Pyrazole

Endpoint summary

Description of key information

oral
LD50 rat: 1010 mg/kg bw (Lelbach et al. 1969)
LD50 rat: 1157 mg/kg bw (Magnusson et al. 1972)
LD50 mouse: 408 mg/kg bw (Magnusson et al. 1972)
inhalation
LC50 rat, 4h, vapour: > 0.37 mg/L (OECD 403; BASF 1990)
dermal
LD50 rabbit, 24 h exposition: 400 mg/kg bw (standardized test protocol; BASF 1980)

Additional information

There are reliable data from animal studies available to assess the acute oral and dermal toxicity of the substance.

oral

In a study using the standard acute method, several dose levels between 840 and 1214 mg/kg bw of the test substance (purity unknown) were administered once orally to groups of 40 rats. The LD50 was 1010 mg/kg bw. The minimal lethal dose was 850 mg/kg bw. After single doses larger than 1000 mg/kg bw leading to a comatose state with death occurring within 12 -36 h, no liver cell alterations were seen microscopically; livers of rats dying 6 -11 days after 850 -1000 mg/kg bw showed extensive centrolobular necrosis with inflammatory reactions and appearance of fat ill surviving liver cells (Lelbach et al. 1969).

In a further publication, another standard acute toxicity study with rats and mice was reported by Magnusson et al. (1972). Here, groups of six male Sprague-Dawley rats were treated with doses of 3.6 to 24 mmol/kg bw corresponding to ca. 245 to 1632 mg/kg bw. The LD50 after 7 days was 1157 mg/kg bw (= 17 mmol/kg bw) and the LD50 after 24 hours was 1430 mg/kg bw (=21 mmol/kg bw). In the trial with mice, groups of 10 male NMRI mice were treated with doses of 14 to 23 mmol/kg bw corresponding to ca. 952 to 1564 mg/kg bw. The LD50 after 7 days was 408 mg/kg bw (= 6 mmol/kg bw) and the LD50 after 24 hours was 1498 mg/kg bw (=22 mmol/kg bw). No further informations were reported.

inhalation

In a limit test according to OECD test guideline 403, five male and female Wistar rats were whole-body exposed for 4 hours to a dynamically produced vapour with a analytical concentration of 0.37 mg test substance (purity 100%) per liter. This concentration is the maximum concentration that could be achieved technically. There were no mortalities and no necropsy findings observed. Clinical signs (wiping of snouts, restlessness and attemps to escape) were only observed during exposure. The body weight gain of the males was not affected while the body weight gain of the females was retarded in the second week of the observation period. The LC50 of this study is > 0.37 mg/L (BASF 1990).

dermal

Following a standardized test protocol (BASF test), groups of three male and three female Vienna White rabbits were treated for 24 hours with doses of 200 mg/kg bw or 400 mg/kg bw of the test substance (purity unknown, prepared in 50% water) epicutaneously under occlusive conditions. Three of six animals died in the high dose treatment and 0/6 in the low dose treatment, leading to a LD50 of 400 mg/kg bw. Clinical signs were apathy and diarrhoea. At necropsy, acute dilatation of the heart (right), degeneration, loamy liver with acute dystrophy and sandy kidneys with nephrosis were observed in animals that died; sacrificed animals were found without substance-related findings (BASF 1980).

Justification for classification or non-classification

According to the available test results, the test substance Pyrazole has to be classified as harmful if swallowed (R 22 following 67/548/EEC and acute oral Cat. 4 following GHS requirements, respectively).

According to the available test result, the test substance has to be classified as toxic in contact with skin (R 24 following 67/548/EEC and acute dermal Cat.3 following GHS requirements, respectively).

According to the available test result, there is no indication given for a classification of the acute inhalative toxicity of the test substance following 67/548/EEC and GHS requirements, respectively.