δ-valerolactone

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

1990-10-29 to 1991-01-31

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Proprietary study conducted to GLP, similar to guidelines.

Justification for data waiving:

other:

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1992

Report date:

1992

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Hexan-6-olide

EC Number:

207-938-1

EC Name:

Hexan-6-olide

Cas Number:

502-44-3

Molecular formula:

C6H10O2

IUPAC Name:

oxepan-2-one

Test material form:

other: colourless liquid with stong ketone odour

Details on test material:

- Name of test material: e-Caprolactone

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

68 male and 65 female Sprague-Dawley rats, 34 days of age were obtained from Harlan Sprague-Dawley. A pretest health screen was conducted on 5 animals per sex, randomly selected. Blood samples of 3 sacrificed rats were collected for serologic evaluation and the major organs were fixed and examined microscopically.
Rats were housed individually in wire cages. All animals were separated by sex and treatment group. Room temperature and relative humidity were monitored constantly; 19.4-23.3oC and 45-59% respectively. The photoperiod was 12 hour light/dark. Individuals were identified by tail tattoos. Body weights and physical condition of the rats were monitored for 2 weeks prior to group placement. During non-exposure periods, food and water were provided ad libitum, food and water were withheld during exposure periods. During exposured rats were individually housed and separated by sex and exposure group in wire cages.

Administration / exposure

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

other: unchanged (no vehicle)

Remarks on MMAD:

MMAD / GSD: Not relevant: exposure to vapour

Details on inhalation exposure:

e-Caprolactone was delivered as a vapour at 0, 15 or 45ppm concentrations: liquid e-Caprolactone was metered from a syringe pump and a piston pump for the 15 and 45 ppm concentrations respectively, into a glass evaporator. The syringe pump was equipped with a 10ml syringe for the 15ppm exposure, and the piston pump was equipped with a 1/8inch piston for the 45ppm exposure. The temperature in the evaporator was maintained at a level sufficient to vaporise the test substance.
The inhalation chambers were constructed from stainless steel with glass windows for animal observations. The volume of the chamber was approximately 900l, and the airflow rate was approximately 200L/min (13-14 air changes per hour). Air rate was calibrated with a trasnducer and flow computer. A pressure gauge was used to monitor airflow. Temperature and relative humidity were monitored at least 12 times per exposure. The daily mean temperature values were 23, 24 and 24oC for the 0, 15 and 45ppm concentrations respectively. The daily mean relative humidity values were 45, 51 and 47% for the 0, 15 and 45ppm concentrations respectively.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The concentrations of e-Caprolactone vapour were analysed 6 times during each daily 6 hour exposure period by sampling the chamber atmosphere using sorbent tubes. The samples were desorbed with carbon disulfide and analysed by flame ionisation gas chromatography. The control chamber was analysed once during each exposure period.

Duration of treatment / exposure:

Rats (now 49 days of age) were exposed 5 days a week for 13 weeks, in the last week the rats were exposed for 3 days. Each exposure period lasted 6 hours. An additional group underwent a post-exposure recovery period of 4 weeks.

Frequency of treatment:

Rats were exposed 5 days a week for 13 weeks, in the last week the rats were exposed for 3 days.

Doses / concentrations

Remarks:

Doses / Concentrations:
0, 15, 45 ppm
Basis:
nominal conc.

No. of animals per sex per dose:

10 rats per sex per dose plus 10 additional males and females in the 0 and 45ppm groups for 4 week recovery observations.

Control animals:

yes, concurrent no treatment

Details on study design:

Test substance concentrations were determined by the sponsor prior to study initiation.
A pretest health screen was carried out on 5 rats per sex to test for parasites, and for microscopic evaluation of the major organs. Rats were assigned to 2 test groups and 1 control group using a computer-based randomisation program. Only rats with body weights within 2 standard deviations of the mean weight were selected. There were an extra 10 males and females in each of the 0ppm and 45ppm groups; these rats were not euthanased after 13 weeks' exposure and instead were monitored for 4 weeks for recovery.

Positive control:

No positive control was used.

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS/DETAILED CLINICAL OBSERVATIONS/BODY WEIGHT:
- All rats were weighed on the morning prior to the first exposure. They were then weighed weekly throughout the exposure regimen and immediately prior to sacrifice. The animals that were held for a 4 week recovery period were weighed weekly and immediately prior to sacrifice.
- During non-exposure days the rats were examined once a day for overt clinical signs and twice a day for mortality. All rats were individually observed for signs of toxic effects except during exposure. During the exposures, observations were made on a group basis. Preceeding and following each exposure, observations were recorded for animals exhibiting overt clinical signs. Detailed observations were performed on all animals at the time of body weight determination and immediately prior to sacrifice.
OPHTHALMOSCOPIC EXAMINATION:
- Ophthalmic examinations took place 1 week before the exposure regimen began, and following the last exposure. The recovery animals were examied at the end of the 4 week recovery period.
FOOD CONSUMPTION/WATER CONSUMPTION:
- Food and water consumption measurements were obtained on a weekly basis during the first 4 weeks of exposure.
URINALYSIS:
- Urine was collected from individually housed animals using metabolism cages following day 64 for the males and day 65 for the females. Urine was also collected from the rats in the 4 week recovery group.
HAEMATOLOGY/CLINICAL CHEMISTRY:
- Haematology and serum clinical chemistry evaluation was performed on blood samples collected from all rats at the end of the exposure regimen and in the recovery groups after the 4 week recovery period. Blood was collected from the orbital sinuses of anaesthetised rats. Food was removed from the cages prior to the start of the blood collection period, whilst water was provided ad libitum.

Sacrifice and pathology:

GROSS PATHOLOGY/HISTOPATHOLOGY:
After sacrifice weights were recorded of the brain, liver, lungs, kidneys, testes and ovaries from all animals at sacrifice. Organ weights were recorded as absolute weights and relative weights. Complete necropsy was performed on each animal; gross examinations were performed on all animals and selected tissues were fixed in 10% formalin. Microscopic evaluations were performed on a large number of tissues in the control and high dose groups only (excluding the recovery groups);

Other examinations:

No further examinations were made.

Statistics:

Continuous parametric variables were analysed by Levene's test, ANOVA and t-tests. Frequency data were compared using Fisher's exact test. p<0.05 was considered significant.

Results and discussion

Results of examinations

Details on results:

CLINICAL SIGNS AND MORTALITY
- No mortality occurred during the study. Swollen periocular tissues were observed in the control and 45ppm groups, but no exposure relationship was evident.

OPHTHALMOSCOPIC EXAMINATION
- No lesions were observed in the ophthalmic examinations.

BODY WEIGHT AND WEIGHT GAIN
- The mean values for the body weight and body weight gain values were lower, but not statistically significantly lower, than control values for males and females at the 14 week sacrifice, and for males and the 18 week sacrifice.

FOOD CONSUMPTION
- On week 4, males exposed to 45ppm showed a significantly decreased food consumption.

WATER CONSUMPTION
- No decreased water consumption was observed during the course of the study.

ORGAN WEIGHTS
- At the 14 week sacrifice there were no significant differences in organ weights between treatment groups. At the 18 week sacrifice, the absolute and relative lung weights for males in the 45ppm group were significantly increased. The relative (as a percentage of brain weight) lung weight for the females in the 45 ppm group was significantly increased. The relative (as a percentage of brain weight) kidney weight for the males in the 45ppm group was significantly decreased. The absolute ovary weight in the 45ppm group was significantly decreased, however, one control animal had an ovarian cyst which doubled in weight and therefore increased the mean weight in the controls.

HAEMATOLOGY AND CLINICAL CHEMISTRY
- At the 14 week sacrifice, female rats had no significant differences in the haematologic and serum chemistry results. Male rats in the 45ppm group had a significant decrease in eosinophil counts and a significant increase in serum calcium values. At the 18 week sacrifice, female rats in the 45 ppm group had significant decreases in MCV and MCH values, significant increases in glucose, total protein, albumin and globulin, and a significant decrease in serum phosphorous. Male rats in the 45ppm group had a significant decrease in platelet counts, and no changes in the serum chemistry results were recorded.

URINALYSIS
- At the 14 week sacrifice there were no significant differences in urinalysis in male or female rats in the 15 and 45ppm groups. At the 18 week sacrifice female rats in the 45ppm group had a significant decrease in urine pH. A decrease in urine volume and an increase in osmolality were noted in the female rats in the 45ppm group.

HISTOPATHOLOGY: NON-NEOPLASTIC
- The only e-Caprolactone exposure-related lesions at the 14 week sacrifice were perinasal and periocular encrustation and eyelid swelling in a small number of males in the 45ppm group.

Effect levels

1

Dose descriptor:

NOAEC

Remarks:

local

Effect level:

15 ppm

Based on:

test mat.

Sex:

male

Basis for effect level:

other: The only e-Caprolactone exposure-related lesions at the 14 week sacrifice were perinasal and periocular encrustation and eyelid swelling in a small number of males in the 45ppm group.

2

Dose descriptor:

NOAEC

Remarks:

local

Effect level:

45 ppm

Based on:

test mat.

Sex:

female

Basis for effect level:

other: The only e-Caprolactone exposure-related lesions at the 14 week sacrifice were perinasal and periocular encrustation and eyelid swelling in a small number of males in the 45ppm group.

3

Dose descriptor:

NOAEC

Remarks:

systemic

Effect level:

45 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: No effects indicative of systemic toxiicty were seen in this study

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

Analysis of e-Caprolactone performed prior to and following the exposure regimen showed no significant compositional change, the purity was >99%. The target exposure concentrations were 15 and 45 ppm of e-Caprolactone vapour. GC analysis of the chamber atmosphere resulted in mean concentrations (±SD) of 14.2±1.13 and 42.4±4.02 ppm. e-Caprolactone was not detected in the control chamber. The mean analytical-to-nominal concentrations were 0.86 and 0.73 for the 15 and 45 ppm groups respectively.