Hydrocarbons, C10-C13, n-alkanes

Neurotoxicity

Description of key information

Acute CNS effects:

Inhalation

Hydrocarbons, C10-C12, isoalkanes, <2% aromatics: NOAEC in rats = 1500 mg/m³

n-decane: NOAEC in rats = 1500 mg/m³ (based primarily on volatility)

Dermal

Hydrocarbons, C11-C14, n-alkanes, <2% aromatics: NOAEL in rats >2000 mg/kg bw/day

Key value for chemical safety assessment

Effect on neurotoxicity: via oral route

Endpoint conclusion

Endpoint conclusion:

no study available

Effect on neurotoxicity: via inhalation route

Link to relevant study records

Reference

Reference 1

Endpoint:

neurotoxicity: acute inhalation

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1999/09/29-1999/10/22

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Acceptable well-documented study report which meets basic scientific principles: GLP.

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:

no guideline followed

Principles of method if other than guideline:

The aim of this study was to evaluate the behavioral effects of exposure to Hydrocarbons, C10-C12, isoalkanes, <2% aromatics in rats. Test methods included selected functional observational measures, automated motor activity assessment and visual discrimination performance.

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

other: WAG/RijCrlBR

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Deuschland, Sulzfeld, Germany
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 13 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-25
- Humidity (%): 33-50
- Air changes (per hr): 10
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

inhalation: vapour

Vehicle:

unchanged (no vehicle)

Details on exposure:

Test atmosphere was generated by pumping liquid Hydrocarbons, C10-C12, isoalkanes, <2% aromatics into stainless steel tubing using peristaltic pumps. The tubing was led through a water bath at 60 deg C and the resulting vapour was transported with an air stream from a compressed air source and added to the main airflow system. The test atmospheres were analysed by two total carbon analysers.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

two total carbon analysers

Duration of treatment / exposure:

8 hours

Frequency of treatment:

3 days

Remarks:

Doses / Concentrations:
0 (air), 0.5 g/m3 (85ppm), 1.5 g/m3 (260ppm), 5 g/m3 (860ppm)
Basis:
nominal conc.

No. of animals per sex per dose:

8 animals

Control animals:

yes, concurrent no treatment

Details on study design:

Animals were exposed to the test atmosphere in modified H100 inhalation chambers Hazleton System Inc., USA). Each chamber was fitted with a manometer that allowed monitoring the slightly negative pressure inside. Three test groups (with one control) comprising of 8 rats each were exposed to Hydrocarbons, C10-C12, isoalkanes, <2% aromatics at different concentrations including: 0 (air), 0.5 g/m3 (85ppm), 1.5 g/m3 (260ppm), 5 g/m3 (860ppm). Animals were exposed to the test atmosphere 8 hours/day for 3 consecutive days. All rats were checked for health and viability at least once daily. Body weight was recorded during randomization on days of testing.

Details on results:

Results of the behavioral tests showed some mild effects of exposure to Hydrocarbons, C10-C12, isoalkanes, <2% aromatics on learned performance measurements in the highest exposed test group (5 g/m3). Measures of performance speed were sensitive to the effects of Hydrocarbons, C10-C12, isoalkanes, <2% aromatics, while measures of discrimination accuracy and stimulus control were not affected. Correct choice latencies were slightly increased and only significant in the 5 g/m3 exposure group. Drink response latency was not significantly changed. No significant effects were observed in functional observational measurements and in measurements of motor activity.

Dose descriptor:

NOAEC

Effect level:

> 1 500 mg/m³ air (nominal)

Sex:

male

Remarks on result:

other:

Conclusions:

Short-term, high-level exposure to Hydrocarbons, C10-C12, isoalkanes, <2% aromatics induced mild, non-persistent neurobehavioral effects on measures of learned performance. Effects were observed during or after 3 consecutive 8 hour exposures at the highest tested concentration of 5 g/m3. Exposure to 0.5 g/m3 or 1.5 g/m3 of Hydrocarbons, C10-C12, isoalkanes, <2% aromatics did not induce exposure-related neurobehavioral effects.

Executive summary:

Short-term, high-level exposure to Hydrocarbons, C10-C12, isoalkanes, <2% aromatics induced mild, non-persistent neurobehavioral effects on measures of learned performance. Effects were observed during or after 3 consecutive 8 hour exposures at the highest tested concentration of 5 g/m³. Exposure to 0.5 g/m³ or 1.5 g/m³ of Hydrocarbons, C10-C12, isoalkanes, <2% aromatics did not induce exposure-related neurobehavioral effects.

Reference 2

Endpoint:

neurotoxicity: acute inhalation

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1998/03/11-1998/04/03

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Acceptable well-documented study report which meets basic scientific principles: GLP.

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:

no guideline followed

Principles of method if other than guideline:

The aim of the study was to evaluate the behavioral effects of exposure to n-decane in rats and to determine internal levels of exposure at which effects occur. Test methods included selected functional observational measures, automated motor activity assessment and visual discrimination performance.

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

other: WAG/RijCrlBR

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Deuschland, Sulzfeld, Germany
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 13 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-21
- Humidity (%): 40-65
- Air changes (per hr): 10
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

inhalation: vapour

Vehicle:

unchanged (no vehicle)

Details on exposure:

Test atmosphere was generated by pumping liquid n-decane into stainless steel tubing using peristaltic pumps. The tubing was led through a water bath at 86 deg C and the resulting vapour was transported with an air stream from a compressed air source and added to the main airflow system. The test atmospheres were analysed by a total carbon analyser.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

total carbon analyser

Duration of treatment / exposure:

8 hours

Frequency of treatment:

3 days

Remarks:

Doses / Concentrations:
0 (air), 0.5 g/m3 (85ppm), 1.5 g/m3 (260ppm), 5 g/m3 (860ppm)
Basis:
nominal conc.

No. of animals per sex per dose:

8 animals

Control animals:

yes, concurrent no treatment

Details on study design:

Animals were exposed to the test atmosphere in modified H100 inhalation chambers Hazleton System Inc., USA). Each chamber was fitted with a manometer that allowed monitoring the slightly negative pressure inside. Three test groups (with one control) comprising of 8 rats each were exposed to n-decane at different concentrations including: 0 (air), 0.5 g/m3 (85ppm), 1.5 g/m3 (260ppm), 5 g/m3 (860ppm). Animals were exposed to the test atmosphere 8 hours/day for 3 consecutive days. All rats were checked for health and viability at least once daily. Body weight was recorded during randomization on days of testing.

Details on results:

Functional observations indicated a significant reduction in forelimb grip-strength in the highest exposure group (5 g/m3) after the third exposure (8 h). Results of visual discrimination testing indicated mild n-decane induced disturbances in measures of learned performance. Measures of performance sped were sensitive to the effects of n-decane. The effects were reversible as demonstrated by the absence of significant differences in post-test measurements.

Dose descriptor:

NOAEC

Effect level:

>= 1 500 mg/m³ air (nominal)

Sex:

male

Remarks on result:

other:

Conclusions:

Short-term, high-level exposure to n-decane induced mild, reversible neurobehavioral effects on functional observations and measurements of learned performance. Effects were observed during or after 3 consecutive 8 hour exposures at the highest tested concentration of 5 g/m3 of n-decane. Exposure to 0.5 g/m3 or 1.5 g/m3 of n-decane did not induce exposure-related neurobehavioral effects.

Executive summary:

Short-term, high-level exposure to n-decane induced mild, reversible neurobehavioral effects on functional observations and measurements of learned performance. Effects were observed during or after 3 consecutive 8 hour exposures at the highest tested concentration of 5 g/m³ of n-decane. Exposure to 0.5 g/m³ or 1.5 g/m³ of n-decane did not induce exposure-related neurobehavioral effects.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEC

1 500 mg/m³

Study duration:

subacute

Species:

rat

Quality of whole database:

2 supporting acute studies available from structural analogues.

Effect on neurotoxicity: via dermal route

Link to relevant study records

Reference

Endpoint:

neurotoxicity: short-term dermal

Remarks:

subacute

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1993/04/20-1993/04/27

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Acceptable well-documented study report which meets basic scientific principles.

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 424 (Neurotoxicity Study in Rodents)

GLP compliance:

yes

Limit test:

no

Species:

rabbit

Strain:

New Zealand White

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Hazelton Research Products
- Age at study initiation: Males: 13 weeks; Females: 11-12 weeks
- Weight at study initiation: Males: 1.96-2.19 g; Females: 1.90-2.26g
- Housing: Single Housed
- Diet (e.g. ad libitum): Agway Certified Diet RCA Rabbit, restricted feeding
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 8 days


ENVIRONMENTAL CONDITIONS
- Temperature (°F): 65 to 70
- Humidity (%): 40 to 60
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

other: occlusive

Vehicle:

unchanged (no vehicle)

Details on exposure:

TEST SITE
- Area of exposure: dorsal surface
- % coverage: 10
- Type of wrap if used: appled under the gauze patch and secured with a piece of Saran wrap
- Time intervals for shavings or clipplings: twice per week


REMOVAL OF TEST SUBSTANCE
- Washing (if done): washed the dosed site with 1.0% mixture of baby shampoo
- Time after start of exposure: after 6 hours of exposure, the test material was washed off

USE OF RESTRAINERS FOR PREVENTING INGESTION: yes

Analytical verification of doses or concentrations:

no

Duration of treatment / exposure:

6 hours a day; applied once a day for the duration of the experiment

Frequency of treatment:

once a day

Remarks:

Doses / Concentrations:
doses: 500, 1000, 2000 mg/kg positive control (n-hexane): 2000 mg/kg
Basis:
nominal conc.

No. of animals per sex per dose:

2 males and 2 females per treatment group

Control animals:

yes, concurrent no treatment

Details on study design:

The study was conducted to assess the dermal irritation potential and systemic toxicity of repeated topical application of MRD-92-405 at dose levels of 500, 1000, and 2000 mg/kg in the rabbit when administered daily for 7 days. Four groups consisting of 2 rabbits/sex/group were used. To serve as a comparison control, one group of animals was treated with n-hexane.

Clinical observations were made daily as to the nature, onset, severity, and duration of toxicological signs. Dermal irritation was assessed prior to dosing on days 0, 4, and 7 and immediately after dosing on Day 0. Body weights were recorded the week prior to dosing, on day 0 and day 7. Food consumption was measured once during the test period. The study was terminated after 7 days of dosing and all rabbits in the 2000 mg/kg group and n-hexane group were subjected to whole body perfusion fixation. A modified gross necropsy, which did not include examination of the cranial cavity, was conducted on each of these animals. A gross necropsy was performed on the 500, 1000 mg/kg dosed animals and tissues with gross abnormalities were taken and preserved. Positive control (n-hexane): 2000 mg/kg

Observations and clinical examinations performed and frequency:

Clinical observations were made daily as to the nature, onset, severity, and duration of toxicological signs. Dermal irritation was assessed prior to dosing on days 0, 4, and 7 and immediately after dosing on Day 0. Body weights were recorded the week prior to dosing, on day 0 and day 7. Food consumption was measured once during the test period.

Sacrifice and (histo)pathology:

The study was terminated after 7 days of dosing and all rabbits in the 2000 mg/kg group and n-hexane group were subjected to whole body perfusion fixation. A modified gross necropsy, which did not include examination of the cranial cavity, was conducted on each of these animals. A gross necropsy was performed on the 500, 1000 mg/kg dosed animals and tissues with gross abnormalities were taken and preserved.

Statistics:

Means and standard deviations of body weight, body weight change, and food consumption.

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 examined

Clinical biochemistry findings:

not examined

Behaviour (functional findings):

no effects observed

Gross pathological findings:

no effects observed

Neuropathological findings:

no effects observed

Details on results:

CLINICAL SIGNS AND MORTALITY
All animals survived to the end of the study. All animals in the 1000 and 2000 mg/kg dose groups were observed with erythema, ranging from very slight to severe, throughout the study. The severity of erythema for these two groups increased as the study progressed. Two of the four 500 mg/kg dose group animals were observed with very slight to well-defined erythema on days 4 and 7. All animals in the n-hexane group were observed with erythema on days 4 and 7, ranging from very slight to severe. One n-hexane group animal was observed with very slight erythema on day 0. Edema, ranging from very slight to slight, was observed in all dose groups on days 4 and 7. Supplemental dermal observations consisting of desquamation and/or exfoliation, atonia, and cracking were observed in all dose groups on day 7. Fissuring was observed in the 1000 mg/kg and 2000 mg/kg groups and in the n-hexane group. One n-hexane dose group animal was observed with eschar on day 7. No additional observable abnormal clinical signs were noted in treated animals except for one female animal that was observed with mucoidal stool on day 2.

BODY WEIGHT AND WEIGHT GAIN
There were small decreases in body weight from the day 0 weights observed in individual animals from all groups.


FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study)
There were no apparent differences in food consumption between the groups.

GROSS PATHOLOGY
Dermal irritation was the most significant postmortem finding and was consistent with the supplemental dermal observations noted. No other finding was considered the result of test material administration.

NEUROTOXICITY
Topical application of MRD-92-405 for seven days did not cause any gross signs of neurotoxicity.

Dose descriptor:

NOAEC

Remarks:

LD50

Effect level:

>= 2 000 mg/kg bw/day (actual dose received)

Sex:

male/female

Basis for effect level:

other: no sub-acute neurotoxicity noted

Remarks on result:

other:

Conclusions:

Dermal application of 2000mg/kg MRD-92-405 for seven days did not cause any gross signs of neurotoxicity or any clinical signs except for skin irritation. All animals survived to study termination; NOAEL >2000 mg/kg.

Executive summary:

The study was conducted to assess the dermal irritation potential and systemic toxicity of repeated topical application of MRD-92-405 at dose levels of 500, 1000, and 2000 mg/kg in the rabbit when administered daily for 7 days. Four groups consisting of 2 rabbits/sex/group were used. To serve as a comparison control, one group of animals was treated with n-hexane. Dermal application of 2000 mg/kg MRD-92-405 for seven days did not cause any gross signs of neurotoxicity or any clinical signs except for skin irritation, with erythema ranging from very slight to severe. All animals survived to study termination; NOAEL >2000 mg/kg.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

2 000 mg/kg bw/day

Quality of whole database:

1 supporting acute study available from a structural analogue.

Additional information

No studies are available for Hydrocarbons, C10 -C13, n-alkanes, <2% aromatics, however; neurotoxicity studies from structural analogues, Hydrocarbons, C10-C12, isoalkanes, <2% aromatics, n-decane, and Hydrocarbons, C11-C14, n-alkanes, <2% aromatics are available.

 

Inhalation

 

Hydrocarbons, C10-C12, isoalkanes, <2% aromatics

In a supporting study (ExxonMobil, 2001), short-term, high-level exposure to Hydrocarbons, C10-C12, isoalkanes, <2% aromatics induced mild, non-persistent neurobehavioral effects on measures of learned performance. Effects were observed during or after 3 consecutive 8 hour exposures at the highest tested concentration of 5 g/m³. Exposure to 0.5 g/m³or 1.5 g/m³of Hydrocarbons, C10-C12, isoalkanes, <2% aromatics did not induce exposure-related neurobehavioral effects.

 

n-decane

In a supporting study (ExxonMobil, 1999), short-term, high-level exposure to n-decane induced mild, reversible neurobehavioral effects on functional observations and measurements of learned performance. Effects were observed during or after 3 consecutive 8 hour exposures at the highest tested concentration of 5 g/m³of n-decane. Exposure to 0.5 g/m³or 1.5 g/m³of n-decane did not induce exposure-related neurobehavioral effects.

 

Dermal

 

Hydrocarbons, C11-C14, n-alkanes, <2% aromatics

A supporting study (Exxon, 1993) was conducted to assess the dermal irritation potential and systemic toxicity of repeated topical application of the test material (Hydrocarbons, C11-C14, n-alkanes, <2% aromatics) at dose levels of 500, 1000, and 2000 mg/kg in the rabbit when administered daily for 7 days. Four groups consisting of 2 rabbits/sex/group were used. To serve as a comparison control, one group of animals was treated with n-hexane. Dermal application of 2000 mg/kg test material for seven days did not cause any gross signs of neurotoxicity or any clinical signs except for skin irritation, with erythema ranging from very slight to severe. All animals survived to study termination; NOAEL >2000 mg/kg.

Justification for classification or non-classification

Based on the available read across data, Hydrocarbons, C10 -C13, n-alkanes, <2% aromatics is unlikely to present a hazard as a neurotoxicant.