Benzene, C15-16-alkyl derivs.

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

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

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: GLP study published in peer-reviewed journal.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 416 (Two-Generation Reproduction Toxicity Study)

Version / remarks:

EPA/TSCA

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories
- Housing: wire mesh cages
- Diet (e.g. ad libitum): Ralson Purina commercial laboratory feed, ad libitum
- Water (e.g. ad libitum): tap water, ad libitum


ENVIRONMENTAL CONDITIONS
- Temperature (°F): 65-79
- Humidity (%): 17-76
- Photoperiod (hrs dark / hrs light): 12 hrs light/12 hrs dark

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on mating procedure:

- M/F ratio per cage: 1/1
- Length of cohabitation: 7 nights, if female was still not pregnant, she was moved to another male for an additional 7 nights, and then to a third male if needed
- Proof of pregnancy: vaginal plug or sperm in vaginal smear referred to as day 0 of pregnancy
- After successful mating each pregnant female was caged (how): individually

Analytical verification of doses or concentrations:

yes

Duration of treatment / exposure:

daily

Frequency of treatment:

F0: Treatment was started 10 weeks before mating. For males, dosing continued for 2 weeks after mating (total of 105 days). For females, dosing continued through lactation for a total of 127 treatment days.

F1: The F1 generation was treated similarly to the F0 generation, but were exposed beginning 11 weeks pre-mating.

Remarks:

Doses / Concentrations:
0, 5, 50 and 500 mg/kg
Basis:
actual ingested

No. of animals per sex per dose:

30 animals of each sex per dose

Control animals:

yes, concurrent vehicle

Parental animals: Observations and examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily


DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: weekly


BODY WEIGHT: Yes
- Time schedule for examinations: males - weekly, females - weekly before mating, days 0, 7, 14, and 20 of gestation, and days 0, 4, 14, and 21 of lactation


FOOD CONSUMPTION: weekly

Litter observations:

STANDARDISATION OF LITTERS
F1 pups were selected for mating at weaning, at least one pup per litter was selected for the adult F1 generation


PARAMETERS EXAMINED
The following parameters were examined in F1 and F2 offspring:
number and sex of pups on days 0, 4, 7, 14, and 21 of lactation, postnatal mortality and presence of gross anomalies daily, weights on days 0, 4, 7, 14, and 21 of lactation

GROSS EXAMINATION OF DEAD PUPS:
yes

Postmortem examinations (parental animals):

SACRIFICE
- Male animals: All surviving animals 2 weeks after mating.
- Maternal animals: All surviving animals at weaning.


GROSS NECROPSY
- Gross necropsy consisted of examination for gross lesions


HISTOPATHOLOGY / ORGAN WEIGHTS
pituitary glands, testes and epididymides, prostate and seminal vesicles, vagina, uterus, ovaries, and gross lesions

Postmortem examinations (offspring):

SACRIFICE
- The F1 offspring not selected as parental animals and all F2 offspring were sacrificed at weaning.
- These animals were subjected to postmortem examinations similar to parental animals above.

Reproductive indices:

mating index, pregnancy rate, fertility index

Offspring viability indices:

pup survival

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

Reproductive performance:

effects observed, treatment-related

CLINICAL SIGNS AND MORTALITY (PARENTAL ANIMALS)
No mortality attributed to treatment was observed.


BODY WEIGHT AND FOOD CONSUMPTION (PARENTAL ANIMALS)
Mean body weights of high-dose-group (500 mg/kg bw/d) males were significantly and consistently reduced {12 = 0.01) in the FO (since premating week); mean body weights of high-dose females were significantly decreased in the FO generation since the 9th week of premating until the first week of lactation (p = 0.05); body weight reduction was significant on day 20 of gestation in both generations (p = 0.01


REPRODUCTIVE PERFORMANCE (PARENTAL ANIMALS)
Mating, pregnancy and fertility rates were not influenced.


GROSS PATHOLOGY (PARENTAL ANIMALS)
No gross postmortem findings.

HISTOPATHOLOGY (PARENTAL ANIMALS)
No histopathological findings.

Dose descriptor:

NOAEL

Effect level:

50 mg/kg bw/day

Basis for effect level:

other: Maternal and paternal general toxicity was reduced weight gain in the high dose group. Reduced litter size in the high dose group.

Mortality / viability:

mortality observed, treatment-related

Body weight and weight changes:

effects observed, treatment-related

VIABILITY (OFFSPRING)
Litter size: Fl and F2 : significant decrease at 500 mg/kg bw/d (p = 0.05 and 0.01 respectively);
pup viability index at birth: Fl: significant decrease at 50 and 500 mg/kg bd/d (p = 0.05) F2: significant decrease at 500 mg/kg bw/d (p = 0.05), since effects at 50 mg/kg bw/d was only noted in a single generation, these effects were not considered biologically significant; survival of pups at day 4 was significantly decreased at 500 mg/kg bw/d in the Fl and F2 litters; survival of pups at day 21 (related to day 4) was significantly decreased only in the F2 litter at 50 mg/kg bw/d (p = 0.05), since effects at 50 mg/kg bw/d was only noted in a single generation, these effects were not considered biologically significant

BODY WEIGHT (OFFSPRING)
mean pup weight:
Fl litters; significant reduction at 50 and 500 mg/kg bw/d at day 7 and only at 500 mg/kg bw/d at day 14 and 21 (p = 0.05), since the reduction in the 50 mg/kg bw/d group was only noted at day 7 and only in the F1 generation, this effect was not considered biologically significant
F2 litters: significant reduction at 500 mg/kg bw/d at day 14 and 21 (p = 0.05).


OTHER FINDINGS (OFFSPRING)
In the high-dose-group, gestation length was significantly increased for the F2 litter interval (22.4 d compared to 22.0 in controls).

Dose descriptor:

NOAEL

Generation:

F1

Effect level:

50 mg/kg bw/day

Basis for effect level:

other: Reduced survival and weight gain in high dose group. Sporadic occurrences at mid dose level.

Dose descriptor:

NOAEL

Generation:

F2

Effect level:

50 mg/kg bw/day

Basis for effect level:

other: Reduced survival and weight gain in the high dose group. Sporadic occurrences at mid dose level.

Reproductive effects observed:

not specified

Litter Size and Pup Survival Indices

Dose (mg/kg/day)	Litter size (mean)	Pup viability index at birth (%)	Pup survival days 0-4 (%)	Pup survival days 0-4 (%)^1	Pup survival days 4-21 (%)
F1 litters
0	12.7	99.1	93.8		95.7
5	12.8	98.0	93.4		91.0
50	13.1	95.4	92.3		84.2
500	10.0	95.4	85.0		94.7
F2 litters
0	11.3	98.6	80.2	93.5	98.1
5	11.6	98.2	87.3	94.4	97.1
50	13.1	97.3	89.5	92.3	89.1
500	7.0	89.0	84.1	85.9	97.3

¹Excludes data for litters in which all pups died during the Day 0-3 interval.

Mean Pup Weights (g)

Dose (mg/kg/day)	Day 0	Day 4- Precull	Day 4- Postcull	Day 7	Day 14	Day 21
F1 litters
0	6.0	8.4	8.4	13.2	27.0	42.7
5	5.9	8.1	8.1	12.9	27.3	42.1
50	5.8	7.5	7.6	11.4	25.1	39.6
500	5.8	8.1	8.1	11.4	23.5	37.7
F2 litters
0	5.8	8.1	8.3	13.9	27.0	40.5
5	5.8	8.5	8.5	14.4	26.9	42.0
50	6.0	8.1	8.1	13.4	25.3	39.5
500	5.8	8.1	8.1	12.1	22.3	34.6

Conclusions:

The NOEL for the maternal and paternal generation was 50 mg/kg bw/day and for the offspring generations.

Executive summary:

In cases where no data were available on the target substance, Benzene, C15 -16 -alkyl derivs., data were read across from a structurally related material (the test substance).

This study examined the effects of exposure to the test substance on reproduction. Groups of 30 female and 30 male rats were exposed to concentrations of 0, 5, 50 and 500 mg/kg day of test substance by oral gavage beginning ten weeks before mating. Animals were then mated. The resulting generation was also exposed to the test substance and mated. Exposure continued through the mating period, and in females through the gestation and lactational periods. All animals were sacrificed and necropsied after exposure. Pups not used for mating were sacrificed at weaning. During the study, animals were observed for clinical signs, mortality, and body weight. Pups were examined for viability and body weight gain. Reproductive indices were also calculated. The NOAEL for parental toxicity was 50 mg/kg/day and the LOAEL was 500 mg/kg/day based on reduced weight gain and litter size in the high dose group. The NOAEL for offspring was 50 mg/kg/day based on reduced body weight gain and survival in the high and mid-dose groups. The LOAEL for offspring was 50 mg/kg/day.

Effect on fertility: via oral route

Endpoint conclusion:

no adverse effect observed

Effect on fertility: via inhalation route

Endpoint conclusion:

no study available

Effect on fertility: via dermal route

Endpoint conclusion:

no study available

Additional information

In cases where no data were available on the target substance, Benzene, C15-16-alkyl derivs., data were read across from a structurally related material (the test substance).

In a two-generation reproductive toxicity study (Robinson and Schroeder 1992) in rats for a read-across source substance for Benzene, C15-16-alkyl derivs., the only effects in the parental generation were body weight reductions and reduced litter size in the highest dose (500 mg/kg). No effects were observed in mating, pregnancy or fertility.

This key study examined the effects of exposure to the test substance on reproductive and developmental toxicity. In a two-generation reproductive study conducted under GLP conditions, CD rats were given a single daily dose via gastric intubation of 5, 50 or 500 mg/kg-bw/day over a 35-week period. Clear evidence of toxicity was observed at the 500 mg/kg-bw/day dose level, with the most consistent effects being depressed weight gains in adults, smaller litters, fewer live pups, and decreased pup survival. At 50 mg/kg-bw/day, the only effect was a temporary reduction in pup weight gain at day 7 that returned to normal at days 14 and 21. This temporary reduction occurred in one generation only, and thus was not consistent across generations. Therefore, given the significant effects at 500 mg/kg-bw/day and the non consistent effects at the lower dose, the NOEL for reproductive toxicity is 50 mg/kg-bw/day for both parental and neonatal animals.

Short description of key information:
In a two-generation reproductive toxicity study in rats for a read-across source substance for Benzene, C15-16-alkyl derivs., the only effects in the parental generation were body weight reductions and reduced litter size in the highest dose (500 mg/kg). No effects were observed in mating, pregnancy or fertility.

Effects on developmental toxicity

Description of key information

In a two-generation reproductive toxicity study in rats for a read-across source substance for Benzene, C15-16-alkyl derivs., the only effects in the parental generation were body weight reductions and reduced litter size in the highest dose (500 mg/kg).  No effects were observed in mating, pregnancy or fertility. In the offspring, effects observed in the F1 and/or F2 generations included viability index, survival, body weight reduction, and gestation length at the highest and middle doses.  The resulting NOAEL is 50 mg/kg bw/day.  In a developmental test, maternal rats exposed to oral doses up to 2000 mg/kg bw/day during gestation days 6-15 experienced similar body weight reductions and food consumption, though both increased again following the end of treatment.  No embryotoxicity was observed with the exception of some ossification variation in the highest two doses. The NOAEL is considered to be 125 mg/kg bw/day. Since no embryotoxicity was observed at doses of the test substance that did not also result in effects to the maternal animals, Benzene, C15-16-alkyl derivs. is not classified as teratogenic.

Effect on developmental toxicity: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

125 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Effect on developmental toxicity: via inhalation route

Endpoint conclusion:

no study available

Effect on developmental toxicity: via dermal route

Endpoint conclusion:

no study available

Additional information

In cases where no data were available on the target substance, Benzene, C15-16-alkyl derivs., data were read across from a structurally related material (the test substance).

In a two-generation reproductive toxicity study (Robinson and Schroeder 1992) in rats for a read-across source substance for Benzene, C15-16-alkyl derivs., the only effects in the parental generation were body weight reductions and reduced litter size in the highest dose (500 mg/kg). No effects were observed in mating, pregnancy or fertility. In the offspring, effects observed in the F1 and/or F2 generations included viability index, survival, body weight reduction, and gestation length at the highest and middle doses. The resulting NOAEL is 50 mg/kg bw/day. In a developmental test, maternal rats exposed to oral doses up to 2000 mg/kg bw/day during gestation days 6-15 experienced similar body weight reductions and food consumption, though both increased again following the end of treatment. No embryotoxicity was observed with the exception of some ossification variation in the highest two doses. The NOAEL is considered to be 125 mg/kg bw/day. Since no embryotoxicity was observed at doses of the test substance that did not also result in effects to the maternal animals, Benzene, C15 -16 -alkyl derivs. is not classified as teratogenic.

This key study examined the potential developmental toxicity of the test substance. Groups of 24 mated female rats were exposed to concentrations of 0, 125, 500, and 2000 mg/kg bw/d of test substance by oral gavage during days 6-15 of gestation. On day 20 of gestation, the animals were sacrificed and the uterine contents examined. Pups were removed by caesarean section and soft tissue and skeletal examinations performed. In the maternal parameters, mean body weight gains were significantly decreased from the 10th day of gestation in the 2000 mg/kg bw/d group and from the 12th to 15th day of gestation in the 500 mg/kg bw/d group. Compensatory increases of weight gains occurred in the posttreatment period in these groups. Food consumption was significantly reduced during treatment and significantly increased after treatment in the 500 mg/kg bw/d and 2000 mg/kg bw/d groups. Therefore, the LOAEL for maternal toxicity was 500 mg/kg bw/day based on reduced body weight gain. The NOAEL for maternal toxicity was 125 mg/kg bw/day. Regarding embryotoxicity, no treatment related increases in soft tissue malformations and variations were found. The incidence of fetuses with at least one ossification variation was significantly increased in the 2000 mg/kg/ bw/d group. The main variations were incomplete ossification of several cranial bones and vertebral elements and in addition in the 500 mg/kg bw/d group the incidence of rudimentary rib structures. A significant decrease of those variations in the 125 mg/kg bw/d group was not considered treatment related. Therefore, the LOAEL for embryotoxicity was also 500 mg/kg bw/day based on increased incidence of incomplete ossification. The NOAEL for embryotoxicity was also 125 mg/kg bw/day. Since no embryotoxicity was seen at doses of the test substance that were not toxic to the maternal animals, Benzene, C15 -16 -alkyl derivs. is not classified as teratogenic.