2,6-dimethylheptan-2-ol

Toxicity to reproduction

Administrative data

Endpoint:

screening for reproductive / developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2015

Report date:

2015

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)

Test guideline 2

Qualifier:

according to guideline

Guideline:

OECD Guideline 421 (Reproduction / Developmental Toxicity Screening Test)

Test guideline 3

Qualifier:

according to guideline

Guideline:

other: OPPTS 870.3650, Combined Repeated Dose Toxicity Study with the Reproduction/Developmental Toxicity Screening Test, July 2000.

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

2,6-dimethylheptan-2-ol

EC Number:

236-244-1

EC Name:

2,6-dimethylheptan-2-ol

Cas Number:

13254-34-7

Molecular formula:

C9H20O

IUPAC Name:

2,6-dimethylheptan-2-ol

impurity 1

Reference substance name:

Unknown impurities

Molecular formula:

not applicable

IUPAC Name:

Unknown impurities

Test material form:

liquid

Specific details on test material used for the study:

Identification: Dimetol
Chemical name (IUPAC) 2,6-dimethylheptan-2-ol
Molecular weight 144.20
CAS Number 13254-34-7
EC Number 236-244-1
Description Clear colourless liquid (determined at WIL Research Europe B.V.)
Batch PE00090447
Purity/Composition See Certificate of Analysis (APPENDIX 5)
Test substance storage In refrigerator (2-8°C) protected from light
Stable under storage conditions until 28 May 2016 (expiry date)
* Batch A diets were used until 15 February 2015. Batch B was used to prepare diets from 04 February onwards; these were frozen until use on 16 February 2015.

All information for Batch B is the same as Batch A except for the following:
Batch PE00105624 (taken from label)
Purity/Composition 99.4%
Stable under storage conditions until 14 December 2016 (expiry date) (taken from label)

Test animals

Species:

rat

Strain:

Wistar

Sex:

male/female

Administration / exposure

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Details on exposure:

Diet: Standard powder rodent diet (SM R/M-Z from SSNIFF® Spezialdiäten GmbH, Soest, Germany).

Method: The test substance was mixed without the use of a vehicle, directly with some powder feed (premix) and subsequently mixed with the bulk of the diet. No correction was made for the purity/composition of the test substance.

Frequency of preparation: Diets were prepared weekly. Diets were kept frozen ≤ -15°C until needed and were stored at room temperature thereafter. Stability of the test substance in diet was performed in the method validation study; diets in the range of 500 and 15000 ppm (mg test substance/kg diet) were found to be stable for at least 8 days at room temperature (Project 506530).

Storage conditions: After preparation diets were frozen ≤ -15°C until needed at which the diet used was kept at room temperature in the diet store room in the animal house for a maximum of 8 days.

Details on mating procedure:

Following a minimum of 14 days of exposure for the males and females, one female was cohabitated with one male of the same treatment group, avoiding sibling mating. Detection of mating was confirmed by evidence of sperm in the vaginal lavage or by the appearance of an intravaginal copulatory plug. This day was designated Day 0 post-coitum. Once mating occurred, the males and females were separated. A maximum of 14 days was allowed for mating, after which females who had not shown evidence of mating were separated from their males. Detection of mating was not confirmed for animal no. 47. Her single pup was found dead at the first litter check. The mating date of this animal was estimated at 21 days prior to the actual delivery date. This day was designated Day 0 post-coitum.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Analyses were conducted on a single occasion (23 January 2015), according to a validated method (Project 506530). Samples of diets were analyzed for homogeneity (highest and lowest concentration) and accuracy of preparation (all concentrations). Stability of the test substance in diet for at least 8 days at room temperature in the range of 500 and 15000 ppm (mg test substance/kg diet) was confirmed in the method validation study (Project 506530) and was not tested again in the present study.
The accuracy of preparation was considered acceptable if the mean measured concentrations were 80-120% of the target concentration. Homogeneity was demonstrated if the coefficient of variation was ≤ 10%.
Random samples were taken from all Groups and stored at ≤-15°C for possible future analysis. Any remaining samples will be discarded at finalization of the study report.

Duration of treatment / exposure:

The males and females were exposed for at least 14 days prior to mating, during mating, and up to the day prior to scheduled necropsy. Males were exposed for 29 days and females were exposed for 39-57 days.
Pups were not dosed directly but could have potentially be exposed to the test substance in utero, via maternal milk or from exposure to maternal urine/faeces.

Frequency of treatment:

Oral, by inclusion in the diet - Ad libitum

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

100 ppm (nominal)

Doses / concentrations 2

Dose / conc.:

3 000 ppm (nominal)

Doses / concentrations 3

Dose / conc.:

10 000 ppm (nominal)

No. of animals per sex per dose:

10 animals/sex/dose

Control animals:

yes

Examinations

Parental animals: Observations and examinations:

Mortality / Viability: At least twice daily.

Clinical signs: Daily from treatment onwards up to the day prior to necropsy, detailed clinical observations were made for all animals. Once prior to start of treatment and at weekly intervals during the treatment period this was also performed outside the home cage in a standard arena.
The time of onset, grade and duration of any observed sign was recorded. Signs were graded for severity and the maximum grade was
predefined at 3 or 4. Grades were coded as slight (grade 1), moderate (grade 2), severe (grade 3) and very severe (grade 4). For certain signs,
only its presence (grade 1) or absence (grade 0) was scored. In the data tables, the scored grades were reported, as well as the percentage of
animals affected in summary tables.

Functional Observations: The following tests were performed on the selected 5 animals/sex/group:
- hearing ability, pupillary reflex and static righting reflex (Score 0 = normal/present, score 1 = abnormal/absent).
- fore- and hind-limb grip strength were recorded as the mean of three measurements (Series M4-10, Mark-10 Corporation, J.J. Bos, Gouda, The Netherlands).
- locomotor activity (recording period: 1-hour under normal laboratory light conditions, using a computerized monitoring system, Kinder Scientific LLC, Poway, USA). Total movements and ambulations were reported. Ambulations represent movements characterized by a relocation of the entire body position like walking, whereas total movements represent all movements made by the animals, including ambulations but also smaller or more fine movements like grooming, weaving or movements of the head.

The selected males were tested during Week 4 of treatment and the selected females were tested towards the end of the scheduled lactation
period (from lactation Day 4 onwards). These tests were performed after observation for clinical signs (incl. arena observation, if applicable).

Body weights: Males and females were weighed on the first day of exposure and weekly thereafter. Mated females were weighed on Days 0, 4, 7, 11, 14, 17 and 20 post-coitum and during lactation on Days 1 and 4.

Food consumption: Weekly, except for males and females which were housed together for mating and for females without evidence of mating. Food consumption of mated females was measured on Days 0, 4, 7, 11, 14, 17 and 20 postcoitum and on Days 1 and 4 of lactation.

Water consumption: Subjective appraisal was maintained during the study, but no quantitative investigation was introduced as no treatment related effect was suspected.

General reproduction data Male number paired with, mating date, confirmation of pregnancy, and delivery day were recorded. Palpation was used to aid in confirmation of pregnancy. Pregnant females were examined to detect signs of difficult or prolonged parturition, and cage debris of pregnant females was examined to detect signs of abortion or premature birth. Any deficiencies in maternal care (such as inadequate construction or cleaning of the nest, pups left scattered and cold, physical abuse of pups or apparently inadequate lactation or feeding) were examined.

Oestrous cyclicity (parental animals):

not examined

Sperm parameters (parental animals):

not examined

Litter observations:

Each litter was examined to determine the following, if practically possible:
Mortality / Viability: The numbers of live and dead pups were determined on Day 1 of lactation and daily thereafter. If possible, defects or cause of death were evaluated.
Clinical signs: At least once daily, detailed clinical observations were made for all animals.
Body weights: Live pups were weighed on Days 1 and 4 of lactation.
Sex: Sex was determined for all pups on Days 1 and 4 of lactation.

Postmortem examinations (parental animals):

All males and the selected 5 females/group were deprived of food overnight (with a maximum of 24 hours) prior to planned necropsy, but water was provided. Non-selected females were not deprived of food and thus were exposed to the test diet until the day of necropsy.
All animals surviving to the end of the observation period were deeply anaesthetized using isoflurane (Abbott B.V., Hoofddorp, The Netherlands) and subsequently exsanguinated and subjected to a full post mortem examination, with special attention being paid to the reproductive organs. Descriptions of all macroscopic abnormalities were recorded.

Necropsy was conducted on the following days:
Condition Day of necropsy
Females which delivered Lactation Days 5-7.
Females which failed to Post-coitum Days 25 (female with evidence of mating) or approximately 21 days after the last day of the mating period (females without evidence of mating).
deliver1 (nos. 58,59 and 67)
Females with total litter loss Within 24 hours of litter loss.
(nos. 47 and 55)
Males Following completion of the mating period (a minimum of 28 days of dose administration)

Statistics:

The following statistical methods were used to analyze the data:
- If the variables could be assumed to follow a normal distribution, the Dunnett-test (Ref. 2; many-toone t-test) based on a pooled variance estimate was applied for the comparison of the treated groups and the control groups for each sex.
- The Steel-test (Ref. 3; many-to-one rank test) was applied if the data could not be assumed to follow a normal distribution.
- The Fisher Exact-test (Ref. 4) was applied to frequency data.
- The Kruskal-Wallis nonparametric ANOVA test (Ref. 5) was applied to motor activity data to determine intergroup differences.

All tests were two-sided and in all cases p < 0.05 was accepted as the lowest level of significance.

Group means were calculated for continuous data and medians were calculated for discrete data (scores) in the summary tables. Test statistics were calculated on the basis of exact values for means and pooled variances. Individual values, means and standard deviations may have been rounded off before printing. Therefore, two groups may display the same printed means for a given parameter, yet display different test statistics values.

Results and discussion

Results: P0 (first parental generation)

General toxicity (P0)

Clinical signs:

no effects observed

Description (incidence and severity):

There were no adverse clinical signs with treatment up to 10000 ppm. The only clinical sign noted was piloerection, seen for a single day for one female at 1000 ppm. As it was transient and seen for a single low dose female, it was considered incidental.

Body weight and weight changes:

effects observed, non-treatment-related

Description (incidence and severity):

Body weight gains were significantly lower for males at 10000 ppm from Day 8 of the premating period and continuing through the duration of treatment. Body weight gains were lower for females at 3000 and 10000 on Day 8 of the premating period only

Food consumption and compound intake (if feeding study):

effects observed, non-treatment-related

Description (incidence and severity):

There were no toxicologically relevant effects on food consumption with treatment up to 10000 ppm.

Animals at 10000 ppm (both sexes) had lower absolute and relative food consumption during the first week in treatment. Relative food consumption was lower for females at 3000 ppm during this time. This is likely secondary to palatability issues as food consumption recovered to levels comparable to controls thereafter. Food consumption was higher for all treated males during the first week of the mating period. This was secondary to slightly low values obtained for one cage of control males and was not considered to be treatment related. Absolute and relative food consumption was significantly higher Days 7-11 of the post coitum period for females at 1000 ppm. In the absence of a dose-dependent distribution, it was not considered to be toxicologically relevant.

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

effects observed, non-treatment-related

Description (incidence and severity):

There were no toxicologically relevant effects on haematology parameters seen up to 10000 ppm.
Statistically significant decreases in red blood cell count, haemoglobin, and haematocrit were noted for females at 1000 and 3000 ppm and statistically significant increases were seen in red blood cell distribution width (RDW) and platelet counts for females at 1000 ppm. Significantly lower mean corpuscular haemoglobin concentration (MCHC) was noted for males at 1000 and 3000 ppm. The statistically significant changes observed at 1000 and 3000 ppm were not toxicologically relevant as
the values remained within the range considered normal for this age and strain and/or no dose dependent effect was observed.

Urinalysis findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, non-treatment-related

Description (incidence and severity):

Macroscopic examination
There were no treatment related effects on macroscopic findings noted up to 10000 ppm.
Incidental findings seen for control and/or treated animals included isolated or several reddish foci on the lungs, dark red or reddish discoloration of the mandibular lymph node, abnormal shape of the sternum, enlarged thyroid glands, yellowish, hard nodule on the epididymis, reduced size of the seminal vesicle, flaccid kidney and tan focus on the clitoral gland. These findings are occasionally seen for animals of this age and strain and in the absence of a treatment related distribution, they were not considered to be toxicologically relevant. An early resorption in the right uterine horn was noted for the control female with a total litter loss (no. 47).

Microscopic examination
Test item-related microscopic findings were present in males in the kidney where hyaline droplet accumulation was present at increased incidence and severity in males treated at 10000 ppm up to a moderate degree. Tubular basophilia was present at an increased incidence and severity in males treated at 10000 ppm up to a slight degree. Granular casts were present in a single male treated at 10000 ppm at slight degree. There were no morphological findings in the reproductive organs of either sex which could be attributed to the test item and spermatogenic staging profiles were normal for all males examined. In female Wistar Han rats, there were no test item-related morphologic alterations after treatment with Dimetol for at least 28 days at a dose up to 10000 ppm.

Reproductive function / performance (P0)

Reproductive function: oestrous cycle:

not examined

Reproductive function: sperm measures:

not examined

Reproductive performance:

no effects observed

Description (incidence and severity):

No toxicologically relevant effects on reproductive parameters were noted.

Details on results (P0)

See Section 7.2 in report

Effect levels (P0)

Key result

Dose descriptor:

NOAEL

Effect level:

3 000 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: See remark

Results: F1 generation

General toxicity (F1)

Clinical signs:

effects observed, non-treatment-related

Description (incidence and severity):

Observations remained within the range considered normal

Dermal irritation (if dermal study):

not examined

Mortality / viability:

mortality observed, non-treatment-related

Description (incidence and severity):

There were 2, 3 and 3 pups that died or went missing during the first days of lactation in the control, 1000, and 10000 ppm groups, respectively. There were no pups lost at 3000 ppm. Missing pups were most likely cannibalised. No toxicological relevance was attributed to these dead/missing pups since the mortality incidence did not show a dose-related trend and remained within the range considered normal for pups of this age.

Body weight and weight changes:

no effects observed

Description (incidence and severity):

Body weights of pups were unaffected by treatment up to 10000 ppm

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Sexual maturation:

not examined

Details on results (F1)

See Section 7.3

Effect levels (F1)

Dose descriptor:

NOAEL

Generation:

F1

Effect level:

10 000 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

clinical signs

mortality

body weight and weight gain

Overall reproductive toxicity

Reproductive effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

In conclusion, treatment with Dimetol by dietary administration in male and female Wistar Han rats at dose levels of 1000, 3000 and 10000 ppm revealed parental toxicity at 10000 ppm. No reproductive or developmental toxicity was observed for treatment up to 10000 ppm.
Based on these results, a parental No Observed Adverse Effect Level (NOAEL) of 3000 ppm was determined and a reproductive and developmental NOAEL of at least 10000 ppm was derived.
When corrected for mean test article intake, the parental NOAEL of 3000 ppm corresponds to 228-231 mg/kg for males and 251-382 mg/kg for females. The reproductive and developmental NOAEL of 10000 ppm corresponds to 714-734 mg/kg for males and 830-1216 mg/kg for females.

Executive summary:

Accuracy and homogeneity of diets were demonstrated by analyses.

Parental results:

Parental toxicity was evident at 10000 ppm and was characterized by lower body weight gains for males Day 8 of the premating period onwards. Palatability issues of the test diet likely contributed to

the lower gains as food consumption was lower during the first week of treatment. Males and females at this dose level had higher absolute and relative liver weights with relative liver weights approximately 16% and 20% higher for males and females than controls, respectively. At the microscopic examination, cortical hyaline droplets representing alpha2uglobulin were recorded at an increased incidence and severity in the kidneys of males treated at 10000 ppm. These changes resulted from the increased/altered liver metabolism resulting in excessive accumulation of alpha- 2uglobulin in the renal proximal tubular epithelial cells and are regarded as specific to the male rat. Alpha-2uglobulin does not occur in the human kidney and that this finding does not indicate any potential risk to human health. This was accompanied by an increased incidence and severity of corticomedullary tubular basophilia and in one instance by granular casts. These granular casts are considered to be indicative of primary tubular injury and therefore this finding was considered to be adverse.

There were no relevant microscopic findings noted for females at 10000 ppm.

No treatment-related changes were noted in any of the remaining parental parameters investigated in this study (i.e. clinical appearance, functional observations, clinical laboratory investigations and

macroscopic examination).

Reproductive results:

No reproductive toxicity was observed up to the highest dose level tested (10000 ppm).

Developmental results:

No developmental toxicity was observed up to the highest dose level tested (10000 ppm)