1-Heptanol, 2-propyl-, 1,1'-carbonate

Endpoint summary

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

In the first study, the test item was assessed for its skin sensitising potential using the Local Lymph Node Assay (LLNA) in mice according to OECD guideline 429 and EU guideline B.42. Test item solution at different concentrations was prepared in the vehicle acteone: olive oil (4+1 v/v). A local lymph node assay was performed using test item concentrations of 10, 25, and 50% (w/w). The highest concentration tested was the highest concentration that could be used and applied whilst avoiding systemic toxicity and excessive local skin irritation (as determined by a pre-experiment). The animals did not show any signs of systemic toxicity or local skin irritation during the course of the study and no cases of mortality were observed. A statistically significant increase in ear weights was observed in the high dose group in comparison to the vehicle control group (p<0.05). Although thus indicates some irritation effects, this was considered to be of limited biological relevance, as the mean value of the high dose group was only slightly above the range of historical vehicle control data for the ear weight and as the observed increase did not exceed the threshold value of 25% for excessive local skin irritation mentioned in OECD guideline 429. Furthermore, the cutoff-value of 1.1 for a positive response regarding the ear weight index of 1.1 reported for BALB/c mice was not exceeded in any dose group. A test item is regarded as a sensitiser in the LLNA if exposure to one or more test item concentration results in a 3-fold or greater increase in incorporation of 3HTdR compared with concurrent controls, as indicated by the Stimulation Index (S.I.). The estimated test item concentration required to produce a S.I. of 3 is referred to as the EC3 value. In this study Stimulation Indices (S.I.) of 1.59, 2.12, and 4.47 were determined with the test item at concentrations of 10, 25 and 50% (w/w) in acetone:olive oil (4+1 v/v), respectively. A clear dose response was observed. The S.I. determined with the positive control item was 5.85 demonstrating the validity of the study. Based on the S.I.s obtained with 25 and 50% test item concentration, an EC3 value of 34.4% (w/w) was calculated. An outlier was identified in the high dose group. However, as the corresponding lymph node weight and –cell count values confirmed the result of the DPM value and as exclusion of the outlier did not change the overall test result, the value in question was not excluded from calculation. A statistically significant and biologically relevant increase in DPM value, lymph node weight and – cell count was observed in the high dose group in comparison to the vehicle control group (p<0.05). Furthermore, the cutoff-value for a positive response regarding the lymph node cell count index of 1.55 reported for BALB/c mice was exceeded in the high dose group (index of 2.4). Thus, the test item has to be regarded as a skin sensitizer under the test conditions of this study (at least at high concentrations of > 30%).

In the second study, the dermal sensitizing potential of the test item was investigated in the Buehler Test according to OECD guideline no. 406 and EU method B.6. The main study was performed on 30 giunea pigs in total. A control group of 10 animals and a test group of 20 animals were formed. The test concentrations for the main study were selected based on the results of a preliminary investigation. The main study started with an

induction phase including an occlusive patch topical application for 6 hours once a week for three consecutive weeks. The animals of the test group 2 were induced with the test item, 75 % (w/w), whereas the animals of the control group 1 were induced with olive oil. All group animals did not show any signs of skin irritation during the induction phase. A discrete or patchy erythema (grade 1) was observed in 7 test group animals after second induction and 3 test group animals after the third induction. The 6 -hour challenge procedure of an occlusive topical application of the test item on the flank of all animals followed four weeks after the first induction. The skin reactions were evaluted 24 hours and 48 hours after the challenge application. For challenge the test item was used in a concentration of 50 % (w/w). In the test group 1 out of 20 animals responded with a moderate skin reaction to the challenge treatment after 24 hours and 48 hours. In the control group one of the animals showed slight skin reactions after 24 hours. Thus, the test item did not cause evidence of delayed contact hypersensitivity.

In the third study, the reactivity of test item towards synthetic cysteine (C)- or lysine (K)-containing peptides was evaluated in the Direct Peptide Reactivity Assay (DPRA). For this purpose the test substance was incubated with synthetic peptides for ca. 24 hours at room temperature and the remaining non-depleted peptide concentrations were determined by high performance liquid chromatography (HPLC) with gradient elution and UV-detection at 220 nm. As no molecular weight of the test substance was available a gravimetric procedure was applied. The test substance was solved in acetonitrile at a concentration of 3.76% (corresponding to a theoretical molecular weight of ca. 375 g/mol). Three samples of the test substance were incubated with each peptide in ratios of 1:5 (for C-peptide) or 1:24 (for K-peptide) based on absolute mass. Additionally triplicates of the concurrent vehicle control (= NC) were incubated with the peptides. Further, a co-elution control was performed in order to detect possible interference of the test substance with the peptides. The samples consisted of the test substance, vehicle and the respective peptide buffer but without peptide. Moreover the samples were additionally analyzed by measuring UV absorbance at 258 nm and the area ratio 220 / 258 was calculated as a measure of peak purity. The test substance was soluble in acetonitrile. However when mixed with the peptide stock solutions the samples became slightly cloudy directly after preparation. After 24 hours precipitates were noticed in the samples of the C-peptide. Thus the samples were centrifuged prior to HPLC analysis. The mean C-peptide depletion, caused by the test substance was determined to be -0,2%. The mean K-peptide depletion, caused by the test substance was determined to be -1,1%. Negative depletions were considered to be “zero” for calculation of the mean peptide depletion, which was thus calculated to be 0%. No co-elution of test substance and peptides was noticed. Based on the observed results, it was concluded that the test item shows per definition a minimal chemical reactivity in the DPRA.

In the fourth study, the dermal sensitizing potential of the analogue substance (for read across justification see IUCLID chapter 13) was investigated in a Buehler test according to OECD guideline no. 406 and EU method B.6. The study was performed on 30 guinea pigs divided into a test group of 20 animals, and a control group of 10 animals. The study included an induction and a challenge phase. The animals in the test group were induced with the test article and the animals in the control group were induced with sesame oil. The induction procedure included a closed patch topical application for 6 hours once a week for 3 consecutive weeks. The challenge procedure included a closed patvh topical treatment of the test article on the flank 4 weeks after the first induction. All animals were challenged for 6 hours. The skin reactions were evaluated 24 and 48 hours after termination of the challenge application. The undiluted test article was used for the inductions. A 75 % test article concentration was used for the challenge. The test item caused no evidence of delayed contact hypersensitivity.

In the fifth study, another analogue substance (for read across justification see IUCLID chapter 13) was tested in a modified Local lymph node assay (IMDS) on 24 female NMRI mice (6 animals per group) according to OECD guideline no. 429. The vehicle was corn oil and the tested concentrations of the test item were 0 (vehicle control), 2, 10 and 50 %. Compared to vehicle treated animals neither cell counts nor weights of the draining lymph nodes reached or exceeded the positive levels. These results show that there is no indication for a skin sensitizing effect after administration of a concentration of up to 50 %.

In the sixth study, the same analogue substance (for read across justification see IUCLID chapter 13; for details see IUCLID chapter 7.10.4)

as in the IMDS was tested in a repeated insult patch Test in one hundred fifteen qualified subjects. Approximately 0.2 mL of the test material was applied on the surface. The test item did not indicate a clinically significant potential for dermal irritation or allergic contact sensitization.

In the seventh study, the test item was tested in a repeated insult patch Test for details see IUCLID chapter 7.10.4) in one hundred fifteen qualified subjects. Approximately 0.2 mL of the test material was applied on the surface. The test item did not indicate a clinically significant potential for dermal irritation or allergic contact sensitization.

Although the LLNA at high concentrations (> 30%) revealed some indication of sensitising properties, no such effects were noted in a Bühler test tested up to 50% or in human repeated insult patch test. Furthermore neither data for analogues substances (synthesised by the same route as the test item) nor for the starting material revealed any indication for a skin sensitisation potential even at concentrations >= 50%.

The effects noted false positive in the LLNA might be due to irritation, which are indicated by increased easy thickness for the high dose group (see also "Opinion on the Murine Local Node Assay (LLNA) adopted SCCNFP during the 12th pienary meeting of 3 May 2000").

Taken all data together (WoE) the test item is consequently evaluated as non-sensitising to humans.

Migrated from Short description of key information:
The sensitizating potential of the substance was tested in three in-vivo studies (LLNA, Buehler test, human repeated insult patch test (HRIPT)) and one in vitro study (DPRA test) with different results (LLNA: sensitising, Bühler: non-sensitising, DPRA: minimal chemical reaction, no indication for protein intraction, as sign for a potential sensiting effect). Furthermore, three studies was carried out with two analogue substances.