(Z)-pent-2-enenitrile

Endpoint summary

Description of key information

Repeated dose toxicity, oral: NOAEL = 3 mg/kg bw/day based on degeneration of the olfactory mucosa at 10 mg/kg bw/day observed only on 2/10 
females (OECD 422, GLP).
Repeated dose toxicity, inhalation:  NOAEL = 3 ppm based on microscopic nasal lesions observed in female rats at 30 ppm and above, on the 
changes in sorbitol dehydrogenase activity at 30 ppm and above and on the body weight reduction observed in males at 30 ppm.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Endpoint conclusion

Dose descriptor:

NOAEL

3 mg/kg bw/day

Study duration:

subacute

Species:

rat

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Dose descriptor:

NOAEC

9.95 mg/m³

Study duration:

subacute

Species:

rat

Additional information

Repeated dose toxicity: oral

The combined repeated dose toxicity study with the reproduction/developmental toxicity screening test (Lewis, 2005) conducted with cis-2-pentenenitrile according to the OECD test guideline No. 422 and in compliance with GLP is identified as the key study. Crl:CD®(SD)IGS BR rats (10/sex/dose level) were dosed once daily by gavage at dose levels of 0, 1, 3, or 10 mg/kg/day (dose volume of 10 mL/kg in deionized water) for approximately 28 days prior to cohabitation and during the cohabitation period. Only general effects were reported below. Reprotoxic efects were summarise section 7.8.1.

There were no effects considered to be related to treatment on the following parameters at any dose level:

- Mortality and clinical signs of toxicity in P1 males and females

- Body weight and body weight gain in P1 males

- Food consumption in P1 males and females

- Functional observational battery, motor activity, or grip strength in P1 males and females

- Hematology and coagulation parameters in P1 males and females

- Organ weights and gross pathology in P1 males and females

- Microscopic pathology in P1 males

Effects considered by the authors to be related to treatment were limited to the 10 mg/kg/day group and comprised:

Adverse effects:

- Degeneration of the olfactory mucosa in Level II of the nose in P1 females observed in 2/10 females.

Non-adverse effects:

- Decreased body weight, body weight gain, and food efficiency in P1 females

- Increased albumin in P1 males and females

Under the conditions of this study, the no-observed-adverse-effect level (NOAEL) for systemic toxicity in P1 rats was 3 mg/kg/day, based on degeneration of the olfactory mucosa in P1 females at 10 mg/kg/day even if only 2/10 females were affected. This value is supported by Mackenzie, 2001study in which same effects were observed with more serious histopathologic changes such as submucosal fibrosis and degeneration of subjacent olfactory nerve fibers at 10mg/kg bw/day in male and female rats after 28 day exposure.

The study of MacKenzie (2001) is considered as a supporting study. In this sub-acute study performed according to OECD 407 guideline and in compliance with GLP, cis-2-Pentenenitrile (98.8 % pure) diluted in water was administered by oral gavage to Crl:CD®(SD)IGS BR rats (10/sex/group) initially at 10, 30 or 100 mg/kg bw/day for four weeks. Under the conditions of this study, there is no no-observed-adverse-effect level (NOAEL). This lack of a NOAEL is based on compound related reductions in body weight and nutritional parameters, reductions in hindlimb grip strength (females only), and degeneration/atrophy of nasal dorsal olfactory mucosa in male and female rats dosed with 10 mg/kg/day and above. Other adverse compound-related effects observed in high-dose rats included reduced forelimb grip strength and motor activity, clinical and histological corneal lesions, reduced red cell mass with associated reticulocytosis and splenic hematopoiesis (females), spermatid retention (males), and degeneration/atrophy of the dorsal olfactory nasal mucosa. Most parameters demonstrated at least partial reversal over the 2 month recovery phase; however, nasal histopathology did not demonstrate reversal. A LOAEL of 10 mg/kg bw/day was identified in rats based on this study particularly for serious histopathologic change of olfactory mucosa.

Repeated dose toxicity: inhalation

The integral report of the potential key study is not available, however the summary is usefull for the assessment. The study of Malley (1994) was conducted to determine the potential subacute toxicity from repeated inhalation exposure to stripped 2-pentenenitrile. CRL:CD®BR Rats (15/sex/group) were exposed nose-only to cis-2-pentenenitrile vapor for 6 hours/day over approximately a 4-week period (total of 20 exposures) at concentrations of 0, 3, 30, 100 and 300 ppm. A compound-related decrease in body weight and body weight gain occurred in males at exposure concentrations of 3, 30, 100, and 300 ppm. At 3 ppm, the body weight reduction observed in males is very low and therefore, this effect was not considered as adverse at this concentration. The lower body weight may be due in part to lower food consumption and lower food efficiency that were observed in males at concentrations of 30 ppm and above, and in females at 300 ppm. Serum sorbitol dehydrogenase activity was decreased in 100 and 300 ppm males and females, and in 30 ppm females. In addition, serum aspartate aminotransferase activity was significantly decreased in the 100 and 300 ppm females. The mechanism(s) related to the decreases in serum enzyme activity have not been determined, however, the decreased activities were considered to be compound-related and potentially adverse. Females exposed to 300 ppm also had increased urine volume and decreased urine osmolality, which were consistent with diuresis. Diuresis was not apparent in males. In females, a compound-related increase in absolute and relative liver weights occurred at 300 ppm, and an increase in relative liver weights occurred at 100 ppm, however, microscopic morphological changes were not evident. Compound-related microscopic effects were observed in the nose of both male and female rats exposed to 30 ppm and above. These changes consisted of primary olfactory epithelial degeneration with secondary necrotic exudate, regeneration/metaplasia, and vacuolation of the olfactory nerve bundles. For females, the NOAEL was 3 ppm based on microscopic nasal lesions observed in female rats at 30 ppm and above, and on the changes in sorbitol dehydrogenase activity at 30 ppm and above. For males, the NOAEL is also 3 ppm for body weight reduction.

Repeated dose toxicity: via oral route - systemic effects (target organ) respiratory: nose

Repeated dose toxicity: inhalation - systemic effects (target organ) respiratory: nose

Justification for classification or non-classification

Based on serious histopathologic changes such as submucosal fibrosis and degeneration of subjacent olfactory nerve fibers observed in male and female rats at 10 mg/kg bw/day after 28 day exposure and on the fact that same effects were observed by inhalation in female rats at 3 ppm, Cis-2 -Pentenenitrile is classified in Category 1 H372 (Causes damage to organs (nose) through prolonged or repeated exposure (oral and inhalation route of exposure)) according to the Regulation 1272/2008 and T; R48/23/25 (Danger of serious damage to health by prolonged exposure) according to the Directive 67/548/EC.