Docosyl methacrylate

Endpoint summary

Description of key information

Skin sensitisation: sensitising

Respiratory tract sensitisation: Due to the very low vapour pressure of the substance and the resulting lack of significant exposure, respiratory tract sensitisation is not considered as relevant.

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

With a very low water solubility of <1 µg/L dermal uptake of Docosyl methacrylate from the stratum corneuminto the epidermis is likely to be low. With log P_ow> 6 the rate of transfer between thestratum corneumand the epidermis will be slow and will limit absorption across the skin. Uptake into thestratum corneumitself is expected to be slow. For the alkyl-methacrylate esters, their absorption rates correlate with their molecular volume in the sense that smaller esters permeate membranes more rapidly than larger esters. Therefore, C12-22 methacrylates are expected to be absorbed to a very low extend.

Only after special treatment, docosyl methacrylate could be made bioavailable.To be tested in the LLNA, the solid waxy test material had to be heated up to 50° C and then dissolved in methylethyl ketone. Under these special conditions Docosyl methacrylate was at least partly made bioavailable and showed a sensitizing potential in the LLNA. TheEC3 based on the thymidine incorporation was determined to be 9.3%; the EC1.5 based on the cell count stimulation index was 19.4%. (BASF SE, 2018) 

In a dermal sensitization study with 2-Propenoic acid, 2-methyl-, C16-20-alkyl esters dissolved in acetone : olive oil (4 +1, v/v) as a vehicle, 16 (4 per dose group) 7 week old female CBA/CaOlaHsd mice were tested using the LLNA method of OECD TG 429. Three groups each of four female mice were treated daily with the test item at concentrations of 2.5 %, 5 % and 10 % (w/v) in acetone/olive oil (4/1, v/v) by topical application. In the course of the study no cases of mortality were observed. Neither clinical / local signs nor were other findings observed in any animals of the control group, Group 2 (2.5 %) or Group 3 (5 %). One day after the first topical application, slight ear erythema was observed at both dosing sites in all mice of Group 4 (10 %), persisting for a total of two days. In this study Stimulation Indices (S.I.) of 0.9, 0.9, and 1.9 were determined with the test item at concentrations of 2.5, 5.0, and 10% in acetone : olive oil (4 +1, v/v), respectively. No dose-response relationship was observed. The EC3 value could not be determined because this calculation requires a S.I. value of greater than 3. The test item is not a dermal skin sensitizer (Evonik RohMax GmbH UNTER 06-018).

A further LLNA was conducted using a conventional protocol according OECD TG 429. The test article was Isotridecyl methacrylate delivered in a 4:1 mixture of acetone and olive oil (AOO) with the selected test concentrations being (w/v) 12.5 % and 25%. In the group treated with 25% test item concentration on day 1-3, a distinct lymphocyte proliferation was observed (S.I. = 3.06). However, as the response of animals challenged with 25% test item on day 16 (S.I. = 1.43) was lower and not distinctly higher than the primary response obtained with the same test item concentration directly after the sensitization phase, it can be concluded that the induced response does not bear any immunological memory. Thus, the lymphocyte proliferation observed in the sensitization phase is not due to a sensitizing effect but results from irritation caused by the test item as also supported by the ear weight data. This is also supported by the fact that in the group treated with 12.5% test item concentration (day 1-3), where no relevant increase in ear weights (no irritation) was observed in comparison to the control group, the obtained S.I. was below the threshold of 3. On this basis the clear interpretation is that the test article Isotridecyl methacrylate lacks the potential to cause skin sensitization (Evonik RohMax GmbH UNTER 10-022).

The third LLNA was conducted using according OECD TG 429. The test article was a long-chain methacrylate ester 17.4 (C16-C20 main constituents approximately 28 % hexadecyl methacrylate and 65 % octadecyl methacrylate) delivered in a 4:1 mixture of acetone and olive oil (AOO) with the selected test concentrations being (w/v) 2.5%, 5% and 10%. At none of these test concentrations was an SI of 3 or greater achieved relative to concurrent vehicle control values (2.5% = SI of 0.9; 5% = SI of 0.9; 10% = 1.9). On this basis the clear interpretation is that methacrylic acid ester 17.4 lacks the potential to cause skin sensitization (Evonik RohMax GmbH UNTER 09-004).

Conclusion

Docosyl methacrylate has a sensitizing potential.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information:

Respiratory sensitisation

Due to the very low vapour pressure of the substance and the resulting lack of significant exposure, respiratory tract sensitisation is not considered as relevant.

Justification for classification or non-classification

Classification, Labelling, and Packaging Regulation (EC) No. 1272/2008

The substance is considered to be classified for skin sensitisation under Regulation (EC) No. 1272/2008, as amended for the tenth time in Regulation (EU) No. 2017/776. Skin Sens. 1B; H317: May cause an allergic skin reaction.