Methyloxirane

Endpoint summary

Description of key information

An in vitro skin corrosion test was available, performed according to OECD guideline 431. In this test propylene oxide was considered non-corrosive Harlan 2010a ).In an in vivo skin irritation study in rabbits (GLP and OECD 404) propylene oxide was considered not skin irritating (Harlan 2010b).

Key value for chemical safety assessment

Skin irritation / corrosion

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Eye irritation

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irritating)

Additional information

Information available from human reports indicates propylene oxide is irritating to the eye and respiratory tract. Studies in animals confirm that propylene oxide is irritating to the respiratory tract. Clinical observations of respiratory tract irritation were observed in acute tests on rats, mice and guinea pigs that inhaled high exposure concentrations of propylene oxide (Rowe et al., 1956; NTP, 1985) and clinical signs and pathology evidence of respiratory tract irritation were observed in rats and mice that were exposed to repeated high concentrations of propylene oxide (NTP, 1985; Harkema, 2006; Dow Chemical Company, 2009).

There are no reports of human skin irritation associated with propylene oxide exposure. Propylene oxide has been tested in anin vitrotest and on animals and the results demonstrate this substance is not a skin irritant.

An initial assessment of propylene oxide skin irritancy/corrosion potential was performed using thein vitroEPISKIN test. In this test the substance is applied topically to the stratum corneum surface, at the air interface, so that undiluted and or end use dilutions can be tested directly. The test is based on the experience that corrosive chemicals are sufficiently cytotoxic after a short term exposure to the EPISKIN model. Corrosive chemicals are able to penetrate the stratum corneum and are sufficiently cytotoxic to cause cell death in the underlying cell layers. Toxicity is determined by the metabolic conversion of the vital dye MTT to formazan by viable cells in the test material treated cultures relative to the negative. Validation studies have shown that tests employing human skin models are able to reliably distinguish between known skin corrosives and non-corrosives. The relative mean viability of the propylene oxide treated tissues in EPISKIN test were as follows: 240 minute-exposure: 96.4%, 60 minute-exposure: 119.4% and 3 minute-exposure: 141.3%. The test material was considered to be Non-Corrosive to the skin (Harlan Laboratories Ltd., 2010c)

Propylene oxide was also tested in anin vivotest in rabbits (according to OECD 404 and GLP). Both the erythema and oedema mean scores were not above 2.0 from the timepoints 24 hours onwards (Harlan Laboratories Ltd, 2010d) demonstrating the low skin irritancy of this substance.

The results of both studies indicate that classification of propylene oxide as a skin irritant is not justified.

Effects on eye irritation: irritating

Effects on respiratory irritation: irritating

Justification for classification or non-classification

According to EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008 - 9th ATP 19 July 2016, the classification is Cat. 2 for eye; H319 (Causes serious eye irritation) and Cat.3, H335 (may cause respiratory irritation).

However, based on the results of new test data, propylene oxide is demonstrated not irritating to the skin and hence classification as a skin irritant, either according to DSD/DPD or CLP is not justified.