1-Dodecene, mixed with 1-decene and 1-octene, dimers, hydrogenated

Endpoint summary

Description of key information

Acute Toxicity Oral, 3 key studies- LD50 >5000 mg/kg for rat (OECD TG 401), read-across 1-decene dimer, hydrogenated;  1-decene dimer with 1-dodecene, hydrogenated; 1-dodecene dimer, hydrogenated
Acute Toxicity Inhalation 1 Key study,- LC50 =1170 mg/m3 for rats (OECD TG 403), read across 1-decene dimer, hydrogenated; 4 supporting studies- read-across 1-decene dimer, hydrogenated; 1-dodecene dimer, hyrogenated
Acute Toxicity Dermal, 2 key studies- LD50 >2000 mg/kg for rats (OECD TG 402), read-across 1-decene dimer with 1-dodecene, hydrogenated; 1-dodecene dimer, hydrogenated
Acute Toxicity – Other, Category 1 aspiration hazard based on physical and chemical properties

Key value for chemical safety assessment

Acute toxicity: via inhalation route

Endpoint conclusion

Dose descriptor:

LC50

Value:

1 170 mg/m³ air

Additional information

No acute toxicity data were found for the registered substance. However, data for structurally analogous substances are available. All of the animal studies were performed in a manner similar or equivalent to currently established OECD guidelines. Based on these data, this substance is minimally toxic by the oral and dermal routes, and is moderately toxic by the inhalation route.   

Acute Oral Toxicity

No acute toxicity data were found for the registered substance. However, several studies are available on the acute oral toxicity of structurally analogous substances: 1-decene dimer, hydrogenated; 1-decene dimer with 1-dodecene, hydrogenated; and 1-dodecene dimer, hydrogenated. All of the animal studies were performed in a manner similar or equivalent to currently established OECD guidelines. Summaries of these studies are presented below. Based on these data, the registered substance is minimally toxic by the oral route of exposure.

One key study was identified for 1-decene dimer, hydrogenated (EM 1990a). In this study, the test material was administered by oral gavage to 5 male and 5 female Sprague Dawley rats at a dose of 5.0 mg/kg to assess the acute oral LD50. Clinical observations were made at 0.5, 1, and 4 hours after test substance administration and daily thereafter with the exception of weekends. There were no deaths following administration of the test substance. At the end of the study, the LD50 was determined to be greater than 5.0 mg/kg.

One key study was identified for 1-decene dimer with dodecene, hydrogenated (Chevron, 1989a). In this study, single doses of 5.0 g/kg of undiluted test material were intragastrically administered to five male and five female Sprague-Dawley rats while five fasted, untreated animals of each sex served as controls. Animals were observed daily for 14 days post dosing.  No deaths, clinical signs of toxicity or treatment-related macroscopic lesions were observed. The oral LD50 for the test material was > 5.0 mg/kg. 

One key study was identified for 1-dodecene dimer, hydrogenated (Chevron, 1995a). In this study, the test substance was administered undiluted, neat by oral intubation to Sprague-Dawley rats (5 males and 5 females) at a dose of 5000 mg/kg. Animals were observed daily for 14 days post dosing. There were no deaths reported. No clinical signs of systemic toxicity were noted during the study. No abnormalities were noted at necropsy. The acute oral LD50 dose of the test substance in the Sprague-Dawley rat strain was established to be greater than 5000 mg/kg body weight.

The results of these studies indicate that the submission substance has an LD50 of greater than 5000mg/kg and is therefore not acutely toxic by the oral exposure route. These findings do not warrant classification of the registered substance as an acute toxicant under EU GHS guidelines and do not warrant classification under EU requirements for dangerous substances and preparations guidelines.

Acute Inhalation Toxicity

No acute toxicity data were found for the registered substance. However, several studies are available on the acute inhalation toxicity of structurally analogous substances. In total, four studies were identified for 1-decene dimer, hydrogenated and one study identified for 1-dodecene dimer, hydrogenated. All of the animal studies were performed in a manner similar or equivalent to currently established OECD guidelines.  Summaries of these studies are presented below. Together, these studies support the conclusion that an acute inhalation LC50 for aerosol exposure to the registered substance is in the range at or above 1.17mg/l supporting the hazard conclusion that this substance may be harmful by acute inhalation

In the key study for 1-decene dimer, hydrogenated (Chevron, 1981), rats (5/sex) were exposed whole body to a graded series of aerosol concentrations of 0, 0.76, 0.93, 1.10, 1.40 or 5.10 mg/L; MMAD 2.9 um for 4-hours. The animals were observed for 14 days after exposure. Clinical signs observed during and after exposure included dyspnea and nasal discharge. Deaths occurred within the first 2 days after exposure in all female groups and the male groups exposed to 1100 mg/m³or more of the test substance. The high dose groups gained less body weight during the first week after exposure, but the body weight gain was normal in the second week post-exposure. Macroscopic changes were observed in the animals that died following exposure and included red nasal discharge and congested lungs. Microscopic examination was not conducted in the rats exposed to 770-1400mg/m³. In the 5100 mg/m³group, pulmonary congestion was observed in all the animals. Mural protein casts were observed in the terminal and respiratory bronchioles. The control animals were normal.  The LC50 for acute inhalation exposure to an aerosol of the test material is calculated to be 1170 mg/m³with 95% confidence limits of 940-1460 mg/m³. 

In the second study (ExxonMobil, 1995a), groups of rats (10/sex) were exposed whole-body to respirable aerosol concentrations of 1-decene dimer, hydrogenated at 0.46 mg/L (MMAD = 1.99 um) or 1.81 mg/L (MMAD = 1.30 um) for 4-hours, with one half of the animals scheduled for necropsy on study day 2 and the remainder on study day 14.  In all other respects the study design appeared near-guideline. One half of the animals were sacrificed on day 2, the day after exposure; the remaining animals were sacrificed after a 2 week biophase. One female in group 3 died as a result of exposure and was found on the morning of day 2. Animals in group 3 exhibited respiratory rales on day 2. Both males and females in group 3 had significantly reduced mean body weights on day 2. Macroscopic examination of lungs revealed dark red focal lesions in group 3 (10 of 10) and group 2 (9 of 10) on day 2. Microscopic examination of the lungs of group 3 animals revealed acute inflammation on day 2. The macroscopic lesions and acute inflammation resolved by final sacrifice on day 14. The LC50 for acute inhalation exposure to the test material is >1.81 mg/L. The LOAEC for lung inflammation is 0.46 mg/m3.

In the third study for 1-decene dimer (ExxonMobil, 2002), hydrogenated, rats (5 males/5 females) were exposed whole-body to a respirable aerosol (MMAD around 1 um) at 4.80 mg/L for 4-hours followed by observation for up to 14 days. The investigation followed OECD guideline 403. Seven of ten animals were found dead between day 0 and day 2. The reported LC50 from this study was <4.80 mg/L.

In the fourth study (Chevron, 1994a), rats (5/sex) were exposed whole body to either to a single level of 1-decene dimer, hydrogenated (5.17 mg/L; MMAD 1.9 um) for 1-hour. The study was OECD guideline 403 compliant. Animals were observed for fourteen days following exposure. Only one treated female survived. All other animals died or were sacrificed one to three days following exposure. The LC50 for this investigation was <5.15 mg/L.

In the fifth study (Chevron, 1995b), the acute inhalation toxicity of 1-dodecene dimer, hydrogenated was measured in a GLP compliant OECD guideline 403 study. Sprague-Dawley rats (females and males) were exposed to an aerosol concentration up to 5.06mg/L for 4 hours. In male rats exposed to 5.06 mg/L aerosol concentrations, there was one death out of five animals. In female rats, there were two, three and four deaths out of five per dose group at concentrations of 1.19, 2.57 and 5.06 mg/L, respectively. At necropsy, animals that died during the study commonly showed swollen and abnormally dark lungs and dark liver and several showed reddening of the small intestine. No abnormalities were detected in surviving animals at necropsy. The 4 hr LC50 for acute inhalation exposure to the test material aerosol was determined to be 1.71 mg/L in female Sprague-Dawley rats and to be greater than 5.06 mg/L in male Sprague-Dawley rats.

 

As described in section R.6.2.2.1 of the ECHA document ‘Guidance on Information requirements and chemical safety assessment Chapter R.6: QSARS and grouping of chemicals’, (ECHA 2008e), the known value of a property for the source chemical can be used to estimate the unknown value of the same property for the registered substance. Section R.6.2.2.1 goes on to say that one way in which the missing data point can be estimated is “by using the endpoint value of a source chemical”. In this case, 1-decene, hydrogenated and 1-dodecene dimer, hydrogenated are analogous to the registered substance through a number of unifying considerations (as described in the read-across justification) including structural similarity, physical chemical properties, and manufacturing processes. Therefore, these substances serve as reliable and adequate source chemicals for filling data gaps for the registered substance both qualitatively and quantitatively. 

The available experimental data indicate the occurrence of mortality in rats exposed for 4 hr to respirable concentrations of analogous material and together support an acute inhalation LC50 for aerosol exposure to the registered substance in the range above 1mg/L and below 5mg/L. These data adequately support hazard identification and classification of the registered substance as R20 (Harmful by inhalation) as defined by EU Dangerous Substance Directive 67/548/EEC (R20) and as a Category 4 inhalation hazard, in accordance with CLP Regulation 1272/2008 (GHS aligned).

 

Acute Dermal Toxicity

No acute toxicity data were found for the registered substance. However, two studies are available on the acute dermal toxicity of structurally analogous substances: 1-decene dimer with 1-dodecene, hydrogenated; and 1-dodecene dimer, hydrogenated. All of the animal studies were performed in a manner similar or equivalent to currently established OECD guidelines.  Summaries of these studies are presented below. Based on these data, the registered substance is minimally toxic by the dermal route of exposure

One key study was identified for 1-decene dimer with dodecene, hydrogenated (Chevron, 1989b). In this study, the test material was applied to the clipped backs of ten Sprague-Dawley rats for 24 hours at a dose of 2000mg/kg under occlusive conditions. Five clipped, untreated animals of each sex were similarly wrapped and served as sham controls. The animals were observed frequently on the day of dosing for any physiological or behavioral abnormalities and daily thereafter. No deaths or signs of systemic toxicity were observed.  Skin irritation including erythema, cracking and scarring was seen in both control and treated animals; however, irritation was more severe and persistent in treated animals than in controls. The dermal LD50 for the test material is greater than 2000 mg/kg. 

One key study was identified for 1-dodecene dimer, hydrogenated (Chevron, 1995c). In this study, the test material was applied to the clipped backs of ten Sprague-Dawley rats (5 males, 5 females) for 24 hrs under semi-occlusive conditions. Clinical observations were performed at 1, 2.5 and 4 hr after dosing and once daily thereafter for a total of 14 days. Application of the test material at a dose level of 2000 mg/kg/bw showed no evidence of systemic toxicity under the conditions of the test and all animals survived to study termination. There were no treatment-related clinical signs and there were no abnormalities at necropsy. There were no signs of skin irritation in any of the animals throughout the study. Based on the results of this study, the dermal LD50 for the test material was greater than 2000 mg/kg.

The results of these studies indicate that the submission substance has an LD50>2000mg/kg and is therefore not acutely toxic by the dermal exposure route. These findings do not warrant classification of the registered substance as an acute toxicant under EU GHS guidelines and do not warrant classification under EU requirements for dangerous substances and preparations guidelines.

Aspiration Toxicity

 Regulatory classification and labeling for aspiration toxicity relies on the measured or calculated kinematic viscosity of a substance at 40°C rather than results from toxicological studies with animals. The typical reported kinematic viscosity value for the registered substance is 1.8-1.9 cSt at 100°C (~5.2 cSt at 40 °C). This value meets the criteria for classification for aspiration toxicity under DSD and CLP regulations (< 7 cSt and < 20.5 cSt, at 40°C respectively). Therefore, the registered substance is classified as Xn; R65 harmful (May cause lung damage if swallowed) under EU Dangerous Substances Directive 67/548/EEC and as Category 1 for aspiration toxicity (H304: May be fatal if swallowed and enters airway).

 

Read-across justification

Several criteria justify the use of the read-across approach to fill data gaps for the registered substance using 1-decene dimer, hydrogenated; 1-decene dimer with dodecene, hydrogenated; and 1-dodecene dimer, hydrogenated as analogues substances. These substances are all hydrogenated poly alpha olefins, i. e., minimally branched paraffins (also known as alkanes) produced by oligomerization of 1-octene, 1-decene, and/or 1-dodecene. As described in the read-across justification appended to the CSR, these substances are similar in molecular structure, physicochemical properties, use, and manufacturing processes. Furthermore, data provided in CSR section 5.1 (IUCLID chapter 7.1) support similar toxicokinetic behavior of these minimally branched paraffins within this small carbon number range. Based on these unifying considerations, the slight difference in carbon number among these analogues is not expected to significantly impact mammalian toxicity. Therefore, it is scientifically reasonable to predict the toxicological properties for the registered substance from the properties determined for the analogues.

 

The nature of the read-across approach utilized here is aligned with the analogue approach as described in section R.6.2.3 of the ECHA document ‘Guidance on Information requirements and chemical safety assessment Chapter R.6: QSARS and grouping of chemicals’ (ECHA, 2008e). The similarity among molecular structure and molecular weight which provides the basis for the read-across justification is scientifically founded and therefore adequately clarifies why the properties of the registered substance may be predicted from the properties of the read-across substance(s) and more specifically, why the data submitted for 1-decene, hydrogenated (C20); 1-decene dimer with dodecene, hydrogenated (C20-C24); and 1-dodecene dimer, hydrogenated (C24) are appropriate for the purposes of classification and labeling and/or risk assessment of the registered substance which contains similar molecules with carbon numbers in the ranges of 18 – 24 carbon atoms (at least85% C20 and C22). 

A legislative goal of the REACH Regulation is to avoid unnecessary animal testing through promotion of replacement, reduction, or refinement of testing on vertebrate animals. Article 13 of the REACH regulation (EC) 1907/2006 states ”Information on intrinsic properties of substances may be generated by means other than tests, provided that the conditions set out in Annex XI are met. In particular for human toxicity, information shall be generated whenever possible by means other than vertebrate animal tests, through the use of alternative methods”. The use of read-across data is one mechanism identified in Annex XI as an appropriate alternative method for fulfilling information requirements. It is the Registrants scientific opinion that the available read-across information demonstrating that saturated aliphatic hydrocarbons ranging in carbon numbers from C20 to C24 have a low potential for toxicity for this endpoint is ample evidence to support a rational judgment regarding hazard identification, classification and labeling and risk assessment for the registered substance (with a carbon number range of C18-C24). It is the Registrants scientific opinion that no new information will be gained through additional testing in vertebrate animals.

Justification for classification or non-classification

Based on evaluation of the acute oral and dermal toxicity data discussed above, the registered substance does not meet the criteria for classification as an acute oral or dermal toxicant under the EU Dangerous Substances Directive 67/548/EEC or CLP EU Regulation 1272/2008 because the reported LD50 values exceed the limits for classification defined in the regulations. 

Based on its reported LC50 values, the registered substance meets the criteria for classification and labelling as an acute inhalation toxicant under EU Dangerous Substances Directive 67/548/EEC and CLP EU Regulation 1272/2008. Therefore, the registered substance is classified as Xn, R20: Harmful by inhalation under EU Dangerous Substances Directive 67/548/EEC and as a Category 4 acute inhalation toxicant; H332: Harmful if inhaled, under CLP EU Regulation 1272/2008 (GHS aligned).

The registered substance is classified as Xn; R65 harmful (May cause lung damage if swallowed) in accordance with EU Dangerous Substances Directive 67/548/EEC and as Category 1 for aspiration toxicity (H304: May be fatal if swallowed and enters airway) in accordance with CLP EU Regulation 1272/2008 (GHS aligned) based on its kinematic viscosity at 40°C.