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Description of key information

Oral LD50 (rat) = 2047 mg/kg bw
Dermal LD0 (rat) >3000 mg/kg bw
Inhalation LC50 (rat)
- vapour: no mortality at 0.89 mg/L (4h) or when exposed to saturation concentration (1, 2, 4, and 8 h)
- aerosol: between 1 and 4 mg/L

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records
Reference
Endpoint:
acute toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1969
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Comparable to guideline study with some resctrictions in documentation
Reason / purpose:
reference to same study
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 401 (Acute Oral Toxicity)
Deviations:
yes
Remarks:
non-fasted animals
GLP compliance:
no
Remarks:
Pre-GLP study
Test type:
standard acute method
Limit test:
no
Species:
rat
Strain:
Wistar
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Mellon Institute of Industrial Research, Pittsburgh, Pennsylvania
- Age at study initiation: 4 -5 weeks
- Weight at study initiation: 90 - 120 g
- Fasting period before study: none
- Housing: no data
- Diet (e.g. ad libitum): Rockland rat diet, complete
- Acclimation period: not required; rats were reared at the Institute's own facilities


Route of administration:
oral: gavage
Vehicle:
not specified
Doses:
Dosages were given in a logarithmic series differing by a factor of 2. Doses actually used are not specified.
No. of animals per sex per dose:
5 male rats per dose level.
Control animals:
not specified
Details on study design:
- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: no data
- Necropsy of survivors performed: no
- Other examinations performed: clinical signs, body weight,organ weights, histopathology, other: no
Statistics:
LD50 values were calculated by the method of Thompson [Thompson WR (1947) Bacteriol Rev 11:115]. The figures in parentheses show the limits of +/- 1.96 standard deviations.
Sex:
male
Dose descriptor:
LD50
Effect level:
ca. 2 047 mg/kg bw
RS-Freetext:
LD 50 = 2.460 ml/kg (1.820 - 3.300 ml/kg). Taking the density into account (0.832 kg/l) this corresponds to 2047 (1514 - 2746) mg/kg.
Interpretation of results:
not classified
Remarks:
Migrated information Criteria used for interpretation of results: EU
Conclusions:
The acute oral LD50 was 2047 mg/kg bw in male rats.
Executive summary:

The acute oral toxicity of 2 -EH was determined in groups of 5 male Wistar rats receiving the test material by oral gavage. The dosages were spaced by a factor of 2. The observation period was 14 days. The LD50 and a range of +/- 1.96 SD was calculated according to the method of Thomson (1947). Overall the study was conducted in accordance with the recently replaced OECD test guideline 401.

The acute oral LD50 was 2047 mg/kg bw in rats (Smyth et al., 1969).

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
LD50
2 047 mg/kg bw
Quality of whole database:
Various studies with high reliability show comparable results. The quality of the database is high.

Acute toxicity: via inhalation route

Link to relevant study records
Reference
Endpoint:
acute toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1989-03-30 through 1989-04-12
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Acceptable, well-documented study report which meets basic scientific principles. Original report available as copy. Restriction: low number of animals, short observation period. Only 2 dose levels tested. Restriction acceptable because of low test substance volatility. No data on gross pathology.
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 403 (Acute Inhalation Toxicity)
Deviations:
yes
Remarks:
only 2 dose levels; low animal numbers; 7 day observation period
Principles of method if other than guideline:
Method: similar to OECD 403 with restrictions: 2 dose levels tested. 3 animals per sex and dose level were tested. Test atmosphere concentration and particle size was determined. Observation period was 7 days.
GLP compliance:
yes
Test type:
standard acute method
Limit test:
yes
Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Breeding Laboratories, Inc., Raleigh, North Carolina
- Age at study initiation: Group I Group II
Males 8 weeks 9 weeks
Males 9 weeks 11 weeks

- Weight at study initiation: Group I Group II
Males: range: 230-238 g; 350-335 g
mean: 235g 353g
Females: range: 221-228 g; 250-265 g
mean: 225g 258g



- Fasting period before study:
- Housing: in stainless steel wire mesh cages; in groups of 2 during the first week of acclimatisation; singly thereafter
- Diet (e.g. ad libitum): standard laboratory diet (Purina Rodent laboratory Chow Brand Animal Diet #5001)
- Water (e.g. ad libitum): automated watering system
- Acclimation period: 1 week (Group I) and 3 weeks (Group II)


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 67-76°F
- Humidity (%): 40-70%
- Air changes (per hr):
- Photoperiod (hrs dark / hrs light): 12hrs dark/12 hrs light

Route of administration:
other: Group I: vapour + aerosol; Group II: vapour
Type of inhalation exposure:
whole body
Vehicle:
other: air
Details on inhalation exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Plexigla / glass exposure chamber
- Exposure chamber volume: 100 L
- Method of holding animals in test chamber: animals were caged
- Source and rate of air: house-supply air
- System of generating particulates/aerosols:
Group I: the test material was placed into a 250 mL Erlenmeyer flask from where it was delivered by a fluid metering pump into the fluid inlet of an air atomizing nozzle. House-supply air was delivered through the air inlet to the atomizer to generate the aerosol which was directed into the exposure chamber.
Group II: air was drawn through 2 glass bubblers, place in water bath in tandem, which contained the test material. The air was heated to 50°C in the first and 30°C in the second bubbler; the air was then directed to a 3-neck flask containing glass wool before the filtered air was directed to the exposure chamber.

- Method of particle size determination:
Group I: once during exposure using a Delron DCI-6 Cascade Impactor.
Group II: hourly during exposure using a TSI Aerodynamic Particle Sizer (Model 3300)



TEST ATMOSPHERE
- Brief description of analytical method used:
Group I: gravimetric determination of test material drawn from the breathing zone onto glass microfibre filter paper followed by a charcoal tube. The gravimetric concentration (aerosol/vapour/total) was calculated by dividing the weight difference in mg by the volume of air sampled in L.

Group II: hourly samples were drawn and directed to a IRAN 1A Ambient Air Analyzer. The exposure level was determined from the absorbance using a calibration curve constructed using the same equipment.

- Samples taken from breathing zone: yes


VEHICLE
- Composition of vehicle (if applicable): air
- Concentration of test material in vehicle (if applicable): none


TEST ATMOSPHERE (if not tabulated)
- Particle size distribution: Group I: 81% of particles < 10 microns
- MMAD (Mass median aerodynamic diameter) / GSD (Geometric st. dev.): Group I: 5.6 microns (geometric st. dev. 1.9)
Group II: no aerosol formation was considered, due to very low levels of particulates (0.015 mg/m³)

Analytical verification of test atmosphere concentrations:
yes
Duration of exposure:
4 h
Concentrations:
0.89 mg/L (vapour) and 5.3 mg/L (mixed vapour and aerosol)
No. of animals per sex per dose:
3
Control animals:
other: historical controls
Details on study design:
- Duration of observation period following administration: 7 days
- Frequency of observations and weighing: viability was assessed twice daily. Body weights were determined on days 1 (immediately prior to exposure) and on day 8 (prior to sacrifice).
- Necropsy of survivors performed: no
Statistics:
none
Sex:
male/female
Dose descriptor:
LC50
Effect level:
> 0.89 - <= 5.3 mg/L air
Exp. duration:
4 h
Remarks on result:
other: 0.89 mg/L (vapour); 5.3 mg/L (mixed vapour (1.1 mg/L) and aerosol (4.3 mg/L))
Mortality:
Group I: all animals died (6/6)
Group II: no animals died (0/6)
Clinical signs:
Group I: 4 animals died during the exposure period or shortly thereafter. Observations included laboured breathing, nasal discharge, prostration, and closed eyes.
Body weight:
Group I: 4 animals died during the exposure period or shortly thereafter.
Group II: decreased activity was noted during exposure; after the exposure the animals were unremarkable, and most gained weight during the following week.
Gross pathology:
No data
The proportion of inspirable aerosol was high in the first experiment with Group I, and there was a large discrepancy between the measured and the nominal concentration which was calculated from the amount of test material consumed during the exposure.

In experiment I the measured concentration was only 12.3% compared to the nominal concentration which was calculated from the consumed test material.

The differences in nominal and measured exposure concentrations are attributed to impaction or sedimentation or absorption of the aerosol/vapour on the surfaces in the exposure chamber.

Group

Concentration (mg/L)

aerosol

vapour

total

nominal

         I      

4.3

1.1

5.3

43

II

-

0.89

0.89

2.5

Within the study report the vapour saturation concentration was calculated to be 1.4 mg/L at 20°C, based on the vapour pressure of 0.2 mm Hg (i.e. 0.267 hPa).

When using the vapour pressure of 0.93 hPa, which was obtained in a highly reliable and newly available study, a saturated vapour concentration of 4.9 mg/L (i.e. 4884 mg/cubicmetre) can be calculated.

Interpretation of results:
Toxicity Category IV
Remarks:
Migrated information Criteria used for interpretation of results: EU
Conclusions:
Under the The LC50 was >0.89 mg/L. The complete mortality in the first experiment was attributed to the high proportion of respirable aerosol.
Executive summary:

Following the 4 hour inhalation exposure to 0.89 mg 2-EH/L no mortalities or clinical signs of toxicity were noted in male and female Sprague-Dawley rats within the 7-day observation period.

In contrast, all animals of the 5 mg/L target concentration group died, 4 of them during the exposure or shortly thereafter. It was, however, demonstrated that only 20% of the measured concentration was attributable to vapour whereas 80% was represented by particulates. The majority of the particulates (81%) had a mean aerodynamic diameter of 10 µm and were thus respirable by rats. The measured concentration was only 12.3% compared to the nominal concentration which was calculated from the consumed test material.

Based on the above it is concluded that the 4-hour LC50 in rats was >0.89 mg/L (BioDynamics, 1989).

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Quality of whole database:
Results from the only GLP study are of high reliability. Studies of lower reliability (Klimisch score 3 and 4) support the low inhalation toxicity of 2-EH. The overall quality of the database is high.

Acute toxicity: via dermal route

Link to relevant study records
Reference
Endpoint:
acute toxicity: dermal
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1987-09-15 to 1987-09-29
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Non-GLP guideline study
Qualifier:
according to
Guideline:
OECD Guideline 402 (Acute Dermal Toxicity)
GLP compliance:
no
Test type:
fixed dose procedure
Limit test:
yes
Species:
rat
Strain:
other: WISW (SPF TNO)
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: F. Winkelmann, Borchen, Germany
- Age at study initiation: no data
- Weight at study initiation: 173.1 g (mean)
- Fasting period before study: no data
- Housing: Macrolon cages Type III, in groups of 1 to 5 animals
- Diet (e.g. ad libitum): R10 rat diet; Ssniff Spezialfutter GmbH, Soest, Germany
- Water (e.g. ad libitum): tap water
- Acclimation period: 4 to 8 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 +/- 1 °C
- Humidity (%): 60 +/- 5
- Air changes (per hr): 15
- Photoperiod (hrs dark / hrs light): 12 / 12 hours


IN-LIFE DATES: From: day -1 To:day 14 after initiation
Type of coverage:
semiocclusive
Vehicle:
unchanged (no vehicle)
Details on dermal exposure:
TEST SITE
- Area of exposure: >10% of the body surface; clipped 24 h before initiation
- % coverage: >10
- Type of wrap if used: the test site was covered with a gauze patch (5x7cm) and fixed with a cotton wrap.

REMOVAL OF TEST SUBSTANCE
- Washing (if done): no
- Time after start of exposure: 24 hours

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 3.604 ml/ kg bw, i.e. 3000 mg/kg bw
- Concentration (if solution): neat

Duration of exposure:
24 hours
Doses:
3000 mg/kg bw
No. of animals per sex per dose:
5 per sex
Control animals:
no
Details on study design:
- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: days -1, 1, 7, and 14 after initiation
- Necropsy of survivors performed: yes
- Other examinations performed: clinical signs, body weight,organ weights, histopathology
Statistics:
The LD50 was calculated according to Litchfield and Wilcoxon (1949). Pharmacol. Exp. Ther. 96: 99
Preliminary study:
There was no mortality neither in male nor female rats. The dermal LD50 was >3000 mg/kg body weight in rats.
Sex:
male/female
Dose descriptor:
LD0
Effect level:
> 3 000 mg/kg bw
Mortality:
There was no mortality neither in male nor female rats.
Clinical signs:
Animals were excited until 1 hour after test substance application, and free of symptoms thereafter.
Body weight:
Body weight development was not affected by the treatment compared to controls (contol data not reported). Mean body weights were as tabulated below. Mean body weight gain was 28.7 g within 14 days after treatment.


Day after initiation Mean body weight [g]
0 before treatment 173.1
1 171.4
7 186.5
14 201.8



Gross pathology:
Mucosa of the small intestine was hyperaemic in 2 animals; red coloured urine was noted in one rat, associated with changes in the kidney.

Body weight development in treated rats (combined males and females):

Day after initiation

Mean body weight [g]

0 before treatment

173.1

1

171.4

7

186.5

14

201.8

Interpretation of results:
not classified
Remarks:
Migrated information Criteria used for interpretation of results: EU
Conclusions:
The dermal LD0 was >3000 mg/kg body weight in male and female rats.
Executive summary:

The acute dermal toxicity of 2-ethylhexanol was tested in rats according to OECD 402. 5 animals of either sex were exposed to 3000 mg/kg bw for 24 hours under a semiocclusive dressing. There were no mortalities within the 14 days observation period. The body weight development was not affected, and there were no clear clinical signs or observations during necropsy which could be related to the treatment. Therefore, the dermal rat LD0 was >3000 mg/kg bw in this study (Hüls AG, 1987).

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
discriminating dose
3 000 mg/kg bw
Quality of whole database:
Results from the KEY study are of high reliability. Studies of lower reliability (Klimisch 2 and 3) support the low acute dermal toxicity.

Additional information

The acute toxicity key studies are summarised as follows:

The acute oral toxicity of technical grade 2 -EH was examined in a protocol that was similar to the recently retracted OECD test guideline 401. 36 fasted male rats received the unchanged test material by oral gavage; the doses were geometrically spaced. The dose levels and the number of animals per dose level were not reported. The study is therefore regarded to be valid with restrictions.

The LD50 was 3290 mg/kg bw [range (p=0.05): 2870 – 3790 mg/kg bw] in fasted male rats receiving the undiluted 2-EH by oral gavage. Deaths occurred within 2 days, and the animals died in narcosis without any other signs of toxicity (Schmidt P, Gohlke R, and Rothe R, 1973).

Other studies with similar reliability support the low oral toxicity of 2-ethylhexanol. Scala and Burtis (1973) reported a LD50, rat of 3730 mg/kg bw, and Smyth et al. (1969) reported an approx. acute oral LD50 in rats of 2047 mg/kg bw which basically supports the finding that 2 -EH is of low acute oral toxicity.

In the end the study by Smyth et al. (1969) was selected as key study as it presented the lowest LD50 reported in a reliable acute oral toxicity study.

In further studies with low reliability LD50 values in the range of 3700 to 7000 mg/kg were identified for rats. There are more studies available examining other species but being also of low reliability (RL3 or RL4). LD50 values for guinea pigs were in the range of 630 -2820 mg/kg. In mice LD50 varied in between 2870 for females up to 4460 for males with the diluted test material. In rabbits LD50 values of 1180 up to 1470 mg/kg were found.

Following the 4 hour inhalation exposure to 0.89 mg 2-EH/L (vapour) no mortalities or clinical signs of toxicity were noted in male and female Sprague-Dawley rats within the 7-day observation period.

In contrast, all animals of the 5 mg/L target concentration group died, 4 of them during the exposure or shortly thereafter. It was, however, demonstrated that only 20% of the measured concentration was attributable to vapour whereas 80% was represented by particulates. The majority of the particulates (81%) had a mean aerodynamic diameter of 10 micrometre and were thus respirable by rats. The measured concentration was only 12.3% compared to the nominal concentration which was calculated from the consumed test material (differences due to impaction or sedimentation or absorption of aerosol/vapour on the surfaces in the exposure chamber).

Based on the above it is concluded that the 4-hour LC50 in rats was >0.89 mg/L (vapour).

The absence of deaths within the 14 -day observation period in Inhalation Risk Tests (IRT) performed by Smyth et al. (1969) and BASF (1963) indicates that the acute inhalation toxicity of 2 -EH is low. The rats were exposed in the IRT to saturated atmospheres for up to and including 8 hours.

The vapour saturation concentration was calculated to be 1.4 mg/L at 20°C, based on the vapour pressure of 0.2 mm Hg(i.e. 0.267 hPa; BioDynamics, 1989). According to another source (Auergesellschaft Berlin (1988) AUER Technikum, p. 326/327) the vapour pressure is 0.48 mg Hg at 20°C, and the saturation concentration is 2.6 mg/L).When using the vapour pressure of 0.93 hPa, which was obtained in a highly reliable and newly available study, a saturated vapour concentration of 4.9 mg/L (i.e. 4884 mg/cubicmetre)

can be calculated.

In further studies of low reliability (RL 3 or 4) no LC50 could be determined as no mortalities were observed. In these studies 2 -EH was assumed to be applied near saturation concentrations to mice, rats or guinea pigs for exposure periods up to 8 hours. Using a QSAR method to determine the dose for reduction of the respiratory rate to 50% in mice yielded a RD50 value of 44 ppm (i.e. 234 mg/m³).

The acute dermal toxicity of 2-ethylhexanol was tested in rats according to OECD 402. 5 animals of either sex were exposed to 3000 mg/kg bw for 24 hours under a semiocclusive dressing. There were no mortalities within the 14 days observation period. The body weight development was not affected, and there were no clear clinical signs or observations during necropsy which could be related to the treatment. Therefore, the dermal rat LD0 was >3000 mg/kg bw in this study (Hüls AG, 1987).

The above is supported by the results obtained in a less well documented study where clinical signs and mortality lacked following dermal exposure of rabbits to 2 -ethylhexanol (up to 2600 mg/kg bw; abdominal skin, occlusive exposure). In another study (Smyth 1962/1969) the approximate LD50 was determined at around 1980 mg/kg bw (1414 -2778 mg/kg bw; in range-finding study using 4 male rabbits per dose level weighing 2.5 to 3.5 kg; 24 h exposure period, 14 day observation period, no necropsy or histopathological examinations reported). However, there are restrictions which limits the reliability of this study, as test conditions (test substance purity, dose levels used), and results (signs of toxicity, mortality) are poorly described. Moreover, the number of test animals per dose level was low, and only male animals were tested. The reported LD50 value should therefore be regarded as a supporting, range-finding value, but should not be used for classification if there are more precise and adequate studies available.

Overall the three studies point out the absence of (or a low) acute dermal toxicity of 2 -ethylhexanol.

It is justified to select the the OECD TG 402 study as Key Study, and to use the higher value, as there were no mortalities in either study.


Justification for selection of acute toxicity – oral endpoint
Low LD50 reported from adequate study of high reliability (Klimisch score 2)

Justification for selection of acute toxicity – inhalation endpoint
Low LC50 (range) from only reliable study (Klimisch score 2)

Justification for selection of acute toxicity – dermal endpoint
Reliable study (Klimisch 1)

Justification for classification or non-classification

Acute oral toxicity: the LD50 was 2047 mg/kg bw in rats. This exceeds the cut-off value for classification according to Regulation (EC) no 1272/2008 (i.e. 2000 mg/kg bw).

Acute inhalation toxicity: the 4-hour LC50 (vapour) in rats was >0.89 mg/L (BioDynamics, 1989).

It is concluded that 2 -EH is of low inhalation toxicity not requiring classification with respect to vapours because there was no mortality seen in rats exposed to 0.89 mg/L for 4 hours, and exposed to saturation concentration for 1, 2, 4, and 8 hours.

However, under aerosol formation conditions, 4 out of 6 animals died when exposed to a mixture of 1.1 mg/L vapour and 4.3 mg/L aerosol at 20°C during the exposure or shortly thereafter. The remaining animals died on day 2 after exposure (BioDynamics, 1989).

The LC50 concentration of the aerosol is expected to be between 1 and 4 mg/L corresponding to a classification as inhalative acute toxicity category 4.

Acute dermal toxicity:

two valid dermal toxicity studies are known to exist. There was no mortality up to and including the highest dose levels which were 2600 and 3000 mg/kg bw, respectively. Therefore, the dermal rat LD0 was >3000 mg/kg bw. This exceeds the cut-off value for classification according to Regulation (EC) no 1272/2008 (i.e. 2000 mg/kg bw).

Overall, the acute oral, inhalation,and dermal toxicity of 2-EH is low and does only require classification with regard to inhalative toxicity (aerosol formation conditions) (acute category 4).