COASOL 290 PLUS

Endpoint summary

Description of key information

No data are available for the di(iso)butyl esters, however read-across data are available for the dimethyl esters:

- Oral route (14-days, rat): NOEL = 10000 ppm (equivalent to 980 mg/kg bw)

- Dermal route (14-days, rat): NOEL (systemic toxicity) = 1000 mg/kg bw

- Inhalation (90-days, rat):  NOEC (respiratory local toxicity) = 50 mg/m3

In addition to data on the esters, studies on the dicarboxylic acids (glutaric and adipic acid) are also available.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Reference 1

Endpoint:

short-term repeated dose toxicity: oral

Type of information:

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

Adequacy of study:

supporting study

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

documentation insufficient for assessment

Justification for type of information:

See attached document with the justification for the category/read-across approach.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Groups of 10 rats per concentration received the test item in feed for 14 consecutive days. An additional group of 10 rats served as controls and was fed standard chow only. All rats were weighed daily (weekends excluded) during the test period and observations for clinical signs were made at the same time. Food consumption for the test period was recorded. On day 14, 5 rats from each group were sacrificed. The remaining half of each group were weighed every other day and observed for a 14-day recovery period on standard feed without test item. All rats were examined grossly, selected tissues were weighed, and selected tissues and organs evaluated histologically.

GLP compliance:

not specified

Limit test:

no

Species:

rat

Strain:

Crj: CD(SD)

Sex:

male

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Details on oral exposure:

The test material mixed with ground Purina Lab Chow (GPLC) was fed .

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

14 days of treatment. Half of the animals were observed for further 14 days without treatment.

Frequency of treatment:

daily

Remarks:

Doses / Concentrations:
10, 20, 50 g/kg feed
Basis:
nominal in diet

Remarks:

Doses / Concentrations:
10000, 20000, 50000 ppm
Basis:
nominal in diet

No. of animals per sex per dose:

10 male animals per sex and dose

Control animals:

yes, plain diet

Details on study design:

- Post-exposure recovery period in satellite groups: 14 days

Positive control:

no positive control used

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: daily

BODY WEIGHT: Yes
- Time schedule for examinations: treatment phase: daily; recovery period: every other day

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: No

FOOD EFFICIENCY: No

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): No

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: No

CLINICAL CHEMISTRY: No

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes (see table 1)
HISTOPATHOLOGY: Yes (see table 1)

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

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

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

not examined

Details on results:

CLINICAL SIGNS AND MORTALITY
No deaths occured during the study period.
No clinical signs other than initial and sporadic weight loss were observed.

BODY WEIGHT AND WEIGHT GAIN
The rate of body weight gain was reduced in rats fed either 20 or 50 g/kg feed. This reflects, at least in part, lower food intake by these rats. Upon return to the ground lab chow (control diet), test rats in these 2 groups gained slightly more weight than did the controls although the rats in the 50 g/kg feed group weighed approximately 7% less than controls at the end of the recovery period.

GROSS PATHOLOGY AND HISTOPATHOLOGY
No gross or microscopic pathologic changes that could be attributed to exposure of DBE were detected.

Critical effects observed:

not specified

Table 2:Weight and Food Consumption Data

Dose [ppm]	Dose [g/kg feed]	Average initial weight [g]	Average weight, day 14 [g]	Average weight, after 14 day recovery [g]	Average food consumption during test period [g/day/rat]	Estimated test item uptake [mg/kg bw/day] ^a)
0 (control)	0 (control)	244	329	391	26	-
10’000	10	245	325	401	24	980
20’000	20	239	302	394	22	1841
50’000	50	240	290	364	19	3958

^a) Estimation based on average food consumption and average initial body weight

Conclusions:

Except for the observed slight weight gain effects, under the conditions of this test, DBE appeared to be devoid of general toxicity in this 14-day feeding study.

Executive summary:

Dibasic Esters (DBE) has been tested in a 14-day oral toxicity study on Crl:CD rats.

Groups of 10 male rats received feed containing DBE at concentrations of 0 (control), 10’000, 20’000, or 50’000 ppm for 14 consecutive days. All rats were weighed daily during the test period and observations for clinical signs were made at the same time. Food consumption for the test period was recorded. On the 14th test day, half of the rats of each test group were sacrificed. The remaining half of each group were weighed every other day, observed for a 14-day recovery period, and sacrificed 14 days later. All rats were examined grossly, selected tissues were weighed, and selected tissues and organs evaluated histologically.

Oral administration of DBE to rats over 14 days produced no deaths. No gross or microscopic pathologic changes that could be attributed to exposure of DBE were detected. No clinical signs other than initial and sporadic weight loss were observed. The rate of body weight gain was reduced in rats of the mid- and high-dose group which is reflected, at least in part, by lower food intake by these rats. During the recovery period, test rats in these 2 groups gained slightly more weight than the controls although the high-dose rats weighed approximately 7% less at the end of the recovery period.

Except for the observed slight weight gain effects, under the conditions of this test, DBE appeared to be devoid of general toxicity in this 14-day feeding study.

Reference 2

Endpoint:

chronic toxicity: oral

Type of information:

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

Adequacy of study:

supporting study

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Appears a well conducted study and reporting is sufficient to make a judgement on quality. However there are certain deficiencies relating to the reporting of the study, for example, no date is in the report, not all animals are properly accounted for in the study reporting.

Justification for type of information:

See attached document with the justification for the category/read-across approach.

Qualifier:

equivalent or similar to guideline

Guideline:

EU Method B.30 (Chronic Toxicity Studies)

GLP compliance:

not specified

Limit test:

no

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

Rats acclimatised on control diet for 12 days prior to study start. Kept in cages and housed in either the Sias laboratory, Brooklyn Hospital (3 and 6 months sacrifice groups) or at the MIT facility (12 and 24 months groups).
Animals were randomised and assigned to 4 groups - control, low, mid and high dose groups.
86 animals per group, were subdivided into 4 sub groups of 8, 8, 20 and 50 rats for the 3, 6, 12 and 24 month sacrifices respectively.

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Details on oral exposure:

Test material mixed into diets. Control Diet was 'Diet IX'. this was used as the base diet for addition of the test material.

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

rats were dosed for 3, 6, 12 and 24 months

Frequency of treatment:

daily in the diet

Remarks:

Doses / Concentrations:
0.1, 0.5, 2.5% in the diet
Basis:
nominal in diet

No. of animals per sex per dose:

3 months: 8 animals per dose group (half male, half female)
6 months: 8 animals per dose group
12 months: 20 animals per dose group
24 months: 50 animals per dose group

Control animals:

yes, plain diet

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

no effects observed

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

not specified

Ophthalmological findings:

not specified

Haematological findings:

not specified

Clinical biochemistry findings:

not specified

Urinalysis findings:

not specified

Behaviour (functional findings):

not specified

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

no effects observed

Dose descriptor:

NOAEL

Effect level:

2 500 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: no adverse effects observed on any parameter examined - data from 24 months not considered due to high mortality in all groups including control.

Critical effects observed:

not specified

3 months:

All animals survived the dosing period. The bodyweight gain over the course of he study was similar to control, with treated animals slightly heavier than the control, although statistical comparison is limited by the smaller animal numbers (8 per group). There did not appear to be any effects on weight gain over the course of the study.

Food consumtpion was consistent across the treated groups (taking into account the difficulties in measuring due to spillage). the small increase in bodyweight in the higher dose groups appears to be associated with a slightly higher food intake. Neither of these findings is considered to be treatment related. Average food consumption appeats to be around 25 grams per day.

Organ weights showed variations across the treatment groups but none of the findings of small fluctiations appeared to be treatment related.

Pathology identified no significant findings in the treated animals compared to control.

NOEL at 3 months is highest dose tested (2.5% in the diet)

6 months:

No mortalities occurred during the study (although 1 high dose animal apparently escaped!)

Bodyweight gain: In the highest dose group there was a lower weight gain over the course of the study (average weight at 6 months = 276g compared to control, 312g)

Other groups gained weight in a manner consistent with control, although the lowest dose group did appear tohave a higher weight than control at the end of the study (365g compared to 312g)

Food consumption - food consumption appears to be lower in the highest dose group, however the estimated weight gain per gram of food appears to be consistent across the group. However it is considered likely that the differences observed in bodyweight appear to be associated with differences in food intake and so it is not considered that bodyweight fluctuations and differences between groups provide evidence of systemic toxicity.

Organ weights - There were some organ weight differneces across groups and compared to control however there was no dose repsonse and changes in organ weight appear to be associated with differencs between bodyweight rather than an effect on organ weight specifically. There do not appear to be any adverse effects on organ weights in the animals dosed up to 6 months.

There were also no histopathological findings that would indicate an adverse treatment related effect.

12 months:

Initially 20 rats were assigned to the 12 month study period, however mortality in some of the groups meant that only 16 animals (8 of each sex) were sacrificed at 12 months to ensure that sufficient animals were present at the 24 month time point.

Bodyweights: Bodyweight gains at 12 months were consistent with controls, although the mid and low dose group appeared to have a slightly greater increase in bodyweight compared to control (unlikely to be statistically significant)

Food consumnption was greater in the control animals, but overall food intake across the treated groups appears consistent. It is also to be noted that due to spillage it is not possible to make an accuate judgement on test material loss due to spillage and what was actually eaten.

Organ Weights: No effects observed.

Pathology:

IN both control and treated males there was some 'bladder concretion' evident (i.e. calculi). Due to presence in both control and treated groups it is not considered that thsi finding is related to test material administration. It was not observed in females. Other than this finding there were no other significant findings evident of systemic toxicity.

24 months:

Mortality appears to have been high in all dose groups and control animals. As such only 8 mid dose animal (0.5% in the diet) and 2 control animals are covered in the results section.

It is not reported that animals in the low and high dose had all died at 24 months. Nor are any data reported from animals dying during the study. As such the value of the information at the 24 month timepoint is of very limited value.

The authors of the study report that it is not considered the test material adminsitration was responsible for mortality, since mortality in the control group was also high with only 2 out of 50 original animals surviving to study termination.

Overall it appears that based on the minimal findings throughout the study, the NOAEL is set as the highest dose group - 2.5% in the diet.

Considering the poor quality information on feed intake an estimate of actual dose ingested is made using an average weight of 250g, and 25g feed per day.

0.1% = 100 mg/kg bw/day

0.5% = 500 mg/kg bw/day

2.5% = 2500 mg/kg bw/day

Conclusions:

After at least 12 months of dietary administration of diisobutyl adipate to rats there were no significant treatment related adverse effects observed at the highest dose (approx 2500 mg.kg bw.day)

Reference 3

Endpoint:

short-term repeated dose toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 407 (Repeated Dose 28-Day Oral Toxicity Study in Rodents)

Deviations:

not specified

Principles of method if other than guideline:

not applicable

GLP compliance:

not specified

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 Laboratries Japan Inc.
- Age at study initiation: 5 weeks
- Weight at study initiation: 131-155 grams for males and 121-134 grams for females. Individual body weights were confirmed to be within ±20% of the mean body weight for each sex of each group.

- Housing: Two animals/sex/cage
- Diet (e.g. ad libitum): pelleted diet ad libitum - (MF, Oriental Yeast Co., Ltd.) in which contaminants such as pesticide residue were below the concentrations prescribed in the SOP of the testing facility and feed was changed once weekly.
- Water (e.g. ad libitum): The animals were allowed free access to the tap water which was passed through a 5 μm filter and irradiated with ultraviolet light. Drinking water was changed once weekly. The quality of water is examined periodically in accordance with the Water Supply Act in Japan and was confirmed to be within the ranges prescribed as per the Ministry of Health and Welfare Ordinance No. 56.
- Acclimation period: 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-25°C
- Humidity (%): 40-70 %
- Air changes (per hr): 12 fresh air changes/hour
- Photoperiod (hrs dark / hrs light): 12 hours light/dark cycle

Route of administration:

oral: gavage

Vehicle:

olive oil

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS: The test substance was dissolved in olive oil (Lot No. 3525, Maruishi Pharmaceutical Co., Ltd.) to yield the specified concentrations. The dosing formulations were prepared once weekly and stored under refrigeration until just prior to dosing. A stability test of the dosing formulations was conducted by the supplier of the test substance, Daihachi Chemical Industry Co., Ltd., and the dosing formulations have been confirmed to be stable for 10 days after preparation when stored in a dark cold place.
The dosing formulations were administered via oral gavage using syringes fitted with gastric intubation tubes.
The dose volume for each animal was set at 0.5 ml/100 g of body weight and the dosing volume for each animal was calculated based on the most recent body weight measurement.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The lot of the test substance used for the study was analyzed and confirmed to be stable by the sponsor prior to initiation and after termination of dosing.

Duration of treatment / exposure:

28 days

Frequency of treatment:

Dosing was conducted in the morning once daily for 28 days.

Remarks:

Doses / Concentrations:
0 mg/kg
Basis:
other: oral by gavage

Remarks:

Doses / Concentrations:
20 mg/kg
Basis:
other: oral by gavage

Remarks:

Doses / Concentrations:
140 mg/kg
Basis:
other: oral by gavage

Remarks:

Doses / Concentrations:
1000 mg/kg
Basis:
other: oral by gavage

No. of animals per sex per dose:

6 male + 6 female/group (main groups)
6 male + 6 female/group (reversal groups - control and high dose)

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: During a preliminary 8-day repeated dose study conducted at dose levels of 0, 100, 300 and 1000 mg/kg using 3 animals/sex, no death occurred and no changes attributable to the test substance were noted in the clinical observations, body weights or gross pathology. Therefore, 1000 mg/kg, the upper limit stipulated in the Guidelines, was selected as the highest dose level for this study and then 140 and 20 mg/kg were selected as the mid and low dose levels, respectively. A control group receiving the solvent alone was included in this study
- Rationale for animal assignment: The animals were distributed into groups to nearly equalize the body weights in each group 1 day prior to initiation of dosing using a stratified randomization procedure based on the body weights.
- Post-exposure recovery period in satellite groups: control and high dose recovery groups

Positive control:

not applicable

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- All animals were observed daily for mortality and the appearance/behavior, etc. In addition, more detailed observations, including palpation, were conducted once weekly.

BODY WEIGHT: Yes
- All animals were weighed on the first day of dosing and once weekly thereafter using an electronic balance

FOOD CONSUMPTION: Yes
- Weights of feed, including the feeders, were measured for all cages on the first day of dosing and once weekly thereafter to calculate mean daily food consumption in each animal based on the weekly food consumption. An electronic balance (EB-5000, Shimadzu Corporation) was used for measurement.

OPHTHALMOSCOPIC EXAMINATION:No

HAEMATOLOGY: Yes
- Blood samples were collected from the posterior vena cava of all nonfasting animals which were anesthetized with thiopental sodium (RAVONAL, Tanabe Seiyaku Co., Ltd.) by intraperitoneal injection and necropsied at each scheduled interval. A 3.13% sodium citrate aqueous solution was used for prothrombin time and activated partial thromboplastin time and EDTA-2K was used for the other parameters as anticoagulants. The following parameters were analyzed –
Red blood cell count (RBC), White blood cell count (WBC), Platelet count, Hemoglobin concentration, Hematocrit, Differential count of leukocytes, Reticulocyte count, Prothrombin time, Activated partial thromboplastin time, Mean corpuscular volume, Mean corpuscular hemoglobin, Mean corpuscular hemoglobin concentration on an automated hematology analyzer (NE-4500, Toa Medical Electronics Co., Ltd.), Blood cell analyzer (MICROX HEG-70A, OMRON Tateisi Electronics Co., Ltd.), an automated reticulocyte counter (R-2000, Toa Medical Electronics Co., Ltd.) and an automated coagulation analyzer (KC-10A, Amelung)

CLINICAL CHEMISTRY: Yes
- The remaining portion of the blood samples used for hematology were allowed to stand for approximately 30 minutes at room temperature and centrifuged at 3000 rpm for 10 minutes. Serum samples obtained under non-fasting conditions were analysed for - total protein, albumin, A/G ratio, glucose, triglycerides, total cholestrol, urea nitrogen, creatinine, calcium, inrganic phosphorous, GOT (AST), GPT (ALT), gamma-GTP, ALP, sodium, potassium and chloride on a clinical analyzer (Hitachi 736-10)

URINALYSIS: Yes
- Fresh urine was collected from all animals 4 days prior to the terminal necropsy and analysed for pH, occult blood, protein, glucose, ketone bodies, bilirubin and urobilinogen on a urine anlyser (Clinitek 10)

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
- All animals for necropsy at each scheduled interval were sacrificed by exsanguination from the abdominal aorta after blood sampling and observed for the presence/absence of lesions macroscopically

HISTOPATHOLOGY: Yes
- The following organs were removed from all animals and fixed and preserved in 10% neutral phosphate buffered formalin, with the exception that the eyes and Harderian glands were fixed and preserved in Davidson’s solution. Brain, pituitary, eyes with Harderian glands, lungs, stomach, thyroids with parathyroids, heart, liver, spleen, kidneys, adrenals, urinary bladder, testes or ovaries and femoral bone marrow The heart, liver, kidneys, adrenals and spleen from males and females necropsied at termination of dosing in the control and 1000 mg/kg groups were routinely embedded in paraffin, thin-sectioned and stained with hematoxylin and eosin. The specimens were examined for the presence/absence of histological lesions by light microscopy.

Other examinations:

The following organs from all animals necropsied at each scheduled interval were weighed using an electronic even balance (ED-H60, Shimadzu Corporation). In addition, relative organ weights were calculated based on the terminal body weights. Brain, liver, kidneys, adrenals and testes or ovaries

Statistics:

Quantitative data were analyzed for statistical significance using a multiple comparison test between the control and each test substance treated group. The data were analyzed for homogeneity of variance using Bartlett’s test. When the variance was homogeneous, one-way analysis of variance was conducted. When significant differences were noted between the groups, mean group values were compared using Dunnett’s or Scheffe’s test depending on whether the number of animals in each group was equal or not. When the variance was heterogeneous based on Bartlett’s test, Kruskal-Wallis H-test was conducted. When significant differences were noted between the groups, a rank sum test of the Dunnett type or Scheffe type was conducted depending on whether the number of animals in each group was equal or not.
Data obtained in the urinary qualitative tests were analyzed using Armitage’s χ2 test.

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

no effects observed

Details on results:

CLINICAL SIGNS AND MORTALITY - No mortality was observed and during the dosing period, salivation was observed transiently for the males and females in the 1000 mg/kg group, this was not observed after cessation of dosing.

BODY WEIGHT AND WEIGHT GAIN - Body weight changes in males and females in each treated group were similar to those in the control group.

FOOD CONSUMPTION - Food consumption of males and females in each treated group was comparable to those in the control group

HAEMATOLOGY - Shortening of APTT was noted in males in the 20 mg/kg group at termination of the dosing period and decreased MCHC and increased white blood cell counts were noted in males in the 1000 mg/kg group at termination of the recovery period. These were considered to be incidental changes within the ranges of physiological variation since they were not dose-dependent or were minimal changes.

CLINICAL CHEMISTRY - No appreciable changes were noted in any group.

URINALYSIS - Acidic pH changes were noted in females in the 20 mg/kg group prior to termination of dosing. However, this was considered to be an incidental change since it was not dose-dependent and was a minimal change.

ORGAN WEIGHTS - A decrease in the wet kidney weight was noted in males in the 140 mg/kg group at termination of the dosing period. However, this was considered to be an incidental change within a range of physiological variation since it was not dose-dependent and was a minimal change.

GROSS PATHOLOGY - No gross pathological lesions attributable to treatment with the test substance were observed in any treated group. Incidental lesions of a white nodule (1 cm in diameter) in the spleen and focal hemorrhage in the lungs were observed in 1 animal each.

HISTOPATHOLOGY: NON-NEOPLASTIC - No histopathological lesions attributable to treatment with the test substance were
observed in any group.
Diffuse fatty changes and microgranuloma in the liver and basophilic changes of the tubular epithelium, a hyaline cast and hyaline droplets in the tubular epithelium of the kidneys were sporadically observed in the control or 1000 mg/kg group. These were spontaneous lesions occasionally observed and no dose-relationship was noted in the incidences.

Dose descriptor:

NOEL

Effect level:

1 000 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: based on overall effects - No changes attributable to treatment with the test substance were noted in the clinical observations, body weights, food consumption, hematology, clinical chemistry, urinalysis and pathology.

Critical effects observed:

not specified

None

Conclusions:

Under the conditions of the study, the no observed effect level (NOEL) of dibutyl adipate was considered to be 1000 mg/kg for males and females.

Executive summary:

Dibutyl adipate was administered to male and female SD rats for 28 days. A 14-day recovery period was set for the control and high dose groups. Dibutyl adipate was dissolved in olive oil and administered via oral gavage using gastric intubation tubes. Three dose levels were selected at 20, 140 and 1000 mg/kg and the control animals received olive oil alone. The dose volume was 0.5 ml per 100 g of body weight in all groups.

No death occurred throughout the observation period. No changes attributable to treatment with the test substance were noted in the clinical observations, body weights, food consumption, hematology, clinical chemistry, urinalysis or pathology.

Based on these results, the no observed effect level (NOEL) of dibutyl adipate is considered to be 1000 mg/kg for males and females under conditions of this study.

Reference 4

Endpoint:

chronic toxicity: oral

Remarks:

combined repeated dose and carcinogenicity

Type of information:

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

Adequacy of study:

supporting study

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

documentation insufficient for assessment

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 453 (Combined Chronic Toxicity / Carcinogenicity Studies)

Deviations:

not applicable

GLP compliance:

no

Limit test:

no

Species:

rat

Strain:

other: Carworth farms

Sex:

male/female

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

2 years

Frequency of treatment:

daily in the feed

Remarks:

Doses / Concentrations:
males: 0, 0.1, 1.0, 3.0, 5.0% ; females: 0, 1.0%
Basis:
nominal in diet

Remarks:

Doses / Concentrations:
estimated 0, 1.69, 174.88, 506.07, and 813.62 mg/rat per day
Basis:
actual ingested

No. of animals per sex per dose:

Males: 20 per dose and control
females: Control - 10, test - 19

Control animals:

yes, plain diet

Critical effects observed:

not specified

Males: The percent survival for each test group was better than for the control group. There were no body weight differences throughout the 2-year period in rats treated with 0.1 or 1.0% adipic acid. During the rapid growth period, the weight gains of the 3.0 and 5.0% adipic acid groups were significantly less than the control groups. Throughout the latter half of the study, the average body weights were not remarkable, although the 5.0% dose group was consistently the lowest. There was a slight, but consistent, reduction in food consumption at 5.0%. Throughout the study, the following clinical signs were observed among all groups, including controls: wheezing, blood-tinged crust about the noses and eyes, and body sores. The incidence of these findings did not appear to be significantly different among the groups although a lower incidence of signs indicative of respiratory infection and body sores occurred in the 5.0% adipic acid group. The incidence of lung pathology and tumor growth appeared to be equally distributed among all groups, including the controls. When the surviving males were sacrificed at the end of the 2-year period, there was no significant gross pathology that was test substance-related. Soft edematous testes were noted at least as frequently in the controls as in the experimental animals. There was no significant difference in organ weights or microscopic examination.

Females: There were no significant differences in body weight gains or food consumption. Clinical signs noted in control and test groups included blood-tinged crust about the eyes and noses, unthriftiness, and body sores. There were no significant differences in organ weights, gross, or microscopic pathology. Two of the surviving control rats and 1 experimental animal had ovarian tumors; ovarian cysts were noted in both control and experimental rats.

Conclusions:

Adipic acid was not considered to be carcinogenic in this study.

Reference 5

Endpoint:

sub-chronic toxicity: oral

Type of information:

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

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Justification for type of information:

See attached document with the justification for the category/read-across approach.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)

GLP compliance:

no

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

90 days

Frequency of treatment:

daily

Remarks:

Doses / Concentrations:
0, 0.5, 1.0, 2.0%
Basis:
nominal in diet

No. of animals per sex per dose:

15

Control animals:

yes

Dose descriptor:

NOAEL

Effect level:

> 1 other: % in diet

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: reduced weight gain in top dose group femails and non-significant depression in weight gain in males at top dose

Critical effects observed:

not specified

No treatment-related mortality was found. Statistically significantly reduced weight gain in the 2% females and depression in weight gain of the 2% males (not statistically significant) were observed. Food consumption was normal in all groups. No differences were noted in hematology, clinical chemistry, or urinalysis. There were no histopathological findings or organ weight changes attributable to the test substance. No difference was observed in absolute organ weights, organ to body weight, and organ to brain weight ratios for testes and ovaries. No effects were observed following histological examination of the testes, seminal vesicles, ovaries, or uterus. The NOAEL was ≥1% and the LOAEL was 2%.

Reference 6

Endpoint:

sub-chronic toxicity: oral

Type of information:

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

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Justification for type of information:

See attached document with the justification for the category/read-across approach.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 409 (Repeated Dose 90-Day Oral Toxicity Study in Non-Rodents)

GLP compliance:

no

Limit test:

no

Species:

dog

Strain:

Beagle

Sex:

male/female

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

90 days

Frequency of treatment:

daily

Remarks:

Doses / Concentrations:
0, 1, 3, 5% (for days 1-10) 0, 0.5, 1, 2% (for days 11-90)
Basis:
nominal in diet

No. of animals per sex per dose:

4

Control animals:

yes

Dose descriptor:

NOAEL

Effect level:

> 2 other: % in diet

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Body weight suppression in high dose group

Critical effects observed:

not specified

Body weight loss was observed in the 5% male and female groups and in the 3% female group after 10 days. Reduced food consumption paralleled weight loss. Overall study weight gains for the low dose and mid dose groups were equal to the control group, while the high dose group had 5/8 dogs without weight gain. No treatment-related effects were seen in any other study parameters. No differences were observed in absolute or relative weights across treatment groups (1 high dose male was nomorchidic). No changes attributable to treatment were observed upon histological examination of the testes or ovaries. The NOAEL was ≥2% and the LOAEL was 3%.

Reference 7

Endpoint:

sub-chronic toxicity: oral

Type of information:

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

Adequacy of study:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Justification for type of information:

See attached document with the justification for the category/read-across approach.

Principles of method if other than guideline:

Four groups of male and female rats (30/sex/group) were administered daily by gavage 0, 30, 125 or 500 mg/kgbw/d for either 6 or 13 weeks.

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, Inc., Portage, Michigan, U.S.A.
- Age at study initiation: 36-37 d
- Mean weight at study initiation: males 90 g, females 86 g
- Housing: individually
- Diet (e.g. ad libitum): Purina Certiofied Rodent Laboratory Chow #5002 (pellet)
- Water (e.g. ad libitum): filtered municipal water
- Acclimation period: 7 days before the pretreatment week

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21 +/- 1
- Humidity (%): 48 +/- 9
- Photoperiod (hrs dark / hrs light): 12:12

Route of administration:

oral: gavage

Vehicle:

water

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS:
Dosing solutions of butanol in deionized water were used.

VEHICLE
- Concentration in vehicle: not specified
- Amount of vehicle (if gavage): 10 ml/kg was the constant dosing volume

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

GC-FI

Duration of treatment / exposure:

6 (interim sacrifice) or 13 weeks

Frequency of treatment:

daily

Remarks:

Doses / Concentrations:
0, 30, 125, 500 mg/kg bw
Basis:
actual ingested

No. of animals per sex per dose:

30 (further 10 were sacrificed prior to dosing for determination of clinicopathological baseline levels)

Control animals:

yes, concurrent vehicle

Positive control:

no data

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: twice daily

BODY WEIGHT: Yes
- Time schedule for examinations: Body weights were recorded weekly


FOOD CONSUMPTION: Yes
-Time schedule: Food consumption was recorded weekly


OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: Ophthalmic examination was conducted prior to treatment and during week 13 before final necropsy.
- Dose groups that were examined: no data


HAEMATOLOGY: Yes
- Time schedule for collection of blood: before the start of the study, during week 6 and during week 13
- Anaesthetic used for blood collection: No data
- Animals fasted: No data
- How many animals: 10 males and 10 females
- parameters: hemoglobin ( HGB), hematocrit (PCV), erythrocyte count (RBC), mean cell volume (MCV), mean cell hemoglobin (MCH),mean cell hemoglobin concentration (MCHC) total and differential leucocyte counts (WBC), estimated platelet count (PLT)


CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: before the start of the study, during week 6 and during week 13
- Animals fasted: No data
- How many animals: 10 males and 10 females
- parameters: alkaline phosphatase (Alk phos) blood urea nitrogen (BUN), glutamate pyruvate transaminase (SGPT), glutamate oxalacetate transaminase (SGOT), glucose (Gluc), total protein (TP), albumin (Alb), A/G ratio (calculated), globulin (calculated), total bilirubin (Tot. bili.), sodium (Na), potassium (K ), chloride (Cl), calcium (Ca), inorganic phosphate (Phos), carbon dioxide (TCO2), total serum cholesterol (Chol), creatinine.


URINALYSIS: Yes
- Time schedule for collection of urine: before the start of the study, during week 6 and during week 13
- Metabolism cages used for collection of urine: No data
- Animals fasted: No data
- parameters: pH, specfic gravity, glucose, protein, ketones, bilirubin, urobilinogen, microscopy of sediment


NEUROBEHAVIOURAL EXAMINATION: No data

Sacrifice and pathology:

GROSS PATHOLOGY: Yes: Ten male and ten female rats from each group were necropsied on study days 43 to 44 and the remaining animals on study days 92 to 93. Gross pathology of all animals was assessed and organs from animals necropsied on study days 92 to 93 were weighed.
HISTOPATHOLOGY: Yes: A complete histopathological investigation was made of all animals of the control and high-dose groups. In the low and mid-dose groups, histopathology included the liver, kidney, and heart from all animals and all gross lesions. All animals found dead or killed in extremis were also microscopically examined.

Statistics:

no data

Details on results:

CLINICAL SIGNS AND MORTALITY
Ataxia and hypoactivity (lasting less than 1 h) were observed 2 to 3 minutes after dosing in both sexes of the high-dose group (500 mg/kg bw/d) during the final 6 weeks of dosing. Such ataxia and hypoactivity are typically seen following high oral doses of alcohols. The rapid induction/remission of these effects and the reported increased incidence after the interim kill may be due to the fact that personnel were able to collect post-dose observations more quickly since fewer animals required dosing.
No significant changes between treated groups and controls were observed concerning mortality (three rats were found dead or sacrificed in extremis, but these deaths could not be attributed to the test article.).

BODY WEIGHT AND WEIGHT GAIN
no significant changes between treated groups and controls were observed

FOOD CONSUMPTION
no significant changes between treated groups and controls were observed

OPHTHALMOSCOPIC EXAMINATION
no significant changes between treated groups and controls were observed

HAEMATOLOGY
At the interim clinical pathological evaluation, red blood cell count (RBC) packed cell volume (PCV), and hemoglobin (HGB) averages of the 500 mg/kg/day dose group females were 5% below control averages. Although these differences were statistically significant, they were small and no differences between the parameters were observed in the males of the interim evaluation or between control and treated groups of either sex at the final evaluation. Therefore, even if the lower red blood cell parameters in the 500 mg/kg/day females were an actual treatment-related effect, it was small and transitory and thus not considered as adverse.

CLINICAL CHEMISTRY
no significant changes between treated groups and controls were observed

URINALYSIS
no significant changes between treated groups and controls were observed

ORGAN WEIGHTS
no significant changes between treated groups and controls were observed

GROSS PATHOLOGY
no significant changes between treated groups and controls were observed

HISTOPATHOLOGY: NON-NEOPLASTIC
no significant changes between treated groups and controls were observed

Dose descriptor:

NOAEL

Effect level:

125 mg/kg bw/day (nominal)

Sex:

male/female

Basis for effect level:

other: no effects observed

Dose descriptor:

LOAEL

Effect level:

500 mg/kg bw/day (nominal)

Sex:

male/female

Basis for effect level:

other: clinical signs of SNC depression (ataxia and hypoactivity)

Critical effects observed:

not specified

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

2 500 mg/kg bw/day

Study duration:

chronic

Species:

rat

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEC

400 mg/m³

Study duration:

subchronic

Species:

rat

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion

Dose descriptor:

NOAEL

1 000 mg/kg bw/day

Study duration:

subacute

Species:

rat

Repeated dose toxicity: dermal - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

There are no data available on the reaction mass of dibutyl esters of adipic and glutaric acid. However data are available for dibutyl adipate (oral 28 -day study in rats, dermal studies in rabbits and dogs), diisobutyl adipate (12 -24 month oral study in rats) and the mix of dimethyl esters of adipic, glutaric and succinic acid (90 -d inhalation studies). In addition, studies on the dicarboxyllic acids (adipic and glutaric acid) are available that can lend support to the repeated dose toxicity assessment of this substance.

Attached to section 13 of this IUCLID is a document justifying the use of data on these various substances to support the hazard assessment of this substance. In brief, the substances used to support the hazard characterisation are either components of the substance (dibutyl adipate), esters using a different alcohol (Diisobutyl adipate, methyl esters of the 3 acids) or the dicarboxyllic acids used to make these esters. The justification is that they will all hydrolyse in the body to release the component acids and alcohols and this is expected to happen at similar rates due to the structural similarities of the compounds. Following hydrolysis, the systemic exposure will be to the component acids and alcohols, and these are characterised well by the available studies.

Data on dibutyl adipate:

In a standard guideline 28 -day study in rats, the NOEL following oral exposure to dibutyl adipate was the top dose of 1000 mg/kg bw. No treatment related adverse effects were observed during the study.

Data on Di-isobutyl adipate:

In a sub-chronic to chronic study using the oral route, rats (Wistar, male and female) were dosed over the period of 24 months with interim sacrifices at 3, 6, and 12 months. Three dose levels were used, 0.1, 0.5 and 2.5% in the diet (approx equivalent to 100, 500 and 2500 mg/kg bw). In this study there were no treatment related effects observed at any dose up to 12 months dosing. Unfortunately due to high mortality across all groups including control, information for the 24 month sacrifice was limited to 8 animals in the mid dose group and 2 in the control group. As such it was not considered in the overall judgement. It should be noted that the mortality observed was not attributed to test material and that in the animals surviving at 24 months in the mid dose group there were no signs of test material related adverse effects. Observations in this study were limited to bodyweight, organ weight and pathology of a limited selection of organs. Despite the limited reporting/scope of the study it appears that under the conditions of the study, diisobutyl adipate was of very low toxicity. This is consistent with data coming from the methyl esters of these acids. The NOAEL at 12 months is 2500 mg/kg bw/day

Data on the Dimethyl esters

Oral route:

One study of reliability 4 according to Klimisch criteria (due to limited documentation) is available and was selected as a supporting study. In this sub-acute study, dibasic ester blend was administered in feed at 10000, 20000 or 50000ppm (equivalent to 980, 1841 or 3958 mg/kg bw/day, respectively, based on average food consumption and body weight changes over the dosing period). Initial and sporadic decreases in body weight and body weight gain were observed at 20000 and 50000ppm. At the end of a 2-week recovery period, body weight had returned to normal, except at 50000ppm where it was still 7% lower than in controls. The lower bodyweight in the mid and high dose animals appears to be related more to the palatability of the feed rather than a general toxic effect. This is demonstrated by the decreased food consumption in the mid and high dose groups. As such it is likely that the mid dose tested did not produce systemic toxicity and can be considered as a NOAEL (since bodyweight recovered after cessation of test material administration). In the highest dose tested the bodyweight increased in a consistent manner after exposure was terminated, but the animals did not achieve a weight similar to the mid, low and control dose groups. This is not necessarily evidence of systemic toxicity and could still be attributed to the decreased food consumption during the 14 day study period.

Dermal route:

One study of reliability 1 according to Klimisch criteria is available and was selected as a key study. In this subacute study, dibasic ester blend was administered dayly at 0, 100, 300 or 1000 mg/kg bw. There was a low incidence of local findings illustrative of minimal to mild dermal irritation as erythema and/or edema (graded as very slight) and an increased incidence of focal eschar formation (scabbing) or desquamation in all groups applied the dibasic ester blend, starting around the end of the first week of dosing. No test article-related findings were seen in clinical observations, food consumption, clinical pathology, urinalyis, ophthalmology or anatomic pathology. The NOEL for systemic toxicity was therefore 1000 mg/kg over 14 days of dermal application to rats.

Considering the effects observed on the skin in this study (local irritation) it might be considered appropriate to calculate a Dermal DNEL for local effects. However this has not been done for the following reasons:

1) the substance is a solvent and so repeated exposure might be expected to be irritating to the skin under the occlusive conditions of the study due to the drying and de-fatting of the skin by the solvent.

2) the study protocol used a 6 hour occlusive exposure to the skin for 14 days. Such an exposure condition is designed to ensure the best take up of the compound through the skin, however it does not represent realistic exposure conditions for a worker or consumer.

Taking these into account it is argued that the LOEL for irritation from this study is not relevant to a human exposure scenario and therefore cannot be used as the basis for the calculation of a local DNEL.

Inhalation route:

Two studies are available. A 90-day study on the individual components of dibasic ester blend (dimethyl glutarateat 10,50 or 400 mg/m3, dimethyl succinate at 400 mg/m3 and dimethyl adipate at 400 mg/m3) of reliability 1 according to Klimisch cotation criteria was selected as the key study. In this study, the main findings consisted of degeneration/atrophy of the olfactory mucosa of the dorsal meatus or dorsomedial aspect of the dorsal endoturbinate, and focal respiratory metaplasia of the olfactory mucosa of the dorsal meatus at 400 mg/m3 of all three esters. Decreases in serum testosterone concentrations were also noted in males exposed to 50 or 400 mg/m3 dimethyl glutarate. Decreases in serum luteinizing hormone (LH) concentrations were observed in males exposed to 400 mg/m3 dimethyl glutarate. Serum estradiol concentrations were also decreased in females exposed to 400 mg/m3 dimethyl succinate. The hormone level changes occurred together with significantly increased epididymal sperm counts in males exposed to 50 or 400 mg/m3 dimethyl glutarate or 400 mg/m3 dimethyl succinate. The NOEC for systemic toxicity was therefore set at 10mg/m3 based on decreases in hormone levels and increased epididymal sperm counts at 50 mg/m3 and above. However, those hormonal changes and sperm counts may be considered irrelevant as they were not observed in a similar study using the dibasic ester blend (see also section "7.8. Toxicity to reproduction" for further details). As such it is considered appropriate to take the highest dose (400 mg/m3) as a systemic NOAEC, and the 50 mg/m3 DMG dose level as the NOEC for local effects in the respiratory tract.

In a similar 90-day study, of reliability 1 according to Klimisch cotation criteria and selected as a supporting study, the concentrations tested were 20, 76 and 390 mg/m3 of dibasic ester blend. Olfactory epithelial lesions similar to those seen in the key study were observed at 76 and 390 mg/m3 in both genders, but also in females exposed to 20 mg/m3 and control females. A peer-review of nasal tissues by certified pathologists was performed (Ref. Pathology peer review of nasal tissue slides from two 90-day studies on behalf of Invista SARL, Experimental Pathology Laboratories, Inc., EPL Report No.: 851-001,18 September 2009). The peer review showed that olfactory epithelial lesions in the control females were seen with a roughly similar incidence and severity than in the females exposed to 20 mg/m3. This similarity between 20 mg/m3 and control females casts doubt on whether these lesions at this level of exposure are clearly related to the test substance. Furthermore, several male and female rats showed squamous metaplasia of the respiratory epithelium. This change which was clearly unrelated to the test substance may be a confounding factor in evaluating low-dose effects. Therefore, the study is regarded as inconclusive as to the respiratory local changes and 20 mg/m3 is likely a NOEC in this study, and 76 mg/m3 likely a LOAEC, which is consistent with the NOEC of 50 mg/m3 determined in the key study. The NOAEC for systemic toxicity from this study appears to be the highest dose tested (390 mg/m3) due to the minimal and non-adverse findings observed in the study at this dose level. This is consistent with the NOAEC for systemic effects observed in the key study.

Overall, the top dose tested in both studies appears to be the NOAEL for systemic effects. In the absence of any adverse treatment related systemic toxicity it is not considered appropriate to derive systemic DNELs. This is consistent with data from the diisobutyl adipate and dibutyl adipate which show a low order of systemic toxicity following repeated exposures to these substances.

Additional supporting information:

Adipic acid - 2 -year cancer bioassay

In a 2-year chronic feeding study, male and female Carworth Farms rats were fed diets containing 0, 0.1, 1.0, 3.0 and 5.0% (males) or 0 and 1% (females) adipic acid—corresponding to approximately 2.7, 280, 809 and 1302 mg - kg-bw/day, respectively. In males, body weight gain was suppressed in the 3 and 5% dose groups. There was a slight but consistent reduction in food consumption in the 5% exposure group. The following clinical signs were noted in all groups, including control animals, throughout the study: wheezing, bloody crust about eyes and nose and body sores. There was a lower incidence of signs indicative of respiratory infection and body sores in animals from the 5% exposure group. Soft edematous testes were noted in control and treated animals. No marked differences between control and treated groups were noted in organ weights or microscopic examination. In females, body weight gain and food consumption were not affected by treatment. Clinical signs noted in control and treated groups were bloody crust about eyes and noses, lack of vigorous growth, and body sores. There were no marked differences between control and treated animal’s organ weights or gross or microscopic pathology.

LOAEL = 3% (approximately 809 mg/kg-bw/day, based on decreased body weight gains and food consumption in males)

NOAEL = 1% (approximately 280 mg/kg-bw/day)

Glutaric acid - 90 -day studies in rat and dog

Groups of male and female Sprague-Dawley rats were fed glutaric acid at 0, 0.5, 1.0 and 2.0% (approximately 250, 500 and 1000 mg/kg-bw/day) for 90 days. No treatment-related mortality was noted. Body weight gain was markedly decreased in the 2% group in both sexes. No effects were seen on food consumption, hematology, clinical chemistry, urinalysis, absolute or relative organ weights or histopathology. No difference between control and treatment groups was observed in absolute or relative testes and ovary weights. Histopathological examination of testes, seminal vesicles, ovaries and uterus did not reveal any treatment-related effects.

LOAEL = 2% (approximately 1000 mg/kg-bw/day; based on decreased body weight gain)

NOAEL = 1% (approximately 500 mg/kg-bw/day)

In a 90-day study, groups of male and female Beagle dogs were fed diets containing 0, 1, 3 and 5% glutaric acid for days 1 – 10 and 0.5, 1, 2 and 2% glutaric acid for days 11 – 90. Body weight loss was seen in male and females in the 5% group and in females of the 3% group after 10 days. The dogs in the high-dose group did not gain weight during the study whereas the body weight gain for animals from the low- and mid-dose groups was comparable to the control group. No changes to other parameters, including histology of testes or ovaries, were noted.

LOAEL = 2% (approximately 500 mg/kg-bw/day; based on decreased body weight gain)

NOAEL = 1% (approximately 250 mg/kg-bw/day)

In the available data on the acids, the only adverse effects observed were associated with bodyweight change and no other findings associated with any specific toxic effect were reported. All of these studies were conducted prior to guidelines and the use of GLP and so they are not considered to be reliability 1. However their results are consistent with the overall database that there are minimal systemic effects following exposure to these substances for sub chronic periods in multiple species.

With respect to the alcohols in these esters, the repeat dose toxicity of methanol from an oral 90 day gavage study gives a no effect level of 500 mg/kg and a low effect level of 2500 mg/kg bw in rats. In a 90-day oral study on butanol, four groups of male and female rats (30/sex/group) were dosed daily by gavage with 0, 30, 125 and 500 mg/kg/day for 13 weeks. Six weeks after the initiation of dosing, an interim sacrifice of 10 rats/sex was performed to evaluate clinical, biochemical and gross morphological changes. The remaining animals continued in the experiment until the day of the final sacrifice (day 92 or 93). Data generated from this study on body and organ weight changes, food consumption, moribundity, mortality, and ophthalmological, gross, and histopathologic examinations did not show any dose-related differences between control and treated animals. Slight but significant reductions in some hematologic parameters were observed in the mid- and high-dosed females at the interim, but not at final sacrifice. This effect was considered to be transitory rather than adverse. Ataxia and hypoactivity were consistently observed in high-dosed (500 mg/kg/day) males and females during the final 6 weeks of the dosing period. Thus, the 125 mg/kg/day dose of butanol is considered a NOAEL for central nervous system effects in rats.

It is possible that following exposure to the dibutyl ester that the apparent neurotoxicity observed following butanol exposure could be reduced; certainly it was not observed in the 28 day study with dibutyl adipate. Leaving this effect to one side, there was minimal evidence of other systemic toxic effects at any dose.

Taking into consideration the entire database, the toxicity following repeated dose exposure to these chemicals appears to be relatively minor with effects limited to local effects (see below) following inhalation exposure and general toxicity evident as a decrease in bodyweight.

Specific comments on potential for irritation:

Irritating effects on the respiratory epithelium, and atrophy/degeneration of the nasal and olfactory epithelium are critical effects consistently observed with various ester derivatives (butyl acrylate, methyl acrylate, methylmethacrylate, methyl acetate, ethyl acrylate, lactate esters). These effects are thought to be related to a mechanism common between esters (including dibasic esters) which involves hydrolysis by unspecific carboxylesterases located in the nasal/olfactory epithelium to release corresponding acids and alcohols. However, there are well-known differences in the anatomy and physiology of the nasal and olfactory epithelia between rats and humans. Although some variability in the experimental results of carboxylesterase activity exists, depending on the methodology and the substrate used, there is a general trend supporting lower nasal esterase activity towards esters from human tissues compared to those from rat tissues. (Ref. Frederick C.B. et al. Use of a hybrid computational fluid dynamics and physiologically based inhalation model for interspecies dosimetry comparisons of ester vapours. Toxicol Appl Pharmacol. 183(1): 23-40, 2002). The respiratory local effects should therefore be of a lower concern in the human situation. These effects are thought to be overpredictive in the rat model compared to humans, because of the morphological and physiological differences.

Even though these local effects are considered to be of lower reference to humans, it is considered appropriate to derive a DNEL for local effects (inhalation). When extrapolating from the methyl esters to the butyl esters in calculating a local effects DNEL, a factor of 2 will be taken into consideration to account for the difference in irritancy between butanol and methanol (butanol is more irritating to the respiratory tract than methanol). However it is recognised that the far lower vapour pressure of the dibutyl esters will mean that the potential inhalation exposure to this substance is minimal compared to the methyl esters.

Repeated dose toxicity: inhalation - systemic effects (target organ) respiratory: other

Justification for classification or non-classification

Based on the classification criteria of Annex VI Directive 67/548/EEC, no R37 classification is warranted because no signs of immediate or massive upper respiratory tract irritation are observed following inhalation of dibasic ester blend in rats or humans.

 

Based on the classification criteria of UN/EU GHS, 'STOT – single exposure Cat. 3' classification is NOT warranted because nasal lesions appear to be subchronic effects in rats. No 'STOT – repeated exposure' classification is warranted because the toxicological relevance of rat findings to humans is limited based on interspecies differences.

 

No classification is warranted based on repeat-dose experimental data on dibasic esters.