Dimethyl phthalate

Endpoint summary

Description of key information

DMP was not sensitising in an OET. the strucurally related analogue DEP was not sensitising in an LLNA and a Buehler test.
DMP did not cause positive patch test reactions in several studies and failed to induce sensitization in humans. Reliability of most studies is limited.

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

Skin sensitisation:

DMP was tested for skin sensitisation in an open epicutaneous test (OET; Skin primary irritation and senitization test) in guinea pigs [TSCAT/OTS0215032, 1970]. 0.05ml of neat material was given over a three-week period as nine topical applications to the abraded skin of ten male albino guinea pigs. After a two-week rest period, animals received challenge applications to intact and abraded skin. No skin reactions were observed.

In three studies, more than 1000 persons were patch tested with DMP. Only one positive reaction to a mixture of several substances was observed, leading to the conlcusion that none of those persons was sensitized with DMP. But due to unclear prior exposure to the test substance, the relevance of this finding is not certain.

In another human volunteer study, DMP failed to induce sensitization in 16 individuals.

All of the above studies have limitations in reporting, used only a low number of animals or volunteers or do not provide details on prior exposure. But so far there is no indication that DMP causes skin sensitization.

To support this conclusion, additional studies from the structurally related low molecular weight phthalate Diethyl phthalate (DEP, CAS 84 -66 -2) have been provided. DEP was tested in a standard Mouse Local Lymph Node Assay (LLNA) protocol according to Kimber and Basketter [1992]. Female CBA/Ca mice were treated dorsally once daily for 3 consecutive days with 3 concentrations (25%, 50% and 100% v/v) of test substance solution in acetone/olive oil (4:1). 5 days after treatment radioactively labelled 3H-methylthymidine (3H-TdR) was injected via the tail vein. After 5h incorporation, animals were sacrificed, draining aurical lymph nodes were isolated, prepared and single cell suspension thereof measured in a scintillation counter. The stimulation index SI (=increase in 3H-TdR of ainmal relative to the vehicle treated control) was 1.5 for the 100% v/v dose group. A substance is considered to be a sensitizer if the SI is greater than 3. Consequently, DEP did not cause skin sensitisation in this assay.

Additionally, a Buehler Test was performed with DEP in 1978, before OECD TG 406 (skin sensitisation) was in place (which was adopted in 1992). The test substance was applied occlusivly as a 50% (w/v) aqueous solution (0.5 ml per application) to the shaved backs of the animals. Induction applications were performed three times per week for a total of nine applications. After a two week rest period, the challenge was performed with 0.5 ml in the same area and on an previously untreated patch of ventral skin. No sensitization was observed in two repeat experiments in a total of 21 animals.

Conclusion:

DMP is not sensitising to skin. Read-across data from DEP support these findings. Phthalates are generally known to be no skin sensitizers.

Justification for selection of skin sensitisation endpoint:
Weight of evidence approach used, no single study selected as key.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

GHS classification (GHS UN rev.2, 2007):

- Skin Sensitization:no classification required