2-phenylhexanenitrile

Endpoint summary

Description of key information

In a dietary reproscreen study according to OECD TG 421 several systemic parameters were scored in addition to what is required in the reproscreen in view of the systemic effects seen in the 28 -day oral gavage study. The doses were 13 and 16, 28 and 32 and 70-85 mg/kg bw for males and females, respectively (using the actual intake via food being 134, 284 and 770 ppm (200, 400 and 1000 nominal ppm Salicynalva in feed, respectively). Body weight and clinical signs were similar to control values. For haematology parameters no treatment related findings were seen up to the highest dose. Macroscopic and microscopic observations did not show treatment related effects. Relative liver weights were increased at 70 -80 mg/kg bw in both sexes, circa 10% for males and 20% for females. No organ weight effect were seen in: kidney, spleen, testes and epididymides. Considering systemic effects the NOAEL is considered to be 70 mg/kg bw for both males and females, using the lower value of the males on the intake of the substance. Though the liver weights at this dose are increased in the absence of any and macroscopic and microscopic findings this increase in liver weight is considered to be a non-adverse adaptive change.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

70 mg/kg bw/day

Study duration:

subacute

Species:

rat

Quality of whole database:

The information on repeated dose toxicity from the 28-day study and the reproscreem are both of adequate quality to derive information on the systemic toxicity of the substance

Additional information

Two sub-acute repeated dose toxicity studies are available of at least 28 days of exposure. In addition, there is a 14-days dermal repeated dose toxicity test. These studies are described in more detail below.

The reproscreen study is selected as the key study because in the 28-day repeated dose toxicity study via gavage effects were seen at the high dose of 250 mg/kg bw, which are considered to be partly due to peak dosing when dosing via gavage. This type of peak exposures are being less relevant for the hazard and risk assessment than compared to a more gradual dosing as is simulated via the diet to which the animals were exposed in the reproscreen study. In both studies the liver is the target organ. In addition, the NOAEL of the reproscreen study of 70 mg/kg bw is well below the effect dose of 250 mg/kg bw in the 28-day gavage study and above the NOAEL in the latter, which was the next lower dose: 15 mg/kg bw.

Oral: OECD 407 28-day oral gavage study:

This study was performed to assess the systemic toxicity of Salicynalva to the rat according to OECD TG 407. Salicynalva was administered by oral gavage, once daily, to three groups of rats for a minimum of twenty eight consecutive days, at dosage levels of 1, 15 or 250 mg/kg/day. The test material was prepared as suspensions in corn oil at a maximum dosage volume of 5 ml/kg/day. Control animals received the vehicle (corn oil) alone at the same dose volume (5 ml/kg/day).

All rats of Groups 2 and 3 (1 and 15 mg/kg/day respectively) and five males and five females from each of Groups 1 and 4 (Control and 250 mg/kg/day respectively) were killed following the four-week treatment period. The remaining animals ( five males and five females from Groups 1 and 4) were retained for a two-week recovery period, following which, they were also killed. Bodyweights, food and water consumption and clinical observations were recorded during the study. Blood and urine samples were taken from all rats shortly prior to termination following the four-week treatment and two-week recovery periods. All animals were killed and subsequently examined macroscopically, specified tissues were then prepared for histopathological examination. Treatment resulted in:

Mortality: A male rat from the high dosage group was killed for humane reasons on Day 5. Clinical signs prior to sacrifice included hunched posture, piloerection, gasping and an unwillingness to move. Gastric ulceration, seen macroscopically and microscopically, was considered to be the factor contributory to death. Also one high dosage group male rat was killed for humane reasons on Day 7. Prior to death this animal was lethargic, unwilling to move, had partially closed eyelids, piloerection, hunched posture and had a thin ungroomed appearance. A post mortem examination revealed haemorrhagic depressions in the duodenum and microscopically, mucosal ulceration in the duodenum was noted . Duodenal ulceration was considered to be the factor contributory to death. There were no further mortalities that were considered to be related to treatment. Clinical signs: Ungroomed appearance was noted for high dosage group rats frequently throughout the study from Day 6 (males) or Day 14 (females). This sign persisted for approximately one week into the recovery period. Bodyweights: Bodyweight gains were statistically significantly lower than control for high dosage group male rats during the treatment period. During the recovery period bodyweight gains for these rats were higher than controls. This may be due to lower food consumption because lower than control food consumption was noted for male rats receiving 250 mg/kg/day. Food consumption was similar to control during the recovery period. Water consumption: Higher than control water was noted for high dosage group male and female rats during Week 3 . Water consumption was similar to control during the recovery period.

Haematology: Lower than control white blood cell counts, haemoglobin concentration and hence lower mean corpuscular haemoglobin concentration and mean corpuscular haemoglobin levels were recorded for high dosage group male rats at the end of the treatment period. Following the recovery period the haemoglobin concentration and lower mean corpuscular haemoglobin concentration and mean corpuscular haemoglobin levels remained lower than control. Biochemistry: Following the treatment period statistically significantly higher than control alkaline phosphatase, glutamic pyruvic transaminase, glutamic oxaloacetic transaminase and urea nitrogen levels were recorded for male rats receiving 250 mg/kg/day. For rats receiving 250 mg/kg/day, high triglyceride and bilirubin levels (males and females), high cholesterol levels (females) and low glucose levels (males) were recorded. For high dosage group rats higher than control albumin (males and females), globulin (females) and hence total protein (males and females) were recorded. Disturbances in electrolyte levels recorded for high dosage group male rats included higher than control sodium, chloride and inorganic phosphorus levels and lower than control potassium ion levels. There were no differences from control following the two-week recovery period.

Macroscopy and histopathology: Treatment-related changes detected in rats receiving 250 mg/kg/day included the following: Generalised swollen hepatocytes with ground glass cytoplasm in the liver of male and female rats at the end of treatment. Minimal centrilobular hepatocyte necrosis in one male and one female decedent. Reduced colloid in the prostate of one male rats during and at the end of treatment with associated atrophic acini in one decedent male and of doubtful relevance. Minimal epithelial hyperplasia with associated minimal subepithelial inflammation and oedema in the non-glandular region of the stomach in male rats was seen. Gastric ulceration in one decedent male and duodenal ulceration in another decedent male rat were observed both indicating irritation by the substance.

In summary: The mortality and treatment-related findings, in particular in the liver were considered to be systemic adverse effects. The effects seen in the stomach and duodenum of rats from the high dosage group were considered to be local adverse effects. No treatment-related findings were seen following the 2-week recovery period, indicating reversibility of treatment-related effects, resulting in a NOAEL of 15 mg/kg bw.

Oral: OECD 421 reproscreen study

A reproscreen study according to OECD TG 421 has been conducted for the substance. Nominal values of 200, 400 and 1000 ppm have been administered via the diet. Chemical analysis showed mean accuracies of 67%, 71% and 77% for the diets of Groups 2, 3 and 4, respectively, which was below the criterion range 80-120%. Therefore the analysed concentrations were used for determining the doses resulted in circa 15, 30 and 70 to 73 mg substance/kg body weight/day for the males and 79 to 124 mg substance/kg body weight/day for the females. No toxicologically significant parental toxicity was observed up to the highest dose level tested. In the males liver weights were slightly increased but without microscopic changes. Therefore the liver effects were considered to be of an adaptive nature to administration of the test substance. No fertility toxicity was observed up to 70 mg/kg bw. Therefore a parental and fertility NOAEL of at least 70 mg/kg bw was established.

Dermal: 14-day range finding study

A 14-day dermal range finding study was performed to assess the systemic toxic potential of Salicynalva, to the rat, in order to assess the suitability of the dermal route of administration. The protocol of the OECD TG 410 was used. The test substance was administered dermally (occlusive dressing over the treatment area for 6 hours per day) to groups of five male and five female rats at 50, 140, 400 or 1000 mg/kg/day (at a dosage volume of 2 ml/kg/day) in corn oil. A further group of five male and five female rats received the vehicle (corn oil) alone, at the same dose volume as control. The study started initially for a period of seven days, though this was extended to fourteen days by the Sponsor, since the initial seven days of treatment did not reveal any clear adverse effects of treatment. All animals were killed on Day 15. Clinical signs including examination of the dermal test site of each animal, bodyweight, food consumption, liver and prostate weights, macroscopic and microscopic examinations were recorded for the study. The dermal route of administration was well tolerated at dosages up to 1000 mg/kg/day, with no treatment-related effects at the site of administration. There were no treatment-related effects on bodyweight gain, food consumption, liver and prostate weights or macroscopic findings at any dosage. Males receiving 1000 mg/kg/day showed slight centrilobular hepatocyte hypertrophy (indicating that dermal absorption occurred) although a similar effect was not seen in females and no associated increase in liver weight was noted in males. The No Observed Adverse Effect Level (NOAEL) was 1000 mg/kg/day for males and females.

Conclusion

The local effects seen in the 28-oral gavage study at the highest dose of 250 mg/kg bw are considered irritant effects due to high peak exposures and are not considered for systemic effects. The moderate liver effects and heamatology effects seen at this highest dose are considered to be a LOAEL. Only slight and non-adverse liver effects were seen in the reproscreen study and no effects on haematology at 70 mg/kg bw. Therefore the highest dose in this study is considered to be an overall NOAEL for the repeated dose toxicity study. The 14-day dermal toxicity study with slight non-adverse liver effects at 1000 mg/kg bw further supports that the NOAEL of 70 mg/kg bw is sufficiently conservative.

Justification for classification or non-classification

Based on the NOAEL of 70 mg/kg bw/day observed in the dietary repeated dose / reproscreen study the substance does not need to be classified for (oral) repeated dose toxicity according to EU CLP (EC No. 1272/2008 and its amendments). Though this NOAEL is just below 100 mg/kg bw classification and labelling is not warranted because the systemic effects found at 250 mg/kg bw in the 28 -repeated dose toxicity study do not indicate severe organ damage also because these effects were not seen after the recovery period. The mortalities at this 250 mg/kg bw are due to local irritant effects likely due to gavage dosing.