Dimethylcyclohex-3-ene-1-carbaldehyde

Endpoint summary

Description of key information

Vertoliff acute oral toxicity is derived from the analogue Triplal for which a study similar to OECD TG 401 was performed: LD50 rat = 3900 mg/kg bw

Acute inhalation toxicity LC50 route to route extrapolation is > 10140 mg/m³

Vertoliff acute dermal toxicity is derived from the analogue Triplal for which a study similar to OECD 402 with rabbits was performed: LD50 > 5000 mg/kg bw

Key value for chemical safety assessment

Acute toxicity: via oral route

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Acute toxicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Acute toxicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Additional information

The acute toxicity information for Vertoliff is derived from Triplal, a close analogue. First, the acute toxicity studies of Triplal will be summarised below. Thereafter, the read-across justification is presented. The accompanying files are attached in the Endpoint summary as well.

Acute oral toxicity with Triplal using an equivalent of OECD TG 401:

A pre-guideline study, equivalent to OECD guideline 401, was performed to identify the acute oral toxicity of the test substance. In this study 10 rats (sex unspecified) were administered with 1.73, 2.47, 3.51 and 5.0 g/kg bw. 3/10, 1/10, 3/10 and 9/10 animals died in the 4 day observation period after exposure to 1.73, 2.47, 3.51 and 5.0 g/kg, respectively. Some additional toxic effects included lethargy, piloerection and comatose. At necropsy, the following organs were affected: nose/mouth (exudate red, yellow and clear), anogenital (exudate), intestines (red and yellow and bloated), liver (mottled and dark), lungs (dark lungs), kidney (dark kidneys) and spleen (dark and large). These dose-related effects were likely irritant effects because the substance becomes an acid when oxidized. Under the conditions of the test, the acute oral LD50 for the test substance in rat was determined to be 3900 mg/ kg bw.

 Acute dermal toxicity with Triplal using an equivalent of OECD 402:

A pre-guideline study, equivalent to OECD guideline 402, was performed to identify the acute dermal toxicity of the test substance. In this study 10 rabbits (sex unspecified) were administered with 5000 mg/kg test substance on the skin. Two out of ten animals died in the 14 day observation period after exposure to the test substance. Some additional toxic effects included anorexia, lessened mobility due to severe edema & eschar of exposure site, ptosis (droopiness of a body part) and skin irritation: moderate redness (1/8), severe redness (7/8), moderate edema (4/8) and severe edema (4/8). At necropsy, the following organs were affected and the following signs observed: yellow exudate in nose/ mouth (2/10), red areas in intestines (3/10), yellow areas in intestines (1/10), bloated intestines (1/10), intestines containing dark green substance (1/10), liver dark (5/10), liver mottled (1/10), liver white nodules (2/10), lungs with areas dark (2/10), kidney mottled (2/10), kidney pale (1/10), skin sloughing of exposure area (1/10), skin edema (8/10), skin redness (9/10), skin hard/ thick (6/10). Under the conditions of the test, the acute dermal LD50 for the substance in rabbits was > 5000 mg/ kg bw. Based on these results, the test substance is not considered to be acute harmful.

Acute Inhalation using route to route extrapolation

The acute inhalation toxicity for the substance can be derived using data on the acute oral toxicity and using the extrapolation formula for inhalation conversion as presented in the ECHA CLP guidance (ECHA CLP guidance (2017, page 250, 3.1.3.3.5), which is: 1 mg/kg bw = 0.0052 mg/L/4hours. The LD50 of the substance for acute oral toxicity is 3900 mg/kg bw. This 3900 mg/kg bw can be converted to 20280 mg/m3 (LD50oral * 5.2 mg/m3 = LDinhal = 20280 mg/m3). Taking into account the inhalation absorption as 100% and oral absorption 50%, the acute inhalation toxicity would become 10140 mg/m3. The maximum saturated vapour pressure for Vertoliff is 3750 mg/m3. This means that Vertoliff cannot reach a concentration higher than 3750 mg/m3. The extrapolated inhalation LC50 cannot be reached because it exceeds the saturated vapour pressure by more than a factor of 2.5.

Other available information on Triplal

Acute inhalation toxicity: In the RIFM database information is available from Union Carbide which presents acute inhalation toxicity. In one of the acute inhalation studies effects in rats were seen. According to the summary of the test result, this was due to the presence of Acroleine. After removal of this impurity, Triplal’s acute inhalation toxicity was >664 ppm (or when converted ca. 3750 mg/m3): its saturated vapour concentration.

Acute dermal toxicity: Also in the RIFM database there is an acute dermal toxicity study of Union Carbide showing acute dermal toxicity in rabbits at 1400 mg/kg bw. This study is also considered to be confounded by Acroleine exposure, because in all other acute dermal toxicity studies in rabbits Triplal LD50 values were all exceeding 2000 mg/kg bw. In a Moreno study at 5000 mg/kg bw, 2/8 animals died (Moreno, 1977). In an additional Moreno study, 2/10 died (Moreno, 1978). In a Givaudan study, 1/2 and 2/2 died at 2800 and 5600 mg/kg bw, respectively. In a Firmenich study, 0/6 died at 2000 mg/kg bw.

In conclusion, the acute dermal toxicity in rabbits exceeds 2000 mg/kg bw and therefore Triplal does not need to be classified for acute dermal toxicity.

Assessing the acute oral and dermal toxicity of Vertoliff (CAS #27939-60-2) using read-across from Triplal (CAS #68039-49-6)

1) Introduction and hypothesis for the analogue approach

Vertoliff (CAS #27939-60-2) is a multi-constituent consisting of two major isomers which are di-methyl-cyclohexene structures with an aldehyde function. The constituents differ in the position of the methyl groups. For this substance no acute oral and dermal 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. by application of alternative methods such as in vitro tests, QSARs, grouping and read-across. For assessing the acute oral and dermal toxicity of Vertoliff the analogue read-across approach is selected because for the closely related isomer Triplal (source) acute toxicity data is available (see data matrix below).

Hypothesis: Vertoliff (target) has a similar acute oral and dermal toxicity compared to Triplal (source) resulting in similar LD50 values. This hypothesis builds on similarity in structure (close isomers), log Kow, metabolic pathway and systemic toxicity.

Available information: An acute oral toxicity study is available for the source substance Triplal. In this pre-GLP study, similar to OECD 401, doses up to 5000 mg/kg bw were tested and an oral LD50 of 3900 was found. The acute dermal toxicity of Triplal was assessed at one concentration in rabbits (5000 mg/kg bw) similar to OECD 402 in a pre-GLP study. Both studies were assigned reliability 2 based on minor limitations in the report.

2) Target and source chemical

Chemical structures of the target chemical and the source chemical are shown in the data matrix, including physico-chemical properties and available toxicological information.

3) Purity / Impurities

Vertoliff contains two major constituents of which the relative abundance is 61% and 39% respectively (see data matrix). The purity of the main constituent of Triplal (CAS #68039-49-6) is ca 100%. As a result, it is not expected that the impurities of the source and target chemicals affect the read-across justification.

4) 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 molecular structure, functional groups, metabolic fate and other information on systemic toxicity . 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 as is presented below.

Analogue selection: Triplal is selected for read-across because it is the most similar substance to Vertoliff based on the structural similarity. Multiple Triplal isomers are known with different CAS numbers. Triplal with CAS 68039-49-6, a mono-constituent substance, is selected because most data available are on this CAS number.

Structural similarities and differences: Vertoliff is a multi-constituent consisting of two major isomers which are di-methyl-cyclohexene structures with an aldehyde function. The data on Triplal (source) is derived from a mono-constituent, which is a close isomer of Vertoliff and only differs in the position of the methyl groups. The Tanimoto similarity between the main constituent of Vertoliff and Triplal was determined to be 0.69 (ChemMine tools). In addition, the position of the methyl group is predicted to have no effect on reactivity and toxicological profile (OECD toolbox). Therefore, the minor structural differences between the close isomers Vertoliff and Triplal are not expected to significantly influence the acute oral and dermal toxicity of these chemicals.

Toxicokinetic similarities and differences: Absorption: Vertoliff and Triplal have the same molecular weight and similar physico-chemical properties indicating similar absorption characteristics (log Kow and vapour pressure). This indicates that Vertoliff and Triplal will be absorbed similarly via all routes. Both substances have a log Kow in the favourable range of absorption. Metabolism: No experimental data are available. The theoretical metabolic reactions are similar between Vertoliff and Triplal since both the functional groups are identical. Fast conversion of the aldehyde moiety to a carboxylic acid function (oxidation) is expected, which is independent on the position of the methyl groups. In addition, reduction can result in a hydroxy metabolite, which is also expected for both Vertoliff and Triplal. Both the carboxyl and hydroxy group in the resulting metabolites are potential targets for conjugation reactions (O’Brien et al., 2005).

 

 

Figure 1 Anticipated metabolic pathways illustrated for the major Vertoliff constituent.

 

Toxicodynamic aspects: The position of the methyl group is predicted to have no effect on reactivity and toxicological profile (OECD toolbox). The anticipated metabolites are acids for both substances.

Experimental data other than acute toxicity: For skin sensitisation, data are available for both Vertoliff and Triplal and they indicate that both have similar sensitization potential. Information on other endpoints is not available for comparison of the toxicological profiles of the target and source substance (see data matrix).

Uncertainty of the prediction: There are no remaining uncertainties regarding the similarities in structure, toxicokinetics and toxicodynamic properties.

5) Data matrix

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

6) Conclusions on acute oral toxicity

For Vertoliff, no acute oral and dermal toxicity data are available. For Triplal a pre-GLP acute oral toxicity study is available which is conducted similar to OECD 401 (Kl2), from which an LD50 of 3900 mg/kg was derived. Regarding acute dermal toxicity, the LD50 was concluded to be above 5000 mg/kg bw in a study conducted similar to OECD 402 (Kl2). No correction for molecular weight has to be performed.

Final conclusion on hazard: Vertoliff has an LD50 of 3900 mg/kg bw and >5000 mg/kg bw for oral and dermal acute toxicity, respectively.

Data matrix for acute toxicity of Vertoliff using read-across from Triplal.

Substance name	Vertoliff	Triplal
Molecular structure	61%                       39% (2 isomers)           (2 isomers)	Major constituent
CAS	27939-60-2 (generic)	68039-49-6 (data presented) and 68039-48-5
Smiles	O=CC1CC=C(C)CC1C (main constituent)	O=CC(C(C=C(C1)C)C)C1 (main constituent)
EINECS	248-742-6	268-264-1
Empirical formula	C9H14O	C9H14O
Molecular weight	138.21	138.21
Physico-chemical properties
Appearance	Liquid	Liquid
Melting point (˚C)	< -20	< -50
Boiling point (˚C)	195.4	195
Vapour pressure at 25˚C (Pa)	66.1	36
Water solubility at 20˚C (mg/L)	381.8	910
Log Kow	3.1	2.7
Human health
Acute toxicity oral	Read-across from Triplal	LD50 = 3900 mg/kg (similar to OECD 401)
Acute toxicity dermal	Read-across from Triplal	LD50 >5000 mg/kg (similar to OECD 402)
Skin sensitisation	Skin sensitizer cat 1B in LLNA study; NOEC is 5% HRIPT at 1%: not sensitising	Skin sensitizer cat 1B (OECD 429) EC3 of 3.25% HRIPT at 5%: not sensitising

References

O’Brien PJ et al. 2005, Aldehyde sources, metabolism, molecular toxicity mechanisms and possible effects on human health. Crit. Rev in Tox 35: 609-662.

Justification for classification or non-classification

The substance does not need to be classified for the acute oral, dermal and inhalation route according to EU CLP (EC No. 1272/2008 and its amendments).