Heptan-2-one

Specific investigations: other studies

Administrative data

Endpoint:

specific investigations: other studies

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

9 months

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Although the study was conducted prior to the introduction of GLPs, the study was conducted by the National Institute for Occupational Safety and Health using acceptable scientific methods to investigate the endpoint in question.

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference Type:

publication

Title:

An Electrodiagnostic Study of the Neurotoxicity of Methyl N-Amyl Ketone

Author:

Johnson BL, Setzer JV, Lewis TR, and Hornung RW

Year:

1978

Bibliographic source:

American Industrial Hygiene Association 39, 866–872.

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

A group of 30 male rats was randomly assigned to one of three treatment groups and rats were administered methyl n-amyl ketone at nominal exposure concentrations of 0 (control), 100, or 1000 ppm by whole-body inhalation 6 hr/day, 5 days/week for 9 months. A concurrent study conducted in monkeys is reported as a separate entry in this submission. This chronic rat study focused on potential neurotoxic effects associated with exposure to methyl n-amyl ketone. A total of 10 neurologic examinations, equally spaced one month apart, were conducted on each animal. To provide a baseline, the first set of measurements was taken while the animals were being acclimated to the exposure chambers but before the first exposure to methyl n-amyl ketone. Subsequent examinations occurred approximately 16 hours after removal of the animal from methyl n-amyl ketone exposure and placement in a holding area. Testing was conducted so that animals had at least 3 days of methyl n-amyl ketone exposure before each examination. Rats were evaluated for neurological function by assessing maximum motor nerve conduction velocity (NCV) of the sciatic-tibial and ulnar nerves, and amplitude of evoked muscle action potential (MAP) of those nerves.

GLP compliance:

no

Remarks:

Conducted prior to GLPs

Type of method:

in vivo

Endpoint addressed:

neurotoxicity

Test material

Test material information

Constituent 1

Reference substance name:

Heptan-2-one

EC Number:

203-767-1

EC Name:

Heptan-2-one

Cas Number:

110-43-0

Molecular formula:

C7H14O

IUPAC Name:

heptan-2-one

Constituent 2

Reference substance name:

606-024-00-3

IUPAC Name:

606-024-00-3

Constituent 3

Reference substance name:

methyl amyl ketone; methyl pentyl ketone; MAK; 1-methylhexanal; butylacetone

IUPAC Name:

methyl amyl ketone; methyl pentyl ketone; MAK; 1-methylhexanal; butylacetone

Details on test material:

- Name of test material (as cited in study report): Methyl n-amyl ketone
- Physical state: liquid
- Analytical purity: 97%
- Impurities:

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories
- Age at study initiation: approximately 2 months of age
- Weight at study initiation:
Control : 272 ± 18 g
100 ppm exposure group: 259 ± 6 g
1000 ppm exposure group: 269 ± 14 g
- Housing: Animals were housed in cages with wire mesh floors. Exposure-group animals were housed in their exposure chambers except when they were placed in a holding area prior to neurological testing. Control animals were housed in cages identical to those used for the methyl n-amyl ketone exposure groups.


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 23-26
- Humidity (%): 40-50

Administration / exposure

Route of administration:

inhalation: vapour

Vehicle:

other: room air

Details on exposure:

EXPOSURE METHOD
- Animals were placed into wire-mesh cages and positioned in two stainless steel (6.37 m^3) inhalation chambers, one for each exposure concentration. Controls were kept in a separate area and received conditioned room air only. Methyl n-amyl ketone was vaporized, mixed with conditioned room air, and passed into the inhalation chambers. Animals were exposed by whole-body inhalation.

TEST ATMOSPHERE
- Chamber test substance concentrations were monitored at least twice daily by sampling 10 and 5 liters of air from the 100 and 1000 ppm chambers, respectively and analyzing them by gas chromatography. Chamber flow rates were adjusted as needed to maintain planned exposure levels. The average value for the daily samples was used to characterize methyl n-amyl ketone exposure on that day.      

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

At least twice each day, samples were removed from each exposure chamber and analyzed by gas chromatography to verify the concentration.

Duration of treatment / exposure:

9 months

Frequency of treatment:

6 hours/day, 5 days/week

Post exposure period:

There was no post-exposure period.

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
131 ± 30 ppm
Basis:
analytical conc.

Doses / concentrations 2

Remarks:

Doses / Concentrations:
1025 ± 118 ppm
Basis:
analytical conc.

No. of animals per sex per dose:

10 male rats/group

Control animals:

yes, concurrent vehicle

Examinations

Examinations:

CAGE SIDE OBSERVATIONS:
Conducted but frequency not reported.

DETAILED CLINICAL OBSERVATIONS:
Animals were examined for locomotion, grip and gait.

BODY WEIGHT:
Animals were weighed prior to the first exposure and then at monthly intervals.

NEUROBEHAVIOURAL EXAMINATION:
All animals in the control and 2 exposure groups were examined prior to the first exposure and then monthly thereafter. Following three days of exposure to methyl n-amyl ketone prior to each subsequent examination for animals in the 131 and 1025 ppm groups, animals were randomly removed from their exposure cages to a holding area for examination the following day. The typical time lag between the end of exposure and actual testing was about 16 hours. To prevent bias, the same investigator examined each animal and was unaware of the exposure history of the animal. Prior to neurologic testing, each animal received injections of 35 mg/kg sodium pentobarbital and 160 mg/kg chloral hydrate by intraperitoneal injection. For each animal, the following endpoints were examined: maximum motor nerve conduction velocity of the sciatic-tibial nerve, nerve conduction velocity of the ulnar nerve, and amplitude of evoked muscle action potential recorded from muscles in response to electrical stimulation of those two nerves.

GROSS PATHOLOGY:
Following the last exposure, animals were euthanized and a gross examination was performed.

HISTOPATHOLOGY:
The following tissues were examined: lungs, heart, liver, spleen, kidneys, adrenals, pancreas, testes, and brain.     

Results and discussion

Details on results:

The no-observed-effect-level (NOEL) in this study was considered to be 1025 ± 118 ppm. No effects were noted on any parameters examined during the study.

CLINICAL SIGNS and MORTALITY:
There was no test-substance related mortality reported and no adverse clinical signs were reported. There were also no reported impairments in locomotion, grip, or gait.

BODY WEIGHT and WEIGHT GAIN:
Body weights were normal and not affected by exposure to methyl n-amyl ketone.

GROSS PATHOLOGY:
No adverse effects were reported at necropsy.

HISTOPATHOLOGY:
All of the tissues examined were normal.

NEUROLOGIC EXAMINATIONS:
Neurologic data from the two methyl n-amyl ketone exposure groups for sciatic-tibial nerve condition velocity, ulnar nerve conduction velocity, and muscle action potential amplitudes following sciatic and ulnar stimulations were not significantly different from the control group.

Applicant's summary and conclusion

Conclusions:

In a chronic inhalation study, groups of 10 male rats were exposed to methyl n-amyl ketone by whole body inhalation at exposure concentrations of 0, 131 ± 30 ppm, or 1025 ± 118 ppm 6 hours/day, 5 days/week for 9 months. There were no statistically significant dose-dependent effects on mortality, clinical signs or body weights. No gross or microscopic changes were reported in organs or tissues examined at necropsy. At monthly intervals, rats were evaluated for neurological function by assessing maximum motor-nerve conduction velocity (NCV) of the sciatic-tibial and ulnar nerves and amplitude of evoked muscle action potential (MAP) in response to stimulation of those two nerves. There were no significant differences between exposure groups and control for any of the electrophysiological tests. The no-observed-effect-level (NOEL) in this study was considered to be 1025 ppm in male rats. Other studies (Johnson et al., 1977) have shown that rats exposed to the structurally similar chemical methyl n-butyl ketone at concentrations of 1000 ppm did exhibit a statistically significant decrease in sciatic-tibial motor nerve conduction velocity after only 4 months of exposure.

The test material is not currently classified for target organ toxicity according to Annex I of Directive 67/548/EEC. Based on an absence of adverse effects observed in this study, methyl n-amyl ketone is not classified for Specific Target Organ Toxicity-Repeated Exposure according to the EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008 or the UN Globally Harmonized System of Classification and Labelling of Chemicals (GHS).

Reference:
Johnson et al., 1977. Effects of Methyl n-Butyl Ketone on Behavior and the Nervous System. Am. Ind. Hyg. Assoc. J., 38:567-579.     

Executive summary:

In a chronic toxicity study, groups of 10 male rats were exposed by whole-body inhalation to methyl n-amyl ketone at concentrations of 0, 131 ± 30 ppm or 1025 ± 136 ppm 6 hours/day, 5 days/week for 9 months.  There were no statistically significant concentration-dependent effects on mortality, clinical signs, or body weights and gross and microscopic examinations at study termination were normal. There were no statistically significant differences from the control in the electrodiagnostic tests used to detect neurotoxicity for either of the methyl n-amyl ketone exposure groups. The no-observed-effect-level (NOEL) for daily exposure to methyl n-amyl ketone for 9 months was determined to be 1025 ppm in male rats.