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EC number: 254-179-7 | CAS number: 38888-98-1
Relative size lymph nodes, radioactivity counts (DPM) and Stimulation Index (SI)
Mean DPM ± SEM(4)
1 TS = test substance (% w/w).
2. Relative size auricular lymph nodes (-, -- or ---: degree of reduction, +,++ or +++: degree of enlargement, n: considered to be normal).
3. DPM = Disintegrations per minute
4. SEM = Standard Error of the Mean
A study was performed to assess the Contact Hypersensitivity to Phenyl-tolyl-ethane in the Mouse (Local Lymph Node Assay). The study was carried out based on the guideline OECD, Section 4, Health Effects, No.429 (2010).
Test substance concentrations selected for the main study were based on the results of a pre-screen test. The two animals treated at 100% were found dead or sacrificed for humane reasons on Day 2. The two animals treated at 50% showed signs of systemic toxicity (hunched posture). It was concluded that these concentrations could not be tolerated well and did not comply with the selection criteria, and therefore the highest test substance concentration selected for the main study was a 25% concentration. In the main study, three experimental groups of five female CBA/J mice were treated with test substance concentrations of 5, 10 or 25% w/w on three consecutive days, by open application on the ears. Five vehicle control animals were similarly treated, but with vehicle alone (Acetone/Olive oil (4:1 v/v)). Three days after the last exposure, all animals were injected with 3H-methyl thymidine and after five hours the draining (auricular) lymph nodes were excised and pooled for each animal. After precipitating the DNA of the lymph node cells, radioactivity measurements were performed. The activity was expressed as the number of Disintegrations Per Minute (DPM) and a stimulation index (SI) was subsequently calculated for each group. The slight irritation of the ears as shown by the animals treated at 25% was considered not to have a toxicologically significant effect on the activity of the nodes. No irritation of the ears was observed in any of the animals treated with vehicle or at test substance concentration of 10% or 5%. No mortality occurred and no clinical signs of systemic toxicity were observed in the animals of the main study. Body weights and body weight gain of the experimental animals remained in the same range as controls over the study period, except for the slight body weight loss noted in two animals treated at 25% and one at 5%. This body weight loss was considered not toxicologically significant. The auricular lymph nodes of the animals of the experimental and control groups were considered normal in size, except for the enlarged nodes found in two animals treated at 25%. No macroscopic abnormalities of the surrounding area were noted in any of the animals. Mean DPM/animal values for the experimental groups treated with test substance concentrations 5, 10 and 25% were 139, 98 and 132 DPM respectively. The mean DPM/animal value for the vehicle control group was 97 DPM. The SI values calculated for the substance concentrations 5, 10 and 25% were 1.4, 1.0 and 1.4 respectively. Since there was no indication that the test substance elicits an SI ≥ 3 when tested up to the highest tolerable concentration of 25%, Phenyl-tolyl-ethane was considered not to be a skin sensitizer. It was established that the EC3 value (the estimated test substance concentration that will give a SI =3) (if any) exceeds 25%. Based on these results, Phenyl-tolyl-ethane would not be regarded as a skin sensitizer according to the recommendations made in the test guidelines.
Members of the diphenylmethane category did not show any skin sensitising properties. There is no information available for respiratory sensitisation. Therefore, there is a data gap in this respect. However, the data gap cannot be fulfilled with experimental data, since there is no internationally accepted animal model for respiratory sensitisation. For skin sensitisation, there is no reason to believe that results obtained in experimental animals would not be applicable to humans.
No further testing is required. The available data is adequate for risk assessment and classification and labelling purposes.
1,1 -DPE is not classified as skin sensitiser.
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