Propane-1,2-diol

Endpoint summary

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

Sensitizing potential of monopropylene glycol has been extensively studied in both experimental animals and humans. The animal study of Basketter et al., 1998 involved Local Lymph Node Assay (LLNA) in CBA mice (4/dose) using propylene glycol as 50% aqueous solution and as a neat substance. The stimulation indices were 1.2 and 1.6, respectively. Guillot et al., 1983 performed an evaluation of different protocols, including Magnusson-Kligman assay and Split adjuvant test, to assess the sensitizing properties of monopropylene glycol in guinea pigs. Guinea pigs were induced and challenged epicutaneously under occlusive conditions. Both tests gave negative results using neat substance. Also negative results in Magnusson-Kligman assay were reported by Kero et al. (1980), who used 70% aqueous solution of monopropylene glycol in water.

Also numerous reports on the investigation of sensitizing potential of monopropylene glycol in humans appeared in the literature, out of which those considered to be most reliable are briefly summarized here. Two repeated insult patch tests with monopropylene glycol using human volunteers under occlusive (Consumer Product Testing Co., 1999) and semi-occlusive (Consumer Product Testing Co., 1999) conditions were available for assessment. Approximately 0.2 ml of the test material was applied as a either occluded or semi-occluded patch to the upper back of 113 volunteers (as a neat substance for subjects 1-47 only, and as a 50% aqueous solution for the rest of the panel). Patches were applied three times per week (Monday, Wednesday, Friday) for a total of nine applications and were removed 24 hours after application. Approximately 2 weeks after the final induction patch application, a challenge patch was applied to a virgin test site adjacent to the original induction patch site, following the same procedure described for induction. The patch was removed and the site scored 24- and 72-hr post-application. One hundred and four subjects completed the study. With the exception of one subject, observations remained within normal limits throughout the test interval. One subject was observed to be hypersensitive in an irritant manner, throughout the induction and challenge phases of the study. Under the conditions of the study, monopropylene glycol did not cause allergic contact dermatitis.

 

Lessmann et al., 2005, reported the analysis of patch test data of 45138 patients with suspected allergic contact eczema, who have been tested with 20% aqueous solution of monopropylene glycol between 1992 and 2002. Out of these, 1044 patients (2.3%) tested positive, 1083 showed a doubtful, follicular or erythematous reaction (2.4%) and 271 explicit irritant reactions (0.6%). This profile of patch test reactions is indicative of a slightly irritant preparation, and thus, many of the "weak positive" reactions must probably be interpreted as false positive. No private or occupational exposures associated with an increased risk of monopropylene glycol sensitization were identified, except for lower leg dermatitis. The authors concluded that monopropylene glycol exhibits very low sensitization potential, and the risk for sensitization to monopropylene glycol on uncompromized skin appears to be very low.

Very similar findings have been reported by Warshaw et a., 2009, who performed a retrospective analysis of cross-sectional data compiled by the North American Contact Dermatitis Group (MACDG) from 1996 to 2006 to characterize the prevalence of positive patch-test reactions to monopropylene glycol and the epidemiology of affected patients. Out of a total of 23359 patients tested by NACDG between 1996 and 2006, 810 patients (3.5%) had an allergic patch-test reaction to 30% aqueous solution of monopropylene glycol. Of these allergic reactions, 12.8% were of definite clinical relevance (positive reaction to a personal product containing monopropylene glycol), 88.3% were considered to be currently relevant (definite, probably or possible relevance) and 4.2% were occupation related. Overall, the results concur with the conclusions of the study of Lessmann et al., 2005, suggesting that monopropylene glycol is a weak sensitizer.

 

Migrated from Short description of key information:
Based on the several animal studies and the data from human study (two retrospective cohort studies and repeated insult patch tests with human volunteers), it is concluded that monopropylene glycol is not a skin sensitizer.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

No data on respiratory sensitization are available. However, in accordance with Section 1 of REACH Annex XI, the study is scientifically unjustified, as respiratory tract sensitization is not expected based on the fact that monopropylene glycol is not skin sensitizer and no human data are available indicating a concern for respiratory sensitization.

Justification for classification or non-classification

Based on the negative results from several animal studies, available studies with human volunteers and two cohort studies, classification of monopropylene glycol as skin and respiratory tract sensitizer is not warranted in accordance with Directive 67/548/EEC and EU Classification, Labeling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008.