Tetrahydro-3-methylfuran

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

Male and female F344/N rats and male and male and female B6C3F1 mice were exposed to 0, 66, 200, 600, 1800 or 5000 ppm tetrahydrofuran (THF) by inhalation, 6 hours/day, 5 days/week, for 14 weeks.  Full histopathological analysis was performed on reproductive organs including the preputial gland (rats), prostate, testis and uterus.  In rats, there were no reported pathological effects.  Female mice displayed uterine atrophy at the highest exposure concentration, manifested as small uteri and microscopically by fewer numbers of uterine glands.  The uterine atrophy observed in this study may represent an acceleration of a normal aging process.  Male and female F344 rats and male and male and female B6C3F1 mice were exposed to 0, 200, 600 or 1800 ppm of tetrahydrofuran by inhalation, 6 hours/day, 5 days/week for 105 weeks. Full histopathological analysis was performed on reproductive organs including the preputial gland, prostate, testis and uterus.  There were no significant histopathological effects reported in rats.  In mice, the incidences of inflammation of the penis and urethra and necrosis of the urethra in the 1800 ppm male mice were greater than those in the chamber controls. These latter effects may have been secondary effects of an ascending urinary tract infection.

Link to relevant study records

Reference

Endpoint:

two-generation reproductive toxicity

Remarks:

based on test type (migrated information)

Type of information:

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

Adequacy of study:

key study

Study period:

14 February 1994 to 27 July 1994

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Studies were conducted according to generally valid and/or internationally accepted testing guidelines.

Qualifier:

according to guideline

Guideline:

other: 87/302/EEC; OECD Guideline No. 416; EPA/TSCA Guidelines 40 CFR, para.798.4700

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Karl THOMAE an der Riss, FRG
- Age at study initiation: (P) 35 +/- 1 days (including acclimatization period); (F1) mated 98 days after weaning
- Weight at study initiation: (P) Males: 126 - 150 g; Females: 108 - 132 g; (F1) Males: 91.2 - 102.3 g; Females: 84.4 - 94.4 g
- Fasting period before study: None
- Housing: During the study period, housed individually in DK III stainless steel wire mesh cages (BECKER & Co., Castrop-Rauxel, FRG) except during mating periods, with males housed in Makrolon (BECKER & Co.) type M III cages for overnight mating. After birth, pregnant animals also housed in Makrolon type M III cages.
- Diet (ad libitum): ground Kliba diet rat/mouse/hamster, 343 meal, KLINGENTALMUHLE AG, Kaiseraugst, Switzerland.
- Water (ad libitum): tap water with added test article
- Acclimation period: 7 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 - 24
- Humidity (%): 30 - 70
- Air changes (per hr): Not stated
- Photoperiod (hrs dark / hrs light): 12/12


IN-LIFE DATES: From: 21 February 1994 To: 16 December 1994

Route of administration:

oral: drinking water

Vehicle:

water

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
Drinking water solutions were prepared once or twice a week in tap water. The required amount of tetrahydrofuran (THF) was added and the mixture agitated with a magnetic stirrer until test substance dissolution. The nominal concentrations of THF were 0 (control), 1000, 3000 or 9000 ppm).

Details on mating procedure:

- M/F ratio per cage: 1:1
- Length of cohabitation: mated overnight for a maximum of 3 weeks
- Proof of pregnancy: vaginal plug / sperm in vaginal smear referred to as day 0 of pregnancy
- After 3 weeks if a F0 or an F1 parental animal had not produced offspring, it was again mated for 3 weeks with a fertile animal from the control group.
- Further matings after two unsuccessful attempts: no
- After successful mating each pregnant female was caged: Makrolon type III cages (BECKER & Co.)
- Any other deviations from standard protocol: No

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The content of THF in drinking water solutions was verified by capillary-column gas chromatography with internal standard evaluation. Analyses were performed at the beginning of the study and approximately at 3-month intervals until study termination. The column used was a fused silica DB 1701; length, 30 m; internal diameter, 0.25 mm; and film thickness 1 micrometer. The carrier gas was helium (30 ml/min). A 1 microliter injection of each sample was analyzed under the following conditions: oven, 80 to 280 deg C at 8 deg C/min; injector, 250 deg C; detector, 300 deg C.

An internal standard solution was prepared in a 100 ml volumetric flask by weighing about 200 mg of 1,4-dioxane and bringing to the mark with N,N-dimethylacetamide.

Each sample was analyzed by weighing about 2 g of the sample and adding 25 ml of internal standard solution and 3 ml of N,N-dimethylacetamide. After mixing, the solution was ready for injection.

The 7-day stability of tetrahydrofuran drinking water solutions was confirmed in a previous range-finding study (Project No. 16R0144/93020). Analysis of nominal 0.52 or 0.51 g/100 g samples indicated no measured changes after 7 days.

All concentration control analyses of drinking water from the study were within acceptable limits of the analytical method. For periodically measured values, analytical results corresponded to 92 to 106% of expected values.

Duration of treatment / exposure:

Test animals were exposed continuously to the test material. The F0 animals received the test article in the drinking water beginning after acclimatization and for at least 70 days prior to mating. Treatment was continued through mating and until pups were weaned (21 days post-parturation), at which time parental animals were sacrificed.

The F1 generation parental animals were exposed continuously to the same dose levels as parental animals. At least 98 days after assignment of F1 parental animals, males and females were mated. Females were allowed to litter. The F1 parental animals were sacrificed after weaning of pups (21 days post-parturition).

Frequency of treatment:

Test article was administered continuously in the drinking water.

Details on study schedule:

- F0 parental animals were treated continuously for at least 70 days prior to mating.
- F1 parental animals were treated continuously for at least 98 days prior to mating.
- Parental animals from the F1 generation were selected randomly before weaning.

Remarks:

Doses / Concentrations:
0, 1000, 3000 or 9000 ppm
Basis:
nominal conc.
in drinking water

No. of animals per sex per dose:

25

Control animals:

yes, concurrent no treatment

Details on study design:

- Dose selection rationale: The doses were chosen based on the results of a previous range-finding study (BASF AG, 1994).

Parental animals: Observations and examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: At least once daily a check was made for dead or moribund animals. If in a moribund state, animals were sacrificed and necropsied.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: All parental animals were checked daily for clinical signs of toxicity. The nesting, littering and lactation behavior of the dams was generally evaluated in the mornings in connection with daily clinical inspections.

BODY WEIGHT: Yes
- Time schedule for examinations: Body weights of male and female parental animals were determined once a week.

FOOD CONSUMPTION:Yes
- For F0 parental animals, food consumption was determined once weekly for the first 10 weeks (or 14 weeks, F1 parental animals). After week 10 (or week 14, F1 animals), food consumption for the females during the gestation period was determined for days 0 - 7, 7 - 14 and 14 - 20. During lactation (animals with litters), food consumption was determined on days 1 - 4, 4 - 7 and 7 - 14. Food consumption was not determined on days 14 to 21 (as per Test Guideline). Food consumption of F0 males was not determined after week 10 (or week 14, F1 animals) until sacrifice.

WATER CONSUMPTION AND COMPOUND INTAKE: Yes
- Time schedule for examinations: For F0 parental animals, water consumption was determined once weekly for the first 10 weeks (time periods of 3 days) (or 14 weeks, F1 parental animals). After week 10 (or week 14, F1 animals), water consumption for the females during the gestation period was determined for days 0 - 1, 6 - 7, 13 - 14 and 19 - 20. During lactation (animals with litters), water consumption was determined on days 1 - 2, 4 - 5, 7 - 8 and 14 - 15. Water consumption was not determined on days 20 to 21 (as per Test Guideline). Water consumption of F0 males was not determined after week 10 (or week 14, F1 animals) until sacrifice.

OTHER: The number of mating days until vaginal sperm could be detected in the female, and the gestational status of the female, were noted for F0 and F1 pairs.

Oestrous cyclicity (parental animals):

Not measured.

Sperm parameters (parental animals):

Not measured.

Litter observations:

STANDARDISATION OF LITTERS
- Performed on day 4 postpartum: Yes
- Individual litters were in general standardized such that each litter contained 4 male and 4 female pups. If 4 pups/sex were not possible, then litters were standardized on 8 total pups. Standardization was not performed on litters containing less than 8 pups. All excess pups were sacrificed by means of CO2 asphyxiation.


PARAMETERS EXAMINED
The following parameters were examined in F1 and F2 offspring:
- Clinical observations: Pups were examined each day for clinical signs (including gross morphological findings).
- Pup number and status at delivery: All pups derived from F0 and F1 parents were examined as soon as possible on the day of birth to determine the total number of live born and stillborn in each litter. Pups which died before the first determination were recorded as stillborn.
- Pup viability/mortality: Checks were made for any dead or moribund pups twice daily on workdays (morning and afternoon) and mornings on weekends and holidays. The number and percentage of dead pups on the day of birth (day 0) and of pups dying between days 1 - 4, 8 - 14 and 15 - 21 of the lactation period were determined; however, pups dying accidentally or which had to be sacrificed due to maternal death were not included in these calculations. The number of live pups/litter was calculated on the day of birth and on lactation days 4, 7, 14 and 21.
- Sex ratio: On the day of birth, the sex of pups was determined and the sex ratio calculated.
- Pup body weight: Pups were weighed on the day after birth (day 1 postpartum) and on days 4 (before standardization), 7, 14 and 21 after birth.
- Developmental stages of the pups were monitored: Appropriate physiological development was assumed if: (1) pinna unfolding on day 4 after birth (before standardization); (2) opening of the auditory canal (day 13 after birth); and openings of the eyes (on day 15 after birth).

BEHAVIORAL TESTS
Up to weaning, several developmental tests were performed on surviving pups:
-Grip reflex: On day 13 after birth (+/- 1 day), pups were tested for this reflex by placing the front extremities on a bar about 3 mm in diameter. Animals clinging to the bar and pulling themselves up were rated as showing a positive response.
- Hearing test (Acoustic startle): On day 21 (+/- 1 day), animals were placed in a soundproof box (49.5 x 49.5 x 38.5 cm). After a short acclimation, animals were exposed (twice at most) to a startle stimulus (sound, 0.1 seconds, 5000 Hz, about 90 dB). Movement of ears or a jerk was considered a positive response.
- Pupillary reflex (Constriction): On day 20 after birth (+/- 1 day), animals pupils were dilated in a low-light environment. Pupillary constriction reflex was assessed by shining a penlight on the eye and observing the reaction of the pupil.

Postmortem examinations (parental animals):

NECROPSY
Animals were sacrificed by decapitation under CO2 anesthesia and assessed by gross pathology. Animals dying prematurely were necropsied as soon as possible and assessed for gross pathology.

ORGAN WEIGHTS
The following were weighed for all animals sacrificed at scheduled dates: anesthetized animals, liver, kidneys, testes, and epididymides.

HISTOPATHOLOGY
The following were fixed in 4% formaldehyde solution: all gross lesions, vagina, uterus (with cervix uteri), ovaries, oviducts, testes, epididymides, seminal vesicles, coagulating gland, prostate gland, pituitary gland, liver, kidneys, esophagus, stomach (glandular and non-glandular), and duodenum.

Postmortem examinations (offspring):

GROSS AND MICROSCOPIC EXAMINATION OF PUPS:
- All culled pups (sacrificed on day 4 postpartum as a result of standardization) and surplus pups (not reared to adulthood) were examined externally, eviscerated, and their organ assessed macroscopically. If there were notable finding, or if abnormalities were found in daily clinical observations after delivery, affected animals were examined using appropriate methods (e.g., skeletal staining) and/or with further processing of the heads according to Wilson’s method.
- All stillborn pups dying up to weaning were examined externally, eviscerated, and their organ assessed macroscopically. If there were notable finding, or if abnormalities were found in daily clinical observations after delivery, affected animals were examined using appropriate methods (e.g., skeletal staining) and/or with further processing of the heads according to Wilson’s method.
- Stained skeletons were evaluated under a stereomicroscope or magnifying glass. All pups without notable findings were discarded after examination.

Statistics:

Dunnett’s test (two-sided) was used to evaluate food and water consumption, body weights and weight changes, number of mating days, duration of gestation and number of pups delivered per litter. The mean weight of each litter was used for statistical analysis (statistical unit = litter). Fisher’s exact test (one-sided) was used to evaluate male and female mating indices, male and female fertility indices, gestation index, females with live born, stillborn, pups that died, pups cannibalized, pups sacrificed moribund, viability indices, lactation indices, and number of litters with affected pups at necropsy. The Wilcoxon test (one-sided) was used for analyzing the proportion of affected pups per litter, with necropsy observations, with physical development and reflex data, and for the proportion of pups reaching the special criteria for each litter (statistical unit = litter).

Mean and standard deviations were calculated for terminal body weights and absolute and relative organ weights for the animals in each test group and tabulated together with the individual values.

Reproductive indices:

MALE REPRODUCTIVE DATA
- A male mating index (%) was calculated for F1 and F2 litters as: the percentage of the number of males with confirmed mating (defined as female with vaginal sperm or that gave birth to a litter or with pups/fetuses in utero) versus numbers of males placed with females.
- A male fertility index (%) was calculated for F1 and F2 litters as: the percentage of the number of males proving their fertility (defined as female giving birth to a litter or with pups/fetuses in utero) versus the number of males placed with females.

FEMALE REPRODUCTION AND FERILITY
- A female mating index (%) was calculated for F1 and F2 litters as: the percentage of females mated (defined as female with vaginal sperm or that gave birth to a litter or with pups/fetuses in utero) versus the number of females placed with males.
- A female fertility index (%) was calculated for F1 and F2 litters as: the percentage of pregnant females (defined as females giving birth to a litter or with pups/fetuses in utero) versus the number of females mated (defined as female with vaginal sperm or that gave birth to a litter or with pups/fetuses in utero).
-A female gestation index (%) was calculated for F1 and F2 litters as: the percentage of females with live pups on the day of birth versus the number of pregnant females.
- A live birth index (%) was calculated for F1 and F2 litters as: the percentage of the number of live born pups at birth versus total number of pups born.

Offspring viability indices:

- A viability index (%) was calculated as: the percentage of live pups on day 4 (before standardization of litters) versus the live pups on the day of birth.
- A lactation index (%) was calculated as: the percentage of live pups on day 21 after birth versus the number of live pups on day 4 after birth (after standardization of litters).

Clinical signs:

no effects observed

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:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

no effects observed

Other effects:

effects observed, treatment-related

Reproductive function: oestrous cycle:

not examined

Reproductive function: sperm measures:

not examined

Reproductive performance:

no effects observed

CLINICAL SIGNS AND MORTALITY (PARENTAL ANIMALS)
There were no significant adverse clinical effects reported in parental animals. There were no deaths attributed to compound administration.

BODY WEIGHT AND FOOD CONSUMPTION (PARENTAL ANIMALS)
Body weight:
For F0 parental animals, there were slight but statistically significant reductions in mean body weights (generally prior to week 5) at the 9,000 ppm dose level during the first study weeks (both sexes) and mean body weights of F0 dams on gestation days 7 and 14 and lactation days 1 - 21.

For F1 parental animals, statistically significantly reduced body weights at the 9,000 ppm dose level in male were recorded throughout the study (in total about 6% lower than concurrent controls). This was accompanied by statistically significantly reduced weight gains in males and in females, but during gestation only.

Food Consumption:
For F0 parental females, food consumption was statistically significantly reduced during premating, gestation and lactation periods (approx. 8% lower than concurrent controls).

For F1 parental males, food consumption was statistically significantly reduced during several intervals of the premating phase (in total about 6% less than concurrent controls); statistically diminished food consumption was also recorded in F1 females, predominantly during lactation (about 14% less than concurrent controls).

TEST SUBSTANCE INTAKE (PARENTAL ANIMALS)
For F0 parental animals, statistically significantly reduced water consumption at the 9,000 ppm dose level in male were recorded during premating (males: about 18% less, females: about 27% less) and in dams during gestation (about 25% less) and during lactation (about 20% less).

For F1 parental animals, generally statistically significantly reduced water consumption at the 9,000 ppm dose level in male were recorded during premating (males: about 14% less, females: about 17% less) and in dams during gestation (about 14% less) and during lactation (about 24% less).

At the 3,000 ppm dose level, slight and only sometimes statistically significant declines in water consumption in F0 males and females was recorded during premating (about 7% less) and in dams during gestation and lactation (about 14% or 12% less). In F1 parental animals at the 3,000 ppm dose level, water consumption in F1 dams was marginally diminished during lactation (about 9%).

The amount of test substance consumed by parental animals (mg/kg bwt/day) was calculated for the periods of premating, gestation, and lactation. The results are shown in Tables 1 and 2.

REPRODUCTIVE PERFORMANCE (PARENTAL ANIMALS)
The fertility of F0 parental males was not adversely influenced by the administration of tetrahydrofuran in the drinking water. In F0 parental females, reproduction and delivery data were not adversely affected by administration of tetrahydrofuran in the drinking water.

The fertility of F1 parental males was not adversely influenced by the administration of tetrahydrofuran in the drinking water. In F1 parental females, reproduction and delivery data were not adversely affected by administration of tetrahydrofuran in the drinking water. Although the mean number of delivered pups/dam was lowest at the 9,000 ppm dose level, the result was without statistical significance but was outside of the range of historical control values. It was considered to be spontaneous in nature both because no such findings appeared in the F0 generation n the current study or in a preceding range-finding study with concentrations employed up to 12,000 ppm.

Summary of Parental (F0) Reproductive Indices for control and dosed groups:
Male Mating Index (%): 100;100;96;100
Male Fertility Index (%): 96;88;92;92
Female Mating Index (%): 100;100;96;100
Gestation Index (%): 100;100;100;100
Pups Delivered (mean): 13.0;12.4;13.3;14.4
Liveborn Index (%): 98;98;98;98

Summary of Parental (F1) Reproductive Indices for control and dosed groups:
Male Mating Index (%): 100;100;100;100
Male Fertility Index (%): 96;92;96;92
Female Mating Index (%): 100;100;100;100
Gestation Index (%): 100;100;100;100
Pups Delivered (mean): 12.4;13.0;12.9;10.4
Liveborn Index (%): 98;93;94;97

ORGAN WEIGHTS (PARENTAL ANIMALS)
At the highest dose level, statistically significantly increased absolute and/or relative kidney weights were recorded in both sexes in F0 parental animals. There were no other relevant organ weight effects noted in any other parental animals.

GROSS PATHOLOGY (PARENTAL ANIMALS)
There were no substance-related gross pathological findings noted in F0 or F1 parental animals.

HISTOPATHOLOGY (PARENTAL ANIMALS)
There were no substance-related histopathological findings noted in F0 or F1 parental animals.

Dose descriptor:

NOAEL

Effect level:

9 000 ppm (nominal)

Sex:

male/female

Basis for effect level:

other: No significant adverse effects on reproductive parameters.

Remarks on result:

other: Generation: F0 and F1 parental (migrated information)

Dose descriptor:

NOAEL

Effect level:

3 000 ppm (nominal)

Sex:

male/female

Basis for effect level:

other: see 'Remark'

Remarks on result:

other: Generation: F0 and F1 parental and F1 and F2 litters (migrated information)

Clinical signs:

effects observed, treatment-related

Mortality / viability:

mortality observed, treatment-related

Body weight and weight changes:

effects observed, treatment-related

Sexual maturation:

effects observed, treatment-related

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

effects observed, treatment-related

Histopathological findings:

not examined

VIABILITY (OFFSPRING)
There were no deaths attributed to test compound administration in F1 or F2 pups.
F1 Litter Viability Indices for control and dosed animals (%): 97;97;94;96
F2 LItter Viability Indices for control and dosed animals (%): 96;82**;93;94
**The reduced viability for the lowest dosed group (1000 ppm) was due to 2 animals (331 and 337). All pups from these dams died before schedule or were cannibalized. This effect was not considered compound related as the 2 higher dose levels were similar to control values and were well within historical control ranges.

CLINICAL SIGNS (OFFSPRING)
There were no significant adverse clinical effects reported in F1 or F2 pups.

BODY WEIGHT (OFFSPRING)
In F1 pups at the 9,000 ppm dose level, statistically significantly lower body weights (about 8% lower than concurrent controls) from day 7 post-partum until 21 were recorded and reduced weight gains from day 4 post-partum up until weaning.

In F2 pups at the highest dose level, statistically significantly reduced body weight gains were reported between days 7 - 14 and 4 - 21 post-partum (approx. 7% lower than concurrent controls); this resulted in marginally (about 5%) lower mean pup body weights on day 21 post-partum.

LACTATION INDEX
There were no substantial differences in the lactation indices for either F1 or F2 offspring.
Summary for Control and dosed F1/F2 Offspring:
Lactation Index F1 (%): 100;95;99;99
Lactation Index F2 (%): 99;97;98;100

SEX RATIOS
There were no substantial differences in the sex ratios of live F1 pups on the day of birth or on day 21 pp.
For Control and dosed animals (F1 litter):
Day 0, live males (%): 54.8;43.1;53.8;50.5
Day 0, live females (%): 45.2;56.9;46.2;49.5
Day 21, live males (%): 52.9;46.7;52.0;51.1
Day 21, live female (%): 47.1;53.3;48.0;48.9

For Control and dosed animals (F2 litter):
Day 0, live males (%): 54.1;54.1;51.6;52.6
Day 0, live females (%): 45.9;45.9;48.4;47.4
Day 21, live males (%): 50.3;50.7;51.4;48.2
Day 21, live female (%): 49.7;49.3;48.6;51.8

SEXUAL MATURATION (OFFSPRING)
In F2 pups there were slight but statistically significantly lower numbers with delayed auditory canal opening and eye openings. The value for auditory canal openings was within historical control ranges but delayed eye openings were considered possibly compound-related. There were no other biologically relevant differences recorded.
For Control and dosed groups:
F2 Pups reaching criteria, auditory canal opening (%): 96.4;100.0;88.9*;98.9 (per litter - mean)
F2 Pups reaching criteria, eye opening (%): 89.9;98.7;94.0;79.2* (per litter - mean)
*Wilcoxon test (one-sided), p <= 0.05

GROSS PATHOLOGY (OFFSPRING)
At necropsy, the minimal findings that were recorded were present in very few animals and were also present in either concurrent controls or had been observed previously in historical control animals.

OTHER FINDINGS (OFFSPRING)
No remarkable differences were recorded between groups in any of the behavioral tests that were conducted on pups up to weaning.

Reproductive effects observed:

not specified

Table 1:

Mean Test Substance Intake F0 Parental Animals (mg/kg bwt/day)

	1,000 ppm	3,000 ppm	9,000 ppm
F0 males	91.3	268.1	714.4
F0 females - premating	104.1	301.2	742.2
- gestation	103.5	288.1	790.0
- lactation	165.6	477.6	1365.4

Table 2:

Mean Test Substance Intake F1 Parental Animals (mg/kg bwt/day)

	1,000 ppm	3,00 ppm	9,000 ppm
F1 males	97.7	293.2	787.7
F1 females - premating	124.8	350.4	882.4
- gestation	106.5	317.7	792.3
- lactation	151.7	454.8	1164.8

Conclusions:

Clear signs of general toxicity were noted at the highest dose level (9,000 ppm). Statistically significantly reduced water intake (27% less in comparison with concurrent controls) occurred in F0 and F1 parents throughout the different study phases. Reductions in water consumption may account, in part, for reduced food consumption and body weight/body weight gains. Slight but sometimes statistically significant reductions in water consumption were also seen in the 3,000 ppm F0 parental animals and F1 dams during lactation. Since there were no other significant effects noted at the 3,000 ppm dose level, the minimal water intake reductions are most likely due to an aversion to the test chemical (lack of palatability). Statistically significant reductions in food consumption occurred in high dose F0 female and F1 males and females during premating, gestation and/or lactation periods. Body weights of the high dose F0 parental rats were statistically significantly reduced during the first premating weeks, in the F0 females during gestation and lactation of F1 litters and in F1 males throughout the study period.

There was no indication that administration of tetrahydrofuran caused adverse effects on the reproductive parameters of the parental animals from any groups. The only developmental toxicity noted consisted of statistically significantly reduced body weight/body weight gains in the F1 and F2 male and female pups at the 9,000 ppm dose level. In the F2 pups, this was associated with an increased number of pups with developmental delays including, most significantly, eye openings.

The lower mean number of high dose F2 pups delivered by F1 parental females was due primarily to 3 dams and although outside of the historical control range, this effect was considered spontaneous in nature due to a lack of such effect in the F0 generation and the lack of reduced litter sizes in a preceding range finding study at concentrations as high as 12,000 ppm.

Mean absolute and/or relative kidney weights of the males and females of the highest dose group of the F0 parental animals were significantly increased. Although treatment-related, these increases in kidney weights did not correlate with any morphological abnormalities. As a result of gross and histopathological examinations, there were no indications that treatment with tetrahydrofuran caused any adverse effects on the reproductive organs of parental animals.

Executive summary:

Tetrahydrofuran was administered to Wistar rats over two generations at concentrations in the drinking water of 1000, 3000 and 9000 ppm. This resulted in mean doses of the test chemical of 104, 305 and 782 mg/kg bwt/day, respectively. Clear clinical signs of general toxicity occurred at the highest dose with significantly reduced water intake (27% less compared to controls) and impaired food consumption that may have been related at least partially to reduced water intake. Slight but sometimes statistically significant reductions in water intake were also seen in the 3000 ppm dosed animals (both sexes). Body weights of the F0 parental rats were statistically significantly reduced during the first premating weeks, in F0 females during gestation and lactation, and in F1 males throughout the study period. Slight impairments in body weight gain were only observed in high dose F1 males.

There were no indications from clinical examinations that tetrahydrofuran administration caused any adverse effects on reproductive parameters of the parental animals. The reduced mean number of F2 pups delivered by F1 dams at the highest dose, although lower than control or the historical control range, was considered spontaneous in nature and not compound related. Statistically significant impairments in body weight/body weight gains were observed in F1 and F2 pups. The only signs of developmental toxicity were noted in F2 pups and consisted of delayed auditory canal opening and eye opening.

Mean absolute and/or relative kidney weights of the males and females in the high dose group were significantly increased. These increases were considered treatment related although no morphological correlates were detected to account for the increases. No gross or microscopic lesions were noted in either male or female rats of the F0 or F1 generation parental animals.

There were no indications from organ weight determinations and gross and histopathological examinations that tetrahydrofuran induced any adverse effects on the reproductive organs of the parental animals.

Effect on fertility: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

300 mg/kg bw/day

Species:

rat

Effect on fertility: via inhalation route

Endpoint conclusion:

no study available

Effect on fertility: via dermal route

Endpoint conclusion:

no study available

Additional information

The reproductive toxicity of Tetrahydro-3-methylfuran (3-methyl-THF) has not been specifically investigated by can be adequately characterized by read-across to a closely related substance, Tetrahydrofuran (THF, CAS# 109-99-9). The reproductive toxicity of THF has been studied in rats following drinking water administration. In a definitive two-generation reproductive and developmental toxicity study following OECD Guideline 416, THF was administered in the drinking water at 0, 1000, 3000 or 9000 ppm to male and female Wistar rats. Clear signs of general toxicity were noted at the highest dose level (9,000 ppm) and consisted of statistically significantly reduced water intake in F0 and F1 parents throughout the different study phases. Reductions in water consumption may have accounted, in part, for reduced food consumption and reduced body weight/body weight gains. Slight but sometimes statistically significant reductions in water consumption were also seen in the 3,000 ppm F0 parental animals and F1 dams during lactation. Body weights of the F0 parental rats were statistically significantly reduced during the first pre-mating weeks, in F0 females during gestation and lactation, and in F1 males throughout the study period. Slight impairments in body weight gain were only observed in high dose F1 males. Mean absolute and/or relative kidney weights of the males and females in the high dose group were significantly increased. These increases were considered treatment related although no morphological correlates were detected to account for the increases. No gross or microscopic lesions were noted in either male or female rats of the F0 or F1 generation parental animals. There were no indications from clinical examinations that THF administration caused any adverse effects on reproductive parameters of the parental animals. The reduced mean number of F2 pups delivered by F1 dams at the highest dose, although lower than control or the historical control range, was considered spontaneous in nature and not compound related. Statistically significant impairments in body weight/body weight gains were observed in F1 and F2 pups. The only signs of developmental toxicity were noted in F2 pups and consisted of delayed auditory canal opening and eye opening. The NOAEL for reproductive effects in the two-generation study was reported as 9,000 ppm based on a lack of significant adverse effects. The NOAEL for toxicity in F0 and F1 parental animals was reported as 3000 ppm based on effects on food and water consumption and on body weight and body weight gains. In the two generation study, mean intakes of THF in F0 and F1 parental males were 714 and 787 mg/kg bwt/day, respectively, at the 9000 ppm exposure concentration. For F0 and F1 females, mean intakes of THF varied from 742 to 1365 mg/kg bwt/day, depending on study phase, at the 9000 ppm exposure concentration.

 

Short description of key information:
Exposure to Tetrahydro-3-methylfuran (3-methyl-THF) is not expected to pose a reproductive hazard. The reproductive toxicity of 3-methyl-THF has not been specifically investigated but can be adequately charcterized by read-across to a closely related substance, Tetrahydrofuran (CAS# 109-99-9). THF was evaluated in both one-generation and two-generation studies in rats following drinking water administration and found to not be a selective reproductive toxicant.

Justification for selection of Effect on fertility via oral route:
Reliable key study on read across analogue

Effects on developmental toxicity

Description of key information

The developmental toxicity / teratogencity of 3meTHF has been charcterized by read-across to a closely related substance, Tetrahydrofuran (CAS# 109-99-9). The developmental toxicity of THF has been studied in both rats and mice following inhalation exposures.  Developmental effects were also assessed in a two-generation reproductive and developmental toxicity studies in rats following drinking water administration.

Link to relevant study records

Reference

Endpoint:

developmental toxicity

Type of information:

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

Adequacy of study:

key study

Study period:

16 June 1987 to 24 August 1987

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Although no specific test guideline was identified, the study was conducted according to valid and internationally recognized test procedures that followed recognized GLP standards.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Principles of method if other than guideline:

Although no specific testing guideline was identified, the study was conducted generally according to the method specified in OECD Guideline 414. Pregnant Swiss (CD-1) female mice were exposed to vapor concentrations of tetrahydrofuran of 0, 600, 1800 or 5000 ppm for 6 hours/day, 7 days/week on days of gestation (DG) 6-17. Developmental evaluations were performed on pregnant mice euthanized on DG 18.

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Species:

mouse

Strain:

other:

Details on test animals or test system and environmental conditions:

- Source: Charles River, Raleigh, NC
- Age at study initiation: 11 weeks
- Fasting period before study: none
- Housing: stainless steel wire racks equipped with automatic watering system (10-11 mice/cage)
- Diet: pelleted NIH-07 (Ziegler Bros. Inc., Gardners, PA) ad libitum except during 6-hour exposure periods
- Water (ad libitum): ad libitum throughout the study including exposure periods
- Acclimation period: quarantined 20 days prior to the start of exposures


ENVIRONMENTAL CONDITIONS
- Temperature (°F): during quarantine, 72 +/- 3; during exposures, 75 +/- 3
- Humidity (%): during quarantine, 50 +/- 15; during exposures, 55 +/- 15
- Chamber airflows: 12 to 18 CFM (average in all chambers, 14.0 to 15.4 CFM)
- Photoperiod (hrs dark / hrs light): 12/12

In-Life Dates: 8 July 1987 (mating) to 24 August 1987 (fetal exams)

Route of administration:

inhalation: vapour

Type of inhalation exposure (if applicable):

whole body

Vehicle:

other: conditioned air

Details on exposure:

Exposure Chambers:
Batelle-designed inhalation exposure chambers (Harford Systems; Lab Products Inc., Aberdeen, MD) were employed. The 2-3 cubic meter stainless-steel chambers (1.7 cubic meters active mixing volume) contained three levels of caging. The cage units accomodated individual animal cages, feed troughs, and automatic watering systems.

Vapor Generation/Exposure System:
Tetrahydrofuran was pumped from a bulk storage reservoir at a steady rate by a liquid micrometering pump into a rotating flask (100 rpm) partially immersed in a hot water bath at 175 deg F. Vapor from the flask was carried by a metered stream of nitrogen. The vapor entered a short distribution manifold from which individual delivery lines carried metered amounts of the vapor to each exposure chamber. Target vapor concentrations were achieved by diluting with filtered air immediately before entering the chambers.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Vapor Concentration Monitoring:
Vapor concentrations were monitored during animal exposures at approximately 30-minute intervals by gas chromatography (Hewlett-Packard 5840 GC) using a 1/8 in. o.d. X 1.0 foot nickel column packed with 1% SP-1000 on 60/80 mesh Carbopack B operated at 145 deg C. An 8-port valve allowed measurements of concentrations of the test material in the three exposure chambers, the control chamber, the holding chamber, the exposure room, an on-line standard, and nitrogen blank. A 400 ppm tetrahydrofuran certified standard in nitrogen (MG Industries Scientific Gases, Los Angeles, CA) was used to check instrument drift throughout the exposure day.

The precision of the on-line concentration monitoring was estimated from 17 consecutive measurements of the 400-ppm on-line THF standard. A 0.26% coefficient of variation was observed. The limit of detection of tetrahydrofuran was 0.04 ppm.

Vapor Concentration Uniformity:
The uniformity of chamber atmosphere vapor concentrations were measured prior to the study and once during the study. All chambers were acceptable with percentage relative standard deviations of

Details on mating procedure:

- Impregnation procedure: co-housed with male mice
- Ratio F/M per cage: 2 or 3 females/male
- Length of cohabitation: overnight
- Mating was conducted for 5 consecutive nights to obtain approximately 33 pregnant animals/group.
- Proof of pregnancy: confirmed by the presence of a vaginal plug, referred to as day of gestation 0 of pregnancy (0 DG)

Duration of treatment / exposure:

12 consecutive days (6-17 DG for mated mice)

Frequency of treatment:

6 hours/day

Duration of test:

18 days

Remarks:

Doses / Concentrations:
0 (filtered air), 600, 1800 or 5000 ppm
Basis:
nominal conc.

No. of animals per sex per dose:

10 virgin (unmated) females and approximately 33 positively mated females

Control animals:

yes

Details on study design:

Virgin female mice were included to provide a reference for any effects that the state of pregnancy may have had on the toxic response. These animals were exposed concurrently with mated animals.

Maternal examinations:

CAGE SIDE OBSERVATIONS:
Animals were observed daily for mortality, morbidity and signs of toxicity. The date and time of death or euthanasia of moribund animals was recorded and the animals necropsied.

DETAILED CLINICAL OBSERVATIONS: No data

BODY WEIGHT: Yes
- Time schedule for examinations: Mated female mice were weighed on DG 0, 6, 9, 12, 15 and 18; virgin mice were weighed prior to the start of exposures and on exposure days 1, 5 and 10 and at euthanization.

POST-MORTEM EXAMINATIONS: Yes
Mice were killed by CO2 asphyxiation, weighed and examined grossly for signs of maternal toxicity.

Ovaries and uterine content:

Both ovaries from each female were saved for sectioning and quantitative follicle counts. Apparently nongravid uteri from positively mated females were stained with 10% ammonium sulfide to detect possible implantation sites. The number, position and status of implants were recorded for each gravid uterus. Placentas were examined and discarded unless abnormal.

Fetal examinations:

- External examinations: Live fetuses were weighed and examined for gross defects.
- Soft tissue examinations: The sex of live fetuses was determined by internal examinations of the gonads after injection of Nembutal(TM) (sodium pentobarbital). Fifty percent of live fetuses and any fetuses with gross external abnormalities were examined for visceral defects by dissection of fresh tissue.
- Skeletal examinations: All fetal carcasses, with and without heads, were prepared for skeletal staining. Cartilage as well as ossified bone were visualized by double-staining using Alcian bue and alizarin red S.
- Head examinations: The heads of 50% of the live fetuses were removed and placed in Bouin’s fixative. After fixation, the heads were serially sectioned with a razor blade and examined for soft-tissue craniofacial abnormalities.

Statistics:

All means and standard deviations for animal data were calculated. Mean body weights (as a mean of litter means for fetal data) analyzed by an analysis of variance (ANOVA) model for unbalanced data. Response variables, either body weights or the arcsin transformations of proportional incidence data, were analyzed against the class variable, treatment, in a one-way ANOVA model. A Tukey’s t-test (two-tailed) was used to assess statistically significant differences between the control and exposed groups. If appropriate, a dose-response relationship was determined by means of an orthogonal trend test (Winer, 1971). In the case of proportional data this test was performed on transformed variables. The litter was used as the basis for analysis of fetal variables.

Indices:

The following parameters, expressed as mean +/- SE, when appropriate, were computed from data for all pregnant animals and their litters:
- Number of dead maternal animals, animals removed from the study and reason for removal
- Summary of maternal toxicity, including incidences of changes detected during clinical observations
- Number and percentage of pregnant animals
- Maternal body weights
- Weights of gravid uterus
- Extragestational weight and weight gain
- Number of implantation sites/litter
- Number of litters with live fetuses
- Number and percent of live fetuses/litter
- Body weight of live fetuses/litter
- Body weight of male and female fetuses/litter
- Sex ratio of fetuses/litter
- Number and percent of early and late resorptions/litter
- Number and percent of non-live/litter (early and late resorptions and dead fetuses)
- Listings of malformations and variations observed in fetuses/litters
- Number and percent of malformed fetuses
- Number and percent of litters with malformed fetuses

Historical control data:

Contemporary control data (based on N=83 litters) for Swiss CD-1 mice was available in addition to the unexposed (0 ppm) control animals:
Maternal Wt (18 DG): 54.4 +/- 5.6
Gravid Uterine Wt: 20.2 +/- 3.6
Extragestational Weight Gain: 6.6 +/- 3.0
Implants: 12.6 +/- 2.1
Live Fetuses: 11.7 +/- 2.2 (93.5 +/- 7.3%)
Early Resorptions: 0.6 +/- 0.8 (4.6 +/- 6.3%)
Late Resorptions: 0.2 +/- 0.5 (1.9 +/- 3.7%)
Dead Fetuses: 0.0 +/- 0.0 (0%)
Total Intrauterine Death: 0.8 +/- 1.0 (6.5 +/- 7.3%)
All Fetuses ( Weight, g): 1.36 +/- 0.11
male (g): 1.39 +/- 0.11
female (g): 1.34 +/- 0.10

Details on maternal toxic effects:

Maternal toxic effects:yes

Details on maternal toxic effects:
Unexpectedly high maternal mortality was observed at the 5000 ppm exposure concentration with 27% of mated females dying between DG 6 and 11 and 30% of virgin females dying during exposure days 1 through 5. Severe depression of the central nervous system may have been a contributing cause since all animals at the 5000 ppm dose level and some at the 1800 ppm dose level were sedated for up to 1 hour following exposures. Sedation at the 1800 ppm exposure level was a clear sign of maternal toxicity. Total numbers of exposures at the 5000 ppm dose level were reduced after 6 days of exposure by placing surviving females in exposure chambers supplied with fresh air until scheduled euthanization.

Mean body weights of virgin females at the highest dose level were significantly less than control animals by exposure day 5, however, this group recovered most of its weight by euthanization. Mean body weights (g) for virgin female mice at the 5000 ppm exposure concentration on exposure days 1, 5, 10 and at sacrifice were:
- 5000 ppm (N = 6 to 8): 26.7 +/- 2.6; 20.5 +/- 2.2*; 25.8 +/- 4.7*; 25.0 +/- 0.9*
Mean body weights for pregnant mice at the 5000 ppm exposure level were also significantly less than controls, but remained low throughout the study. Also, a significant reduction in mean body weights was also observed in the 1800 ppm exposed animals by DG 15. The body weight depression at the 5000 ppm exposure level can be attributed in part to the elevated intrauterine mortality in this group. At the 1800 ppm exposure level, the primary contribution to the reduced mean body weights was a deficit in uterine weight. Mean body weights (g) for control, 1800 ppm-exposed and 5000 ppm-exposed mice on DG 6, 9, 12, 15 and 18 were as follows:
- Control (N=30): 29.3 +/- 1.7; 31.5 +/- 2.1; 36.4 +/- 2.5; 45.5 +/- 2.7; 54.3 +/- 3.8
- 1800 ppm (N=27): 29.3 +/- 1.8; 31.1 +/- 2.5; 35.3 +/- 4.1; 41.7 +/- 6.7*; 49.0 +/- 10.1*
- 5000 ppm (N=20); 26.8 +/- 1.3; 26.8 +/- 2.6*; 27.8 +/- 2.8*; 29.8 +/- 3.3*; 29.4 +/- 5.0*
* significantly different from control groups, p<0.05

Uterine weights (g) were reduced in the 1800 ppm and 5000 ppm exposure groups versus controls. Extragestational weight gains (EGWG: body weight at sacrifice - uterine weight - DG0 weight) were reduced in the 5000 ppm exposed mice:
- Uterine Wts: 20.5 +/- 3.3 (control); 15.6 +/- 7.1* (1800 ppm); 1.0 +/- 3.8* (5000 ppm)
- EGWG: 7.2 +/- 1.9 (control); 1.4 +/- 1.7* (5000 ppm)
* significantly different from control groups, p<0.05

Dose descriptor:

NOAEL

Effect level:

600 ppm (nominal)

Basis for effect level:

other: maternal toxicity

Dose descriptor:

NOAEL

Effect level:

600 ppm (nominal)

Basis for effect level:

other: developmental toxicity

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:yes

Details on embryotoxic / teratogenic effects:
Each exposure group consisted of 33 plug-positive mice and 10 virgin female mice. Exposure to tetrahydrofuran had no effect on the number of implantations per dam. Mean number and percentage of live fetuses/litter at the 1800 and 5000 ppm exposure concentrations were significantly decreased compared to control. Corresponding significant increases in the number and percentage of resorptions/litter in these same groups were reported. Female mice surviving to euthanization had litters with 95% incidence of early resorption. Refer to Table 1.

Neither fetal weights nor fetal sex ratios were affected at the 600 or 1800 ppm exposure concentrations (Table 1). Fetal body weights (as means of litter means) were reduced for the 5000 ppm exposure group when compared to controls. The percentage of male fetuses was reduced at the 5000 ppm exposure concentration (Table 1):
Fetal body weights:
- All fetuses (g): 1.3 +/- 0.1 (control); 1.0 (5000 ppm, only a single litter)
- Males (g): 1.4 +/- 0.1 (control); 1.0 (5000 ppm)
- Females (g): 1.3 +/- 0.1 (control); 1.0 (5000 ppm)

Fetal Malformations:
The incidence of fetal malformations was not significantly affected following gestational exposures to tetrahydrofuran. However, several malformations were observed at low incidences in the 1800 ppm group that were not present either in the 0 ppm controls or contemporary controls: cleft palate (5 fetuses, 2.0%), edema (1 fetus, 0.4%), ectopic ovaries (1 fetus, 0.8%), and undescended testes (2 fetuses, 1.6%). These latter malformations were all observed in fetuses from a single low-weight litter that also had a 54% incidence of resorptions. There was an increased incidence of reduced ossifications of the sternebrae in the 1800 ppm exposure group and these correlated with increasing exposure concentrations. Statistical analysis of the 5000 ppm exposure group was not possible since only a single litter with live fetuses was present at this exposure concentration.

Abnormalities:

not specified

Developmental effects observed:

not specified

Table 1: Reproductive Measures for Mice Exposed to Tetrahydrofuran

	Tetrahydrofuran exposure conc. (ppm)
	0	600	1800	5000
Number of
Plug-positive females	33	33	33	33
Pregnant	31	28	27	27
Implantations/dam	12.8±1.8	12.0±2.2	12.0±1.9	12.6±2.8
Live fetuses/litter^1	11.9±1.9	11.1±3.2	9.3±4.4*	0.6±2.7*
Resorptions/litter
Total	0.9±1.1	0.9±1.8	2.7±4.1	12.0±3.7*
Early	0.6±1.0	0.7±1.8	1.8±3.9	11.9±4.0*
Late	0.3±0.5	0.2±0.5	0.9±2.2	0.1±0.5
Litters with >3 resorptions	1	1	5	19*
Percent of
Pregnant	94	85	82	83
Live fetuses/litter	93.1±8.2	91.2±19.6	77.4±34.8**	4.3±19.2**
Resorptions/litter
Total	6.9±8.2	8.4±19.5	22.6±34.8**	95.7±19.2**
Early	4.7±7.6	6.7±19.4	14.6±31.4**	95.0±3.2
Late	2.1±3.7	1.72±4.5	8.0±21.5	0.7±1.5
Litters with resorptions	60	50	63	100***
Male fetuses	46.6±15.8	47.0±15.0	50.7±16.2	16.7^2

1 Significantly correlated with exposure level (p < 0.05).

2 Based on a single litter.

* Significantly different from controls (p < 0.05).

** Significantly different from controls (p < 0.05, arcsine transformation).

*** Significantly different from controls (p < 0.05, chi-square transformation).

Conclusions:

Exposure of Swiss CD-1 mice to 0, 600, 1800 or 5000 ppm of tetrahydrofuran resulted in significant mortality of pregnant and virgin females (5000 ppm) and was embryotoxic at the 1800 and 5000 ppm exposure concentrations. The embroytoxic effects occurred in the presence of significant maternal toxicity that was expressed as maternal mortality (5000 ppm), significantly prolonged sedation (1800 and 5000 ppm) and reduced mean uterine and body weights (1800 and 5000 ppm). No significant increases in frank malformations or reductions in fetal body weights of live fetuses at the 1800 ppm exposure concentration were observed.

Executive summary:

Pregnant and virgin female Swiss (CD-1) mice were exposed to 0, 600, 1800 or 5000 ppm of tetrahydrofuran vapors whole-body for 6 hours/day, 7 days/week on days of gestation (DG) 6 to 17. Due to an unexpectedly high rate of toxicity (27% between DG 6 and 11) at the highest exposure concentration, exposures were discontinued on DG 11 (total of 6 exposures). A total of 30% of exposed virgin female mice died during exposure days 1 through 5. Severe central nervous system depression was proposed as causing or contributing to death. Sedation lasting for up to 1 hour following exposures was observed in all animals in the 5000 ppm exposure group as well as some animals in the 1800 ppm exposure group. Exposures to THF had no effect on the number of implantations/dam. The number and percentage of live fetuses/litter in both the 1800 and 5000 ppm exposure groups were reduced compared to controls. Neither fetal weights nor fetal sex ratios were affected by exposures at 1800 or 5000 ppm. Because only a single litter with live fetuses was present at the 5000 ppm exposure concentration, statistical analysis at this level was not possible. Although not statistically significant, several malformations were observed at low incidences in the 1800 ppm group that were not present either in the 0 ppm controls or contemporary controls: cleft palate, edema, ectopic ovaries, and undescended testes. These latter malformations were all observed in fetuses from a single low-weight litter that also had a 54% incidence of resorptions. There was an increased incidence of reduced ossifications of the sternebrae in the 1800 ppm exposure group and these correlated with increasing exposure concentrations. Tetrahydrofuran was not judged to be a selective developmental toxicant in Swiss CD-1 mice based on the clear presence of maternal toxicity at embryotoxic exposure concentrations. The NOAEL for both maternal and developmental toxicity in the current study was 600 ppm.

Effect on developmental toxicity: via oral route

Endpoint conclusion:

no study available

Effect on developmental toxicity: via inhalation route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEC

2 114 mg/m³

Species:

mouse

Effect on developmental toxicity: via dermal route

Endpoint conclusion:

no study available

Additional information

DEVELOPMENTAL TOXICITY

The developmental toxicity / teratogenicity of Tetrahydro-3-methylfuran (3meTHF) has been adequately characterized by read-across to a closely related substance, Tetrahydrofuran (CAS# 109-99-9). The developmental toxicity / teratogenicity of tetrahydrofuran (THF) has been studied in both rats and mice following inhalation exposures. Pregnant and virgin female Sprague-Dawley rats were exposed to 0, 600, 1800 or 5000 ppm of tetrahydrofuran vapors whole-body for 6 hours/day, 7 days/week on days of gestation (DG) 6 to 19. Pregnant rats at the 5000 ppm exposure concentration displayed decreased body weights, however, virgin female rats were not similarly affected indicating that pregnancy was a factor in the toxicological response. Mean gravid uterine weights and extra-gestational weight gains were reduced at the 5000 ppm exposure concentration relative to the control, but the differences were not significant. There were no effects on the percentage of live rat fetuses/litter or on fetal sex ratios. Fetal body weights were reduced at the highest exposure concentration. Significant fetal malformations were not observed, but several malformations were observed at low incidences (< 0.4% in all cases) that were not present in either the concurrent control or contemporary (historical) control animals. These included anal atresia, cleft palate, vestigal tail, and vertebral agenesis. The NOAEL for both maternal and developmental toxicity in the rat was 1800 ppm. Pregnant and virgin female Swiss (CD-1) mice were exposed to 0, 600, 1800 or 5000 ppm of tetrahydrofuran vapors whole-body for 6 hours/day, 7 days/week on DG 6 to 17. Due to an unexpectedly high rate of toxicity at the highest exposure concentration, exposures were discontinued on DG 11 (total of 6 exposures). A total of 30% of exposed virgin female mice died during exposure days 1 through 5. Severe central nervous system depression was proposed as causing or contributing to death. Sedation lasting for up to 1 hour following exposures was observed in all animals in the 5000 ppm exposure group as well as some animals in the 1800 ppm exposure group. Exposures to THF had no effect on the number of implantations/dam. The number and percentage of live fetuses/litter in both the 1800 and 5000 ppm exposure groups were reduced compared to controls. Neither fetal weights nor fetal sex ratios were affected by exposures at 1800 or 5000 ppm. Because only a single litter with live fetuses was present at the 5000 ppm exposure concentration, statistical analysis at this level was not possible. Although not statistically significant, several malformations were observed at low incidences in the 1800 ppm group that were not present either in the 0 ppm controls or contemporary controls: cleft palate, edema, ectopic ovaries, and undescended testes. These latter malformations were all observed in fetuses from a single low-weight litter that also had a 54% incidence of resorptions. There was an increased incidence of reduced ossifications of the sternebrae in the 1800 ppm exposure group and these correlated with increasing exposure concentrations. Tetrahydrofuran, although showing clear evidence of embryotoxicity in Swiss CD-1 mice, was not judged to be a selective developmental toxicant in the CD-1 mouse. This appraisal is based on the clear presence of maternal toxicity at the highest dose level and extending to the 1800 ppm dose level. The NOAEL for maternal toxicity in the current study was 600 ppm. The NOAEL for developmental toxicity was 600 ppm. In a second study in rats, THF was administered to pregnant rats by whole-body inhalation from Days 6 through 15 of gestation at nominal concentrations of 0, 200, 500, 2500 and 5000 ppm (Part 1) or 0, 1000 and 5000 ppm (Part 2). There was no maternal mortality but the highest exposure concentration (5000 ppm) was toxic to the dams; toxic responses included significant decreases in feed consumption and body weight gain during the exposure period, lethargy and incoordination, and an absence of response to a noise stimulus. A reduced response to a noise stimulus was also observed at the 1000 and 2500 ppm exposure concentrations. Malformations were not increased following exposure to THF but fetuses at the highest exposure concentration had reduced body weights and sternebral ossification was less that control. Embryotoxicity, expressed as developmental delay, occurred only at 5000 ppm and in the presence of maternal toxicity. Thus, THF was not selectively toxic to the developing rat conceptus in this study.

 

Justification for selection of Effect on developmental toxicity: via inhalation route:
Reliable key study on analogue read-across substance

Toxicity to reproduction: other studies

Additional information

Tetrahydro-3 -methylfuran (3 -methyl-THF) has not been specifically investigated for its potential to cause developmental effects but can be assessed based on information on a close structurally related analogue, tetrahydrofuran (THF, CAS# 109 -99 -9). The developmental toxicity/teratogenicity of THF has been studied in both rats and mice following inhalation exposures. Pregnant and virgin female Sprague-Dawley rats were exposed to 0, 600, 1800 or 5000 ppm of THF vapors whole-body for 6 hours/day, 7 days/week on days of gestation (DG) 6 to 19. Pregnant rats at the 5000 ppm exposure concentration displayed decreased body weights, however, virgin female rats were not similarly affected indicating that pregnancy was a factor in the toxicological response. Mean gravid uterine weights and extra-gestational weight gains were reduced at the 5000 ppm exposure concentration relative to the control, but the differences were not significant. There were no effects on the percentage of live rat fetuses/litter or on fetal sex ratios. Fetal body weights were reduced at the highest exposure concentration. Significant fetal malformations were not observed, but several malformations were observed at low incidences (< 0.4% in all cases) that were not present in either the concurrent control or contemporary (historical) control animals. These included anal atresia, cleft palate, vestigal tail, and vertebral agenesis. The NOAEL for both maternal and developmental toxicity in the rat was 1800 ppm. Pregnant and virgin female Swiss (CD-1) mice were exposed to 0, 600, 1800 or 5000 ppm of THF vapors whole-body for 6 hours/day, 7 days/week on DG 6 to 17. Due to an unexpectedly high rate of toxicity at the highest exposure concentration, exposures were discontinued on DG 11 (total of 6 exposures). A total of 30% of exposed virgin female mice died during exposure days 1 through 5. Severe central nervous system depression was proposed as causing or contributing to death. Sedation lasting for up to 1 hour following exposures was observed in all animals in the 5000 ppm exposure group as well as some animals in the 1800 ppm exposure group. Exposures to THF had no effect on the number of implantations/dam. The number and percentage of live fetuses/litter in both the 1800 and 5000 ppm exposure groups were reduced compared to controls. Neither fetal weights nor fetal sex ratios were affected by exposures at 1800 or 5000 ppm. Because only a single litter with live fetuses was present at the 5000 ppm exposure concentration, statistical analysis at this level was not possible. Although not statistically significant, several malformations were observed at low incidences in the 1800 ppm group that were not present either in the 0 ppm controls or contemporary controls: cleft palate, edema, ectopic ovaries, and undescended testes. These latter malformations were all observed in fetuses from a single low-weight litter that also had a 54% incidence of resorptions. There was an increased incidence of reduced ossifications of the sternebrae in the 1800 ppm exposure group and these correlated with increasing exposure concentrations. THF, although showing clear evidence of embryotoxicity in Swiss CD-1 mice, was not judged to be a selective developmental toxicant in the CD-1 mouse. This appraisal is based on the clear presence of maternal toxicity at the highest dose level and extending to the 1800 ppm dose level. The NOAEL for maternal toxicity in the current study was 600 ppm. The NOAEL for developmental toxicity was 600 ppm. In a second study in rats, THF was administered to pregnant rats by whole-body inhalation from Days 6 through 15 of gestation at nominal concentrations of 0, 200, 500, 2500 and 5000 ppm (Part 1) or 0, 1000 and 5000 ppm (Part 2). There was no maternal mortality but the highest exposure concentration (5000 ppm) was toxic to the dams; toxic responses included significant decreases in feed consumption and body weight gain during the exposure period, lethargy and incoordination, and an absence of response to a noise stimulus. A reduced response to a noise stimulus was also observed at the 1000 and 2500 ppm exposure concentrations. Malformations were not increased following exposure to THF but fetuses at the highest exposure concentration had reduced body weights and sternebral ossification was less that control. Embryotoxicity, expressed as developmental delay, occurred only at 5000 ppm and in the presence of maternal toxicity. Thus, THF was not selectively toxic to the developing rat conceptus in this study and the same would be expected for 3-methyl-THF.

Justification for classification or non-classification

Tetrahydro-3 -methylfuran (3 -methyl-THF) has not been specifically investigated for its potential to cause reproductive or developmental effects. However, based on information on a close structurally related analogue, tetrahydrofuran (THF, CAS# 109 -99 -9), 3 -methyl-THF does not meet the criteria for classification as R60 (May impair fertility), R61 (May cause harm to the unborn chile), R62 (Possible risk of impaired fertility, or R63 (Possible risk of harm to the unborn child) under the EU DSD classification criteria (EU Directive 67/548/EEC) or as a Reproductive Toxicant (Cat. 1 or 2) or Effects on or via Lactation under the EU CLP classification criteria (Regulation (EC) 1272/2008). THF is not a selective reproductive or developmental toxicant based on studies conducted in rats and mice. The NOAEL for reproductive effects was reported as 9,000 ppm THF based on lack of significant adverse effects. In mice, THF did cause embryotoxicity at an inhalation exposure concentration (1800 ppm) that also caused significant maternal effects. Similarly in rats, no selective effect on the developing fetus is observed.