Dimethyl adipate

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Link to relevant study records

Reference

Endpoint:

one-generation reproductive toxicity

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

This IUCLID for dimethyl adipate is compiled using data from the substance itself, a structurally related compound (dimethyl glutarate) and a mixture of dibasic esters (dimethyl adipate, succinate and glutarate). The toxicity of each of these substances is similar and the document attached justifies why data on the category members can be used to support the data gaps for dimethyl adipate.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 415 [One-Generation Reproduction Toxicity Study (before 9 October 2017)]

Deviations:

yes

Qualifier:

equivalent or similar to guideline

Guideline:

EU Method B.34 (One-Generation Reproduction Toxicity Test)

Deviations:

yes

Principles of method if other than guideline:

- Inhalation exposure.
- Male rats were also exposed until end of lactation period.
- Female rats were not exposed from gestation day 19 through postpartum day 3.

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

other: Crl:CD(SD)BR

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River, Kingston, NY;
- Age at study initiation: (P) 4 wks
- Housing: individually, except during mating (1 male, 1 female)
- Diet (e.g. ad libitum): a libitum
- Water (e.g. ad libitum):ad libitum
- Acclimation period: 7 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 - 24°C
- Humidity (%): 40 - 70%
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

other: inhalation of vapor at lower (0.0, 0.16 and 0.40 mg/L) doses; inhalation of aerosol at highest dose (1mg/L)

Type of inhalation exposure (if applicable):

whole body

Vehicle:

unchanged (no vehicle)

Details on exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: 1.4 m³ stainless steel and glass NYU-style inhalation chamber
- System of generating particulates/aerosols: vapour generation: flash-evaporation in a tube maintained at 250-300°C; aerosol vapour: nebulizer
- Air flow rate:300 L/min

TEST ATMOSPHERE
- Brief description of analytical method used: sample collection: in acetone-filled impingers; analysis method: GC-FID
- Samples taken from breathing zone: yes

Details on mating procedure:

- M/F ratio per cage: 1:1
- Length of cohabitation: 5 days
- Proof of pregnancy: vaginal plug day 1 of pregnancy
- After successful mating each pregnant female was caged (how): individually

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Samples of atmospheric DBE were taken from the rat breathing zone at approximately 60-minute intervals by drawing calibrated volumes of chamber atmosphere through fritted glass midget impingers containing acetone. Samples were analyzed using a Hewlett-Packard Model 5710 Gas Chromatograph (GC) equipped with a flame ionization detector. DBB was chromatographed isothermally at 150°C on a 3 ft x 2 mm ID glass column packed with 10% SP-1000 on Chromasorb W-AW 100/120 mesh.

Chamber concentrations were determined by comparing the chamber sample GC response with that obtained from standard samples prepared by quantitative dilution of DBE in acetone. The DBE chamber concentration was calculated after measuring the peak area of the largest DBE component, dimethyl glutarate. In addition, the relative amounts of the 3 largest DBE components (dimethyl-glutarate, -adipate, and -succinate) were qualitatively compared for each sample.

Duration of treatment / exposure:

pre-breeding: 6 h per day
breeding, gestation, lactation: 6 h per day;

Frequency of treatment:

pre-breeding: 5 days per week, 14 weeks;
breeding, gestation, lactation: 7 days per week, 8 weeks;

Dose / conc.:

0 mg/L air (nominal)

Dose / conc.:

0.16 mg/L air (nominal)

Dose / conc.:

0.4 mg/L air (nominal)

Dose / conc.:

1 mg/L air (nominal)

No. of animals per sex per dose:

20 males; 20 females;

Control animals:

yes, concurrent no treatment

Parental animals: Observations and examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: daily

BODY WEIGHT: Yes
- Time schedule: weekly

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): No

OTHER:
Mating performance, fertility, gestation length, and lactation performance were assessed.

Oestrous cyclicity (parental animals):

no data

Sperm parameters (parental animals):

no data

Litter observations:

STANDARDISATION OF LITTERS
- Performed on day 4 postpartum: yes
- If yes, maximum of 8 pups/litter (4/sex/litter as nearly as possible); excess pups were killed and discarded.

PARAMETERS EXAMINED
The following parameters were examined in F1 offspring: number and sex of pups, viability, weight

Postmortem examinations (parental animals):

All parental animals were sacrificed by exanguation under chloroform anesthesia and examined for gross anatomic abnormalities. Additionally, the nasal tissues were examined histologically; other tissues were examined grossly and saved. Mean organ and organ-to-body ratios were calculated for the brain, heart, lungs, liver, spleen, kidneys, testes and thymus.

Postmortem examinations (offspring):

Ten 21-day old arbitrarily selected pups of each sex per dose group were sacrificed by exanguination under chloroform anesthesia and examined for gross anatomic abnormalities. Mean organ and organ-to-body ratios were calculated for the brain, liver, kidneys, and testes.

Statistics:

For parental organ and body weight analyses, data were statistically analyzed by a one-way ANOVA. When the ratio of variance (F) indicated a significant group variation, test groups were compared with appropriate control group by least significant difference test for body weight data and by Dunnett's test for organ and final body weight data. Litter data were analyzed by Mann-Whitney U-test. Significance for statistical tests was judged at the 0.05 probability level.

Clinical signs:

effects observed, treatment-related

Dermal irritation (if dermal study):

not examined

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Body weights were decreased in the 0.40 mg/L group female rats during the last week of the study. Weights were slightly decreased in male and female rats in the 1.0 mg/L group starting around the seventh week of the study.

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, non-treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Histopathologic evaluation of parental generation rat nasal tissues showed squamous metaplasia primarily in the olfactory epithelium in all groups exposed to DBE. The nasal effect was minimal in the 0.16 mg/L group rats and of mild to moderate severity in the 0.40 and 1.0 mg/L groups. The squamous metaplasia was characterized by a flattening and pavementing of epithelial cells which replaced the normal architecture of olfactory epithelium. In some cases, particularly in the 0.40 and 1.0 mg/L rats, this squamous change was accompanied by a very minimal to mild suppurative inflammation. The squamous metaplasia was present primarily in the olfactory epithelium of the dorsal meatus, along the dorsal portion of the nasal septum, and on the tips of the ecto- and endoturbinates in the nasal cavity. There was also an increase in squamous metaplasia of the respiratory epithelium in the nasal cavity in the high-dose rats. The severity of the lesions ranged from absent-to-minimal up to moderate in some rats. One male rat in the 1.0 mg/L group had a meningeal sarcoma surrounding the olfactory region of the brain. Because the tumor did not communicate with the nasal cavity and the tumor cell type was unrelated to any nasal epithelial cell types, the tumor was considered to be unrelated to inhalation of DBE.

Histopathological findings: neoplastic:

effects observed, non-treatment-related

Description (incidence and severity):

One male rat in the 1.0 mg/L group had a meningeal sarcoma surrounding the olfactory region of the brain. Because the tumor did not communicate with the nasal cavity and the tumor cell type was unrelated to any nasal epithelial cell types, the tumor was considered to be unrelated to inhalation of DBE.

Other effects:

not examined

Reproductive function: oestrous cycle:

not examined

Reproductive function: sperm measures:

not examined

Reproductive performance:

no effects observed

Description (incidence and severity):

No treatment-related differences were observed between the control and test groups with regard to male or female fertility, gestation length, litter sizes, viability, or lactation performance.

BODY WEIGHTS AND CLINICAL SIGNS
Body weights were decreased in the 0.40 mg/L group female rats during the last week of the study. Weights were slightly decreased in male and female rats in the 1.0 mg/L group starting around the seventh week of the study. No unusual signs or behaviours that could be associated with exposure to DBE were seen in rats in any of the treated groups. Parental rats in the 1.0 g/L group showed wet fur during exposures from aerosol deposition. The fur dried about 2 hours after exposure.

REPRODUCTION PARAMETERS
No treatment-related differences were observed between the control and test groups with regard to male or female fertility, gestation length, litter sizes, viability, or lactation performance. A slight but statistically significant decrease in viability index at birth (number of pups born alive per number of pups born) was observed in the 0.16 mg/L DBE group but this was considered to be unrelated to DBE exposure because it was not seen at either of the two higher exposure concentrations. All pups delivered by both DBE-exposed and control rats appeared outwardly normal. Body weights at birth and weaning (21 days pp) were significantly lower in the 1.0 mg/L group. The fertility rate in the control group was lower than that of the test groups (60% versus 75 to 90% for the test groups) and is low compared to historical rates for this laboratory. One potential contributing factor to the low fertility rate in the control group is that there were some males that never had the opportunity to mate with a subsequently proven fertile female; three of these males were in the control group, three in the 0.4 mg/L group, and two were in the 0.16 mg/L group. On the other hand all the males in the 1 mg/L group were mated with females who were subsequently proven to be fertile. Although the cause is uncertain, the control group low fertiIity rate did not impact the toxicity evaluation since the fertility rate in the DBE-exposed groups was well within historical limits.

PATHOLOGY
No gross pathologic changes were seen in any of either the parental rats or their offspring. Histopathologic evaluation of parental generation rat nasal tissues showed squamous metaplasia primarily in the olfactory epithelium in all groups exposed to DBE. The nasal effect was minimal in the 0.16 mg/L group rats and of mild to moderate severity in the 0.40 and 1.0 mg/L groups. The squamous metaplasia was characterized by a flattening and pavementing of epithelial cells which replaced the normal architecture of olfactory epithelium. In some cases, particularly in the 0.40 and 1.0 mg/L rats, this squamous change was accompanied by a very minimal to mild suppurative inflammation. The squamous metaplasia was present primarily in the olfactory epithelium of the dorsal meatus, along the dorsal portion of the nasal septum, and on the tips of the ecto- and endoturbinates in the nasal cavity. There was also an increase in squamous metaplasia of the respiratory epithelium in the nasal cavity in the high-dose rats. The severity of the lesions ranged from absent-to-minimal up to moderate in some rats. One male rat in the 1.0 mg/L group had a meningeal sarcoma surrounding the olfactory region of the brain. Because the tumor did not communicate with the nasal cavity and the tumor cell type was unrelated to any nasal epithelial cell types, the tumor was considered to be unrelated to inhalation of DBE.

ORGAN WEIGHTS
In parental rats, liver-to-body weight ratios were slightly lower than the controls in the rats exposed to either 0.40 and 1.0 mg/L. Other incidental differences between test and control rats included slight decreases in absolute heart and kidney weights in female rats in the 0.40 and 1.0 mg/L groups. A slight decrease in absolute spleen weight and a slight increase in relative brain weight were observed in females in the 1.0 mg/L group. These differences were not dose-related and may have been related to the slight body weight differences between the test and control groups and were considered of minimal biological significance.

Key result

Dose descriptor:

NOAEC

Remarks:

for systemic toxicity effects

Effect level:

>= 0.16 mg/L air

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: based on the nasal histopathology data

Key result

Dose descriptor:

NOEC

Remarks:

for reproductive parameters

Effect level:

1 mg/L air

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: no treatment-related effects observed

Key result

Critical effects observed:

yes

Lowest effective dose / conc.:

0.16 other: mg/L

System:

respiratory system: upper respiratory tract

Organ:

nasal cavity

Treatment related:

yes

Dose response relationship:

yes

Relevant for humans:

not specified

Clinical signs:

no effects observed

Dermal irritation (if dermal study):

not examined

Mortality / viability:

mortality observed, non-treatment-related

Description (incidence and severity):

A slight but statistically significant decrease in viability index at birth (number of pups born alive per number of pups born) was observed in the 0.16 mg/L DBE group but this was considered to be unrelated to DBE exposure because it was not seen at either of the two higher exposure concentrations.

Body weight and weight changes:

no effects observed

Description (incidence and severity):

Body weights at birth and weaning (21 days pp) were significantly lower in the 1.0 mg/L group. T

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Sexual maturation:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Description (incidence and severity):

A slight decrease in relative kidney weight was seen in female pups whose parents were exposed to 0.40 mg/L of DBE; however, in the absence of a dose-response relationship, the decreased relative kidney weights were not considered to be related to DBE exposure. No differences were seen in the liver weights of DBE-exposed pups.

Gross pathological findings:

no effects observed

Description (incidence and severity):

All pups delivered by both DBE-exposed and control rats appeared outwardly normal.

Histopathological findings:

no effects observed

Other effects:

no effects observed

Behaviour (functional findings):

not examined

Developmental immunotoxicity:

not examined

A slight but statistically significant decrease in viability index at birth (number of pups born alive per number of pups born) was observed in the 0.16 mg/L DBE group but this was considered to be unrelated to DBE exposure because it was not seen at either of the two higher exposure concentrations. All pups delivered by both DBE-exposed and control rats appeared outwardly normal. Body weights at birth and weaning (21 days pp) were significantly lower in the 1.0 mg/L group. The fertility rate in the control group was lower than that of the test groups (60% versus 75 to 90% for the test groups) and is low compared to historical rates for this laboratory. One potential contributing factor to the low fertility rate in the control group is that there were some males that never had the opportunity to mate with a subsequently proven fertile female; three of these males were in the control group, three in the 0.4 mg/L group, and two were in the 0.16 mg/L group. On the other hand all the males in the 1 mg/L group were mated with females who were subsequently proven to be fertile. Although the cause is uncertain, the control group low fertiIity rate did not impact the toxicity evaluation since the fertility rate in the DBE-exposed groups was well within historical limits. A slight decrease in relative kidney weight was seen in female pups whose parents were exposed to 0.40 mg/L of DBE; however, in the absence of a dose-response relationship, the decreased relative kidney weights were not considered to be related to DBE exposure. No differences were seen in the liver weights of DBE-exposed pups.

Key result

Dose descriptor:

NOAEC

Generation:

F1

Effect level:

>= 1 mg/L air (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: no treatment-related effects observed

Key result

Reproductive effects observed:

no

Reproduction parameters in rats exposed to DBE by inhalation

Parameter	DBE Concentration [mg/L]
	0 (control)	0.16	0.40	1.0
Male fertility [%]	12/20 60	16/20 80	15/20 75	18/20 90
Female fertility [%]	17/20 85	17/20 85	17/20 85	20/20 100
Viability index at birth	100	94.6 *	99.6	99.0
Viability index day 0-4	99.5	93.7	99.2	98.2
Lactation index	100	100	97	99
Gestation index	100	100	100	100
Pups / litter [mean]	13.1	12.5	12.6	12.9
Gestation duration [days]	22.1	22.1	22.1	21.8
Pup weight at birth [g]	6.4 (0.6)	6.4 (0.8)	6.1 (0.1)	5.9 (0.1) *
Pup weight at day 21 [g]            Male            Female	44.3 (2.6) 41.0 (3.9)	44.9 (4.3) 41.7 (4.7)	45.5 (4.1) 44.3 (4.2)	41.8 (2.8) * 40.8 (2.0) *

 * Significantly different to control, p < 0.05

Values in parentheses report standard deviation

Conclusions:

Reproduction in rats was not altered by repeated inhalation exposure to up to 1.0 mg/L DBE, a concentration that produced both body weight and histologic effects in parental rats.

Executive summary:

Dibasic Esters (DBE) has been tested in a reproduction toxicity study on Crl:CD(SD)BR rats after inhalation exposure using a protocol similar to OECD guideline no 415 and EU method B34 in compliance with US TSCA Good Laboratory Practice.

Groups of 20 male and 20 female rats were exposed to DBE at concentrations of 0 (control), 0.16, 0.40 (maximum attainable vapor), or 1.0 mg/L (aerosol) in whole-body inhalation chambers. Exposures were conducted for 6 hours/day, 5 days/week for 14 weeks (pre-breeding) then 7 days/week for 8 weeks (through breeding, gestation, and lactation). The exposures were interrupted for female rats between gestation day 19 and postpartum day 3. Parental examinations included clinical and cage side observations, body weight determination, and assessment of mating performance, fertility, gestation length, and lactation performance. The number and sex of pups, viability, and weight were determined. At the end of the lactation period, all parental rats and ten 21-day old pups of each sex were per group were killed and examined for gross abnormalities. Parental nose tissues were examined histopathologically.

 

No significant differences were observed between control and test rats with respect to mating performance, fertility, length of gestation, or progeny numbers, structure, and viability. Body weights of parental rats and of their offspring were reduced at 1.0 mg/L. The only histopathologic changes detected in the nasal tissues of the parental rats, was an exposure-related increase in squamous metaplasia in the olfactory epithelium. There was an increase in liver-to-body weight ratios in the two higher parental exposure groups and an increase in the lung-to-body weight ratio also seen at 1.0 mg/L. From the results obtained, it can be concluded that reproduction in rats was not altered by repeated inhalation exposure to up to 1.0 mg/L DBE, a concentration that produced both body weight and histologic effects in parental rats.

 

Dibasic Esters (DBE) is not classified for reproduction according to the criteria of Directive 67/548/EC and EU Regulation No. 1272/2008 (CLP).

Effect on fertility: via oral route

Endpoint conclusion:

no adverse effect observed

Effect on fertility: via inhalation route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEC

1 000 mg/m³

Additional information

There are no data available on Dimethyl Adipate, however a 1 -generation study is available for the analogue 'Dibasic Ester Blend'.

One generation study:

The effects of dibasic esters on fertility were assessed by the inhalation route in a one-generation study (equivalent to an OECD 415 study) in rats, exposed to the test concentrations of 0, 160, 400 or 1000 mg/m3 for 14 weeks pre-bredding, and for 8 weeks through breeding, gestation and lactation. No relevant effects occurred in mating performance, fertility, gestation duration, litter size, development or viability, and lactation performance up to the highest concentration tested. The NOEC for reproductive toxicity was therefore 1000 mg/m3.

 

Furthermore, changes in sex hormones were observed in the repeat-dose inhalation toxicity study in rats exposed to each component of the dibasic ester blend for 90 days (for details, see "7.5.3. Repeated dose toxicity: inhalation" section). Increased epididymal sperm counts were noted in male rats exposed to 400 mg/m3 dimethyl adipate, 400 mg/m3 dimethyl succinate, and 50 or 400 mg/m3 dimethyl glutarate. A statistically significant decrease in serum estradiol concentrations was noted in female rats exposed to 400 mg/m3 dimethyl succinate. A significant decrease in serum testosterone concentrations was noted in male rats exposed to 50 or 400 mg/m3 dimethyl glutarate. Serum luteinizing hormone (LH) concentrations were also significantly decreased at 400 mg/m3 dimethyl glutarate. The toxicological significance of these changes was unclear, as a decrease in male sex hormones should have resulted in a reduction of epididymal sperm counts, and yet the opposite was observed. In addition, none of these effects were observed in the dedicated fertility study using the dibasic ester blend. These hormonal variations can therefore be considered incidental.

Short description of key information:

No effects on mating performance, fertility, gestation duration, litter size, development or viability, and lactation performance in rats by inhalation.

Effects on developmental toxicity

Description of key information

No effects on number of resorptions or fetal weight and no increase in external, visceral or skeletal abnormalities in offspring from parent rats exposed by inhalation.

Link to relevant study records

Reference

Endpoint:

developmental toxicity

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

weight of evidence

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Justification for type of information:

This IUCLID for dimethyl adipate is compiled using data from the substance itself, a structurally related compound (dimethyl glutarate) and a mixture of dibasic esters (dimethyl adipate, succinate and glutarate). The toxicity of each of these substances is similar and the document attached justifies why data on the category members can be used to support the data gaps for dimethyl adipate.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

no

GLP compliance:

yes

Limit test:

yes

Species:

rat

Strain:

other: Crl:CD BR

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories Inc., Kingston, NY
- Age at study initiation: females: 63 days, males: 84 days
- Weight at study initiation: females: 146-198g; males: 303-396g
- Housing: individually in stainless steel wiremesh cages
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21-25°C
- Humidity (%): 40-60%
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

inhalation

Type of inhalation exposure (if applicable):

whole body

Vehicle:

unchanged (no vehicle)

Details on exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: 1.4 m3 stainless steel and glass NYU-style inhalation chamber
- Method of holding animals in test chamber: in cages
- System of generating particulates/aerosols: 0.16 and 0.4 mg/L: liquid DBE was metered into a furnace maintained at 50-300°C; for the 1.0 mg/L concentration, mixed aerosol/vapour athmospheres were generated using a Spraying Systems Nebulizer
- Temperature, humidity, pressure in air chamber:
- Air flow rate: about 300 L/min

TEST ATMOSPHERE
- Brief description of analytical method used: GC-FID
- Samples taken from breathing zone: yes

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Samples were analyzed using a Hewlett-Packard Model 5710 Gas Chromatograph (GC) equipped with a flame ionization detector. DBE was chromatographed isothermally at 150°C on a 3' x 2 mm ID glass column packed with 10% SP-1000 on Chromosorb W-AW 1001120 mesh.

Details on mating procedure:

The female rats were cohabited overnight with mature males (1:1). Mating was verified each morning by detection ol a copulation plug in the vagina or on the cage hoard. The day a plug was found was designated Day 1 of gestation (Day 1G). Mated females were stratified by body wcight and assigned to groups by random sampling within each stratum (24 per group).

Duration of treatment / exposure:

In the definitive study, groups of 24 pregnant rats were targeted for exposure to 0 (control), 0.16, 0.4, and 1.0 mg DBE /L. Rats were exposed to whole-body inhalation for 6 hr per day from Days 7 through 16 (10 exposures). The control dams were exposed to air only.

Frequency of treatment:

6h per day

Duration of test:

Day 7 to 16 (10 exposures)

Dose / conc.:

0 mg/L air (nominal)

Remarks:

Measured concentration 0.0 mg/L air

Dose / conc.:

0.16 mg/L air (nominal)

Remarks:

Measured concentration 0.15 mg/L air

Dose / conc.:

0.4 mg/L air (nominal)

Remarks:

Measured concentration 0.38 mg/L air

Dose / conc.:

1 mg/L air (nominal)

Remarks:

Measured concentration 0.99 mg/L air

No. of animals per sex per dose:

24 pregnant rats per dose group

Control animals:

yes, concurrent vehicle

Details on study design:

Dose selection rationale: based on results of a pilot study

Maternal examinations:

Body weights and clinical signs were recorded on the day after arrival and before mating; observations for morbidity and mortality were made daily. Females selected for the study were weighed on Days 1, 7, 9, 11, 13, 15, 17, and 21G. Feed was weighed on Days 1, 3, 9, 11, 13, 15, 17, 19 and 21G and each afternoon on Days 7-16G (the exposure period). Just before euthanasia on Day 21G. each dam was coded, so personnel involved did not know the exposure group to which any dam or fetus belonged. Dams were euthanized by cervical dislocation, a gross pathologic examination was made, and the liver was weighed. The ovaries were removed and the number of corpora lutea were counted at a magnification of 2.5 x (Ednalite).

Ovaries and uterine content:

The uterus was opened and the number and position of all live, dead, and resorbed conceptuses were recorded. Both gravid and empty uteri were weighed. The uterus of each apparently nonpregnant dam was stained with ammonium sulfate solution to determine whether any very early resorption could be identified.

Fetal examinations:

All fetuses were weighed and examined for external alterations at a magnification of 2.5x. About one-half of the live fetuses in each litter (plus all stunted and malformed fetuses) were examined for visceral alterations. For each litter, the maximum stunted weight (MSW) was calculated by subtracting the lightest weight from the total weight dividing by the remaining number of fetuses, and multiplying by 0.666. A fetus weighing the same or less than the MSW was considered stunted, and its weight was omitted after the mean litter weight was calculated. The heads of these fetuses were fixed in Bouin’s solution and examined. All fetuses were sexed internally and then they were fixed in 70% ethanol, eviscerated, macerated in 1% aqueous KOH, and stained with alizarin red S to permit examination of the skeletons for alterations.

Statistics:

The litter was considered the experimental unit for the purpose of statistical evaluation. The level of significance selected was 0.05.

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Clinical observations of perinasal staining (15 rats) and wet fur (20 rats) were seen in the 1.0 mg/L group; while these findings were not seen in the controls. Perinasal staining was seen in 1 rat from the 0.16 mg/L group and in 4 rats from the 0.4 mg/L group; wet fur was also seen in 1 rat from the 0.4 mg/L group. Other clinical observations including alopecia, sores, periocular and facial staining, and swollen extremities were seen but infrequently and with no suggestion of a relationship to DBE exposure.

Dermal irritation (if dermal study):

not examined

Mortality:

no mortality observed

Description (incidence):

All female rats survived the testing period.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Body weight changes in maternal rats exposed to either 0.4 or 1.0 mg/L, were reduced, whereas those from the 0.16 mg/L were not.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

Feed consumption was reduced in the 0.4 and 1.0 mg/L group rats during the first 6 days of exposures (means of 23.3, 20.5, and 20.1 g/day, 0, 0.4, and 1.0 mg/L groups, respectively).

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Description (incidence and severity):

No significant differences in absolute or relative liver weight was found but a significant trend in absolute weight was evident; a trend not seen when related to the body weight where values for all test groups were lower (but not significantly) from that of the controls.

Gross pathological findings:

no effects observed

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

The only histopathologic changes were detected in the nasal tissues of the parental rats, was an exposure-related increase in squamous metaplasia in the olfactory epithelium.

Histopathological findings: neoplastic:

not examined

Other effects:

not examined

Details on results:

No significant differences were observed between control and test rats with respect to mating performance, fertility, length of gestation, or progeny numbers, structure, and viability. Body weights of parental rats and of their offspring were reduced at 1.0 mg/L. The only histopathologic changes detected in the nasal tissues of the parental rats, was an exposure-related increase in squamous metaplasia in the olfactory epithelium. There was an increase in liver-to-body weight ratios in the two higher parental exposure groups and an increase in the lung-to-body weight ratio also seen at 1.0 mg/L. From the results obtained, it can be concluded that reproduction in rats was not altered by repeated inhalation exposure to up to 1.0 mg/L DBE, a concentration that produced both body weight and histologic effects in parental rats.

Number of abortions:

no effects observed

Description (incidence and severity):

The number of pregnant rats/group was not altered by exposure to DBE, with the numbers being 24, 21, 20, and 24, control to high concentration groups, respectively.

Pre- and post-implantation loss:

no effects observed

Total litter losses by resorption:

no effects observed

Early or late resorptions:

no effects observed

Dead fetuses:

no effects observed

Changes in pregnancy duration:

no effects observed

Changes in number of pregnant:

no effects observed

Other effects:

not examined

Details on maternal toxic effects:

All female rats survived the testing period. The number of pregnant rats/group was not altered by exposure to DBE, with the numbers being 24, 21, 20, and 24, control to high concentration groups, respectively. Body weight changes in maternal rats exposed to either 0.4 or 1.0 mg/L, were reduced, whereas those from the 0.16 mg/L were not. Feed consumption was reduced in the 0.4 and 1.0 mg/L group rats during the first 6 days of exposures (means of 23.3, 20.5, and 20.1 g/day, 0, 0.4, and 1.0 mg/L groups, respectively). Clinical observations of perinasal staining (15 rats) and wet fur (20 rats) were seen in the 1.0 mg/L group; while these findings were not seen in the controls. Perinasal staining was seen in 1 rat from the 0.16 mg/L group and in 4 rats from the 0.4 mg/L group; wet fur was also seen in 1 rat from the 0.4 mg/L group. Other clinical observations including alopecia, sores, periocular and facial staining, and swollen extremities were seen but infrequently and with no suggestion of a relationship to DBE exposure. No significant differences in absolute or relative liver weight was found but a significant trend in absolute weight was evident; a trend not seen when related to the body weight where values for all test groups were lower (but not significantly) from that of the controls.

Key result

Dose descriptor:

NOAEC

Effect level:

>= 1 mg/L air (nominal)

Based on:

test mat.

Basis for effect level:

other: no treatment-related effects observed on developmental toxicity parameters

Key result

Dose descriptor:

NOAEC

Effect level:

0.16 mg/L air (nominal)

Based on:

test mat.

Basis for effect level:

other: maternal toxicity

Remarks on result:

not determinable

Remarks:

no NOAEC identified

Fetal body weight changes:

no effects observed

Reduction in number of live offspring:

no effects observed

Changes in sex ratio:

no effects observed

Changes in litter size and weights:

no effects observed

Changes in postnatal survival:

no effects observed

External malformations:

no effects observed

Skeletal malformations:

no effects observed

Visceral malformations:

no effects observed

Other effects:

not examined

Details on embryotoxic / teratogenic effects:

No adverse reproductive effects related to DBE exposure were detected. There was no effect on fetal weights at any exposure level. There was no significant difference between the control and experimental groups in the incidence of external, visceral, or skeletal malformations. Developmental variations among fetuses derived from DBE-exposed female were not significantly different from those of the controls.

Key result

Dose descriptor:

NOAEC

Effect level:

> 1 mg/L air (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: no treatment-related effects observed

Key result

Abnormalities:

no effects observed

Key result

Developmental effects observed:

no

Conclusions:

DBE exerts no adverse effect on prenatal development in the rat following inhalation exposures as high as 1.0 mg/L DBE during the period of organogenesis.

Executive summary:

Dibasic Esters (DBE) has been tested in a developmental toxicity study on Crl:CD(SD)BR rats after inhalation exposure using a protocol similar to OECD guideline no 414 in compliance with Good Laboratory Practice. Pregnant Crl:CD BR rats (7-8 per group) were exposed to either 0.16, 0.4, or 1.0 mg/L DBE by inhalation for 6 hr/day from Days 7 through 16 of gestation (day in which copulation plug was detected was designated Day 1G) in whole-body inhalation chambers. A control group of pregnant rats was exposed simultaneously to air only. Parental examinations included clinical and cage side observations, body weight determination, and determination of feed consumption. Gross pathologic examination was performed on day 21G and included counting of the corpora lutea and determination of number and position of all live, dead, and resorbed conceptuses in the uterus. Liver, gravid and empty uteri were weighed. All fetuses were weighed and examined or external alterations. About one-half of the live fetuses were examined for visceral alterations. All fetuses were sexed and examined for alterations of the skeleton after maceration.

 

A suppression of both food consumption and the rate of body weight gain was seen in the 0.4 and 1.0 mg/L groups during the first 6 exposure days. Staining on the fur and perineal area was seen in rats exposed to 1.0 mg/L and liver weight decreases, although not statistically significant, occurred in the 2 high exposure groups. None of the reproductive parameters were altered in any of the groups and no fetal effects were detected. DBE exerts no adverse effect on prenatal development in the rat following inhalation exposures as high as 1.0 mg DBEL during the period of organogenesis.

Based on the given data, Dibasic Esters (DBE) is not classified for developmental effects according to the criteria of Directive 67/548/EC and EU Regulation No. 1272/2008 (CLP).

Effect on developmental toxicity: via inhalation route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEC

1 000 mg/m³

Additional information

No data are available on dimethyl adipate. Data on the surrogates, dibasic esters blend, and dimethyl glutarate are available instead.

The effects of dibasic esters on prenatal development were assessed by the inhalation route in a teratogenicity study (equivalent to an OECD 414 study) in pregnant rats, exposed 6 hours per day to the test concentrations of 0, 160, 400 or 1000 mg/m3 between gestation days 7 through 16. No relevant effects occurred in the number of resorptions, fetal weight and there was no significant differences in the incidence of external, visceral or skeletal abnormalities between groups including controls. The NOEC for teratogenicity was therefore 1000 mg/m3.

Dimethyl glutarate (DMG) was administered by inhalation to groups of 22 time-mated Hra:(NZW)SPF rabbits. The inhalation exposures were whole-body exposures and animals were exposed for approximately 6 hours each day on days 7 through 28 of gestation. Target chamber concentrations were 0, 30, 100, 300, or 1000 mg/m3. During the in-life period, maternal body weight, food consumption, and clinical observation data were collected daily. Animals were euthanized on day 29 of gestation; dams were subjected to a gross external and internal postmortem examination. Gravid uteri were removed, weighed, and dissected and the uterine contents were described. Each live fetus was weighed, sexed, and examined for external, visceral, and skeletal alterations. At 1000 mg/m3, there was compound-related mortality; one animal was found dead on gestation day 13 and one animal was sacrificed in extremis on gestation day 22. Among survivors, there were compound-related reductions in maternal body weight gains and food consumption and there were compound-related clinical observations (ocular discharge and wet fur). At 300 mg/m3, evidence of compound-related maternal toxicity was limited to reduced maternal body weight gains and increased clinical observations (ocular discharge). Under the conditions of the current study, there was no evidence of compound-related maternal toxicity at 30 or 100 mg/m3 and there was no evidence of developmental toxicity at any level tested. Thus, the no-observed-effect level (NOEL)a for maternal toxicity was considered 100 mg/m3 and the NOEL for developmental toxicity was considered 1000 mg/m3.

Justification for classification or non-classification

Based on the absence of any relevant sign of reproductive or developmental toxicity in rats up to the concentration of 1000 mg/m3 by inhalation exposure, taking account of the classification criteria of Annex VI Directive 67/548/EEC or EU Regulation 1272/2008 (CLP), no classification is warranted for reproductive and developmental toxicity.