Registration Dossier
Registration Dossier
Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.
The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.
Use of this information is subject to copyright laws and may require the permission of the owner of the information, as described in the ECHA Legal Notice.
EC number: 203-692-4 | CAS number: 109-66-0
Endpoint summary
Administrative data
Key value for chemical safety assessment
Effects on fertility
Description of key information
There is no reproductive toxicity data available for Normal-Pentane. However, data is available for structural analogues 2-methylbutane, cyclohexane, and VRU gasoline. This data is read across to Normal-Pentane based on analogue read across and a discussion and report on the read across strategy is provided as an attachment in IUCLID Section 13.
2-methylbutane
One-Generation Reproduction Toxicity Study (OECD TG 415)
Oral NOAEL (Reproductive toxicity) >= 1000 mg/kg/day
Cyclohexane
Two-Generation Reproduction Toxicity Study (OECD TG 416)
Inhalation NOAEC (Reproductive toxicity) = 24080 mg/m3
VRU gasoline
Two-Generation Reproduction Toxicity Study (OECD TG 416)
Inhalation NOAEC (Reproductive toxicity) > 20000 mg/m3
Link to relevant study records
- Endpoint:
- one-generation reproductive toxicity
- Remarks:
- based on test type
- Type of information:
- read-across from supporting substance (structural analogue or surrogate)
- Adequacy of study:
- key study
- Study period:
- 2011
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- other: Conducted according to OECD TG 415. GLP.
- Justification for type of information:
- A discussion and report on the read across strategy is given as an attachment in IUCLID Section 13.
- Reason / purpose for cross-reference:
- read-across: supporting information
- Qualifier:
- according to guideline
- Guideline:
- OECD Guideline 415 [One-Generation Reproduction Toxicity Study (before 9 October 2017)]
- GLP compliance:
- yes
- Species:
- rat
- Strain:
- Sprague-Dawley
- Sex:
- male/female
- Details on test animals or test system and environmental conditions:
- Male and female 5-week-old Sprague - Dawley rats were maintained in an animal room at 22 +/- 3 deg C with a relative humidity of 30-70% under a 12 h light/dark cycle. Rats were housed 2 per cage in stainless wire caging during the premating (2 males or 2 females), mating (1 male and 1 female), and post-mating periods (2 males). Mated females were housed individually during the gestation period. Lactating animals with suckling pups were housed in the same cages. The animals were provided sterilized water, ad libitum.
- Route of administration:
- oral: gavage
- Vehicle:
- corn oil
- Details on exposure:
- 0, 100, 300, and 1000 mg/kg/day. Males were dosed for 10 weeks prior to mating and during mating. Females were dosed from 2 weeks before mating to day 21 of lactation.
- Details on mating procedure:
- After the 70-day premating exposure period was completed, the F0 animals were mated one male to one female, selected randomly within each dose group for 14 days. The observation of a vaginal plug or sperm in a vaginal smear was considered evidence of successful mating. The day a vaginal plug and/or sperm in a vaginal smear were observed was designated as day 0 of pregnancy. Once the vaginal plug or sperm were observed, the animals were separated and housed individually in cages. A female was re-mated with a male of proven fertility within the same experimental group if mating was not confirmed in 2 weeks. Any female that did not show evidence of successful mating after cohabitation was individually housed and euthanized on day 21 after separation. Females were examined daily during the mating period and from GD 20, females were checked two times daily for evidence of onset, progress, and completion of parturition.
All animals were allowed to litter naturally (F1 generation), and rear their own offspring until LD 21. Dams were examined daily for evidence of normal maternal behavior. - Analytical verification of doses or concentrations:
- not specified
- Duration of treatment / exposure:
- Males were dosed for 10 weeks prior to mating and during mating. Females were dosed from 2 weeks before mating to day 21 of lactation.
- Frequency of treatment:
- once per day
- Remarks:
- Doses / Concentrations:
0, 100, 300, and 1000 mg/kg/day
Basis:
nominal conc. - No. of animals per sex per dose:
- 24 rats/sex/dose
- Control animals:
- yes, concurrent vehicle
- Parental animals: Observations and examinations:
- All animals were observed daily for clinical signs when treated with the test chemical, and abnormal signs were recorded individually by type, observation day/time, and duration. Body weight of each male was measured twice weekly until euthanized. Female rats were weighed twice weekly during the premating period and on gestation days (GD) 0, 3, 6, 9, 12, 15, 18, and 20, as well as on lactation days (LD) 1, 4, 7, 14, and 21. In mated females that produced no litters, body weights were measured up to day 21 of the presumed gestation period. The individual amount of food consumed was recorded once a week during the premating period and on GD 0, 3, 6, 9, 12, 15, 18, and 20, as well as on lactation days (LD) 1, 4, 7, 14, and 20. Food consumption was not measured during the mating period.
- Litter observations:
- Pups were examined as soon as possible on the day of birth to determine the number alive and stillborn in each litter. All live pups were individually counted, sexed, weighed, and examined externally. The number of live and dead pups was noted on PND 4, 7, 14, and 21. The body weights of F1 offspring were measured by randomly selecting one pup of each sex from each litter on PND 1, 7, 14 and 21.
- Postmortem examinations (parental animals):
- Males were euthanized at the end of the 14-day mating period; females that delivered were euthanized on day 22 after parturition. All adult animals were subjected to a full and detailed gross necropsy, which included a careful examination of the external surface of the body, the cranial, thoracic, abdominal cavities, and their contents. Special attention was paid to the reproductive organs. At necropsy the following organs were obtained and weighed from all animals: brain, pituitary gland, thymus, heart, lung, liver, kidneys, adrenal glands, spleen, testes, epididymides, prostates, seminal vesicles, ovaries, uterus and abnormal lesions. Testes and epididymides were preserved in Bouin’s fixative. Other tissues were fixed with a 10% neutral buffered formalin solution. The tissues were routinely processed, embedded in paraffin and sectioned at 3-5 um. These sections were stained with hematoxylin-eosin (H&E) for microscopic examination. All tissues taken from the control and high dose groups, and testis and epididymis from the low and middle dose groups were examined microscopically.
- Postmortem examinations (offspring):
- Culled pups and dead pups found during the study were examined macroscopically for structural abnormalities or pathological changes. On PND 22, one male and one female per litter were euthanized and subjected to external and internal macroscopic examination.
- Statistics:
- The data are expressed as mean ± standard deviation (SD). Parametric data were subjected to one-way analysis of variance (ANOVA). Other data were analyzed using Kruskal-Wallis nonparametric ANOVA. If either test showed statistical significance, the data were analyzed using the Dunnett multiple comparison procedure.
Precoital time, duration of gestation, and the numbers of live and dead pups were statistically evaluated using the
Kruskal–Wallis nonparametric ANOVA, followed by the Mann- Whitney U-test when appropriate. Incidence data (e.g. clinical signs and histopathological findings) were compared using Fisher’s exact probability test. - Reproductive indices:
- copulation index, fecundity index, fertility index, delivery index, precoital time, and duration of gestation
- Clinical signs:
- no effects observed
- Body weight and weight changes:
- no effects observed
- Food consumption and compound intake (if feeding study):
- no effects observed
- Organ weight findings including organ / body weight ratios:
- no effects observed
- Histopathological findings: non-neoplastic:
- effects observed, treatment-related
- Other effects:
- no effects observed
- Reproductive function: oestrous cycle:
- no effects observed
- Reproductive function: sperm measures:
- no effects observed
- Reproductive performance:
- no effects observed
- Key result
- Dose descriptor:
- NOAEL
- Remarks:
- systemic toxicity
- Effect level:
- 300 mg/kg bw/day (actual dose received)
- Based on:
- test mat.
- Sex:
- male
- Basis for effect level:
- other: a2u-globulin nephropathy observed in male rats. This effect is not relevant to human health.
- Key result
- Dose descriptor:
- NOAEL
- Remarks:
- systemic toxicity
- Effect level:
- >= 1 000 mg/kg bw/day (actual dose received)
- Based on:
- test mat.
- Sex:
- female
- Basis for effect level:
- other: highest dose given
- Key result
- Dose descriptor:
- NOAEL
- Remarks:
- reproductive toxicity
- Effect level:
- >= 1 000 mg/kg bw/day (actual dose received)
- Based on:
- test mat.
- Sex:
- male/female
- Basis for effect level:
- other: highest dose given
- Clinical signs:
- no effects observed
- Mortality / viability:
- no mortality observed
- Body weight and weight changes:
- no effects observed
- Sexual maturation:
- not examined
- Organ weight findings including organ / body weight ratios:
- no effects observed
- Gross pathological findings:
- no effects observed
- Histopathological findings:
- no effects observed
- Key result
- Dose descriptor:
- NOAEL
- Generation:
- F1
- Effect level:
- >= 1 000 mg/kg bw/day (actual dose received)
- Based on:
- test mat.
- Sex:
- male/female
- Basis for effect level:
- other: pup development
- Key result
- Reproductive effects observed:
- no
- Conclusions:
- The reproductive and developmental NOAEL >= 1000 mg/kg/day, the highest dose tested. The systemic NOAEL for male rats the NOAEL = 300 mg/kg/day based on the a2u-globulin nephropathy observed that is not relevant to human health. The systemic NOAEL for female rats was NOAEL >= 1000 mg/kg/day, the highest dose tested.
- Executive summary:
A one-generation reproductive toxicity study using Sprague-Dawley rats was conducted using the test material 2-methylbutane. Male and female rats (24 per treatment group) were treated by oral gavage with 2-methylbutane at 0, 100, 300, and 1000 mg/kg/day. Males were dosed for 10 weeks prior to mating and during mating and females were dosed from 2 weeks before mating to day 21 of lactation.
No treatment-related effects of 2-methylbutane were found in relation to the reproductive capacity of parental animals or the pre- and post-natal development of the F1 generation.
At 1000 mg/kg/day, a2u-globulin nephropathy observed in male rats. This effect is not relevant to human health. While several organs had altered weights, they changes were within the normal biological range and were considered to be not toxicologically relevant.
Therefore, the reproductive and developmental NOAEL >= 1000 mg/kg/day, the highest dose tested. The systemic NOAEL for male rats the NOAEL = 300 mg/kg/day based on the a2u-globulin nephropathy observed that is not relevant to human health. The systemic NOAEL for female rats was NOAEL >= 1000 mg/kg/day, the highest dose tested.
- Endpoint:
- two-generation reproductive toxicity
- Remarks:
- based on test type
- Type of information:
- read-across from supporting substance (structural analogue or surrogate)
- Adequacy of study:
- key study
- Study period:
- 2000
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- other: This study is classified as reliable without restriction because this study was performed in accordance with GLP and appeared to closely followed OECD 416.
- Justification for type of information:
- A discussion and report on the read across strategy is given as an attachment in IUCLID Section 13.
- Reason / purpose for cross-reference:
- read-across: supporting information
- Qualifier:
- equivalent or similar to guideline
- Guideline:
- OECD Guideline 416 (Two-Generation Reproduction Toxicity Study)
- GLP compliance:
- yes
- Limit test:
- no
- Species:
- rat
- Strain:
- other: Crl:CDBR
- Sex:
- male/female
- Details on test animals or test system and environmental conditions:
- TEST ANIMALS
- Age at study initiation: (P males) 8 weeks; (P females) 8 weeks
- Housing: Individually housed except during cohabitation periods in wire mesh cages. Assumed-pregnant females and those without evidence of copulation were individually housed in polycarbonate pans with bedding. During lactation, adult females were housed with their litters in polycarbonate pans with bedding
- Diet (e.g. ad libitum): Ad libitum, Purina Certified Rodent Checkers
- Water (e.g. ad libitum): Ad libitum
ENVIRONMENTAL CONDITIONS
- Temperature (°C): 23 +/- 2°C
- Humidity (%): 50 +/- 10%
- Photoperiod (hrs dark / hrs light): 12 hours light/dark cycle - Route of administration:
- inhalation: vapour
- Type of inhalation exposure (if applicable):
- whole body
- Vehicle:
- unchanged (no vehicle)
- Details on exposure:
- GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: All exposure chambers were constructed of stainless steel and glass and had a nominal internal volume of 1.4 m3. The chamber volume was chosen so that the total body volume of the test animals did not exceed 5% of the chamber volume. A tangential feed at the chamber inlet promoted gas mixing and uniform chamber distribution of vapor
- Atmospheres of cyclohexane were generated by metering the liquid test substance into a heated glass Instatherm flask with a Fluid Metering Inc. pump. Nitrogen, introduced into the flask, swept the cyclohexane vapor into the inhalation chamber air supply. The chamber concentration of cyclohexane was controlled by varying the amount of the metered liquid evaporated in the chamber air stream. Nitrogen and air were passed through the control chamber at approximately the same flow rates as those used in the exposure chambers.
TEST ATMOSPHERE-The atmospheric concentration of cyclohexane was determined by gas chromatography at approximately 15-minute intervals during each 6-hour exposure. Chamber-atmosphere samples were drawn by vacuum pump from representative areas of the chamber where animals were exposed and were directly injected into a Hewlett Packard model 5880 Gas Chromatograph equipped with a flame ionization. All samples were chromatographed isothermally at 70°C on an HP-20M Carbowax column. The chamber distribution of cyclohexane vapor was determined prior to animal exposures in the high-concentration exposure chamber and while the study was underway with animals in the low- and high-concentration chambers. The results of these determinations indicated the distribution of cyclohexane vapor was sufficiently homogeneous (less than 2% difference in chamber concentration from position to position). - Details on mating procedure:
- No data reported.
- Analytical verification of doses or concentrations:
- yes
- Details on analytical verification of doses or concentrations:
- Achieved concentrations were determined by gas chromatography at approximately 15-minute intervals during each 6-hour exposure. Chamber distribution of cyclohexane was determined prior to animal exposures in the high-concentration exposure chamber. Results showed that the distribution of cyclohexane vapour was sufficiently homogeneous (less than 2% difference in chamber concentration from position to position).
- Duration of treatment / exposure:
- Males and females were exposed prior to mating (at least 10 weeks for the P generation and 11 weeks for the F1 generation). Pregnant females were exposed daily during gestation days 0 through 20; exposure ceased from gestation day 21 until lactation day 4. Exposure resumed on lactation day 5 until litters were weaned. Males continued to be exposed 5 days/week until sacrificed. Neonates were not exposed during lactation.
- Frequency of treatment:
- 6 hours/day, 5 days/week, including holidays
- Details on study schedule:
- P animals were mated after approximately 10 weeks after exposure. Dams were allowed to deliver and rear pups until weaning (postpartum day 25). After at least 11 weeks after weaning, F1 animals were bread to produce F2 litters. Pups were culled on lactation day 4.
- Remarks:
- Doses / Concentrations:
0 (air), 500, 2000, and 7000 ppm
Basis:
nominal conc. - No. of animals per sex per dose:
- P generation: 30 animals/sex/dose
F1 generation: 30 animals/sex/dose - Control animals:
- yes, concurrent vehicle
- Details on study design:
- The high concentration was selected to be 60% of the Lower Explosive Limit; the low concentration was selected because it exceeds the threshold limit for human exposure and was not expected to cause toxicological effects. The mid dose was selected to provide approximately equal spacing between and high and low doses on a log scale.
- Positive control:
- No positive control was used.
- Parental animals: Observations and examinations:
- DETAILED CLINICAL OBSERVATIONS: Yes; Prior to the initiation of each exposure, during exposure, and during the time required to clear the chambers of test substance, the groups of animals within exposure levels were observed for a normal, diminished, or hyper-responsive alerting behavior in response to a standardized auditory stimulus.
BODY WEIGHT: Yes
- Time schedule for examinations: P and F1 rats were weighed weekly during the premating, gestation, and lactation periods.
FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes - Oestrous cyclicity (parental animals):
- No data reported.
- Sperm parameters (parental animals):
- No data reported.
- Litter observations:
- F1 and F2 pup weights and clinical observations were recorded on postpartum days 0, 4, 7, 14, 21, and 25.
- Postmortem examinations (parental animals):
- After litter production, all P and F1 parental animals were euthanized by carbon dioxide and exsanguinated. Reproductive organs and pituitary gland were collected from each animal. Tissues from the high-dose and control animals for both generations were examined microscopically.
- Postmortem examinations (offspring):
- Pups were euthanized by carbon dioxide and exsanguinated.
- Statistics:
- In general, sequential trend testing was applied to the data of each parameter. If a result was significant, data from the high-dose group was excluded; the test was repeated in until no significant trend was detected. Adult body weight and food consumption data were analyzed by pair-wise comparisons. The level of significance selected for all analyses was p≤0.05.
Among study groups, parametric analyses were used to compare continuous data. Linear contrast was performed by conducting a Dunnett's test followed by ANOVA. Litter-related continuous data were analyzed by Jonckheere's test. Foetal and pup weights were analyzed by an Analysis of Covariance followed with a linear contrast of the least square means. Discrete data were evaluated by the Cochran-Armitage test for trend. The incidence of microscopic observations were analyzed by the Fisher's exact test. - Reproductive indices:
- Mating index, fertility index, and mean gestation length were calculated.
- Offspring viability indices:
- The sex ratio, implantation efficiency, gestation index, day 0-4 viability, lactation index, and litter survival were calculated.
- Clinical signs:
- effects observed, treatment-related
- Body weight and weight changes:
- effects observed, treatment-related
- Food consumption and compound intake (if feeding study):
- effects observed, treatment-related
- Organ weight findings including organ / body weight ratios:
- no effects observed
- Histopathological findings: non-neoplastic:
- effects observed, treatment-related
- Reproductive function: oestrous cycle:
- not examined
- Reproductive function: sperm measures:
- not examined
- Reproductive performance:
- no effects observed
- Key result
- Dose descriptor:
- NOAEC
- Remarks:
- Reproductive
- Effect level:
- 7 000 ppm (nominal)
- Sex:
- male/female
- Basis for effect level:
- other: 24,080 mg/m3; there were no adverse compound-related effects on reproductive function.
- Key result
- Dose descriptor:
- LOAEC
- Remarks:
- Parental
- Effect level:
- 2 000 ppm (nominal)
- Sex:
- male/female
- Basis for effect level:
- other: 6880 mg/m3; based on transient treatment-related sedative effect on the rats' alerting response to sound stimulus
- Key result
- Dose descriptor:
- NOAEC
- Remarks:
- Parental
- Effect level:
- 500 ppm (nominal)
- Sex:
- male/female
- Basis for effect level:
- other: 1720 mg/m3
- Key result
- Dose descriptor:
- NOAEC
- Remarks:
- Parental
- Effect level:
- 500 ppm (nominal)
- Sex:
- male/female
- Basis for effect level:
- other: 1720 mg/m3
- Key result
- Dose descriptor:
- LOAEC
- Remarks:
- Parental
- Effect level:
- 2 000 ppm (nominal)
- Sex:
- male/female
- Basis for effect level:
- other: 6880 mg/m3; based on transient treatment-related sedative effect on the rats' alerting
- Key result
- Dose descriptor:
- NOAEC
- Remarks:
- Reproductive
- Effect level:
- 7 000 ppm (nominal)
- Sex:
- male/female
- Basis for effect level:
- other: 24,080 mg/m3; there were no adverse compound-related effects on reproductive function
- Clinical signs:
- no effects observed
- Mortality / viability:
- mortality observed, treatment-related
- Body weight and weight changes:
- effects observed, treatment-related
- Sexual maturation:
- not examined
- Organ weight findings including organ / body weight ratios:
- not examined
- Gross pathological findings:
- no effects observed
- Histopathological findings:
- no effects observed
- Key result
- Dose descriptor:
- NOAEC
- Remarks:
- Offspring
- Generation:
- F1
- Effect level:
- 2 000 ppm (nominal)
- Sex:
- male/female
- Basis for effect level:
- other: 6880 mg/m3
- Key result
- Dose descriptor:
- LOAEC
- Remarks:
- Offspring
- Generation:
- F1
- Effect level:
- 7 000 ppm (nominal)
- Sex:
- male/female
- Basis for effect level:
- other: 24,080 mg/m3; decreased mean pup weight from lactation days 7 through 25
- Key result
- Dose descriptor:
- NOAEC
- Remarks:
- Offspring
- Generation:
- F2
- Effect level:
- 2 000 ppm (nominal)
- Sex:
- male/female
- Basis for effect level:
- other: 6880 mg/m3
- Key result
- Dose descriptor:
- LOAEC
- Remarks:
- Offspring
- Generation:
- F2
- Effect level:
- 7 000 ppm (nominal)
- Sex:
- male/female
- Basis for effect level:
- other: 24,080 mg/m3; decreased mean pup weight from lactation days 7 through 25
- Key result
- Reproductive effects observed:
- no
- Conclusions:
- Decreased sound stimulus observed in 2000- and 7000-ppm animals (both sexes in both generations) was considered to be the most sensitive indicator of parental toxicity. This effect was an expected outcome of overexposure. Additional parental effects include decreased mean body weight and mean body weight gain in 7000 -ppm P and F1 rats. Mean pup weight was statistically significantly reduced from postpartum day 7 throughout the remainder of the 25-day lactation period for 7000-ppm F1 and F2 litters. There were no adverse treatment regarding reproductive function.
- Executive summary:
Executive summary:
In a 2-generation inhalation reproduction study, cyclohexane was administered to 30 Crl:CD BR rats /sex/dose at dose levels of 0, 500, 2000, or 7000 ppm. Whole body exposures were conducted, and animals were exposed 6 hours/day, 5 days/week including holidays. For both generations, animals were exposed prior to mating, and pregnant females were exposed daily during gestation days 0 through 20; exposure cessed from gestation day 21 until lactation day 4. Exposure resumed on lactation day 5 until litters were weaned. Males continued to be exposed 5 days/week until sacrificed. Neonates were not exposed during lactation. Pups were culled on lactation day 4; however, there were no additional details provided on the culling procedure. ECD 416. This study will influence the DNEL.
Decreased sound stimulus observed in 2000- and 7000 -ppm animals (both sexes in both generations) was considered to be the most sensitive indicator of parental toxicity. This effect was an expected outcome of overexposure. Additional parental effects include decreased mean body weight and mean body weight gain in 7000 -ppm P and F1 rats. Decreased male body weights observed at 7000 ppm were considered to be an artefact of body-weight deficits established as pups. Although not established by the study authors, the parental systemic LOAEC appears to be 2000 ppm (6880 mg/m3) in males and females, based on decreased sound stimulus. The parental systemic NOAEC appears to be 500 ppm (1720 mg/m3) in males and females.
Mean pup weight was statistically significantly reduced from postpartum day 7 throughout the remainder of the 25-day lactation period for 7000-ppm F1 and F2 litters. The offspring LOAEC is 7000 ppm (24,080 mg/m3) based on decreased litter weights. The offspring NOAEC is 2000 ppm (6880 mg/m3).
There were no adverse treatment regarding reproductive function. Consequently, the reproductive NOAEC appears to be 7000 ppm (24,080 mg/m3).
This study received a Klimisch score of 1 and is classified as reliable without restriction because this study was performed in accordance with GLP and appeared to closely followed OECD 416. This study will influence the DNEL.
- Endpoint:
- two-generation reproductive toxicity
- Remarks:
- based on test type
- Type of information:
- read-across from supporting substance (structural analogue or surrogate)
- Adequacy of study:
- key study
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- other: According to or similar to OECD Testing Guideline 416 (Two-Generation Reproduction Toxicity Study). GLP.
- Justification for type of information:
- A discussion and report on the read across strategy is given as an attachment in IUCLID Section 13.
- Reason / purpose for cross-reference:
- read-across: supporting information
- Qualifier:
- equivalent or similar to guideline
- Guideline:
- OECD Guideline 416 (Two-Generation Reproduction Toxicity Study)
- GLP compliance:
- yes
- Limit test:
- no
- Species:
- rat
- Strain:
- Sprague-Dawley
- Sex:
- male/female
- Route of administration:
- inhalation: vapour
- Type of inhalation exposure (if applicable):
- whole body
- Vehicle:
- unchanged (no vehicle)
- Details on exposure:
- The experimental and control rats were placed (whole body) into appropriate inhalation chambers which were operated under dynamic conditions. The rats were exposed six hours per day, seven days/week, and remained in the chambers as the test atmosphere cleared for a minimum of the theoretical equilibration time (T99 = 23 minutes). The test material was administered fully vaporized in the breathing air of the animals. The test atmosphere composition and concentration remained constant at each exposure level over the daily six-hour period. All P1 and P2 adult male rats were exposed for at least 10 weeks prior to mating, through the mating period for F1 and F2 litters and until their sacrifice. All P1 and P2 adult female rats were exposed for at least 10 weeks prior to mating, during the mating period, and through Gestation Day 20. Exposure was resumed on postpartum Day 5, and continued until the female rats were sacrificed. Female rats that did not deliver or were not confirmed mated were exposed until their sacrifice.
- Analytical verification of doses or concentrations:
- yes
- Details on analytical verification of doses or concentrations:
- The overall mean chamber concentrations of VRU gasoline during the exposure periods throughout the study were 0 +/- 0, 5076 +/- 146, 10247 +/- 249, and 20241 +/- 373 mg/m3. The concentrations of the test atmosphere were determined approximately hourly during each exposure by on-line gas chromatography (Hewlett Packard GC 6890).
- Duration of treatment / exposure:
- 6 hours/day
- Frequency of treatment:
- 7 days/ week
- Remarks:
- Doses / Concentrations:
0, 5000, 10000, 20000 mg/m3
Basis:
nominal conc. - No. of animals per sex per dose:
- 30 males and 30 females per dose
- Control animals:
- yes, sham-exposed
- Details on study design:
- - Dose selection rationale: The highest concentration was chosen to correspond to approximately half of the lower explosive limit, considered the highest level safe to test.
- Positive control:
- None tested.
- Parental animals: Observations and examinations:
- All test animals were checked twice daily for viability, and clinical observations were carried out on a daily basis. Body weights and food consumption were measured weekly until confirmation of mating and then on GD 0, 7, 14, and 21 and PPD 0, 4, 7, 14, and 21 for P1 and P2, and on PPD 28 for P1 only.
- Oestrous cyclicity (parental animals):
- There was also an ovarian examination that included confirmation of growing follicles and corpora lutea and quantification of primordial oocytes. Five sections per ovary for all ovaries from the high-dose and control group animals were evaluated under light microscopy. As there were no differences between the high dose (20000 mg/m3) and control, tissues from animals in the intermediate groups were not examined. Reproductive parameters evaluated included: male and female fertility indices, male mating index, female fecundity and gestational indices, mean litter size, mean days of gestation, female estrous cycle length, and number of females cycling normally.
- Sperm parameters (parental animals):
- Samples of sperm from the left distal cauda epididymis were collected from all males at terminal sacrifice for evaluation of sperm parameters. These included assessments of total caudal epididymal sperm number, percent progressively motile sperm, and homogenization resistant spermatid count, percent morphologically normal sperm, and percent of sperm with an identified abnormality. To assess progressively motile sperm, the left cauda was sliced and suspended in a petri dish in 10 ml Dulbecco’s phosphate- buffered saline (PBS) with 1.0% bovine serum albumen at 37°C for 15 min. The resulting suspension was swirled gently, and a 1.0-ml sample was added to 9 ml warmed media. A sample was taken up in a cannula by capillary action and assessed by the Hamilton Thorne Research IVOS (Integrated Visual Optical System) from the suspension in the petri dish. Total cauda epididymal sperm counts were also assessed by the IVOS. For evaluation of homogenization-resistant spermatid counts, the testes were placed in 20—30 ml SMT solution (100 mg merthiolate and 0.5 ml Triton X-100 in 1000 ml 0.9% saline), homogenized for 2 min, and allowed to settle. The volume was brought up to 50 ml SMT solution, homogenized again, and allowed to settle for 1 min. An aliquot of the homogenate was then stained for DNA, and quantified using the IVOS system.
Sperm morphology was determined manually under phase contrast microscopy. Ten males were randomly selected from each treatment group. Samples were collected from the left cauda of each animal, and four slides were prepared from each sample. Two of the slides were stained with 1.0% Eosin Y and two with Papanicolaou stain. The Eosin Y slides were evaluated, and the Papanicolaou stained slides were retained for future evaluation. Five hundred sperm from each animal were evaluated. - Litter observations:
- All pups were counted and examined externally on a daily basis until PND 21, and weighed on PND 0, 4, 7, 14, and 21. F1 pups were also examined daily from PND 21 to 28 and weighed on PND 28 and 35. All surviving F1 and F2 pups were evaluated for developmental landmarks, including pinna detachment, hair growth, incisor eruption, eye opening, and the development of the surface righting reflex.
- Postmortem examinations (parental animals):
- For the adult animals, organs weighed included liver, adrenals, brain, uterus, testes, right epididymis, and left caudal epididymis, seminal vesicles (with coagulating glands and fluid), kidneys, spleen, thymus, ovaries, prostate, and lungs. The list of tissues taken for microscopic examination included vagina, uterus, ovaries, right epididymis, seminal vesicles, prostate, oviducts, thymus, trachea, nasal turbinates, spleen, coagulating gland, pituitary, kidneys, liver, mammary gland (females only), testes, brain, tissue masses/gross lesions, larynx, lungs, and adrenals. The tissues from the high-dose (20000 mg/m3) and control animals were evaluated. Kidney sections from all exposure groups were examined.
- Postmortem examinations (offspring):
- All animals dying spontaneously or sacrificed in a moribund condition were necropsied. Culled pups were examined externally but were not necropsied unless there was external evidence of abnormalities. Randomly selected pups were necropsied, and the following organs were weighed: ovaries, liver, adrenals, thymus, testes, kidneys, spleen, and brain. Additionally, the following tissues were taken for microscopic examination: vagina, ovaries, epididymides, prostate, pituitary, spleen, kidneys, thymus, uterus (with cervix), testes, seminal vesicles, coagulating gland, adrenals, liver, brain, and any gross lesions. The majority of the tissues were fixed in 10% neutral buffered formalin, routinely processed, embedded in paraffin, and stained with hematoxylin and eosin (H&E). The right testes were fixed in Bouin’s fixative and stained with the periodic acid-Schiff reaction (PAS). Sections of the kidneys of male rats from all groups of the P1 and P2 generations were stained by Mallory’s Heidenhain technique for the identification of hyaline droplet accumulation.
- Statistics:
- See "Other Information" for additional details.
Continuous data were first evaluated by Bartlett’s test of homogeneity of variance to determine whether the groups had equivalent variances at the 1% level of significance. If the variances were equivalent, the hypothesis that there was no difference in response between groups was tested by standard one-way analysis of variance (ANOVA). If the ANOVA was significant, Dunnett’s test was used to determine which treated groups differed from control. A linear regression to test for a dose-response was also carried out and tested for lack of fit. If the variances were not equivalent, a Kruskal-Wallis (non-parametric) test was used to determine whether the effects were equivalent. If there was a difference, Dunn’s Rank Sum comparison was used to determine which groups differed from control. Jonckheere’s test for ordered response was also performed. - Reproductive indices:
- Reproductive parameters evaluated included: male and female fertility indices, male mating index, female fecundity and gestational indices, mean litter size, mean days of gestation, female estrous cycle length, and number of females cycling normally. Live birth index, survival indices (PPD 1, 4, 7, 14, 21), viability index at weaning, mean live and dead offspring on Day 0, sex ratio at Day 0, offspring inlife observations, offspring body weight, and offspring gross postmortem findings were also assessed.
- Offspring viability indices:
- All pups were counted and examined externally on a daily basis until PND 21, and weighed on PND 0, 4, 7, 14, and 21. F1 pups were also examined daily from PND 21 to 28 and weighed on PND 28 and 35. All surviving F1 and F2 pups were evaluated for developmental landmarks, including pinna detachment, hair growth, incisor eruption, eye opening, and the development of the surface righting reflex. All surviving F1 female offspring were monitored for vaginal opening beginning on PND 29, and F1 male offspring were monitored for preputial separation beginning on PND 35.
- Clinical signs:
- no effects observed
- Body weight and weight changes:
- no effects observed
- Food consumption and compound intake (if feeding study):
- no effects observed
- Organ weight findings including organ / body weight ratios:
- no effects observed
- Histopathological findings: non-neoplastic:
- no effects observed
- Other effects:
- no effects observed
- Reproductive function: oestrous cycle:
- no effects observed
- Reproductive function: sperm measures:
- no effects observed
- Reproductive performance:
- no effects observed
- Key result
- Dose descriptor:
- NOAEC
- Remarks:
- reproductive toxicity
- Effect level:
- >= 20 000 mg/m³ air (nominal)
- Sex:
- male/female
- Basis for effect level:
- other: No adverse effects on reproductive parameters.
- Clinical signs:
- no effects observed
- Mortality / viability:
- no mortality observed
- Body weight and weight changes:
- no effects observed
- Sexual maturation:
- no effects observed
- Organ weight findings including organ / body weight ratios:
- no effects observed
- Gross pathological findings:
- no effects observed
- Histopathological findings:
- no effects observed
- Key result
- Dose descriptor:
- NOAEC
- Remarks:
- reproductive toxicity
- Generation:
- F1
- Effect level:
- >= 20 000 mg/m³ air (nominal)
- Sex:
- male/female
- Basis for effect level:
- other: No adverse effects on reproductive parameters.
- Key result
- Reproductive effects observed:
- no
- Conclusions:
- Based on the data reported, the reproductive NOAEC as defined by this study is >20000 mg/m3, the highest dose tested and approximately half of the lower explosive limit.
- Executive summary:
The two generational reproductive study was conducted at levels up to 20000 mg/m3, approximately half of the lower explosive limit, and the highest level considered safe for use in the laboratory. VRU gasoline did not produce any pathologic changes in reproductive organs. Additionally, there were no differences in mating, fertility, live births, birth weights, and survival or weight gain through weaning. Finally, there were no differences in sperm count, sperm quality, estrous cycling, quantification of primordial oocytes, or developmental landmarks, other than a delay in hair growth in some treated offspring.
There were weight and histopathological changes noted in the kidneys of the high-dose (20000 mg/m3) exposed males from the second parental generation, as well as microscopic evidence of hyaline droplets in the male rat kidneys from both generations. However, as the weight difference was slight (<6%), found only in one generation, and seen only in the males, it was not considered to be adverse. The microscopic changes were consistent with an alpha-2u globulin-mediated process that is unique to male rats and not toxicologically relevant to humans.
Based on the data reported, the reproductive NOAEC as defined by this study is >20000 mg/m3.
- Endpoint:
- extended one-generation reproductive toxicity - with developmental neurotoxicity (Cohorts 1A, 1B without extension, 2A and 2B)
- Data waiving:
- study scientifically not necessary / other information available
- Justification for data waiving:
- the study does not need to be conducted because a two- (or multi-) generation reproductive toxicity study is available
- Species:
- rat
Referenceopen allclose all
Post-dosing salivation was noted in the dosed groups and was observed only immediately after treatment. This is likely due to the irritating effects of the test article rather than an indication of toxicity. Other clinical signs found in the treatment groups, such as loss of fur, scratch wounds, and scabs, were not considered to be related to treatment of 2-methylbutane since they occurred at a very low incidence and did not exhibit a dose-response relationship.
BODY WEIGHT AND FOOD CONSUMPTION (PARENTAL ANIMALS)
A statistical significant suppression of body weight gain observed in the male 1000 mg/kg group which was attributed to the administration to the test chemical, which is consistent with the slightly decreased food consumption observed in the group during the study period. this change did not exhibit a dose-response relationship and was not accompanied by changes in body weight; therefore, it was not considered to be a treatment related effect.
REPRODUCTIVE PERFORMANCE (PARENTAL ANIMALS)
Treatment with 2-methylbutane did not affect any of the fertility and reproductive performance parameters evaluated.
ORGAN WEIGHTS (PARENTAL ANIMALS)
In males, absolute heart weight in the 1000 mg/kg group was significantly decreased in comparison to that of the control group. The relative weight of adrenal glands was significantly increased without a dose-response relationship in comparison to the control group. Relative weights of brain, liver, kidneys, and testes in the 1000 mg/kg group were also significantly increased in comparison to the control group.
2-methylbutane to rats caused a statistically significant suppression in body weight gain in the male 1000 mg/
kg group. The suppressed body weight affected the weights of the heart, brain, liver, and testes in the high dose group. However, the weight changes in these organs were within the limits of normal biological variations and there were no corresponding pathological changes. Previous studies have demonstrated that the function and weight of adrenal glands are adversely affected by various stressful factors. Therefore, these changes are not considered toxicologically significant.
GROSS PATHOLOGY (PARENTAL ANIMALS)
No abnormal gross pathological findings were observed
HISTOPATHOLOGY (PARENTAL ANIMALS)
Renal tubular degeneration/regeneration was observed in 13, 10, 11, and 18 males at 0, 100, 300, and 1000 mg/kg, respectively. These effects were the only treatment related finding and are related to the male rat specific a2u-globulin nephropathy. This finding is not relevant to human health.
At 2000 and 700 ppm, animals exhibited treatment-related transient diminished or absent response to sound stimulus during each exposure session, being at exposures 16 and 15, respectively. Males (P and F1) treated with 2000 and 7000 ppm and 7000-ppm females from both generations were showed significantly increased incidence fur staining and wetness presumably related to salivation. These clinical signs were not considered treatment-related.
BODY WEIGHT AND FOOD CONSUMPTION (PARENTAL ANIMALS)
P males showed no treatment-related body weight changes in any dose group. High-dose F1 males were generally statistically significantly reduced throughout the study. This decrease was considered by the result of pre-existing body weight differences established as pups during the lactation period.
High-dose P females showed a significant decrease in mean body weight and body weight gain by the end of the premating period. High-dose females showed lower body weight and body weight gain, but to a lesser magnitude. Food consumption was similar between control and treated rats for both generations; however, food efficiency was reduced for both generations at the high dose.
During gestation, mean body weight and body weight gain was not affected by treatment. Food consumption for 7000-ppm P females was less than control females during gestation days 0 through 7; no differences were observed for F1 females. During lactation, 2000- and 7000-ppm P females were greater than the control group; these differences were not observed in the F1 generation. There were no differences in food consumption during lactation for either generation; however, 7000-ppm females had better food efficiency than the control group, which was attributable to the difference in body weight gains between the two groups.
REPRODUCTIVE PERFORMANCE (PARENTAL ANIMALS)
There were no statistically significant treatment-related differences in mating, fertility, or gestation indices, implantation efficiency or gestation length in either generations.
GROSS PATHOLOGY (PARENTAL ANIMALS)
There were no treatment-related effects with regard to gross observations in rats of any generation.
HISTOPATHOLOGY (PARENTAL ANIMALS)
There were no treatment-related effects with regard to microscopic findings in rats of any generation. An increased incidence of prostatic inflammation in high-dose males in both generations was observed. The severity of this lesion was only in four P and F1 control animals and four high-dose males, and was considered incidental due to its lack of severity and common occurrence in this species.
There was a significant decrease in the mean percent born alive in high-dose F1 pups; however, this decrease was considered incidental since it was not observed in the F2 pups. There were no other changes observed in viability for F1 or F2 pups at any dose level.
CLINICAL SIGNS (OFFSPRING)
There were no treatment-related effects observed for either F1 and F2 pups.
BODY WEIGHT (OFFSPRING)
Mean pup weight was statistically significantly reduced from postpartum day 7 throughout the remainder of the 25-day lactation period for 7000-ppm F1 and F2 litters (see Table 1 below).
Table 1: Mean Pup Weights (g)
Concentration (ppm) |
0 |
500 |
2000 |
7000 |
0 |
500 |
2000 |
7000 |
F1 generation |
F2 generation |
|||||||
Day 0 |
6.7 |
6.7 |
6.7 |
6.6 |
6.4 |
6.6 |
6.3 |
6.3 |
Day 4 preculling |
11.0 |
11.0 |
11.2 |
10.6 |
10.8 |
10.8 |
10.1 |
10.2 |
Day 4 postculling |
11.0 |
11.0 |
11.3 |
10.6 |
10.9 |
10.8 |
10.1 |
10.1 |
Day 7 |
16.2 |
16.2 |
16.3 |
15.1* |
16.3 |
16.0 |
15.3 |
14.3* |
Day 14 |
30.0 |
29.9 |
29.7 |
26.5* |
31.0 |
30.2 |
28.9 |
26.2* |
Day 21 |
48.5 |
48.5 |
48.3 |
43.1* |
50.0 |
48.3 |
46.4 |
42.8* |
Day 25 |
67.5 |
67.8 |
68.3 |
62.2* |
69.3 |
67.1 |
65.6 |
61.3* |
* Statistically significant difference from control (p ≤0.05) by Analysis of Covariance with litter and sex ration as covariates.
There were no significant differences in absolute organ weights in either males or females from the P1 generation. Among the second parental (P2) generation animals, there were some statistically significant increases in absolute organ weights, including liver, kidney, and testis in the males and lungs in the females, but none of the organ weight differences between the high exposure group and control animals were significantly different. In the absence of clear dose-response relationships, the toxicological significance of these data is unclear. When the data were expressed on an organ to body weight basis, the only significant differences were an elevation of relative kidney weights in the males from the low exposure group of the first parental generation (in the absence of a dose-response this observation was assumed not to be treatment-related) and an elevation of relative kidney weights from the high-exposure group males from the second parental generation. The latter observation may have been treatment-related, but, as described below, was not clinically important.
HISTOPATHOLOGY
There were no compound-related microscopic changes in any of the reproductive tissues or in the tissues of the upper or lower respiratory tract from any of the P1 or P2 generation rats exposed to 20000 mg/m3 VRU gasoline. The only treatment-related histologic changes were observed in the kidneys of male rats of both generations and consisted of exposure-related increases in the amount and size of hyaline droplets. The hyaline droplets in several of the exposed rats were larger and stained more densely with the Heidenhain stain. The enlargement of these droplets was due to coalescing of clusters of hyaline droplets and the accumulation of irregular to somewhat angular-shaped hyaline droplets. The only other treatment related effect in the kidney was seen in three male rats of the high-dosage groups from both the P1 and P2 generations and consisted of granular casts in medullary tubules. These granular casts often accompany increased hyaline droplet accumulations and are consistent with the “hydrocarbon/hyaline droplet nephropathy,” which is unique to male rats, reflecting the exacerbated accumulation of alpha-2-u-globulin in the kidney. This finding is not relevant to human risk assessment.
Reproductive parameters
In the first parental generation, there were no differences in mating index, fecundity, pregnancy, or length of gestation. The results in the second parental generation were similar.
Sperm parameters and Estrous cycle
The sperm analysis was carried out on both P and on P2(F1) males. There were no significant effects on sperm count, progressive motility, or gross appearance in either group. There were no statistically significant differences in mean estrous cycle length, quantification of primordial oocytes, or percent females with abnormal cycles between treated and control females in the P1 or P2 generations.
As noted for the parental animals, the only treatment-related histologic changes were observed in the kidneys of F1 male rats consisted of exposure-related increases in the amount and size of hyaline droplets, granular casts in medullary tubules of the kidney. These findings are consistent with “hydrocarbon/hyaline droplet nephropathy,” which is unique to male rats, reflecting the exacerbated accumulation of alpha-2-u-globulin in the kidney. This finding is not relevant to human risk assessment.
Reproductive parameters
Among the offspring of the first parental generations, there were no differences in mean litter size, fraction of live births, or sex ratio. The results in the second parental generation were similar. Among the offspring, there were no differences in survival of offspring through weaning in the first generation, and, in the second generation, early survival was slightly higher among the offspring from exposed dams than those from controls. There were no differences in the weight of the offspring through weaning in either generation. Finally, there were no unusual postmortem observations that were considered to be treatment related.
Developmental landmarks
There were no significant differences in incisor eruption, pinna detachment, or surface righting reflex in the F1 or F2 offspring, or vaginal patency or preputial separation in the F1 offspring. There was a significant delay in hair growth in the males but not the females of the F1 pups. Eye opening was advanced by approximately one-half a day for the high-dose males, and hair growth was delayed in the low-dose females of the F2 offspring.
Effect on fertility: via oral route
- Endpoint conclusion:
- no adverse effect observed
- Dose descriptor:
- NOAEL
- 1 000 mg/kg bw/day
- Study duration:
- subacute
- Species:
- rat
- Quality of whole database:
- One key read across study from a structural analogue available for assessment.
Effect on fertility: via inhalation route
- Endpoint conclusion:
- no adverse effect observed
- Dose descriptor:
- NOAEC
- 20 000 mg/m³
- Study duration:
- subacute
- Species:
- rat
- Quality of whole database:
- Two key read across studies from structural analogues available for assessment.
Effect on fertility: via dermal route
- Endpoint conclusion:
- no study available
Additional information
There is no reproductive toxicity data available for Normal-Pentane; however, data is available for structural analogues, 2-methylbutane, cyclohexane, and VRU gasoline (~52% C4 and ~37% C5). Cyclohexane is oxidized to cyclohexanol, and excretion and conjugation of cyclohexanol is identical to n-pentane. Therefore, data on the toxicokinetics and reproductive toxicity of cyclohexane can be used to fill data gaps for n-pentane when relevant data for these chemicals are missing.This data is read across to based on analogue read across and a discussion and report on the read across strategy is provided as an attachment in IUCLID Section 13.
Oral
2-methylbutane
A one-generation reproductive toxicity study (OECD TG 415) using Sprague-Dawley rats was conducted using the test material 2-methylbutane (Yu, 2011). Male and female rats (24 per treatment group) were treated by oral gavage with 2-methylbutane at 0, 100, 300, and 1000 mg/kg/day. Males were dosed for 10 weeks prior to mating and during mating and females were dosed from 2 weeks before mating to day 21 of lactation. At 1000 mg/kg/day, a2u-globulin nephropathy observed in male rats. This effect is not relevant to human health. While several organs had altered weights, they changes were within the normal biological range and were considered to be not toxicologically relevant. No treatment-related effects of 2-methylbutane were found in relation to the reproductive capacity of parental animals or the pre- and post-natal development of the F1 generation. Therefore, the reproductive and developmental NOAEL >= 1000 mg/kg/day, the highest dose tested. The systemic NOAEL for male rats the NOAEL = 300 mg/kg/day based on the a2u-globulin nephropathy observed that is not relevant to human health. The systemic NOAEL for female rats was NOAEL >= 1000 mg/kg/day, the highest dose tested.
Inhalation
Cyclohexane
In a two-generation inhalation reproduction study (Kreckmann et al., 2000), cyclohexane was administered to 30 Crl: CD BR rats per sex per dose per group at dose levels of 0, 500, 2000, or 7000 ppm. Whole body exposures were conducted, and animals were exposed 6 hours/day, 5 days/week including holidays. For both generations, animals were exposed prior to mating, and pregnant females were exposed daily during gestation days 0 through 20; exposure ceased from gestation day 21 until lactation day 4. Exposure resumed on lactation day 5 until litters were weaned. Males continued to be exposed 5 days/week until sacrificed. Neonates were not exposed during lactation. Pups were culled on lactation day 4; however, there were no additional details provided on the culling procedure OECD 416. Decreased sound stimulus observed in 2000- and 7000-ppm animals (both sexes in both generations) was considered to be the most sensitive indicator of parental toxicity. This effect was an expected outcome of overexposure. Additional parental effects include decreased mean body weight and mean body weight gain in 7000 -ppm P and F1 rats. Decreased male body weights observed at 7000 ppm were considered to be an artefact of body-weight deficits established as pups. Although not established by the study authors, the parental systemic LOAEC appears to be 2000 ppm (6880 mg/m3) in males and females, based on decreased sound stimulus. The parental systemic NOAEC appears to be 500ppm (1720 mg/m3) in males and females. Mean pup weight was statistically significantly reduced from postpartum day 7 throughout the remainder of the 25-day lactation period for 7000-ppm F1 and F2 litters. The offspring LOAEC is 7000 ppm (24,080 mg/m3) based on decreased litter weights. The offspring NOAEC is 2000 ppm (6880 mg/m3). There were no adverse treatment effects related to reproductive function. Consequently, the parental and reproductive NOAEC appears to be 7000 ppm (24,080 mg/m3).
VRU gasoline
The two generational reproductive study (McKee, 2000) was conducted at levels up to 20000 mg/m3, approximately half of the lower explosive limit, and the highest level considered safe for use in the laboratory. VRU gasoline did not produce any pathologic changes in reproductive organs. Additionally, there were no differences in mating, fertility, live births, birth weights, and survival or weight gain through weaning. Finally, there were no differences in sperm count, sperm quality, estrous cycling, quantification of primordial oocytes, or developmental landmarks, other than a delay in hair growth in some treated offspring.
Effects on developmental toxicity
Description of key information
Developmental toxicity data is available for Normal-Pentane. Additionally, data is available for structural analogue, cyclohexane. This data is read across to Normal-Pentane based on analogue read across and a discussion and report on the read across strategy is provided as an attachment in IUCLID Section 13.
Normal-Pentane
Prenatal Developmental Toxicity Study (OECD TG 414) (rat) - Oral Administration - developmental NOAEL = 1000 mg/kg/day
Cyclohexane
Prenatal Developmental Toxicity Study (OECD TG 414) (rat) - Inhalation Administration - developmental NOAEC = 7000 ppm (24080 mg/m3).
Prenatal Developmental Toxicity Study (OECD TG 414) (rabbit) - Inhalation Administration - developmental NOAEC = 7000 ppm (24080 mg/m3).
Link to relevant study records
- Endpoint:
- developmental toxicity
- Type of information:
- read-across from supporting substance (structural analogue or surrogate)
- Adequacy of study:
- key study
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- other: no restrictions, fully adequate for assessment
- Justification for type of information:
- A discussion and report on the read across strategy is given as an attachment in IUCLID Section 13.
- Reason / purpose for cross-reference:
- read-across: supporting information
- Qualifier:
- equivalent or similar to guideline
- Guideline:
- OECD Guideline 414 (Prenatal Developmental Toxicity Study)
- Deviations:
- yes
- Remarks:
- Because the study examined the inhalation affects related to exposure of cyclohexane, test animals received whole body exposure to the cyclohexane vapour. Test animals failed to be weighed daily but rather were weighed weekly.
- GLP compliance:
- yes
- Species:
- rat
- Strain:
- other: Crl:CD BR
- Details on test animals or test system and environmental conditions:
- TEST ANIMALS
- Age at study initiation: Approximately 11 weeks
- Housing: Animals were housed individually in suspended, wire-mesh, stainless steel cages.
- Diet: Purina "Certified Rodent Checkers" was available ad libitum, except during exposures to all rats other than those in the pair-fed control group of the developmental toxicity study. Beginning with exposure, each animal in the pair-fed control group received an amount of Purina Certified Rodent Checkers approximately equal to the cumulative average amount of food consumed by the high-concentration group (7000 ppm) animals on the corresponding gestation day
- Water: tap water ad libitumexcept during exposures
ENVIRONMENTAL CONDITIONS
- Temperature: 23±2°C
- Humidity: 50±10%
- Photoperiod: 12 hrs dark / 12 hrs light - Route of administration:
- inhalation: vapour
- Type of inhalation exposure (if applicable):
- whole body
- Vehicle:
- unchanged (no vehicle)
- Details on exposure:
- GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: All exposure chambers were constructed of stainless steel and glass and had a nominal internal volume of 1.4 m3. The chamber volume was chosen so that the total body volume of the test animals did not exceed 5% of the chamber volume. A tangential feed at the chamber inlet promoted gas mixing and uniform chamber distribution of vapour.
- Atmospheres of cyclohexane were generated by metering the liquid test substance into a heated glass Instatherm flask with a Fluid Metering Inc. pump. Nitrogen, introduced into the flask, swept the cyclohexane vapour into the inhalation chamber air supply. The chamber concentration of cyclohexane was controlled by varying the amount of the metered liquid evaporated in the chamber air stream. Nitrogen and air were passed through the control chamber at approximately the same flow rates as those used in the exposure chambers.
TEST ATMOSPHERE-The atmospheric concentration of cyclohexane was determined by gas chromatography at approximately 15-minute intervals during each 6-hour exposure. Chamber-atmosphere samples were drawn by vacuum pump from representative areas of the chamber where animals were exposed and were directly injected into a Hewlett Packard model 5880 Gas Chromatograph equipped with a flame ionization. All samples were chromatographed isothermally at 70°C on an HP-20M Carbowax column. The chamber distribution of cyclohexane vapour was determined prior to animal exposures in the high-concentration exposure chamber and while the study was underway with animals in the low- and high-concentration chambers. - Analytical verification of doses or concentrations:
- yes
- Details on analytical verification of doses or concentrations:
- The atmospheric concentration of cyclohexane was determined by gas chromatography at approximately 15 minute intervals during each 6-hour exposure. The results of these determinations indicated the distribution of cyclohexane vapour was sufficiently homogeneous (less than 2% difference in chamber concentration from position to position).
- Duration of treatment / exposure:
- Assumed-pregnant rats (25/concentration level) were exposed on days 6-15 of gestation (6-15G). The day that copulation was confirmed was designated as day 0.
- Frequency of treatment:
- 5 d/wk
- Remarks:
- Doses / Concentrations:
0 (air), 500, 2000 or 7000 ppm
Basis:
nominal conc. - Remarks:
- Doses / Concentrations:
0 (air), 500, 2000 or 7000 ppm
Basis:
other: overall mean measured - No. of animals per sex per dose:
- 25 per concentration level
- Control animals:
- yes, concurrent vehicle
- Details on study design:
- A pair-fed control group was established for the 7000 ppm treatment group. Beginning with exposure, each animal in the pair-fed control group received an amount of Purina Certified Rodent Checkers approximately equal to the cumulative average amount of food consumed by the high-concentration group (7000 ppm) animals on the corresponding gestation day. Each rat received approximately 150 grams per day of Purina Certified Rat Diet HF #5325; feed was not available during exposure.
- Maternal examinations:
- During the exposure period, the animals were weighed daily and clinical signs were recorded before and after exposure. During the pre- and post- exposure periods, rats were weighed weekly and clinical signs were recorded once per day. Near the end of gestation (21 days), the maternal animals were sacrificed and the organs of the thoracic and abdominal cavities were examined grossly. The method of euthanasia was carbon dioxide asphyxiation.
- Ovaries and uterine content:
- The uterus of each animal was removed and opened. The types of implants (live and dead foetuses, and resorptions) were counted and their relative positions were recorded.
- Fetal examinations:
- The foetuses were euthanatized by decapitation or by intraperitoneal injection of sodium pentobarbital. They were weighed, sexed, and examined for external, visceral and skeletal alterations.
- Statistics:
- Sequential trend testing was applied to the data of each parameter. Adult body weight and food consumption data were analyzed by pair-wise comparisons. Parametric analyses were used to compare continuous data. Linear contrast of means from One-way Analysis of Variance (ANOVA) was the method of analysis followed by Dunnett's test. Litter-related continuous data were analyzed by a nonparametric method Jonckheere's trend test. For litter parameters, the litter mean was used as the experimental unit for statistical evaluation. Where the data were tied, exact p values were calculated using permutation methodology. Pup weight data were analyzed by an Analysis of Covariance (covariates: litter size, sex ratio) followed with a linear contrast of the least square means. Discrete data were evaluated by the Cochran-Armitage test for trend. Microscopic observations were analyzed by the Fisher's exact test.
- Details on maternal toxic effects:
- Maternal toxic effects:yes
Details on maternal toxic effects:
There were no unscheduled deaths. Rats exposed to 2000 or 7000ppm exhibited a transient diminished or absent alerting response during each exposure session; this effect was not seen in rats exposed to 500ppm. Overall mean body weight gain for the exposure period (days 6-16) was statistically significantly reduced for rats exposed to 7000 ppm (69% of control) and mean daily food consumption was 89% of control. Mean body weight gain for the exposure and post-exposure period (Days 6-21) calculated using the final body weight minus the gravid uterine weight) was also statistically significantly reduced (75% of control). There was judged to be no effect of exposure to 2000 or 500ppm on maternal bodyweight.
A similar reduction in weight gain was seen in the pair-fed animals. There were no post-mortem findings that were considered indicative of a treatment-related effect - Key result
- Dose descriptor:
- NOAEC
- Effect level:
- 500 - 2 000 ppm
- Basis for effect level:
- other: maternal toxicity
- Details on embryotoxic / teratogenic effects:
- Details on embryotoxic / teratogenic effects:
There were no treatment-related differences in pregancy rate, early delivery rate, abortion rate, total resoption rate, mean number of implantations per litter, the mean number of live foetuses per litter or sex ratio. There were no dead foetuses, nor was there any difference in the incidence of early, late or total resorptions. Foetal weight was unaffected by treatment. There were no effects on the incidence of foetal malformations or variations. - Key result
- Dose descriptor:
- NOAEC
- Effect level:
- 7 000 ppm
- Basis for effect level:
- other: teratogenicity
- Abnormalities:
- not specified
- Key result
- Developmental effects observed:
- no
- Conclusions:
- Cyclohexane was not a developmental toxin in female rats exposed during pregnancy. The foetal NOAEC was 7000 ppm, and the maternal NOAEC was 500 ppm (based upon transient sedation) or 2000 ppm (based upon significant reductions in absolute and adjusted body weight gain).
- Executive summary:
The developmental toxicity of cyclohexane was assessed in Crl:CD BR rats. The animals were exposed whole-body to nominal atmospheric concentrations of 0, 500, 2000, or 7000 ppm cyclohexane vapour. For rats in the 7000 ppm group, statistically significant reductions were observed in overall and adjusted maternal body weight gain while a transient diminished or absent response to a sound stimulus was apparent at 2000 ppm. Therefore the maternal no-observed-adverse-effect concentration (NOAEC) was 500 ppm (1,720 mg/m3) (based upon transient sedation) or 2000 ppm (6,880 mg/m3) (based upon significant reductions in overall and adjusted body weight gain). No compound-related evidence of developmental toxicity was observed at any test concentration, equivalent to a NOAEC of 7000 ppm (24,080 mg/m3).
- Endpoint:
- developmental toxicity
- Type of information:
- read-across from supporting substance (structural analogue or surrogate)
- Adequacy of study:
- key study
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- other: no restrictions, fully adequate for assessment
- Justification for type of information:
- A discussion and report on the read across strategy is given as an attachment in IUCLID Section 13.
- Reason / purpose for cross-reference:
- read-across: supporting information
- Qualifier:
- equivalent or similar to guideline
- Guideline:
- OECD Guideline 414 (Prenatal Developmental Toxicity Study)
- Deviations:
- yes
- Remarks:
- Because the study examined the inhalation affects related to exposure of cyclohexane, test animals received whole body exposure to the cyclohexane vapour. Test animals failed to be weighed daily but rather were weighed weekly.
- GLP compliance:
- yes
- Species:
- rabbit
- Strain:
- other: Hra:(NZW)SPF
- Details on test animals or test system and environmental conditions:
- TEST ANIMALS
- Age at study initiation: Approximately 6 months
- Housing: Animals were housed individually in suspended, wire-mesh, stainless steel cages.
- Diet: Approximately 150 g/day of Purina Certified Rabbit Diet HF #5325 except during exposure.
- Water: tap water ad libitumexcept during exposure.
ENVIRONMENTAL CONDITIONS
- Temperature: 20+/- 1°C
- Humidity: 50+/- 10%
- Photoperiod: 12 hrs dark / 12 hrs light - Route of administration:
- inhalation: vapour
- Type of inhalation exposure (if applicable):
- whole body
- Vehicle:
- unchanged (no vehicle)
- Details on exposure:
- GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: All exposure chambers were constructed of stainless steel and glass and had a nominal internal volume of 1.4 m3. The chamber volume was chosen so that the total body volume of the test animals did not exceed 5% of the chamber volume. A tangential feed at the chamber inlet promoted gas mixing and uniform chamber distribution of vapour
- Atmospheres of cyclohexane were generated by metering the liquid test substance into a heated glass Instatherm flask with a Fluid Metering Inc. pump. Nitrogen, introduced into the flask, swept the cyclohexane vapour into the inhalation chamber air supply. The chamber concentration of cyclohexane was controlled by varying the amount of the metered liquid evaporated in the chamber air stream. Nitrogen and air were passed through the control chamber at approximately the same flow rates as those used in the exposure chambers.
TEST ATMOSPHERE-The atmospheric concentration of cyclohexane was determined by gas chromatography at approximately 15-minute intervals during each 6-hour exposure.
Chamber-atmosphere samples were drawn by vacuum pump from representative areas of the chamber where animals were exposed and were directly injected into a Hewlett Packard model 5880 Gas Chromatograph equipped with a flame ionization. All samples were chromatographed isothermally at 70°C on an HP-20M Carbowax column. The chamber distribution of cyclohexane vapour was determined prior to animal exposures in the high-concentration exposure chamber and while the study was underway with animals in the low- and high-concentration chambers. - Analytical verification of doses or concentrations:
- yes
- Details on analytical verification of doses or concentrations:
- The atmospheric concentration of cyclohexane was determined by gas chromatography at approximately 15 minute intervals during each 6-hour exposure. The results of these determinations indicated the distribution of cyclohexane vapour was sufficiently homogeneous (less than 2% difference in chamber concentration from position to position)
- Duration of treatment / exposure:
- Assumed-pregnant rabbits were exposed on days 6-18 of gestation (6-18G). The day that copulation was confirmed was designated as day 0.
- Frequency of treatment:
- daily
- Remarks:
- Doses / Concentrations:
0 (air), 500, 2000 or 7000 ppm
Basis:
nominal conc. - Remarks:
- Doses / Concentrations:
0 (air), 500, 2000 or 7000 ppm
Basis:
other: overall mean measured - No. of animals per sex per dose:
- 20 per concentration level
- Control animals:
- yes, concurrent vehicle
- Maternal examinations:
- During the exposure period, the animals were weighed daily and clinical signs were recorded before and after exposure. During the pre- and post- exposure periods, rabbits were weighed twice weekly and clinical signs were recorded once per day. Near the end of gestation (29 days), the maternal animals were euthanized and the organs of the thoracic and abdominal cavities were examined grossly. The method of euthanasia was by intravenous injection of sodium pentobarbital.
- Ovaries and uterine content:
- The uterus of each animal was removed and opened. The types of implants (live and dead foetuses, and resorptions) were counted and their relative positions were recorded.
- Fetal examinations:
- Foetuses were euthanized by an oral or intraperitoneal injection of sodium pentobarbital. They were weighed, sexed and examined for external, visceral and skeletal alterations.
- Statistics:
- Sequential trend testing was applied to the data of each parameter. Adult body weight and food consumption data were analyzed by pair-wise comparisons. Parametric analyses were used to compare continuous data. Linear contrast of means from One-way Analysis of Variance (ANOVA) was the method of analysis followed by Dunnett's test. Litter-related continuous data were analyzed by a nonparametric method Jonckheere's trend test. For litter parameters, the litter mean was used as the experimental unit for statistical evaluation. Where the data were tied, exact p values were calculated using permutation methodology. Pup weight data were analyzed by an Analysis of Covariance (covariates: litter size, sex ratio) followed with a linear contrast of the least square means. Discrete data were evaluated by the Cochran-Armitage test for trend. Microscopic observations were analyzed by the Fisher's exact test.
- Details on maternal toxic effects:
- Maternal toxic effects:no effects
Details on maternal toxic effects:
There were no treatment-related effects on maternal bodyweight or body weight gain, food consumption, clinical condition or alerting response. There were no post-mortem findings suggestive of compound-related effects. - Key result
- Dose descriptor:
- NOAEC
- Effect level:
- 7 000 ppm
- Basis for effect level:
- other: maternal toxicity
- Details on embryotoxic / teratogenic effects:
- Embryotoxic / teratogenic effects:no effects
Details on embryotoxic / teratogenic effects:
No compound-related effect on the incidence of foetal malformations or variations was observed. - Key result
- Dose descriptor:
- NOAEC
- Effect level:
- 7 000 ppm
- Basis for effect level:
- other: teratogenicity
- Abnormalities:
- not specified
- Key result
- Developmental effects observed:
- no
- Conclusions:
- Cyclohexane was not a developmental toxin in female rabbits after exposure to 7000 ppm (24,080 mg/m3) during pregnancy.
- Executive summary:
Therefore the maternal NOAEC for rabbits was 7000 ppm. No compound-related evidence of developmental toxicity was observed at any test concentration.
Therefore the developmental NOAEC for rabbits was 7000 ppm (24,080 mg/m3), the highest concentration tested and the highest concentration permissible under national fire protection association standards.
- Endpoint:
- developmental toxicity
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 1996-07-25 to 1997-04-11
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- other: This study is classified as reliable without restriction because it is was performed according to GLPs and in compliance with OECD principles 414.
- Reason / purpose for cross-reference:
- reference to same study
- Reason / purpose for cross-reference:
- reference to other study
- Qualifier:
- according to guideline
- Guideline:
- OECD Guideline 414 (Prenatal Developmental Toxicity Study)
- Deviations:
- no
- Qualifier:
- according to guideline
- Guideline:
- EU Method B.31 (Prenatal Developmental Toxicity Study)
- Deviations:
- no
- GLP compliance:
- yes
- Limit test:
- no
- Species:
- rat
- Strain:
- other: Crl:CD BR VAF/Plus
- Details on test animals or test system and environmental conditions:
- TEST ANIMALS
- Source: Charles River Laboratories, Inc., Portage, Michigan
- Age at study initiation: 14 to 16 weeks (females)
- Weight at study initiation: 243 to 316 grams (females)
- Fasting period before study: no
- Housing: individually-housed except during mating in suspended stainless-steel, wire mesh cages
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 20 days
ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 to 24
- Humidity (%): 40 to 70
- Air changes (per hr): not reported
- Photoperiod (hrs dark / hrs light): 12 hours light and 12 hours dark
- IN-LIFE DATES: From: 1996-10-07 To: 1996-11-08 - Route of administration:
- oral: gavage
- Vehicle:
- corn oil
- Details on exposure:
- PREPARATION OF DOSING SOLUTIONS: Test material formulations were prepared weekly by mixing appropriate amounts of test material with vehicle; test-material formulations were divided into individual samples for each day and stored in a refrigerator until needed.
VEHICLE
- Justification for use and choice of vehicle (if other than water): test material was soluble in carrier
- Concentration in vehicle: not reported
- Amount of vehicle (if gavage): not reported
- Lot/batch no. (if required): not reported
- Purity: not reported - Analytical verification of doses or concentrations:
- yes
- Details on analytical verification of doses or concentrations:
- Test material formulations were evaluated for stability, homogeneity, and achieved concentration. Stability and homogeneity were evaluated prior to the start of the study as part of the dose-range finding study (Study no. 157533; achieved concentration was evaluated on the first and third dosing mixture preparations. Results from the dose-range finding study indicate that the test material formulations were stable for at least 7 days at 2% and 20% w/v and homogenous (with the relative standard deviation being 1% for both sample sets). Test material formulations were found to be within 16% of the nominal concentration.
- Details on mating procedure:
- - Impregnation procedure: [artificial insemination / purchased timed pregnant / cohoused]: cohoused
- If cohoused:
- M/F ratio per cage: 1:1
- Length of cohabitation: not reported
- Females were placed in cage with male. After confirmation of mating, each female was returned to its own cage. New females were then placed in the males' cages until the required number of mated females was obtained by continuous cohabitation in consideration of lab scheduling.
- Further matings after two unsuccessful attempts: not reported
- Verification of same strain and source of both sexes: yes
- Proof of pregnancy: vaginal plug and/or sperm in vaginal rinse referred to as day 0 of pregnancy - Duration of treatment / exposure:
- gestation day (gd) 6 though 15
- Frequency of treatment:
- daily
- Duration of test:
- IN-LIFE DATES: From: 1996-10-07 To: 1996-11-08
- Remarks:
- Doses / Concentrations:
0, 100, 500, or 1000 mg/kg/day
Basis:
nominal conc.
Dosing volumes were 5 mL/kg and based on the most recent individual body weights - No. of animals per sex per dose:
- 25 dams per group
- Control animals:
- yes
- Details on study design:
- - Dose selection rationale: A dose-range finding study (Study no. 157533), in which rats were dosed with n-pentane via gavage at levels of 0, 250, 500, 750, and 1000 mg/kg. Maternal signs of toxicity were observed at 1000 mg/kg and included decreased body weight gain and food consumption over the treatment period and overall gestation interval; no other signs of toxicity were observed in dams or fetuses.
- Rationale for animal assignment (if not random): Mated females were assigned to dose groups in the order of mating. - Maternal examinations:
- CAGE SIDE OBSERVATIONS: Yes
- Time schedule: At least twice daily during treatment and at least once daily at other times during the study
DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Daily during gestation
BODY WEIGHT: Yes
- Time schedule for examinations: gd 0, 6, 9, 12, 15, 18, and 21
FOOD CONSUMPTION: Yes
- Time schedule for examinations: gd 0, 6, 9, 12, 15, 18, and 21
POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day # 21
- Organs examined: Ovaries
OTHER: Surviving dams and those that delivered prior to scheduled necropsy were scarified by carbon dioxide asphyxiation and exsanguination. Dams that delivered prior to scheduled necropsy were examined for gross lesions, and the number of implantation sites or concepti in each horn was counted. Surviving dams were necropsied, and uterine weight with ovaries attached was recorded. Uteri of all non-pregnant females were stained with ammonium sulfide to confirm pregnancy status. - Ovaries and uterine content:
- The ovaries and uterine content was examined after termination: yes
Examinations included:
- Gravid uterus weight: yes
- Number of corpora lutea: yes
- Number of implantations: yes
- Number of early resorptions: yes
- Number of late resorptions: yes
- Other: location of implantations - Fetal examinations:
- - External examinations: yes: all per litter (number of live and dead fetuses was counted; fetuses were weighed, sexed, and examined for gross malformations)
- Soft tissue examinations: yes: half per litter
- Skeletal examinations: yes: half per litter
- Head examinations: yes: half per litter - Statistics:
- Statistical methods used are presented in the table below. Statistical evaluation of equality of means was conducted by a one-way analysis of variance and a test for ordered response in dose groups. Equal variances were evaluated by Bartlett's test. Equal variances were then tested using parametric methods, otherwise nonparametric techniques were used. Percentages, where appropriate, were calculated and transformed by Cochran's transformation, followed by the arc sine transformation. Both raw and transformed percentages were tested for statistical significance. The Bartlett's test was conducted at the 1% level of significance; all other tests were conducted at the 5% and 1% level of significance.
- Indices:
- preimplantation loss
postimplantation loss - Historical control data:
- not provided
- Details on maternal toxic effects:
- Maternal toxic effects:no effects
Details on maternal toxic effects:
There were no treatment-related changes in mean body weight, body weight gain, uterine weight, corrected body weight, food consumption, or uterine implantation data. There were no treatment-related mortalities or clinical signs of toxicity. - Key result
- Dose descriptor:
- NOAEL
- Effect level:
- 1 000 mg/kg bw/day
- Basis for effect level:
- other: maternal toxicity
- Key result
- Dose descriptor:
- NOAEL
- Effect level:
- 1 000 mg/kg bw/day
- Basis for effect level:
- other: developmental toxicity
- Details on embryotoxic / teratogenic effects:
- Embryotoxic / teratogenic effects:no effects
Details on embryotoxic / teratogenic effects:
There were no treatment-related changes in growth or increased fetal death. There were no changes in total malformations or variations. - Key result
- Dose descriptor:
- NOAEL
- Effect level:
- 1 000 mg/kg bw/day
- Basis for effect level:
- other: There were no signs of developmental toxicity observed during this study.
- Abnormalities:
- not specified
- Key result
- Developmental effects observed:
- no
- Conclusions:
- There were no signs of maternal toxicity at any dose level. There were no treatment-related changes in mean body weight, body weight gain, uterine weight, corrected body weight, food consumption, or uterine implantation data. There were no treatment-related mortalities or clinical signs of toxicity. The maternal NOAEL is 1000 mg/kg/day.
There were no signs of developmental toxicity at any dose level. There were no treatment-related changes in growth or increased fetal death. There were no changes in total malformations or variations. The developmental NOAEL is 1000 mg/kg/day. - Executive summary:
In a developmental toxicity study, n-pentane was orally administered via gavage to 25 Crl:CD BR VAF rats per dose at dose levels of 0, 100, 500, or 1000 mg/kg bw/day from days 6 through 15 of gestation. There were no signs of maternal toxicity at any dose level. There were no treatment-related changes in mean body weight, body weight gain, uterine weight, corrected body weight, food consumption, or uterine implantation data. There were no treatment-related mortalities or clinical signs of toxicity. A maternotoxic dose was not used. However, the highest dose tested was 1000 mg/kg/day, and no adverse effects were observed. In general, the highest dose tested does not need to exceed 1000 mg/kg/day unless potential human exposure data indicate the need for higher doses. Therefore, the study reported a maternal NOAEL of 1000 mg/kg/day.
There were no signs of developmental toxicity at any dose level. There were no treatment-related changes in growth or increased fetal death. There were no changes in total malformations or variations. The developmental NOAEL is 1000 mg/kg/day.
This study received a Klimisch score of 1 and is classified as reliable without restriction because it was performed according to GLPs and in compliance with OECD principles 414.
Referenceopen allclose all
Mean maternal bodyweight gain (g) selected timepoints
0 |
0# |
500 |
2000 |
7000 |
|
0 to 6 |
18.7 |
22.4 |
22.3 |
24.6 |
22.1 |
6 to 16 |
64.2 |
32.1† |
60.1 |
57.2* |
44.2* |
6 to 21 (b) |
49.6 |
12.5† |
43.0* |
43.0* |
37.1* |
# - pair fed control b- ANOVA and Dunnets test
†- Significant difference from control (ANOVA and Dunnetts test); p< 0.05
* significant trend (linear contrast of means from ANOVA); p< 0.05
b- bwt gain on GD6-21 after correction for gravid uterus weight
a Data obtained from pages 28 -29 in the study report.
Cesarean section observationsa |
||||
Observation |
Dose (mg/kg bw/day) |
|||
0 |
100 |
500 |
1000 |
|
No. Animals assigned (mated) |
25 |
25 |
25 |
25 |
No. Animals pregnant |
24 |
25 |
23 |
25 |
Pregnancy rate (%) |
96 |
100 |
92 |
100 |
No. Nonpregnant |
1 |
0 |
2 |
0 |
Maternal wastage |
|
|
|
|
No. died |
0 |
0 |
0 |
0 |
No. Died pregnant |
0 |
0 |
0 |
0 |
No. Died nonpregnant |
0 |
0 |
0 |
0 |
No. Aborted |
0 |
0 |
0 |
0 |
No. Premature delivery |
1 |
1 |
0 |
0 |
Corpora lutea/Dam |
15.26±1.63 |
15.88±1.68 |
15.43±1.78 |
15.68±2.21 |
Implantations/Dam |
14.52±1.70 |
14.88±2.33 |
14.83±1.83 |
15.16±2.32 |
Total No. litters |
23 |
24 |
23 |
25 |
Total number of live fetuses Live fetuses/Dam |
310 13.48±1.78 |
346 14.42±2.26 |
318 13.83±2.19 |
359 14.36±2.29 |
Total number of dead fetuses Dead fetuses/Dam |
0 0.0±0.0 |
0 0.0±0.0 |
0 0.0±0.0 |
0 0.0±0.0 |
Total No. resorptions |
24 |
11 |
23 |
19 |
Early |
22 |
11 |
23 |
18 |
Late |
2 |
0 |
0 |
1 |
Resorptions/Dam |
1.04±0.98 |
0.46±0.59 |
1.00±0.95 |
0.76±0.83 |
Early |
0.96±0.98 |
0.46±0.59 |
1.00±0.95 |
0.72±0.84 |
Late |
0.09±0.29 |
0.0±0.0 |
0.0±0.0 |
0.04±0.20 |
Litters with total resorptions |
0 |
0 |
0 |
0 |
Mean fetal weight (g) |
0 |
0 |
0 |
0 |
Males |
5.34±0.38 |
5.45±5.40 |
5.40±0.44 |
5.42±0.46 |
Females |
5.13±0.40 |
5.12±0.37 |
5.21±0.37 |
5.14±0.55 |
Sex ratio (% male) |
49 |
49 |
47 |
50 |
Preimplantation loss (%) |
4.6±7.8 |
6.3±12.5 |
4.0±5.3 |
3.5±4.7 |
Postimplantation loss (%) |
7.1±6.5 |
3.0±3.7 |
7.0±7.0 |
5.3±5.6 |
a Data obtained from pages 32 -34 and 73 -167 in the study report.
External examinationsa |
||||
Observationsb |
Dose (mg/kg bw/day) |
|||
0 |
100 |
500 |
1000 |
|
No. Fetuses (litters) examined |
309 (23) |
346 (24) |
318 (23) |
359 (25) |
No. Fetuses (litters) affected with variations |
0 (0) |
0 (0) |
0 (0) |
0 (0) |
No. Fetuses (litters) affected with malformations |
0 (0) |
0 (0) |
1 (1) |
1 (1) |
a Data obtained from pages 35 in the study report.
b Some observations may be grouped together.
c Fetal (litter) incidence
Visceral examinationsa |
||||
Observationsb |
Dose (mg/kg bw/day) |
|||
0 |
100 |
500 |
1000 |
|
No. Fetuses (litters) examined |
156 (23) |
172 (24) |
161 (23) |
178 (25) |
No. Fetuses (litters) affected with variations |
0 (0) |
3 (2) |
2 (2) |
1 (1) |
No. Fetuses (litters) affected with malformations |
4 (3) |
7 (4) |
2 (2) |
9 (6) |
a Data obtained from page 35 in the study report.
b Some observations may be grouped together.
c Fetal (litter) incidence
Skeletal examinationsa |
||||
Observationsb |
Dose (mg/kg bw/day) |
|||
0 |
100 |
500 |
1000 |
|
No. Fetuses (litters) examined |
154 (23) |
174 (24) |
157 (23) |
181 (25) |
No. Fetuses (litters) affected with variations |
27 (14) |
31 (13) |
25 (13) |
44 (17) |
No. Fetuses (litters) affected with malformations |
0 (0) |
0 (0) |
1 (1) |
0 (0) |
aData obtained from page 35 in the study report.
bSome observations may be grouped together.
cFetal (litter) incidence
Effect on developmental toxicity: via oral route
- Endpoint conclusion:
- no adverse effect observed
- Dose descriptor:
- NOAEL
- 1 000 mg/kg bw/day
- Study duration:
- subacute
- Species:
- rat
- Quality of whole database:
- One key study available for assessment
Effect on developmental toxicity: via inhalation route
- Endpoint conclusion:
- no adverse effect observed
- Dose descriptor:
- NOAEC
- 24 080 mg/m³
- Study duration:
- subacute
- Species:
- rat
- Quality of whole database:
- Two key read across studies from a structural analogue available for assessment.
Effect on developmental toxicity: via dermal route
- Endpoint conclusion:
- no study available
Additional information
Developmental toxicity data in rodents is available for Normal-Pentane. Additionally, data in rats and rabbits is also available for structural analogue, cyclohexane. Cyclohexane is oxidized to cyclohexanol, and excretion and conjugation of cyclohexanol is identical to n-pentane and 2-methylbutane. Therefore, data on the toxicokinetics and reproductive toxicity of cyclohexane can be used to fill data gaps for n-pentane when relevant data for these chemicals are missing.This data is read across to based on analogue read across and a discussion and report on the read across strategy is provided as an attachment in IUCLID Section 13.
Oral
Normal-Pentane
n-Pentane was orally administered via gavage to 25 Crl: CD BR VAF rats per dose at dose levels of 0, 100, 500, or 1000 mg/kg bw/day from days 6 through 15 of gestation (Trimmer, 1997). There were no signs of maternal toxicity at any dose level. There were no treatment-related changes in mean body weight, body weight gain, uterine weight, corrected body weight, food consumption, or uterine implantation data. There were no treatment-related mortalities or clinical signs of toxicity. A maternotoxic dose was not used. However, the highest dose tested was 1000 mg/kg/day, the limit test dose for studies of this type, and no adverse effects were observed. In general, the highest dose tested does not need to exceed 1000 mg/kg/day unless potential human exposure data indicate the need for higher doses. Therefore, the study reported a maternal NOAEL of 1000 mg/kg/day. There were no signs of developmental toxicity at any dose level. There were no treatment-related changes in growth or increased fetal death. There were no changes in total malformations or variations. The developmental NOAEL is 1000 mg/kg/day.
Inhalation
Cyclohexane
A study was identified on the developmental toxicity of rats and rabbits for cyclohexane (Kreckmann et al., 2000). Whole body exposures were used for both rats and rabbits at concentrations of 0, 500, 2000, or 7000 ppm. For rats in the 7000 ppm group, statistically significant reductions were observed in overall and adjusted maternal body weight gain while a transient diminished or absent response to a sound stimulus was apparent at 2000 ppm. Therefore the maternal no-observed-adverse-effect concentration (NOAEC) was 500 ppm (1720 mg/m3) (based upon transient sedation) or 2000 ppm (6880 mg/m3) (based upon significant reductions in overall and adjusted body weight gain). No compound-related evidence of developmental toxicity was observed at any test concentration, equivalent to a NOAEC of 7000 ppm (24,080 mg/m3). For rabbits, no compound-related maternal effects were observed at concentration levels of 7000 ppm and below. Therefore the maternal NOAEC for rabbits was 7000 ppm. No compound-related evidence of developmental toxicity was observed at any test concentration. The developmental NOAEC for rabbits was 7000 ppm (24,080 mg/m3), the highest concentration tested and the highest concentration permissible under national fire protection association standards.
Justification for classification or non-classification
Based on the available substance specific and read across data from structural analogues, Normal-Pentane does not warrant classification as a reproductive or developmental toxicant under the new Regulation (EC) 1272/2008 on classification, labeling and packaging of substances and mixtures (CLP).
Additional information
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.
Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
