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Toxicological information

Repeated dose toxicity: oral

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Administrative data

Endpoint:
sub-chronic toxicity: oral
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
1988
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
A fully peer reviewed GLP study carried out by a reputable organisation to recognised scientific principles. Glycol ether acetates are rapidly hydrolysed in vivo to the parent glycol ethers by plasma esterases and will show the same systemic toxicity as the latter. Data here reported here is from a drinking water study with 2-butoxyethanol. Full details of the justification for the use of an analogue for this end point are included in the document appended to chapter 13 of this dossier.

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
1993

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity in Rodents)
Deviations:
no
Remarks:
, no significant deviations noted
Principles of method if other than guideline:
Toxicology study carried out following a range finder study to determine appropriate doses. Exposure by drinking water with normal end points used for such a repeat dose study, including histopathology, haematology, clinical chemistry, urinalysis and reproductive system parameters.
GLP compliance:
yes
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Supplier: Aldrich Chemicals Co, Milwaukee.
- Lot number: BT00504LP
- Analytical purity: 100.1% by functional group titration, 100.5% by GC against reference compound. Purity taken as >99%
- Impurities (identity and concentrations): <0.1% water, <0.0012meq acid/g of compound

Test animals

Species:
rat
Strain:
Fischer 344
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Taconinc Farms (Germantown, NY)
- Age at study initiation: 6 weeks
- Housing: 5 per cage
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: 1-2 weeks

ENVIRONMENTAL CONDITIONS
- Temperature: 60-77F
- Humidity: 20-70% RH respectively
- Photoperiod: fluorescent tube, 12hrs/day.

IN-LIFE DATES: From: 14-16 June 1988 for base studies. 31/8 to 1/9 1988 for clinical pathology studies. Stop exposure studies: 17/8/98
To: 13-14 Sept 1988 for base studies. 6/7 and 21/22 Sept 1988 for clinical pathology studies. Stop exposure studies: 16/8/98

Administration / exposure

Route of administration:
oral: drinking water
Vehicle:
water
Details on oral exposure:
No further information to add
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Preliminary studies confirmed stability of stock solutions (10,000ppm) for 3 weeks under stored in the dark at 4C and for 4 days in rodent drinking water bottles.
Duration of treatment / exposure:
90 days
Frequency of treatment:
continous
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:
0, 750, 1500, 3000, 4500 or 6000 ppm
Basis:
nominal in water
Remarks:
Doses / Concentrations:
82, 151, 304, 363, 470 mg/kg
Basis:
other: actual ingested - females
Remarks:
Doses / Concentrations:
69, 129, 281, 367, 452 mg/kg
Basis:
other: actual ingested - males
No. of animals per sex per dose:
10 for base studies. 20 for clinical pathology studies
Control animals:
yes, concurrent no treatment
Details on study design:
- Dose selection rationale: 2 week range finder study
- Rationale for selecting satellite groups: used for clinical chemistry 1 and 3 (10 animals per sex and per time point.)
Positive control:
no

Examinations

Observations and examinations performed and frequency:
CAGE-SIDE OBERVATIONS: Yes
- All rats were observed twice daily throughout the study.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: at the beginning of the study and then weekly until the end of the study.

BODY WEIGHT: Yes
- Time schedule for examinations: recorded at the beginning of the study and then weekly until the end of the study.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Estimates of compound consumption based on water consumption by rats as shown above in doses/concentration section. Measured by cage twice per week.

HAEMATOLOGY: Yes, Series 7000 cell counter and a Series 810 whole blood platelet analyzer (Baker Instruments). Supplemental groups of 10 rats/sex/group/time point were included for haematology and clinical chemistry observations at weeks 1 and 3. Parameters checked: HgB, HCT, RBC count, MCV, MCH, MCHC, platelets, reticulocytes, WBC total and differential count, nucleated erythrocytes, methemoglobin concentrations, bone marrow cellularity.

CLINICAL CHEMISTRY: Yes, measured with a Cobra Fara analyser (Roche Diagnostics). Parameters examined: urea nitrogen, creatinine, total protein, albumin, ALP, ALT, creatine kinase, bile acids.

URINALYSIS: Yes
- Time schedule for collection of urine: last 24 hours prior to sacrifice
- Metabolism cages used for collection of urine: Yes
- Animals fasted: No, but no water during collection period.
- Parameters checked: volume, gravity, pH

OTHER: Evaluations of vaginal cytology and sperm morphology were done for the three highest doses tested. Results concerning these examinations are reported in more detail in the reprotoxicity section.
Sacrifice and pathology:
GROSS PATHOLOGY: Sacrifice: 70% CO2:30% O2 asphyxiation. Yes, complete autopsies were made on all study rats. Organs examined in control and high dose groups: adrenals, bone (femur) with marrow, brain (3 transverse sections), esophagus, eyes, heart/aorta, intestines, (cecum, duodenum, jejunum, ileum, colon, rectum), kidneys, larynx, liver, lung, lymph node (mesenteric, mandibular), mammary gland, nasal cavity and turbinates, ovaries, pancreas, parathyroids, pituitary, pharynx, preputial or clitoral glands, prostate, salivary gland, seminal vesicles, skin, spinal cord, spleen, stomach (fore and glandular), testes, thigh muscle, thyroid, tongue, trachea, urinary bladder, uterus, vagina, all gross lesions. In low dose group: bone marrow, epididymis, liver, spleen, testis and uterus. Organs weighed: heart, liver, kidney, lung, thymus and testes were examined.
HISTOLOGY: Tissues to be examined fixed, embedded, sectioned and stained (H&E) for microscopic examination. Tissues were examined from all control group and treated rats. Bone marrow cells collecetd from right femur for total nucleated cell counts.
OTHER: A stop-exposure group of 30 male rats was also included. 30 males were dosed at 0, 1500, 3000 and 6000ppm for 60 days. Groups of 10 were sacrificed at this time point and then 30 and 56 days after recovery.

Other examinations:
none
Statistics:
Parametric multiple comparison methods: Organ and body weight
Non-parametric multiple comparison methods: clinical chemistry/haematology data
Jonckheere's test: for trend/dose response.

Results and discussion

Results of examinations

Clinical signs:
effects observed, treatment-related
Mortality:
mortality observed, treatment-related
Body weight and weight changes:
effects observed, treatment-related
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
effects observed, treatment-related
Ophthalmological findings:
not examined
Haematological findings:
effects observed, treatment-related
Clinical biochemistry findings:
effects observed, treatment-related
Urinalysis findings:
effects observed, treatment-related
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
effects observed, treatment-related
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Histopathological findings: neoplastic:
not examined
Details on results:
CLINICAL SIGNS AND MORTALITY: No mortality seen. Some diarrhea noted but no other clinical observations.

BODY WEIGHT: Body weights in the two top dose groups were notably less than controls, particularly in females where the top dose was only 80% of the control animal weights by the end of the study.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): In males and females there were reductions in drinking water consumption in the higher dose groups, this being clearly concentration related in females, from a mean of 18.8 ml/day in the control group to 10.7 ml/day in the 6000 ppm exposure group

HAEMATOLOGY
A markedly macrocytic and mildly hypochromic anaemia was observed at each time point (clearly indicated by reduced RBC count and less clearly by reduced HCT and HgB concentrations) and reticulocyte counts were moderately increased in weeks 1 and 13. For males there was a decrease in erythrocyte counts at all time points in the 3000 ppm and greater groups, while in females the decrease occurred in the 1500 ppm and greater groups. A consistent thrombocytoapenia was observed at all time points in males and females of the 4500 and 6000 ppm groups; it also occurred in females of the 3000 ppm group at week 13.

CLINICAL CHEMISTRY
Increased BUN and creatinine along with mild decreases in total protein and albumin at weeks 3 and 13. Changes in clinical chemistry were consistent with decreased food intake. ALP increased in high dose group week 1 and two highest dose groups week 13.

URINALYSIS
Decreased volume and increased specific gravity, consistent with reduced drinking water intake.

ORGAN WEIGHTS
Absolute thymus weight reduced in two highest dose groups by week 13. All other changes observed considered secondary to body weight changes.

HISTOPATHOLOGY: NON-NEOPLASTIC
Treatment related changes observed in the liver, spleen and bone marrow of both sexes. Liver lesions, present in all dose groups, included cytoplasmic alteration of minimal to mild severity (more eosinophilic, hepatocellular degeneration (centrilobular and including shrunken hepatocytes, densely stained nucleii, intensely eosinophilic staining) and pigmentation (Kupffer cell cytoplasm which stained positively for iron), present at all doses, but particularly 3 highest doses. Females were slightly more susceptible. Hyperplasia of the bone marrow also observed (3000ppm and upwards) along with increased hematopoeisis in the spleen and hemosiderin pigmentation (1500ppm upwards). All effects showed a clear dose response.


OTHER FINDINGS
Decreased in epididymis weight were consistent with reduced body weight changes. All males showed reduced sperm concentration compared to controls. There were no significant changes seen with the females although there was evidence that the females in the two highest dose groups spent more time in diestrus and less in proestrus, metestrus and estrus than control animals.

Effect levels

open allclose all
Dose descriptor:
NOAEL
Effect level:
< 69 other: mg/kg/bw
Sex:
male
Basis for effect level:
other: histopathology (liver: minimal cytoplasmic alterations). No other adverse effects observed.
Dose descriptor:
NOAEL
Effect level:
< 82 other: mg/kg/bw
Sex:
female
Basis for effect level:
other: histopathology (liver: minimal to mild cytoplasmic alterations). No other adverse effects observed.

Target system / organ toxicity

Critical effects observed:
not specified

Any other information on results incl. tables

No lesions were seen in the stop exposure group, despite the fact that the animals in the 1500ppm dose group accidentally received ethoxyethanol during week 6. As no lesions were seen, none of the organs from this group were processed for examination.

Applicant's summary and conclusion

Conclusions:
No NOAEL established due to cystoplasmic alterations seen in liver histopathology of both males and females rats at lowest dose tested. NOAEL for effects associated with haemolysis was 69mg/kg in males and 82mg/kg in females.
Executive summary:

In a well conducted drinking water study, rats were exposed to 2 -butoxyethanol at concentrations ranging from 750 -6000ppm for a period of 90 days. A NOAEL was not established in the study as the lowest dose tested, equivalent to 69mg/kgbw in males and 82mg/kgbw in females, due to minimal to mild cytoplasmic alterations to hepatocytes being observed at this dose. These were primarily centrilobular hepatocytes and the changes were characterised as shrunken hepatocytes, densely stained nucleii or intense eosinophilic staining and were seen in both sexes. No other adverse changes were observed at this concentration. Benchmark analysis of the results indicated an BMDL10 of 27 and 20mg/kgbw/day for males and females respectively.

Synopsis

NOAEL (91day), rat, male <69mg/kg/day

NOAEL (91day), rat, female <82mg/kg/day

On a molar basis, these results would need to be increased by a factor of 1.36 to covert to equivalent values for butoxyethyl acetate.