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Diss Factsheets

Toxicological information

Repeated dose toxicity: oral

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Administrative data

sub-chronic toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
test procedure in accordance with national standard methods
A fully peer reviewed GLP study carried out by a reputable organisation to recognised scientific principles.

Data source

Reference Type:

Materials and methods

Test guideline
equivalent or similar to guideline
OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)
, 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:
Limit test:

Test material

Constituent 1
Chemical structure
Reference substance name:
EC Number:
EC Name:
Cas Number:
Molecular formula:
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

Fischer 344
Details on test animals or test system and environmental conditions:
- 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

- 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
Details on oral exposure:
No further information to add
Analytical verification of doses or concentrations:
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:
Doses / concentrationsopen allclose all
Dose / conc.:
750 ppm
in drinking water. Target dose 100mg/kgbw day. Actual dose males 69mg/kgbw day, females 82mg/kgbw day
Dose / conc.:
1 500 ppm
in drinking water. Target dose 150mg/kgbw day. Actual dose males 129mg/kgbw day, females 151mg/kgbw day
Dose / conc.:
3 000 ppm
in drinking water. Target dose 250mg/kgbw day. Actual dose males 281mg/kgbw day, females 304mg/kgbw day
Dose / conc.:
4 500 ppm
in drinking water. Target dose 400mg/kgbw day. Actual dose males 367mg/kgbw day, females 363mg/kgbw day
Dose / conc.:
6 000 ppm
in drinking water. Target dose 650mg/kgbw day. Actual dose males 452mg/kgbw day, females 470mg/kgbw day
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:


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

- Time schedule: at the beginning of the study and then weekly until the end of the study.

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

- 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:
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
Description (incidence and severity):
Some diarrhea noted but no other clinical observations.
no mortality observed
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
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 (males were 88%)
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
effects observed, treatment-related
Description (incidence and severity):
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. Changes were only really significant in the top two doses.
Ophthalmological findings:
not examined
Haematological findings:
effects observed, treatment-related
Description (incidence and severity):
At all time points in the hematologic evaluations of 2-butoxyethanol, mild anemia indicated by a decrease in RBC counts was present in male rats in the three highest dose groups (3000, 4500, and 6000 ppm), and thrombocytopenia was present in males in the two highest dose groups (4500 and 6000 ppm). Decreases in HGB concentration were mild at Weeks 1 and 13 and sporadic at Week 3. There were no consistent changes in HCT. The anemia was markedly macrocytic and mildly hypochromic at each time point, and reticulocyte counts were moderately increased at Weeks 1 and 13. Leukocyte counts were mildly to markedly increased (lymphocytosis and neutrophilia) at Week 1 in male rats in the three highest dose groups and unchanged at successive time points. Bone marrow cellularity was mildly increased in the two highest dose groups at Week 1. In female rats, there was mild to moderate anemia, as indicated by decreases in RBC counts and, less consistently, HCT and HGB concentrations, in most dose groups at each time point. The anemia was markedly macrocytic, mildly to moderately hypochromic (normochromic at Week 1), and regenerative, with the exception of Week 3 reticulocyte counts, which were not increased. Platelet counts were mildly increased in animals in the higher dose groups at Week 1 but were decreased at Weeks 3 and 13. Marked leukocytosis (neutrophilia and lymphocytosis) was present at Week 1. There were mild increases in bone marrow cellularity in female rats in the higher dose groups at Weeks 1 and 13.

The most sensitive end points showed significant changes even at the lowest dose of 750ppm for females as follows: reduced hematocrit (week 1, -4%), haemoglobin (week 13, -3%, erythrocytes (week 1, -6%, week 13, -7%); increased mean cell haemoglobin (week 1, +5%
Clinical biochemistry findings:
effects observed, treatment-related
Description (incidence and severity):
Clinical chemistry effects included mild increases in total protein and albumin in males in multiple dose groups at Week 1 and decreases of similar magnitude at Week 13. AP activity was increased in male rats in multiple groups at Week 1 and in the highest dose group (6000 ppm) at Week 3. Increased AP activity is consistent with mild cholestasis. Changes in clinical chemistry variables included moderate, consistent increases in concentrations of urea nitrogen and creatinine (mild, less prevalent) at Weeks 3 and 13 and mild decreases in concentrations of total protein and albumin at these same time points. ALP activity was mildly increased in rats in the highdose group at Week 1 and in the two highest dose groups at Week 13. Changes in clinical chemistry were consistent with decreased food intake. Changes did not always show a consistent dose response. Elevated BUN was seen in week 3 in males but again, there was not a consistent dose response.
Urinalysis findings:
effects observed, treatment-related
Description (incidence and severity):
Decreased volume and increased specific gravity, consistent with reduced drinking water intake.
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Description (incidence and severity):
Absolute thymus weight reduced in two highest dose groups by week 13. All other changes observed considered secondary to body weight changes.
Gross pathological findings:
effects observed, treatment-related
Description (incidence and severity):
The only gross lesion considered to be treatment related was a reduction in the size of the uterus of female rats in the 4500 and 6000 ppm groups.
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
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. Minimal to mild uterine atrophy seen in the two high dose groups and characterized by a decreased thickness of the muscular wall and uterine mucosa was considered to bea change secondary to the reduction in body weight gain.
Histopathological findings: neoplastic:
not examined
Other effects:
effects observed, treatment-related
Description (incidence and severity):
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:
Effect level:
< 69 other: mg/kg/bw
Based on:
test mat.
Basis for effect level:
histopathology: non-neoplastic
Remarks on result:
other: adverse effects seen at lowest tested dose
Dose descriptor:
Effect level:
< 82 other: mg/kg/bw
Based on:
test mat.
Basis for effect level:
histopathology: non-neoplastic
Remarks on result:
other: adverse effects seen at lowest tested dose

Target system / organ toxicity

Critical effects observed:
Lowest effective dose / conc.:
69 mg/kg bw/day (actual dose received)
Treatment related:
Dose response relationship:
Relevant for humans:

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

No NOAEL established since testicular degeneration in males and decreased thymus weights in males and females occurred at the lowest concentration administered.
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.


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

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