2-methylimidazole

Endpoint summary

Description of key information

In rats the oral LD50 was 1500 mg/kg bw. The inhalation of a saturated vapour-air-mixture represents an unlikely acute hazard. In the acute dermal toxicity study a LD50 value of > 2000 mg/kg bw was determined.

Key value for chemical safety assessment

Acute toxicity: via oral route

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LD50

Value:

1 500 mg/kg bw

Acute toxicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Acute toxicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

discriminating dose

Value:

2 000 mg/kg bw

Additional information

Oral toxicity

In an acute oral (gavage) toxicity study, performed comparable to OECD guideline 401, rats (5 animals/sex/dose) were administered 2-methylimidazole by gavage at 200, 400, 800, 1250, 1600, 2000 and 2500 mg/kg bw, which was followed by a 7-day observation period (BASF AG, 1966). No mortality was observed after exposure to 200 to 800 mg/kg bw. At 1250 mg/kg bw, 6/10 animals died after 7 days, at 1600 mg/kg bw, 5/10 animals died after 7 days, at 2000 mg/kg bw, 9/10 animals after 7 days and at 2500 mg/kg bw, 8/10 died after 7 days. Clinical signs included slight shivering, dyspnea and slight swaggering. No abnormal findings were noted at necropsy. The LD50 was ca. 1500 mg/kg bw.

Inhalation toxicity

In accordance with column 2 of REACH Annex VIII, testing for acute inhalation toxicity is not necessary as the substance is classified as corrosive to the skin according to the EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008 (H314, Category 1C). Some limited information (tested concentrations were below any limit concentration) regarding acute inhalation toxicity is given as supporting information.

In an acute inhalation toxicity study, according to the BASF-internal standard (a protocol comparable to OECD guideline 403), in which rats (n=6/sex) were exposed to a saturated vapour of 2-methylimidazol at 20 ºC for 7 hours followed by a 14-day observation period, no deaths were observed (BASF AG, 1980). The average exposure concentration was reported to be 0.26 mg/L. This concentration is below any limit concentration. No clinical signs, effects on body weight or gross pathology changes were reported.

In another acute inhalation toxicity study, according to the BASF-internal standard (a protocol comparable to OECD guideline 403) rats (6 animals/sex/dose) were exposed to a saturated vapour of 2-methylimidazol at 20 ºC for 8 hours, followed by a 7-day observation period (BASF AG, 1966). The exposure concentration was ca. 0.09 mg/L, which is below any limit concentration. None of the animals died during the observation period. No clinical signs, effects on body weight or gross pathology changes were reported.

Dermal toxicity

In an acute dermal toxicity study, comparable to OECD guideline 402, male and female Sprague-Dawley rats (3 animals/sex/dose) were exposed to 1000 and 2000 mg/kg bw 2-methylimidazole by dermal application (area of exposure: 49 cm²) for 24 hours under an occlusive dressing, followed by a 14 day observation period (BASF AG, 1980). No mortality was observed after exposure to 1000 mg/kg bw. At 2000 mg/kg bw, 1/3 males and 1/3 females died after 14 days. Clinical signs included beginning of irregular breathing. Regarding skin effects, 24 hours after the application a weak development of necrosis was observed, which developed to a leathery necrosis within 14 days. No abnormal findings were noted at necropsy for euthanized animals. In the diseased animals acute dilatation of the frontal prechamber and acute congestion / hyperemia of the heart and a slight brightening of the liver were observed. The LD50 was > 2000 mg/kg bw.

In a supporting acute dermal toxicity study, comparable to guideline OECD 402, male and female Vienna White rabbits (5 animals/sex/dose) were exposed to 200 mg/kg bw 2-methylimidazole by dermal application (area of exposure: 50 cm²) for 24 hours under occlusive dressing followed by a 8 day observation period (BASF AG, 1980). None of the animals died during the observation period. No abnormal clinical signs were observed and no abnormal findings were noted at necropsy. The LD50 was > 200 mg/kg bw.

Justification for classification or non-classification

Based on the results of the acute oral and dermal toxicity studies, 2-methylimidazole needs to be classified Cat. 4; H302 according to the Regulation (EC) No. 1272/2008.