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Description of key information

Oral LD50 (rat) = 16000 mg/kg (24 mL/kg)

 

Inhalation LC50 (rat) > 17600 mg/m3 (5000 ppm)

 

Dermal LD50 (rabbit) > 3350 mg/kg (5 mL/kg)

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:
1971
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: This study is classified as reliable with restrictions because there was no GLP statement provided, and limited data on methods were reported, but the study seemed to be well-conducted.
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 401 (Acute Oral Toxicity)
Deviations:
yes
Remarks:
multiple ages tested
Principles of method if other than guideline:
Groups of 6 -12 rats were given doses of the test substance by oral gavage. Rats of 4 different ages were tested, newborns, 14 -days old, young adult, and older adults.
GLP compliance:
no
Test type:
acute toxic class method
Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Age at study initiation: rats of 4 different ages were studied - 24-48 hrs old, 14 days old, young adult rats, and older adult rats
- Weight at study initiation: newborn 5-8 g, immature 16-50 g, young adult 80-160 g, older adult 300-470 g
Route of administration:
oral: gavage
Vehicle:
unchanged (no vehicle)
Details on oral exposure:
None
Doses:
1, 24, 49 ml/kg
No. of animals per sex per dose:
6 male rats were used in the young adult and older adult studies, and groups of 6-12 rats of both sexes were used in the newborn and immature rat studies.
Statistics:
Litchfield, J.T. and Wilcoxen, F. (1949). A simplified method of evaluating dose-effect experiments. J. Pharmacol. Exp. Ther. 96, 99-101.
probit analysis, and parallel probit analysis
Key result
Sex:
male/female
Dose descriptor:
LD50
Effect level:
24 mL/kg bw
95% CL:
22.5 - 25.8
Remarks on result:
other: ~16 g/kg; 14-day old rats
Sex:
male
Dose descriptor:
LD50
Effect level:
49 mL/kg bw
95% CL:
35.5 - 68
Remarks on result:
other: ~32 g/kg; young adult rats
Sex:
male
Dose descriptor:
LD50
Effect level:
43.5 mL/kg bw
95% CL:
31.4 - 58.8
Remarks on result:
other: ~30 g/kg; older adult rats
Mortality:
The test substance was significantly more toxic in 14-day old rats than in adult rats.
Interpretation of results:
other: not classified
Remarks:
Criteria used for interpretation of results: EU
Conclusions:
The LD50 for 14-day old rats was 24 ml/kg. The LD50 for young adult rats was 49 ml/kg. The LD50 for older adult rats was 43.5 ml/kg. The test substance is not classified under EU guidelines.
Executive summary:

This study determined the oral toxicity of hexane in rats of various ages. Groups of 6 -12 rats were given doses of the test substance by oral gavage. Rats of 4 different ages were tested, newborns, 14 -days old, young adult, and older adults.

Due to difficulty in administering small doses, the LD50 for newborn rats could not be determined, but was assumed to be <1.0 ml/kg. The LD50 for 14 -day old rats was 24 ml/kg, which was significantly lower than the LD50 for young adults rats, 49 ml/kg, and older adult rats, 43.5 ml/kg. Since the LD50s for rats older than newborns were 24 ml/kg (~16 g/kg) or above, the test substance would not be classified as toxic under OECD GHS guidelines.

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
LD50
Value:
ca. 16 000 mg/kg bw
Quality of whole database:
1 key substance specific study available for assessment

Acute toxicity: via inhalation route

Link to relevant study records

Referenceopen allclose all

Endpoint:
acute toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1987
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: This study is classified as reliable with restrictions because there was no GLP statement provided, and limited data on methods were reported, but the study seemed to be well-conducted.
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 403 (Acute Inhalation Toxicity)
Deviations:
yes
Remarks:
24 hour exposure; More animals used than TG specify
Principles of method if other than guideline:
A group of 17 male rats were exposed to a concentration of 5000 ppm of test substance vapors for 24 hrs. The animals were observed for clinical signs and body weights. The animals were sacrificed at different time points after exposure: immediately after exposure, and on days 2, 7, 14, and 30 post-exposure. The testes and epididymides were examined for lesions and histopathological changes.
GLP compliance:
no
Test type:
acute toxic class method
Species:
rat
Strain:
Sprague-Dawley
Sex:
male
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Charles River, Italy
- Weight at study initiation: 180-220 g
- Housing: steel wire cages
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum

Route of administration:
inhalation: vapour
Type of inhalation exposure:
whole body
Details on inhalation exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: airtight Lucite boxes
- Method of holding animals in test chamber: cages
- Source and rate of air: 3 l/min
- Method of conditioning air: Air from a compressed air bottle and regulated by a flowmeter conveyed n-hexane vapor from a bubbler immersed in a 23.5 degree C water bath. This air mixed with air from a pump in a glass chamber before entering the control chamber.

TEST ATMOSPHERE
- Brief description of analytical method used: A total hydrocarbon analyzer was connected to the exhaust from exposure group chambers.
Analytical verification of test atmosphere concentrations:
yes
Duration of exposure:
24 h
Concentrations:
5000 ppm
No. of animals per sex per dose:
17 males
Control animals:
yes
Details on study design:
- Duration of observation period following administration: Animals were sacrificed at 0, 2, 7, 14, and 30 days after exposure.
- Frequency of observations and weighing: Daily for clinical observations, and weekly body weights were taken.
- Necropsy of survivors performed: yes
- Other examinations performed: Histopathology of the epididymis and testis was performed.
Statistics:
The pathology index was calculated for effects to the epididymis and testis. Body weight data was analyzed using the Student t-test.
Key result
Sex:
male
Dose descriptor:
LC50
Effect level:
> 5 000 ppm
Exp. duration:
24 h
Remarks on result:
other: 17600 mg/m3
Mortality:
There was no mortality of animals due to a single 24-hr exposure to 5000 ppm test substance.
Clinical signs:
other:
Other findings:
- Histopathology: Four of the six animals sacrificed at the end of the treatment showed lesions of the testis and epididymis. These lesions inlcuded focal degeneration of the spermatocytes and mild exfoliation of elongated spermatids. Leptotene, zygotene, and transitional spermatocytes were more susceptible than pachytene spermatocytes. Some of the epididymal tubules showed degenerating germ cells. In animals sacrificed at day 2 and day 7 after treatment, there were increased dengenerated and exfoliated germ cells and numerous inflammatory cells. In the animals sacrificed at day 14, only occasional degenerated metaphase spermatocytes were seen, suggesting that the testes were beginning to recover. Animals sacrificed at 30 days after treatment had no lesions in the testes, suggesting complete recovery.
Interpretation of results:
other: not classified
Remarks:
Criteria used for interpretation of results: EU
Conclusions:
There was no mortality of animals due to a single 24-hr exposure to 5000 ppm test substance. The LC50 is > 5000 ppm for male rats.
Executive summary:

This study examined the effects of exposure to n-hexane via inhalation for 24 hrs to male rats. A group of 17 male rats were exposed to a concentration of 5000 ppm of test substance vapors for 24 hrs. The animals were observed for clinical signs and body weights. The animals were sacrificed at different time points after exposure: immediately after exposure, and on days 2, 7, 14, and 30 post-exposure. The testes and epididymis were examined for lesions and histopathological changes. Lesions to the epididymis were seen in 4 of 6 animals sacrificed immediately after exposure. 3 of these animals also had lesions to the testis. Lesions in these areas continued to be seen in animals sacrificed up to 14 days after exposure, however, the severity of the lesions lessened. The animals sacrificed at 30 days post-exposure had no lesions in these areas, suggesting complete recovery. The LOAEC for a single 24 -hr exposure is 5000 ppm (17600 mg/m3) based on effects to the epididymis and testes. No animals died from the exposure, therefore the LC50 is > 5000 ppm (17600 mg/m3).

Endpoint:
acute toxicity: inhalation
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
1970
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: This study is classified as reliable with restrictions because it is an acceptable, well-documented publication that closely follows OECD Guideline 403.
Justification for type of information:
A discussion and report on the read across strategy is given as an attachment in IUCLID Section 13.
Reason / purpose for cross-reference:
read-across: supporting information
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 403 (Acute Inhalation Toxicity)
GLP compliance:
no
Test type:
acute toxic class method
Species:
rat
Strain:
Long-Evans
Sex:
male
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Weight at study initiation: 150-300 g

Route of administration:
inhalation: vapour
Type of inhalation exposure:
not specified
Details on inhalation exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure chamber volume: 250 l
- Method of conditioning air: Sample was heated in a water bath at 77 degree F. Air was bubbled through the sample and entered the exposure chamber. For concentrations less than saturation, air flow was divided with part passing over the sample and part passing directly into the exposure chamber.

TEST ATMOSPHERE
- Brief description of analytical method used: GLC

Duration of exposure:
4 h
Concentrations:
73,680 ppm (30-40% of saturation at 25 degree C)
81,800 ppm
No. of animals per sex per dose:
10 males
Details on study design:
- Duration of observation period following administration: at least 6 days
Key result
Sex:
male
Dose descriptor:
LC50
Effect level:
73 860 ppm
Exp. duration:
4 h
Remarks on result:
other: 259354 mg/m3
Mortality:
All deaths occurred during exposure, except one rat in the 81800 ppm group that died on day 6.
Clinical signs:
other: Surviving rats were uncoordinated, prostrate or comatose during exposure but recovered within a few hours of removal from the chamber. The rat that died on day 6 had convulsions during and after exposure.
Interpretation of results:
study cannot be used for classification
Conclusions:
The 4-hr LC50 for rats exposed by inhalation was 73,680 ppm.
Executive summary:

This study examined that acute inhalation toxicity of hexane to male rats. Groups of 10 male rats exposed to various large concentrations of hexane vapor for 4 hrs. Animals were then observed for clinical signs and mortality for at least the next 6 days. Several animals died during the exposure period. Surviving animals experienced severe toxicological effects during the exposure. One animal experienced convulsions during and after exposure, and died on day 6 post-exposure. The LC50 was determined to be 73,680 ppm (259354 mg/m3). Due to the high concentration of the LC50, the test substance would not be classified as toxic by inhalation according to OECD GHS guidelines.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
LC50
Value:
> 17 600 mg/m³ air
Physical form:
inhalation: vapour
Quality of whole database:
1 key and 1 supporting substance specific study and 1 key read across study for a structural analogue available for assessment

Acute toxicity: via dermal route

Link to relevant study records
Reference
Endpoint:
acute toxicity: dermal
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
1970
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: This study is classified as reliable with restrictions because it is an acceptable, well-documented publication that closely follows OECD Guideline 402.
Justification for type of information:
A discussion and report on the read across strategy is given as an attachment in IUCLID Section 13.
Reason / purpose for cross-reference:
read-across: supporting information
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 402 (Acute Dermal Toxicity)
GLP compliance:
no
Test type:
fixed dose procedure
Limit test:
yes
Species:
rabbit
Strain:
New Zealand White
Sex:
male
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Weight at study initiation: 2-3 kg
Type of coverage:
occlusive
Vehicle:
unchanged (no vehicle)
Details on dermal exposure:
TEST SITE
- Type of wrap if used: saran wrap sleeve


REMOVAL OF TEST SUBSTANCE
- Washing (if done): skin was wiped with damp towels
- Time after start of exposure: 4 hrs


TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 5 ml/kg
Duration of exposure:
4 hrs
Doses:
up to 5.0 ml/kg
No. of animals per sex per dose:
3 males
Details on study design:
- Duration of observation period following administration: 14 days
- Other examinations performed: clinical signs
Statistics:
method of Litchfield and Wilcoxen
Key result
Sex:
male
Dose descriptor:
LD50
Effect level:
> 5 mL/kg bw
Remarks on result:
other: 3.35 g/kg
Mortality:
No mortality was observed.
Clinical signs:
other: Animals showed signs of discomfort and were uncoordinated at the end of the exposure period.
Interpretation of results:
other: Not Classified
Remarks:
Criteria used for interpretation of results: EU
Conclusions:
The 4-hr LD50 for dermal exposure in rabbits is > 5.0 ml/kg bw (3.35 g/kg).
Executive summary:

This study examined the dermal toxicity of the hexane. Doses of up to 5.0 ml/kg of test substance was placed on the shaved skin of 3 male rabbits. The test area was then covered with a saran wrap sleeve for 4 hrs. After the exposure period, the test substance washed off, and the animals observed for toxicity and mortality over the next 14 days. No animals died, however, they did show signs of discomfort and uncoordination after the exposure. The LD50 for dermal exposure is > 5.0 ml/kg (3.35 g/kg). The test substance is not classified as toxic under EU GHS guidelines.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
LD50
Value:
> 3 350 mg/kg bw
Quality of whole database:
1 key read across study from a structural analogue and 1 supporting substance specific study available for assessment

Additional information

Acute toxicity data is available for n-hexane. Additional acute toxicity data is available for structural analogue 5-80% n-hexane. This data is read across to n-hexane based on analogue read across and a discussion and report on the read across strategy is provided as an attachment in IUCLID Section 13.

 

Oral

 

n-hexane

In a key acute oral toxicity study (Kimura et al., 1971), groups of 6-12 rats were given doses of n-hexane by oral gavage. Rats of Four different ages were tested: newborns, 14 -days old, young adult, and older adults. Due to difficulty in administering small doses, the LD50 for newborn rats could not be determined, but was assumed to be <1.0 ml/kg. The LD50 for 14-day old rats was 24 ml/kg, which was significantly lower than the LD50 for young adult rats, 49 ml/kg, and older adult rats, 43.5 ml/kg. Since the LD50s for rats older than newborns were 24 ml/kg (~16 g/kg) or above, the test substance is not classifiable under EU guidelines.

 

Inhalation

 

n-hexane

DeMartino et al. (1987) examined the effects of exposure to n-hexane via inhalation for 24 hrs to male rats. A group of 17 male rats were exposed to a concentration of 5000 ppm of test substance vapors for 24 hrs. The animals were observed for clinical signs and body weights. The animals were sacrificed at different time points after exposure: immediately after exposure, and on days 2, 7, 14, and 30 post-exposure. The testes and epididymis were examined for lesions and histopathological changes. Lesions to the epididymis were seen in 4 of 6 animals sacrificed immediately after exposure. 3 of these animals also had lesions to the testis. Lesions in these areas continued to be seen in animals sacrificed up to 14 days after exposure, however, the severity of the lesions lessened. The animals sacrificed at 30 days post-exposure had no lesions in these areas, suggesting complete recovery. The LOAEC for a single 24 -hr exposure is 5000 ppm (17600 mg/m3) based on effects to the epididymis and testes. No animals died from the exposure, therefore the LC50 is > 5000 ppm (17600 mg/m3). 

 

In an acute inhalation toxicity study (Phillips Petroleum Company, 1982), groups of 5 male and 5 female rats were exposed by inhalation route to n-Hexane for 4 hours at a nominal concentration of 31.86 mg/L. Animals then were observed for 14 days. Other than animals appearing hyperactive in the first hour of observation, no treatment related clinical signs were apparent. No exposure related trends were apparent in the body weight data or gross pathology data. The inhalation LC50 was not determined in males or females.

 

5-80% n-hexane

Hine et al. (1970) exposed groups of 10 male rats exposed to concentrations of hexane vapor for 4 hours. Animals were then observed for clinical signs and mortality for at least 6 days post-exposure. Several animals died during the exposure period. Surviving animals experienced severe toxicological effects during the exposure. One animal experienced convulsions during and after exposure and died on day 6 post-exposure. The LC50 was determined to be 73,680 ppm (259354 mg/m3).

 

Dermal

 

5-80% n-hexane

In a key dermal toxicity study from C-6 normal and iso paraffins (hexanes) and naphthenes (methyl-cyclohexane, dimethylcyclohexane), 25-35% n-hexane (Hine et al., 1970 Klimisch=2), 5.0 ml/kg of test substance was placed on the shaved skin of 3 male rabbits. The test area was then covered with a saran wrap sleeve for 4 hrs. After the exposure period, the test substance washed off, and the animals observed for toxicity and mortality over the next 14 days. No animals died; however, they did show signs of discomfort and uncoordination after the exposure. The LD50 for dermal exposure is > 5.0 ml/kg (3350 mg/kg). Therefore, the test substance is not classified under EU criteria.

 

n-hexane

In an acute dermal toxicity study (Phillips Petroleum Company, 1982), groups of 3 male and 3 female rabbits were dermally exposed to n-Hexane for 4 hours at dose of 2,000 mg/kg bw. Animals then were observed for 14 days. Dermal irritation was scored using the method of Draize. Erythema and edema scores did not exceed well-defined erythema or moderate edema. Very slight erythema persisted in one male until day 7, all other rabbit erythema cleared by day 7. Very slight edema was noted in all rabbits on Day 1 and had cleared by Day 3. No deaths occured amoung the study animals throughout the study. Further, there were no treatment related clinical signs, necropsy findings or changes in body weight. With the exception of phonation the animals appear normal throughout the study period. All animals gained weight between study initiation and termination. No observable gross pathology was observed in any of the test animals upon necropsy. The dermal LD50 was determined to be > 2,000 mg/kg in males, females, and combined male/female rabbits.

Justification for classification or non-classification

Based on available substance specific and read across data, n-hexane is minimally toxic via ingestion where the LD50 is 16000 mg/kg bw, via dermal exposure where the LD50 is > 3350 mg/kg bw, and by inhalation where the LC50 is > 17600 mg/m3.  These findings do not warrant classification under the new Regulation (EC) 1272/2008 on classification, labeling and packaging of substances and mixtures (CLP).

 

N-hexane is classified under EU CLP guidelines as STOT Single Exposure Category 3 (narcosis) based on non-lethal narcotic effects observed in acute inhalation exposure.

 

N-hexane is classified under EU CLP guidelines as a Category 1 aspiration hazard based on its physical and chemical properties (hydrocarbon fluid, viscosity ≤ 20.5 mm2/s).