Registration Dossier

Administrative data

Key value for chemical safety assessment

Effects on fertility

Link to relevant study records
Reference
Endpoint:
screening for reproductive / developmental toxicity
Remarks:
based on test type (migrated information)
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2006
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: This study was conducted in accordance with GLP Guidelines.
Reason / purpose:
reference to same study
Qualifier:
according to
Guideline:
OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)
Deviations:
no
Qualifier:
according to
Guideline:
other: USEPA OPPTS 870.3650 (2000)
Deviations:
no
Principles of method if other than guideline:
not applicable
GLP compliance:
yes
Limit test:
no
Species:
rat
Strain:
other: CRL:CD(SD)
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source:
- Age at study initiation: Approximately eight weeks of age at initiation of treatment
- Weight at study initiation: Males: ave 271.1 ± 10.8 g; Females: ave 197.6 ± 12.2 g;
- Housing: animals were housed singly in stainless steel cages, except during breeding (one male and one female) and during the littering phases of the study. During littering, dams (and their litters) were housed in plastic cages provided with ground corn cob nesting material from
approximately GD 19 until completion of lactation.
- Diet (e.g. ad libitum): Animals were provided LabDietâ Certified Rodent Diet #5002 (PMI Nutrition International, St. Louis, Missouri) in meal form,
provided ad libitum.
- Water (e.g. ad libitum): Drinking water obtained from the municipal water source, provided ad libitum.
- Acclimation period: At least one week prior to teh start of the study.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): The average room temperature was maintained at 22 ± 1°C (with a maximum permissible excursion of ± 3°C).
- Humidity (%): The relative humidity was maintained within a range of 40-70%, with the exception of one deviation of 32%.
- Air changes (per hr): Room air was exchanged approximately 12-15 times/hour.
- Photoperiod (hrs dark / hrs light): A 12-hour light/dark photocycle was maintained for all animal room(s) with lights on at 6:00 a.m. and off at 6:00 p.m.

IN-LIFE DATES: Gavage dosing began two weeks prior to breeding on July 20, 2005 for both males and females. Adult males were necropsied on
August 22, 2005 and adult females were necropsied on September 10, 2005.
Route of administration:
oral: gavage
Type of inhalation exposure (if applicable):
not specified
Vehicle:
other: 0.5% Methyl Cellulose
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:

Dose solutions were prepared in a 0.5% METHOCEL solution to achieve dose levels of 0, 50, 150 and 500 mg/Kg/day, body weight adjusted.

Oral gavage is the preferred route of exposure according to OECD Guideline 422.Male rats were dosed daily for 14 days prior to mating and
continuing throughout the mating period for a total of 33 days. Female rats were dosed once daily for 14 days prior to breeding, and continuing
through breeding (two weeks), gestation (three weeks), and lactation (four days).

The test material was administered in a 0.5% METHOCEL A4M vehicle, such that a dose volume of 4 ml/kg body weight yielded the targeted dose.
Dose volumes were adjusted using the most current body weight. Dose suspensions were prepared periodically throughout the study period based upon stability.
Details on mating procedure:
Breeding of the adults commenced after approximately two weeks of treatment. Each female was placed with a single male from the same dose level
(1:1 mating) until pregnancy occurred or two weeks had elapsed. During the breeding period, daily vaginal lavage samples were evaluated for the
presence of sperm as an indication of mating. Theday on which sperm was detected or a vaginal copulatory plug was observed in situ was
considered GD 0. The sperm- or plug-positive (presumed pregnant) females were thenseparated from the males and returned to their home cages. If
mating had not occurred after two weeks, the animals were separated without further opportunity for mating.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Analyses of all dosing suspensions from the initial mix revealed mean concentrations ranging from 99.2 to 104% of targeted concentrations.
Analyses of aliquots for the low- and high-dose suspensions indicated that the test material was homogeneously distributed. DIBC in 0.5% methylcellulose was found to be stable for 25 and 64 days at concentrations of 2.50 and 250 mg/ml.
Duration of treatment / exposure:
Oral gavage is the preferred route of exposure according to OECD Guideline 422.
Male rats were dosed daily for 14 days prior to mating and continuing throughout the
mating period for a total of 33 days. Female rats were dosed once daily for 14 days prior
to breeding, and continuing through breeding (two weeks), gestation (three weeks), and
lactation (four days).
Frequency of treatment:
Once Daily
Details on study schedule:
0 (control), 50, 150, or 500 mg/kg/day
- F1 parental animals not mated until [...] weeks after selected from the F1 litters.
- Selection of parents from F1 generation when pups were [...] days of age.
- Age at mating of the mated animals in the study: [...] weeks
Remarks:
Doses / Concentrations:

Basis:
actual ingested
Gavage
No. of animals per sex per dose:
12 male and 12 female.
Control animals:
yes
Details on study design:
- Dose selection rationale: A preliminary range-finding study was performed to aid in dose level selection for the main study. In this study, five
rats/sex were administered DIBC by gavage for 14 days at dose levels of 0, 250, 500,
750, or 1000 mg/kg/day. All animals survived to the scheduled necropsy. Transient increased salivation (perioral soiling clear) was recorded in
both males and females at doses >/= 500 mg/kg/day. Feed consumption and body weights were not obviously altered at any dose level. The most
noteworthy effect was an increase in liver weights in both sexes at all dose levels. The liver weight increases ranged from 19.7-41.8% in males and
4.8-37.6% in females. Kidney weights were also increased, but to a lesser extent. There were no treatment-related gross observations recorded at
necropsy.

The high-dose level was based upon data obtained from a preliminary range-finding study (see above) and was expected to induce some toxic
effects, but not death or obvious suffering. The lower dose levels were selected to provide dose response data for any toxicity that may have been
observed among the high-dose group rats and to establish a NOEL.

- Rationale for animal assignment (if not random): Prior to test material administration, animals were stratified by body weight and thenrandomly
assigned to treatment groups using a computer program designed to increase the probability of uniform group mean weights and standard
deviations at the start of the study. Animals that were placed on study were uniquely identified via subcutaneously implanted transponders
Positive control:
Not applicable
Parental animals: Observations and examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: At least twice daily
- Cage side observations: This examination was
typically performed with the animals in their cages and was designed to detect significant clinical abnormalities that were clearly visible upon a
limited examination, and to monitor the general health of the animals. The animals were not hand-held for these observations unless deemed
necessary. Animals were examined for abnormalities such as, but were not limited to: decreased/increased activity, repetitive behavior,
vocalization, incoordination/limping, injury, neuromuscular function (convulsion, fasciculation, tremor, twitches), altered respiration, blue/pale
skin and mucous membranes, severe eye injury (rupture), alterations in fecal consistency, and fecal/urinary quantity. In addition, all animals were observed for morbidity, mortality, and the availability of feed and waterat least twice daily.

DETAILED CLINICAL OBSERVATIONS: Yes See TABLE 1
- Time schedule: Detailed clinical observations (DCO) were conducted on all rats pre-exposure and weekly throughout the study. Mated females
received DCO examinations on GD 0, 7, 14, and 20, and LD 3. The DCO was conducted at approximately the same time each examination day
prior to dosing, according to an established format. The examination included cage-side, hand-held and open-field observations, which are
recorded categorically or using explicitly defined scales (ranks).

BODY WEIGHT: Yes / No / No data
- Time schedule for examinations:


OTHER:
Oestrous cyclicity (parental animals):
Data not collected however, There were no treatment-related effects at any dose level on reproductive indices such as time to mating.
Sperm parameters (parental animals):
Parameters examined in adult male parental generations: testis weight and epididymis weight.
Litter observations:
STANDARDISATION OF LITTERS
Litters were not standarized, during littering, dams (and their litters) were housed in plastic cages provided with ground corn cob nesting material
from approximately GD 19 until completion of lactation.

PARAMETERS EXAMINED
The following parameters were examined in offspring: All litters were examined as soon as possible after delivery. The following information was
recorded on each litter: date of parturition, litter size on the day of parturition (LD 0), the number of live and dead pups on LD 0, 1, and 4 , and the
sex and the weight of each pup on LD 1 and 4. Any visible physical abnormalities or demeanor changes in the neonates were recorded as they were observed during the lactation period (see Daily In-Life Observations). In addition, pup clinical observations were recorded on each litter on days 0
through 4 postpartum.

GROSS EXAMINATION OF DEAD PUPS: Any pups found dead were sexed and examined grossly, if possible, for external and visual defects and then
discarded.
Postmortem examinations (parental animals):
SACRIFICE - All Animals survived through necropsy.
- Male animals: Adult males (fasted) were submitted for necropsy after at least four weeks (actual: TD 34) of exposure.
- Maternal animals: Adult females (fasted) were terminated on LD 5, or at least 24 days after the end of the mating period for females not producing a litter.

GROSS NECROPSY
- A complete necropsy was conducted on all animals.

HISTOPATHOLOGY / ORGAN WEIGHTS
The tissues indicated in Table [#] were prepared for microscopic examination and weighed, respectively.
Postmortem examinations (offspring):
All pups surviving to LD 4 were euthanized by oral administration of sodium pentobarbital solution, examined for gross external alterations, and
then discarded. Any pups found dead or which were euthanized in moribund condition were examined to the extent possible and discarded.
Statistics:
See Table 1 Below.
Reproductive indices:
There were no treatment-related effects at any dose level on reproductive indices, time to mating, gestation length, postimplantation loss, pup
survival or pup sex ratio.
Offspring viability indices:
Not evaluated
Clinical signs:
no effects observed
Body weight and weight changes:
no effects observed
Description (incidence and severity):
See Body Wt in Table 1 below
Food consumption and compound intake (if feeding study):
no effects observed
Description (incidence and severity):
See Body Wt in Table 1 below
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
See Table 1 below
Other effects:
no effects observed
Reproductive function: oestrous cycle:
not examined
Reproductive function: sperm measures:
not examined
Reproductive performance:
no effects observed
All aminals lived through necropsy
Dose descriptor:
NOAEL
Effect level:
150 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: see 'Remark'
Dose descriptor:
NOEL
Effect level:
50 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: No systemic effects observed
Clinical signs:
not examined
Mortality / viability:
not examined
Body weight and weight changes:
not examined
Sexual maturation:
not examined
Organ weight findings including organ / body weight ratios:
not examined
Histopathological findings:
not examined
All pups surviving to LD 4 were euthanized by oral administration of sodium pentobarbital solution, examined for gross external alterations, and then discarded. Any pups found dead or which were euthanized in moribund condition were examined to the extent possible and discarded.
Dose descriptor:
NOEL
Generation:
F1
Effect level:
500 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: No reproductive/developmental toxicity observed
Reproductive effects observed:
not specified

Table 1. Final Body Weight and Organ Weight Effects

 mg/Kg/day:  0  Historical1  50  150  500
 

MALES

 Final Body Weight (g)  375.0  354.1 -447.2  385.5  401.2  383.7
 Relative Adrenals (g / 100g bw)  0.017  0.014 -0.021  0.014*  0.015  0.016
 Relative Kidneys (g / 100g bw) 0.763   0.713 -0.801  0.740  0.773  0.882
 Absolute Liver (g)  10.519  10.108 -13.420  11.469  12.278*  13.421*
 Relative Liver (g / 100b bw)  2.800  2.719 -3.298  2.972  3.062*  3.493*
 

FEMALES         

 Final Body Weight (g)  277.5 251.2 -290.4   268.0  278.3 258.8*
 Absolute Adrenals (g)  0.089  0.070 -0.094  0.084  0.079  0.132
 Relative Adrenals (g / 100g bw) 0.032   0.027 -0.037  0.031  0.029  0.051$
 Relative Kidneys (g / 100g bw)  0.686  0.696 -0.742  0.741  0.755*  0.773*
 Absolute Liver (g)  9.882  8.185 -10.433  9.714  10.315  10.860
Relative Liver (g / 100g bw)   3.557  3.155 -3.748  3.628  3.696  4.195*

*Statistically Different from Control Mean by Dunnett’s Test, Alpha = 0.05.

$Statistically Different from Control Mean by Wilcoxon’s Test, Alpha = 0.05

1Historical controls group mean range from recent OECD 422 studies.

Bold typeindicates the effects judged to be treatment related.

Conclusions:
Oral gavage administration of 500 mg/kg/day of DIBC resulted in decreased feed consumption and body weights in females only. The liver was the primary target organ for systemic toxicity. Treatment-related statistically significant increases in absolute liver weights were noted in males of the middle (17%) and high dose (28%) groups as well as the high dose females (10%). Corresponding increases in relative liver weights were statistically identified in these groups. The higher liver weights corresponded with very slight hypertrophy of centrilobular hepatocytes in males given 150 or 500 mg/kg/day and females given 500 mg/kg/day. Males given 500 mg/kg/day and females given 150 or 500 mg/kg/day had higher relative kidney weights that were interpreted to be treatment related. There were no corresponding clinical pathologic or histopathologic alterations for the higher kidney weights. There was no evidence of systemic toxicity in rats given 50 mg/kg/day. Additional treatment-related effects that were interpreted to be nonadverse consisted of transient salivation noted only around the time of dosing in the highdose males and females, slightly decreased urine pH in males at all dose levels, as well as increased serum total protein and cho lesterol in males or females given 500 mg/kg/day. Degeneration and/or inflammation of the olfactory and respiratory epithelium were noted in 1, 2-3, and 4-6 rats/sex in the 50, 150, and 500 mg/kg/day groups, respectively. These nasal effects were interpreted to be the result of local irritation of the test material
associated with the gavage procedure. There were no adverse effects of DIBC on neurological or reproductive function at any dose level.
Based on these data, the no-observed-adverse effect level (NOAEL) for general toxicity was considered to be 150 mg/kg/day. The NOEL for reproductive and neurological effects was 500 mg/kg/day, the highest dose level tested.
Effect on fertility: via oral route
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
NOAEL
500 mg/kg bw/day
Study duration:
subacute
Species:
rat
Quality of whole database:
good
Effect on fertility: via inhalation route
Endpoint conclusion:
no study available
Effect on fertility: via dermal route
Endpoint conclusion:
no study available
Additional information

Data on DIBC:

In an oral gavage OECD 422 reproductive developmental screening study combined with a repeated dose study in rats, there were no reproductive or developmental findings at any dose level (50, 150 and 500 mg/kg bw/day). As such the highest dose level tested was the NOEL for reproductive toxicity.

Supporting data on DIBK:

In an oral gavage OECD 421 reproductive developmental screening study in rats there were no effects on reproductive or developmental parameters at any dose (top dose of 1000 mg/kg bw/day).

Supporting data on MIBK (inhalation):

The reproductive toxicity of methyl isobutyl ketone (MIBK) was evaluated in a GLP-compliant multi-generation toxicity study in Crj: CD(SD) rats. The study design was equivalent to OECD test guideline 416. Rats were administered MIBK at target concentrations of 0, 500, 1000 and 2000 ppm (mean measured concentrations were 0, 491, 999, and 1996 ppm or 0, 2012, 4093, and 8178 mg/m3) by whole body inhalation. Parental (F0) findings included transient decreased body weight during the first 2 weeks of exposure at the 2000 ppm dose concentration and increases in absolute and relative liver weights at 2000 ppm. Significant increases in parental F0 and F1 mean absolute and relative kidney weights were observed for males in all MIBK-treated groups relative to the control group; however, mean kidney weights of female rats were unaffected. These increases in mean kidney weight were attributed to an alpha2µ-mediated mechanism and are not considered relevant to human risk identification (see Section 7.9.3). Offspring findings included a single mortality and signs of CNS depression in the F1 group following MIBK exposure on postnatal day (PND) 22 to 25. As a result, F1 MIBK exposure was suspended until PND 27. CNS depressive effects were observed until PND 31, but not after. F1 animals in the 1000 and 2000 ppm groups showed reduced reactivity to novel stimulus during exposure, which was attributed to a sedative effect. There were no effects on reproductive parameters reported. Based on these findings the NOAEL for parental systemic toxicity and neonatal toxicity was considered to be 1000 ppm. The NOAEL for reproductive toxicity was considered to be 2000 ppm, the highest dose tested.

The data on DIBC, DIBK and the structurally similar MIBK are consistent. There were no adverse effects on fertility in any of the studies. In the 2 -generation study using MIBK there was some evidence of toxicity in the F1 generation during the first month following parturition, however these effects occured only at the highest dose (8178 mg/m3) and were due to CNS depression rather than evidence of reproductive or developmental toxicity.


Short description of key information:
Reproductive screening study on DIBC.
Supporting information (reproducitve screening study and a two generation study) comes from category members DIBK, and MIBK

Justification for selection of Effect on fertility via oral route:
Standard guideline OECD 422 study on the registered substance

Effects on developmental toxicity

Description of key information
Oral OECD 422 on DIBC
rat and mice developmental toxicity studies (inhalation) using MIBC
Link to relevant study records
Reference
Endpoint:
developmental toxicity
Type of information:
migrated information: read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Study period:
1984
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Well documented, according to accepted guidelines
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
Deviations:
no
GLP compliance:
yes
Limit test:
no
Species:
rat
Strain:
Fischer 344
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Hilltop Lab Animals, Inc., Scottdale, PA
- Age at study initiation: not reported
- Weight at study initiation: not reported
- Housing: individual
- Diet (e.g. ad libitum): Standard rodent chow ad libitum, except during exposure
- Water (e.g. ad libitum): ad libitum, except during exposure
-Acclimation: 2 week quarantine period

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 24-25°C
- Humidity (%): 44-50%
- Photoperiod (hrs dark / hrs light): 12/12


IN-LIFE DATES: Not reported
Route of administration:
inhalation: vapour
Type of inhalation exposure (if applicable):
whole body
Vehicle:
unchanged (no vehicle)
Details on exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: glass and stainless steel inhalation chamber
- Method of holding animals in test chamber: in cage
- Temperature, humidity, pressure in air chamber: not reported
- Airflow : 1000 L/minute
- Treatment of exhaust air: chamber atmospheres containing MIBK were filtered before leaving an exhaust stack


TEST ATMOSPHERE
- Brief description of analytical method used: Each chamber atmosphere was analyzed for MIBK approximately once every hour during each 6-hour exposure. Daily nominal concentrations (an estimated concentration calculated from the amount of test material delivered and the chamber airflow during the exposure period) were also calculated for each chamber.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
MIBK concentration was checked approximately 10 times during each exposure, and verified using a gas chromatograph equipped with a flame ionization detector.
Details on mating procedure:
- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1:1
- Length of cohabitation: 4 days
- Further matings after two unsuccessful attempts: no
- Verification of same strain and source of both sexes: yes
- Proof of pregnancy: vaginal plug referred to as day 0 of pregnancy
Duration of treatment / exposure:
Rats were exposed to MIBK (or vehicle) on gestational days 6 through 15.
Frequency of treatment:
Exposures were 6 hours/day, for 10 consecutive days
Duration of test:
25 days
Remarks:
Doses / Concentrations:
300, 1000 and 3000 ppm
Basis:
other: target concentrations
Remarks:
Doses / Concentrations:
1229, 4106, 12,292 mg/m3
Basis:
analytical conc.
No. of animals per sex per dose:
35
Control animals:
yes, sham-exposed
Details on study design:
- Dose selection rationale: based on results of a previous range finding study
- Rationale for animal assignment (if not random): random
Maternal examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: daily

BODY WEIGHT: Yes
- Time schedule for examinations: gestational days 0, 6, 9, 12, 15, 18, and 21.

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 21
- Organs examined: The gravid uteri, ovaries (including corpora lutea), cervices, vagina, and peritoneal and thoracic cavities were examined grossly. Ovarian corpora lutea of pregnancy were counted. Maternal liver, kidney and gravid uterine weights were determined.
Ovaries and uterine content:
The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
Fetal examinations:
- External examinations: Yes: all per litter
- Soft tissue examinations: Yes: half per litter
- Skeletal examinations: Yes: half per litter
- Head examinations: Yes: half per litter
Statistics:
Results of quantitative continuous variables were compared to the control group using Levene’s test for equal variances, ANOVA, and t-tests with Bonferroni probabilities. Non-parametric data were analyzed using the Kruskal-Wallis test and the Mann-Whitney U-test. Incidence data were compared using Fischer’s exact test. For all tests, a 2-tailed limit of 0.05 was used as the criterion for significance.
Indices:
no
Historical control data:
none
Details on maternal toxic effects:
Maternal toxic effects:yes

Details on maternal toxic effects:
maternal toxicity was indicated by mortality, clinical signs and elevated absolute and relative liver weight at 3000 ppm.
Dose descriptor:
NOAEL
Effect level:
1 000 ppm
Basis for effect level:
other: maternal toxicity
Details on embryotoxic / teratogenic effects:
Embryotoxic / teratogenic effects:yes

Details on embryotoxic / teratogenic effects:
Fetal toxicity was indicated by reduced fetal body weight at 3000 ppm in rats, an increase in fetal deaths at 3000 ppm and by the increased incidence of poorly ossified or unossified skeletal elements observed in rat fetuses at 3000 ppm.
Dose descriptor:
NOAEL
Effect level:
1 000 ppm
Basis for effect level:
other: fetotoxicity
Dose descriptor:
NOAEL
Effect level:
3 000 ppm
Basis for effect level:
other: teratogenicity
Abnormalities:
not specified
Developmental effects observed:
not specified

 Parameter

 0 ppm

300 ppm

1000 ppm

3000 ppm

Number of dams removed from study at sacrifice (not required)

6

5

4

0

Number of early deliveries

0

0

0

0

Number of aborted fetuses

0

0

0

0

Number of dead dams

0

0

0

0

% non-pregnant at sacrifice

13.8

13.3

19.4

34.3

Number of litters examined

25

26

25

23

Corpora lutea

12.40 ± 1.04

12.46 ± 1.42

12.44 ± 1.39

12.44 ± 1.41

Total implants

9.92 ± 3.43

11.12 ± 2.61

10.88 ± 2.47

11.04 ± 2.32

Percent pre-implantation loss

20.04 ± 26.48

11.23 ± 18.41

13.44 ± 16.76

11.19 ± 16.24

Live fetuses per litter

9.48 ± 3.28

10.77 ± 2.63

10.60 ± 2.52

10.65 ± 2.21

Non-viable implants per litter

0.44± 0.71

0.35± 0.69

0.28± 0.68

0.39± 0.58

Table 2          Offspring outcomes

 Parameter

 0 ppm

300 ppm

1000 ppm

3000 ppm

Body weight (per litter; g)

4.46 ± 0.22

4.33 ± 0.12*

4.39 ± 0.14

4.18 ± 0.13*

Body weight (per litter; males; g)

4.59 ± 0.21

4.46 ± 0.13*

4.54 ± 0.14

4.32 ± 0.14*

Body weight (per litter; females; g)

4.34 ± 0.23

4.20 ± 0.13*

4.25 ± 0.15

4.04 ± 0.15*

External malformations (% of fetuses)

0.4

0.4

0.0

0.0

Visceral malformations (% of fetuses)

0.8

1.4

0.0

0.0

Skeletal malformations (% of fetuses)

0.9

0.0

0.0

0.0

Total malformations (% of fetuses)

1.3

1.1

0.0

0.0

Percent live fetuses

96.11± 5.97

96.96± 6.29

97.47± 6.18

96.72± 4.83

Sex ratio (% males)

44.6± 18.5

49.5± 13.9

46.4± 14.5

47.8± 14.5

Conclusions:
Exposure of Fischer 344 rats to MIBK by inhalation, on GD 6 to 15, resulted in maternal (evidenced by the observation of reductions in body weight and food consumption, increased clinical signs of toxicity, increased kidney weights, in the 3000 ppm group relative to the control) and fetal (evidenced by observation of reduced fetal body weight in the 300 and 3000 ppm groups relative to the control, and retarded ossification in the 3000 ppm group relative to the control) toxicity; however, no evidence of teratogenicity was observed. 
Executive summary:

Developmental and maternal toxicity were evaluated in groups of 35 pregnant Fischer 344 rats exposed by inhalation to 0, 300, 1000, or 3000 ppm (0, 1229, 4106, 12,292 mg/m3) MIBK for 6 hrs/day on gestation days 6 through 15. Animals were sacrificed on gestation day 21. Dams were evaluated for exposure-related changes in clinical signs, body weight, food consumption, organ weights (kidney, liver, and gravid uterus), and reproductive parameters; fetuses were evaluated for exposure-related changes in body weight and viability, and for external, skeletal, and thoracic and peritoneal visceral alterations. Maternal mean body weight, weight gain, and food consumption were significantly decreased in rats exposed to 12,292 mg/m3(but not to 4106 mg/m3or lower ) during the exposure period, but they had recovered to control levels by the day of sacrifice. Maternal clinical signs observed in rats included coordination loss, hindlimb weakness, paresis, irregular gait, hypoactivity, ataxia, unkempt fur, negative tail or toe pinch, piloerection, lacrimation, or red perioral encrustation. These clinical signs were observed only during the exposure period and only at 12,292 mg/m3. No exposure-related deaths occurred in the rat exposure groups. Statistical analyses by the authors were per dam or per litter. No exposure-related effects were observed in rats with respect to numbers of corpora lutea, total implants, percent implantation loss, live fetuses per litter, nonviable implants per litter, percent live fetuses, and sex ratio. Fetal body weights (litter weight, male weight per litter, and female weight per litter) were significantly reduced in rats exposed to 1229 (the mean by 3%) and 12,292 mg/m3 (the mean by 6%) but not to 4106 mg/m3. The authors indicated that the reduction in rat fetal body weight was confounded by a skewed distribution of litter size, whereby higher doses had very small litters and smaller litters had varied mean weights across dose, while lower-dosed dams appeared to have larger litters and larger litters showed a dose-dependence in mean weight. There was no statistically significant increase in the number of rat fetuses per litter. The authors decided the reductions in rat fetal body weight was not treatment-related. No exposure-related change in the incidence of malformations of any type were observed in rat fetuses. The number of litters with observations indicating retarded skeletal ossification was significantly increased to various degrees in rats at 12,292 mg/m3 relative to controls for a variety of skeletal endpoints, with scattered increases in litters with retarded ossification at lower exposure levels that were not considered by the authors to be exposure-related. 4106 mg/m3 was considered to be the NOEL for both maternal animals and offspring.

 

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
4 106 mg/m³
Study duration:
subacute
Species:
other: rat and mouse
Quality of whole database:
good
Effect on developmental toxicity: via dermal route
Endpoint conclusion:
no study available
Additional information

Data available on DIBC:

In an OECD 422 reproductive screening study in rats, oral gavage exposure at doses up to 500 mg/kg bw/day failed to produce any evidence of overt developmental toxicity (observations limited to weight, sex, number, and gross pathology).

No OECD guideline developmental studies are available for DIBC. Therefore data from the read across analogue, MIBK is used to address this endpoint. Support for the use of read across to address this endpoint is included in the document attached to section 13. In brief, the available toxicokinetic data demonstrate that DIBC and DIBK are metabolised to each other and to the same final metabolite. This metabolic pathway and the metabolites produced are structurally similar to those of MIBC and MIBK. Based on the structural similarity, common metabolic pathways and consistency in the systemic toxicity it is considered justified to utilise data on MIBK and DIBK to assess the hazards of DIBC.

Data on MIBK:

Developmental and maternal toxicity were evaluated in groups of 35 pregnant Fischer 344 rats and 30 pregnant CD-1 mice exposed by inhalation to 0, 300, 1000, or 3000 ppm (0, 1229, 4106, 12,292 mg/m3) MIBK for 6 hrs/day on gestation days 6 through 15 (Tyl, 1984; Tyl et al., 1987). Animals were sacrificed on gestation day 21 (rats) or 18 (mice). Dams were evaluated for exposure-related changes in clinical signs, body weight, food consumption, organ weights (kidney, liver, and gravid uterus), and reproductive parameters; fetuses were evaluated for exposure-related changes in body weight and viability, and for external, skeletal, and thoracic and peritoneal visceral alterations. Maternal mean body weight, weight gain, and food consumption were significantly decreased in rats exposed to 12,292 mg/m3 (but not to 4106 mg/m3 or lower) during the exposure period, but they had recovered to control levels by the day of sacrifice; maternal body weight was not affected in mice. Maternal clinical signs observed in rats or mice included coordination loss, hindlimb weakness, paresis, irregular gait, hypoactivity, ataxia, unkempt fur, negative tail or toe pinch, piloerection, lacrimation, or red perioral encrustation. These clinical signs were observed only during the exposure period and only at 12,292 mg/m3. Three maternal deaths (12% of the animals in the group) occurred in mice exposed to 12,292 mg/m3 after the first exposure on gestation day 6; no further deaths occurred in that group, and no exposure-related deaths occurred in the other mouse or rat exposure groups. Neonates from those dams were not considered in the final evaluation. Statistical analyses by the authors were per dam or per litter. No exposure-related effects were observed in rats or mice with respect to numbers of corpora lutea, total implants, percent implantation loss, live fetuses per litter, nonviable implants per litter, percent live fetuses, and sex ratio. In mice, there was an increased mean number of dead fetuses per litter at 12,292 mg/m3 (0.6 per litter compared to 0.1 in controls). Fetal body weights (litter weight, male weight per litter, and female weight per litter) were significantly reduced in rats exposed to 1229 (the mean by 3%) and 12,292 mg/m3 (the mean by 6%) but not to 4106 mg/m3; and in mice, fetal body weights were statistically significantly reduced at 12,292 mg/m3 (the mean by 13%) but not at 4106 mg/m3 or below. The authors indicated that the reduction in rat fetal body weight was confounded by a skewed distribution of litter size, whereby higher doses had very small litters and smaller litters had varied mean weights across dose, while lower-dosed dams appeared to have larger litters and larger litters showed a dosedependence in mean weight. There was no statistically significant increase in the number of rat or mouse fetuses per litter. The authors decided the reductions in rat fetal body weight was not treatment-related. No exposurerelated change in the incidence of malformations of any type were observed in rat and mouse fetuses. The number of litters with observations indicating retarded skeletal ossification was significantly increased to various degrees in both rats and mice at 12,292 mg/m3 relative to controls for a variety of skeletal endpoints, with scattered increases in litters with retarded ossification at lower exposure levels that were not considered to be exposure-exposure-related.

Based on the findings in these two studies, the NOAEC for maternal and fetal toxicity was confirmed as the mid dose group, 4106 mg/m3.

When considering how to apply this NOAEC for developmental toxicity to DIBC the differences in vapour pressure between MIBK and DIBC should be considered. MIBK has a vapour pressure of 2640 Pa whereas DIBC has a vapour pressure of 18.9 Pa. Based on this vapour pressure, the highest attainable vapour concentration for DIBC would be 184 ppm, which is approximately half of the NOAEC from the MIBK developmental toxicity studies. Based on this, and taking into consideration the other toxicological data (including repeated dose and reproductive toxicity studies), it is considered very unlikely that DIBC would be developmentally toxic at concentrations up to and exceeding the saturated vapour pressure.


Justification for selection of Effect on developmental toxicity: via inhalation route:
Key study available on read across analogue

Justification for classification or non-classification

In the available studies for the members of this small category, there are no findings in the reproductive or developmental studies that would trigger classification for reproductive or developmental toxicity.