Tetrakis(2-ethylhexane-1,3-diolato)titanium

Repeated dose toxicity: oral

Administrative data

Endpoint:

sub-chronic toxicity: oral

Type of information:

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

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Justification for type of information:

Read-across justification: The substance is hydrolytically unstable. When it comes in contact with water or moisture complete hydrolysis will take place with no significant reaction products other than alcohol and hydrated titanium dioxide. This rapid hydrolysis (hydrolysis half-life < 3 minutes to < 2 hours) is the driving force for the toxicokinetics of target substance. Because of the rapid hydrolysis, the influence of the mode of administration through inhalation, dermal and oral is related to the hazardous degradation product (alcohol) released from the target substance. The identification of degradation products from the hydrolysis study conducted for the target substance verifies that there are no impurities in the alcohol released from the target substance, which might change the hazardous properties of the target substance compared to the properties of the pure alcohol. As there is a mechanistic reasoning to the read-across, the unnecessary animal testing is avoided by using the read-across data from the degradation product (relevant alcohol) to evaluate irritation, sensitization and the short term and long-term toxicological effects and mutagenicity of the target substance.

Cross-reference

Reason / purpose for cross-reference:

read-across source

Reference

Endpoint:

short-term repeated dose toxicity: oral

Type of information:

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

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Justification for type of information:

Read-across justification: The substance is hydrolytically unstable. When it comes in contact with water or moisture complete hydrolysis will take place with no significant reaction products other than alcohol and hydrated titanium dioxide. This rapid hydrolysis (hydrolysis half-life < 3 minutes to < 2 hours) is the driving force for the toxicokinetics of target substance. Because of the rapid hydrolysis, the influence of the mode of administration through inhalation, dermal and oral is related to the hazardous degradation product (alcohol) released from the target substance. The identification of degradation products from the hydrolysis study conducted for the target substance verifies that there are no impurities in the alcohol released from the target substance, which might change the hazardous properties of the target substance compared to the properties of the pure alcohol. As there is a mechanistic reasoning to the read-across, the unnecessary animal testing is avoided by using the read-across data from the degradation product (relevant alcohol) to evaluate irritation, sensitization and the short term and long-term toxicological effects and mutagenicity of the target substance.

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes

Limit test:

no

Species:

mouse

Strain:

B6C3F1

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Age at study initiation: 49 - 61 days
- Weight at study initiation: 22-29 g (males); 17-20 g (females)
- Fasting period before study: no data
- Housing: singly in plastic cages
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: 6 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-24
- Humidity (%): 30-70
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

oral: gavage

Vehicle:

water

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS:
Doses were prepared daily by dispersing 2EH in an aqueous solution of Cremophor EL (5 µg/100 ml) by ultra high speed sonication for 1 min.
Homogeneity was maintained by magnetic stirring throughout dosing.


VEHICLE
- Justification for use and choice of vehicle (if other than water): a surfactant (Cremophor) was used to facilitate mixing 2-EH with water
- Concentration in vehicle: 5 µg/100 ml
- Amount of vehicle (if gavage): dose volume was 10 ml/kg bw

Details on analytical verification of doses or concentrations:

Concentrations and homogeneity were checked by gas chromatographic analysis of samples from each dose level at the start of the preliminary 11 -day studies and periodically in 13-week studies.

Duration of treatment / exposure:

90 days

Frequency of treatment:

5/week

Remarks:

Doses / Concentrations:
0, 25, 50, 250, 500mg/kg bw /day
Basis:
actual ingested

No. of animals per sex per dose:

10

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: based on the results of preliminary 11-day studies
- Rationale for animal assignment (if not random): random
- Rationale for selecting satellite groups: determination of peroxisome prolieferation (3 animals per dose level; Table [4])
- Post-exposure recovery period in satellite groups: none
- Section schedule rationale (if not random): random

Positive control:

not required

Sacrifice and pathology:

GROSS PATHOLOGY: Yes. Adrenals, brains, kidneys, livers, stomachs, testes, and ovaries from all animals were weighed, and with other
organs and tissues listed in U.S. EPA Health Effects Guidelines (1987b) fixed in 4% formalin.
HISTOPATHOLOGY: Yes. All tissues from high dose and control animals were stained with hematoxylin—eosin and examined microscopically.
Lungs, livers (including gallbladders in mice), spleens, kidneys, stomachs, sternums, femurs, and femur bone marrows were examined microscopically at intermediate dose levels.
Skin, eyes, female mammary glands, thigh musculatures, and extraorbital lacrymatory glands were not examined in the absence of signs of toxicity.
Livers were also stained with oil red for lipid content and examined microscopically.

Other examinations:

Hepatic peroxisome proliferation: livers were removed at termination and weighed, and cyanide-insensitive pCoA
activities (Lazarow, 1981) and protein concentrations (Lowry et al, 1951) were determined (week 13; ancillary group; 3 animals per dose level)

Statistics:

Means and standard deviations were calculated for body weights, food and water consumption, clinical pathology results, and organ weights.
Values for test groups were compared with controls in the main study by ANOVA followed by Dunnett's test (Dunnett, 1955, 1964)
and in ancillary studies by ANOVA followed by Student's t test (Winer, 1971).

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Food efficiency:

not specified

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

not specified

Ophthalmological findings:

not examined

Haematological findings:

effects observed, treatment-related

Clinical biochemistry findings:

effects observed, treatment-related

Urinalysis findings:

not examined

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 specified

Details on results:

MORTALITIES AND CLINICAL SIGNS
One female mouse at 250 mg/kg died during treatment; there were no other mortalities or clinical findings differing from controls at any treatment level.

BODY WEIGHT AND WEIGHT GAIN
There were no differences from controls in body weight gain or food consumption in mice (data not shown).

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study)
Food consumption was not different from that of controls.

FOOD EFFICIENCY
n.a.

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study)
n.a.

OPHTHALMOSCOPIC EXAMINATION
n.a.

HAEMATOLOGY
There were no differences from controls in clinical pathology parameters in treated mice (data not shown).

CLINICAL CHEMISTRY
There were no differences from controls in clinical pathology parameters in treated mice (data not shown).

URINALYSIS
n.a.

NEUROBEHAVIOUR
n.a.

ORGAN WEIGHTS
Relative organ weights: significant differences from control mice were moderate and limited to the liver and the stomach at 250 and 500 mg/kg. Organ weights were increased in both male and female rats (cf. table).


Table: Relative organ weights (a) in mice at termination of the 13-Week oral gavage mouse study (b)
--------------------------------------------------------------------------------------
Males [Dose (mg/kg bw/day)] Females [Dose (mg/kg bw/day)]
0 250 500 0 250 500
--------------------------------------------------------------------
Liver 3.43 3.82* 4.23** 3.48 3.90 4.16**
Stomach 0.76 0.88 1.03** 0.87 1.03** 1.12**
--------------------------------------------------------------------------------------
values are mean organ/body weight ratios
there were no significant differences from controls in groups at 25 and 125 mg/kg bw/day
* p<0.05; ** p<0.01



GROSS PATHOLOGY
Gross lesions differing from controls in both species were seen at 500 mg/kg bw/day only. In the mouse there were dark red foci in the glandular stomach of 2/10 females at 500 mg/kg which may have been incidental.

HISTOPATHOLOGY: NON-NEOPLASTIC
Dose-related findings in mice findings were limited to a moderate focal or multifocal acanthosis in the forestomach of 2/10 males and 1/10 females at 500 mg/kg.

HISTOPATHOLOGY: NEOPLASTIC (if applicable)
n.a.

HISTORICAL CONTROL DATA (if applicable)
n.a.

OTHER FINDINGS
Peroxisome proliferation:
The hepatic cyanide-insensitive palmitoyl Coenzyme A activity was not increased at any dose level compared to control mice (table).

--------------------------------------------------------------------------------------
Dose (mg/kg bw/day)
0 25 125 250 500
--------------------------------------------------------------------
Mean PCoA activity (nanomol/min/mg of protein)
Males 4.35 4.76 3.67 3.87 4.33
Females 3.17 4.66 5.40 5.31 4.49
--------------------------------------------------------------------------------------

Dose descriptor:

NOEL

Effect level:

125 mg/kg bw/day (actual dose received)

Sex:

male/female

Basis for effect level:

other: absence of treatment-related effects on target organs

Dose descriptor:

NOAEL

Effect level:

250 mg/kg bw/day (actual dose received)

Sex:

male/female

Basis for effect level:

other: absence of treatment-related systemic effects on target organs

Critical effects observed:

not specified

Read-across justifications and data matrices are presented in IUCLID section 13.

Conclusions:

Valid subchronic oral gavage mouse study.
(1) The toxicity of 2-EH was low at all dose levels up to and including 500 mg/kg bw/day; based on
- lack of mortality and of clinical sign;
- lack of body weight reduction including groups at 500 mg/kg bw/day;
- lack of effects on clinicochemcial and hematological parameters;
(2) Target organs were the liver and the stomach; based on significantly increased relative organ weights at termination
(3) Local irritating effects in the forestomach; low incidence at 500 mg/kg bw
(4) Systemic effects minor; based on lack of treatment-related findings in other organs, including testes
(5) 2-EH did not induce peroxisome proliferation in male and female mice at 500 mg/kg bw/day or below
(5) The NOEL (no observable effect level) was 125 mg/kg bw/day. A NOAEL (no observable adverse effect level) was not derived, but may be estimated to be 250 mg/kg bw/day, based on the above

Executive summary:

The subchronic effects of 2 -EH were studied in a 90-day oral gavage study using male and female B6C3F1 mice (10 animals per sex and dose). The test dose levels were 0, 25, 125, 250, and 500 mg/kg bw/day, based on the results of preliminary 11-day studies.

Key results include:

• there were no mortalities or clinical findings differing from controls
• food consumption was comparable to controls
• body weight gain was comparable to controls
• there were no clinicochemical or hematological changes at any dose level
• Organ weight changes: target organs were liver and forestomach; a dose-related increase of relative weight was seen in males and females; a level of statistical significance (p<0.05) was gained in males at 250 and 500 mg/kg bw/day
• Male and female reproductive organs: no weight change noted
• Histopathology revealed a low incidence of inflammatory changes only in high dose animals; regarded to be incidental; possibly attributable to the irritation properties of 2 -EH
• 2 -EH was not a peroxisome proliferator in B6C3F1 mice at up to and including 500 mg/kg bw/day
• The subchronic NOEL was 125 mg/kg bw/day in male and female rats. The estimated NOAEL is 250 mg/kg bw/day.

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

1996

Report date:

1996

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

2-ethylhexan-1-ol

EC Number:

203-234-3

Cas Number:

104-76-7

Molecular formula:

C8H18O

IUPAC Name:

2-ethylhexan-1-ol

Details on test material:

- Analytical purity: 99.8% by gas chromatography

Test animals

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Age at study initiation: 42-43 days
- Weight at study initiation: 105-114 g (males); 86-97 g (females)
- Fasting period before study: no data
- Housing: singly in stainless steel cages
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: 6 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-24
- Humidity (%): 30-70
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

water

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS:
Doses were prepared daily by dispersing 2EH in an aqueous solution of Cremophor EL (5 µg/100 ml) by ultra high speed sonication for 1 min.
Homogeneity was maintained by magnetic stirring throughout dosing.


VEHICLE
- Justification for use and choice of vehicle (if other than water): a surfactant (Cremophor) was used to facilitate mixing 2-EH with water
- Concentration in vehicle: 5 µg/100 ml
- Amount of vehicle (if gavage): dose volume was 10 ml/kg bw

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Concentrations and homogeneity were checked by gas chromatographic analysis of samples from each dose level at the start of the preliminary 11 -day studies and periodically in 13-week studies.

Duration of treatment / exposure:

13 weeks

Frequency of treatment:

5/week

Doses / concentrations

Remarks:

Doses / Concentrations:
0, 25, 125, 250, 500mg/kg bw /day
Basis:
actual ingested

No. of animals per sex per dose:

10

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: based on the results of preliminary 11-day studies
- Rationale for animal assignment (if not random): random
- Rationale for selecting satellite groups: determination of peroxisome prolieferation (3 animals per dose level; Table [4])
- Post-exposure recovery period in satellite groups: none
- Section schedule rationale (if not random): random

Positive control:

not required

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Animals were inspected twice daily for morbidity or mortality, or once daily on nontreatment days. Clinical observations were
made daily.


DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: at start and thereafter at weekly intervals


BODY WEIGHT: Yes
- Time schedule for examinations: at start and thereafter at weekly intervals


FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): n.a.


FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No data


WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): No data
- Time schedule for examinations:


OPHTHALMOSCOPIC EXAMINATION: No data
- Time schedule for examinations:



HAEMATOLOGY: Yes
- Time schedule for collection of blood: on study days 29 and 84.
- Anaesthetic used for blood collection: No data
- Animals fasted: Yes
- How many animals: not specified
- Parameters examined: leucocytes, erythrocytes, hemoglobin, hematocrit, mean corpuscular volume, mean corpuscular
hemoglobin, mean corpuscular hemoglobin concentration, platelets and differential leucocytes, and reticulocytes


CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: on study days 29 and 84.
- Animals fasted: No data
- How many animals: not specified
- Parameters checked in table [1] were examined.


URINALYSIS: No
- Time schedule for collection of urine: n.a.
- Metabolism cages used for collection of urine: No
- Animals fasted: No data



NEUROBEHAVIOURAL EXAMINATION: No data



OTHER:

Sacrifice and pathology:

GROSS PATHOLOGY: Yes. Adrenals, brains, kidneys, livers, stomachs, testes, and ovaries from all animals were weighed, and with other
organs and tissues listed in U.S. EPA Health Effects Guidelines (1987b) fixed in 4% formalin.
HISTOPATHOLOGY: Yes. All tissues from high dose and control animals were stained with hematoxylin—eosin and examined microscopically.
Lungs, livers (including gallbladders in mice), spleens, kidneys, stomachs, sternums, femurs, and femur bone marrows were examined microscopically at intermediate dose levels.
Skin, eyes, female mammary glands, thigh musculatures, and extraorbital lacrymatory glands were not examined in the absence of signs of toxicity.
Livers were also stained with oil red for lipid content and examined microscopically.

Other examinations:

Hepatic peroxisome proliferation: livers were removed at termination and weighed, and cyanide-insensitive pCoA
activities (Lazarow, 1981) and protein concentrations (Lowry et al, 1951) were determined (week 13; ancillary group; 3 animals per dose level)

Statistics:

Means and standard deviations were calculated for body weights, food and water consumption, clinical pathology results, and organ weights.
Values for test groups were compared with controls in the main study by ANOVA followed by Dunnett's test (Dunnett, 1955, 1964)
and in ancillary studies by ANOVA followed by Student's t test (Winer, 1971).

Results and discussion

Results of examinations

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):

no effects observed

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

not specified

Haematological findings:

effects observed, treatment-related

Clinical biochemistry findings:

effects observed, treatment-related

Urinalysis findings:

not examined

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
There were no mortalities or clinical findings differing from controls at any treatment level.

BODY WEIGHT AND WEIGHT GAIN
There was decreased weight gain in male and female rats at 500 mg/kg, starting at Week 4 in males and Week 11 in females,
amounting to weight losses of 7% in males and 6% in females at termination (both p<0.01).

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study)
n.a.

FOOD EFFICIENCY
n.a.

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study)
n.a.

OPHTHALMOSCOPIC EXAMINATION
n.a.

HAEMATOLOGY
There was a 25% increase in reticulocyte numbers in male and female rats at 500 mg/kg in Week 13.

CLINICAL CHEMISTRY
Differences from controls rats were seen mostly at 84 days (data not shown).
Males at 500 mg/kg/day: 13% decreases in total protein and albumin concentrations.
Females at 250 mg/kg/day: 30 % decrease in serum ALT activities
Females at 500 mg/kg/day: 36% decreases in serum ALT activities;
16% decrease in serum cholesterol concentration

URINALYSIS
n.a.

NEUROBEHAVIOUR
n.a.

ORGAN WEIGHTS
Relative organ weights: significant differences from control rats were moderate and limited to the brain, kidneys, liver, stomach, and testes at 250 and 500 mg/kg. Organ weights were increased in both male and female rats (cf. table).


Table: Relative organ weights (a) in rats at termination of the 13-Week oral gavage rat study (b)

Males [Dose (mg/kg bw/day)] Females [Dose (mg/kg bw/day)]
0 250 500 0 250 500
--------------------------------------------------------------------
Brain 0.68 0.70 0.72** 1.07 1.1 1.1
Kidneys 0.69 0.75** 0.81** 0.77 0.81* 0.82**
Liver 2.77 2.98** 3.57** 2.67 2.88** 3.07**
Stomach 0.57 0.58 0.63** 0.71 0.75* 0.82**
Testes/Ovaries 1.11 1.16 1.17* 0.041 0.037* 0.039
--------------------------------------------------------------------------------------
values are mean organ/body weight ratios
there were no significant differences from controls in rats at 25 and 125 mg/kg bw/day
* p<0.05; ** p<0.01



GROSS PATHOLOGY
Gross lesions differing from controls in both species were seen at 500 mg/kg bw/day only. In rats 2/10 males and 4/10 females exhibited single
or multiple slightly elevated foci in the forestomach.

HISTOPATHOLOGY: NON-NEOPLASTIC
Dose-related findings in rats (data not shown) were limited to the forestomach and liver at 500 mg/kg.
Forestomach: there was a generalized acanthosis of the forestomach mucosa in 1/10 males with ballooning degeneration of the epithelial wall and acanthosis of the forestomach mucosa in 2/10 males and 5/10 females.
Liver: there was a moderate decrease in hepatic peripheral lobular fatty infiltration in 4/10 males and 2/10 females and adrenal ß-cell hyperplasia in 3/10 female rats.

HISTOPATHOLOGY: NEOPLASTIC (if applicable)
n.a.

HISTORICAL CONTROL DATA (if applicable)
n.a.

OTHER FINDINGS
Peroxisome proliferation:
In Week 13, increases in pCoA activity were 6.5-fold in male rats (p<0.001) and 3.4-fold in females (p<0.05) at 500 mg/kg . Reportedly, decreases in body weight gain were similar to those in the main study animals.

--------------------------------------------------------------------------------------
Dose (mg/kg bw/day)
0 25 125 250 500
--------------------------------------------------------------------
Mean PCoA activity (nanomol/min/mg of protein)
Males 3.38 4.49 5.21 6.24 22.0*
Females 2.95 4.54 5.01 6.6 9.92**
--------------------------------------------------------------------------------------
*p<0.001 and **p<0.05 by ANOVA/Students ttest

Effect levels

1

Dose descriptor:

NOEL

Effect level:

125 mg/kg bw/day (actual dose received)

Sex:

male/female

Basis for effect level:

other: absence of treatment-related effects on target organs

2

Dose descriptor:

NOAEL

Effect level:

250 mg/kg bw/day (actual dose received)

Sex:

male/female

Basis for effect level:

other: absence of treatment-related systemic effects on target organs

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

 Table: Relative organ weights (a) in rats at termination of the 13-Week oral gavage rat study (b)

	Males [Dose (mg/kg bw/day)]			Females [Dose (mg/kg bw/day)]
	0	250	500	0	250	500
Brain	0.68	0.70	0.72**	1.07	1.1	1.1
Kidneys	0.69	0.75**	0.81**	0.77	0.81*	0.82**
Liver	2.77	2.98**	3.57**	2.67	2.88**	3.07**
Stomach	0.57	0.58	0.63**	0.71	0.75*	0.82**
Testes/Ovaries	1.11	1.16	1.17*	0.041	0.037*	0.039

(a) values are mean organ/body weight ratios

(b) there were no significant differences from controls in rats at 25 and 125 mg/kg bw/day

* p0.05; ** p0.01     
    
    
    
    
    
    
    

Read-across justifications and data matrices are presented in IUCLID section 13.



















 
  
  
  
  
  
  

Read-across justifications and data matrices are presented in IUCLID section 13.

Applicant's summary and conclusion

Conclusions:

Valid subchronic oral gavage rat study.
(1) 2-EH was moderately toxic at all dose levels up to and including 500 mg/kg bw/day; based
- on lack of mortality and clinical signs;
- moderately reduced body weights in groups at 500 mg/kg bw/day;
- minor effects of low relevance on clinicochemcial and hematological parameters
(2) Target organs were the liver, forestomach, and the kidneys; based on significantly increased relative organ weights at termination
(3) Local irritating effects prevailed; systemic effects were low; based on
- inflammation in the forestomach,
- and lack of treatment-related findings in other organs, including testes
(4) 2-EH induces peroxisome proliferation in rats; observed at 500 mg/kg bw/day in rats of both sexes
(5) The NOEL (no observable effect level) was 125 mg/kg bw/day. A NOAEL (no observable adverse effect level) was not derived, but may be estimated to be 250 mg/kg bw/day, based on the above

Executive summary:

The subchronic effects of 2 -EH were studied in a 90-day oral gavage study using male and female rats (10 animals per sex and dose). The test dose levels were 0, 25, 125, 250, and 500 mg/kg bw/day, based on the results of preliminary 11-day studies.

Key results include:

• Mortalities or clinical findings were not different from controls
• Food consumption was comparable to controls
• Body weight gain was reduced in the high dose groups, resulting in decreased terminal weights in males (-7%) and females (-6%); (both p<0.01)
• Clinicochemical changes were seen in high dose groups (males:total protein and albumin -13%; females: serum cholesterol -16%); biological significance is unclear
• Hematology: reticulocytes were increased (25%) in high dose males and females
• Organ weights: target organs were liver, forestomach, and kidneys; based on increased relative weights (p<0.01) in male and female groups at 250 and 500 mg/kg bw/day. No weight changes were noted at 25 and 125 mg/kg bw/day.
• Reproductive organs: relative weight of testes was increased, and that of ovaries decreased, at 250 and 500 mg/kg bw/day.
• Histopathology revealed changes only in high dose animals. Predominantly inflammatory changes in the forestomach which are attributable to the irritation properties of 2 -EH
• 2 -EH at 500 mg/kg bw/day caused peroxisome proliferation, as evidenced by a statistically significant increase of the hepatic cyanide-insensitive palmitoyl coenzyme A activity in male (p<0.001) and female (p<0.05) rats in Week 13.
• The subchronic NOEL was 125 mg/kg bw/day in male and female rats. The estimated NOAEL is 250 mg/kg bw/day.