Methyloxirane

Endpoint summary

Description of key information

Acute toxicity data by oral, inhalation and dermal route indicate that propylene oxide is harmful by all routes. The studies for the oral and inhalation route were performed in rats comparable to the respective OECD guidelines 401 and 403, giving an oral LD50 of 382-587 mg/kg bw and an LC50 of 9.95 mg/L. For the dermal route data also indicate that PO is also harmful by this route, with an LD50 of 950 mg/kg bw (using rabbits). 

Key value for chemical safety assessment

Acute toxicity: via oral route

Endpoint conclusion

Dose descriptor:

LD50

Value:

382 mg/kg bw

Acute toxicity: via inhalation route

Endpoint conclusion

Dose descriptor:

LC50

Value:

9 950 mg/m³ air

Acute toxicity: via dermal route

Endpoint conclusion

Dose descriptor:

LD50

Value:

950 mg/kg bw

Additional information

Acute toxicity data from animal studies for oral, dermal, and inhalation exposure routes are available. The oral toxicity study was performed comparable to OECD guideline 401 in which 5 rats per sex per dose were used. From this study an LD50 range of 382-587 mg/kg bw was obtained (Shell Research Ltd., 1968). In the inhalation route study performed comparable to OECD guideline 403 (Shell Research Ltd., 1977), rats were whole-body exposed at 3000-5970 ppm, giving rise to an LC50 of 4197 ppm (9.95 mg/L). The dermal acute study predates GLP and OECD guidelines, but gives sufficient details to contribute to the assessments (Smyth et al., 1969). This study elicited a dermal LD50 of 1250 mg/kg.

Very limited acute toxicity information is reported for humans. A summary of a single case of poisoning reported that an individual exposed to 1500 ppm after 10 min exhibited respiratory tract and eye irritation and, after 2 hrs, became cyanotic and collapsed but with medical assistance recovered after 14 hrs (Gosselin, 1984). The EU RAR (2002) concluded this information to be questionably reliable due to lack of details on exposure.

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 H331, Cat. 3, H311, Cat. 3 and H302, Cat. 4.

Classification as aspiration hazard is not warranted based on expert judgment of several physico-chemical properties ofpropylene oxide. Viscosity ofpropylene oxideis 0.374 mm²/s, which is below the cut-off value for aspiration. However, no cases in humans have ever been described. Based on this observation, as well as, other physicochemical properties, in particular high water solubility (>40%), classification as aspiration hazard is not warranted.