read-across. For assessing the repeated dose toxicity of Orange Flower Ether the analogue approach is selected because for a closely related analogue, Terpineol-multi repeated dose information is available which can be used for read across.

In accordance with Column 2 of the REACH Annex VIII regulation on repeated dose toxicity a 28-day toxicity can be waived when a longer-term toxicity study is available. In the present case a 90-day repeated dose inhalation study from Terpineol-multi will be used for covering this endpoint.

Hypothesis: Orange Flower Ether has no adverse effects after repeated exposure because Terpineol-multi has no adverse effects in a 90-day repeated dose inhalation toxicity study. The methyl ether bond versus the alcohol group is not expected to influence the long term repeated dose systemic effects.

Available information: The key source chemical Terpineol-multi is tested in a 90-day subchronic inhalation toxicity study (OECD TG 413). This study is well-conducted and performed according to the GLP guidelines and therefore receives a reliability of 1.

Target chemical and source chemical(s)

Chemical structures of the target chemical and the source chemicals are shown in the data matrix, including physico-chemical properties and toxicological information, thought relevant for repeated dose of both substances.

Purity / Impurities

Orange Flower Ether is a mono-constituent and contains impurities with the functional group, the ether bond, is absent or at another spot in the structure. This is similar to Terpineol-multi in which the functional group, the alcohol can be absent or at a different spot in the structure. Therefore it is not expected that the impurities of the source and target chemicals affect the read-across justification.

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. When using read across the result derived should be applicable for C&L and/or risk assessment and it should be presented with adequate and reliable documentation. In accordance with ECHA guidance (2015, RAAF) Terpineol-multi was selected from a group of 4-substituted cyclohexene/hexane type of substances of which Terpineol-multi contained the most recent OECD TG 413 repeated dose toxicity information.

Structural similarities and differences:Orange Flower Ether is metabolized into Terpineol (multi) and therefore this Terpineol can be used for read across. In the case that some non-metabolised substance enters the system via the dermal or inhalatation route it can be seen that structurally both substances are very similar. The only difference is that the Orange Flower Ether contains a methyl ether whileTerpineol-multi has an alcohol group at this position. These groups have similar low reactivity and are not anticipated to present differences in repeaed dose toxicity.

Toxico-kinetic similarities and differences:Absorption:Orange Flower Ether and Terpineol-multi both have physic-chemical properties that present full oral absorption and significant dermal and inhalation absorption. Though Orange Flower Ether has lower water solubility and a higher log Kow the values are still in the range of high absorption. The difference in vapour pressure may be due to a volatile impurity (see Data matrix.

Metabolism: Orange Flower Ether metabolises into Terpineol (multi) by demethylation of the ether CH3 group, resulting in Terpineol-alpha.

 

 

Fig. 1   Orange Flower Ether metabolises into Terpineol-alpha by demethylation of the CH3 group attached to the ether bond.

 

Toxico-dynamic aspect: Reactivity:For systemic toxicity (after metabolism) the starting substance will be Terpineol-alpha, which data will be used for the read across.

Experimental data similarity and difference:For systemic toxicity (after metabolism) the starting substance will be Terpineol (multi), which data will be used for the read across.Except acute toxicity there are no endpoints with which the repeated dose toxicity really can be compared with. For systemic toxicity the starting material is Terpineol-alpha (after metabolisation) and therefor the 90-day inhalation toxicity information can be directly used for Orange Flower Ether.

Uncertainty of the prediction:There is no remaining uncertainty, in view of a 90-day repeated dose toxicity information compared to the required 28-day study in an Annex VIII), the similarities in structure and Orange Flower Ether being metabolized into Terpineol (multi) , the read across is justified.In accordance with ECHA guidance (2015, RAAF) the read across would receive a score of 5.

Data matrix

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

Conclusions per endpoint for Hazard assessment and C&L

In a 90-day inhalation repeated dose toxicity test, performed in accordance with OECD TG 413 with Terpineol-multi, no treatment related adverse effects were observed up to 2.23 mg/L (2230 mg/m3). The saturated vapour pressure of Terpineol-multi is 411 mg/m3 and therefore the maximum concentration used is above the limit concentration. Orange Flower Ether has a maximum saturated vapour pressure of 685 mg/m3 and therefore also for Orange Flower Ether no adverse systemic effects are anticipated for Orange Flower Ether at the limit dose.

Final conclusion on hazard, C&L and risk characterization:For Orange Flower Ether no adverse effects are anticipated based on information of Terpineol-multi. Therefore the conclusion is ‘no hazard identified’. The substance therefore does not need to be classified for repeated dose toxicity according to CLP Regulation (EC) No. 1272/2008 and its updates. Also a DNEL for repeated dose toxicity does not have to be derived.

 

Data matrix for the read across to Orange Flower Ether from Terpineol-alpha

Common names	Orange Flower Ether	Terpineol-multi
Chemical structures
	Target	Key Source
CAS no	14576-08-0	8000-41-7
EC no	238-620-0 (Registration in 2018)	232-268-1 (Registered in 2010):
Empirical formula	C11H20O	C10H18O
Smiles	O(C([C@@H]1CCC(=CC1)C)(C)C)C	C([C@@H]1CCC(C)=CC1)(C)(C)O
Physico-chemical data
Molecular weight	168.28	154.25
Physical state	Liquid	Liquid
Melting point, °C	<-20	<-20
Boiling point, °C	222.2	214 - 225
Vapour pressure, Pa	9.91 at 23°C	300 at 20°C*
Water solubility, mg/L	85 at 23°C	2540 at 20°C
Log Kow	4.5 at 25°C	2.6 at 30°C
Human health endpoints
Acute oral LD50 in mg/kg bw	> 5000 (rat) (OECD TG 401)	>2000 (rat) (OECD TG 401)
Repeated dose InhalationNOAEC	Read across from Terpineol-multi	2230 mg/m3 air (OECD TG 413)
Reproductive toxicity
Fertility NOAEL in mg/kg bw	Read across from Terpineol-multi (OECD TG 413)	≥2230 mg/m3 (OECD TG 413)
Developmental toxicity	Read across from Terpineol	≥600 mg/kg bw (OECD TG 414) (maternal and developmental toxicity)

* The vapour pressure of Terpineol-multi may be an overestimate and due to volatile impurities, because generally the vapour pressure for this type of substances fits well with the EpiSuite calculations, which calculates it to be 2.62 Pa and also have a measure value of 6.8 Pa (MPVPBP, v1.43).

Justification for classification or non-classification

Based on the available information classfication for repeated dose toxicity is not warranted in accordance with EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation No. 1272/2008 and its updates.