Registration Dossier

Toxicological information

Neurotoxicity

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Administrative data

Endpoint:
neurotoxicity: inhalation
Remarks:
other: combined repeated dose and reproduction / developmental screening
Type of information:
migrated information: read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Study period:
2003 - 2008 (date final report signed by Study Director)
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP compliant (except for test substance identity, stability and lot number), guideline study, available as unpublished report, no restrictions, fully adequate for assessment

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2008
Report Date:
2008

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
other: OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)
Deviations:
no
Qualifier:
according to
Guideline:
other: EPA OPPTS 870.3650 (Combined repeated exposure toxicity study with the Reproduction/Developmental toxicity screening test)
GLP compliance:
yes
Remarks:
The identity and stability was not in compliance with GLP regulations. The lot number was not available.
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): butane- Physical state: colourless gas- Analytical purity: 99.5% per supplier- Analytical purity: 99.23% before study, 99.98% after study- Lot/batch No.: not available- Expiration date of the lot/batch: not available- Stability under test conditions: confirmed- Storage condition of test material: Ambient - Other: An archival sample was stored.

Test animals

Species:
rat
Strain:
other: Sprague-Dawley CD
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS- Source: Charles River Laboratories, Raleigh, North Carolina 27610- Age at study initiation: Approximately 8 weeks- Weight at study initiation: males: 241-280 g (mean: 261 g); females 174-229 g (mean 200 g)- Fasting period before study: none- Housing: Individually in stainless steel suspended cages with wire mesh floors and fronts- Diet: Certified Rodent Diet # 5002 (PMI Nutrition Int., St. Louis, Missouri) ad libitum- Water: ad libitum- Acclimation period: Approximately 2 weeksENVIRONMENTAL CONDITIONS- Temperature 20.7-22.4°C- Humidity: 24.28-77.36%- Air changes (per hr): no data- Photoperiod: 12 hrs dark / 12 hrs lightIN-LIFE DATES: From: 29 September 2003 To: 26 April 2006

Administration / exposure

Route of administration:
inhalation
Vehicle:
other: air
Details on exposure:
Not detailed in main report, require access to Appendix II, Volume 3GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION- Exposure apparatus: Whole-body inhalation chamber- Method of holding animals in test chamber: Individually in stainless steel suspended cages with wire mesh floors and fronts- Source and rate of air:- Method of conditioning air:- System of generating particulates/aerosols:- Temperature, humidity, pressure in air chamber:- Air flow rate:- Air change rate:- Method of particle size determination: yes- Treatment of exhaust air:TEST ATMOSPHERE- Brief description of analytical method used: Infrared spectrophotometer (IR) 4 times per chamber per day- Samples taken from breathing zone: yes
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Exposure levels were determined using an infrared spectrophotometer 4 times/chamber/day. The test substance was evenly distributed within each chamber. The mean (± SD) analytical concentrations were 0 ± 0, 930.6 ± 28.1, 3022 ± 58 and 9157 ± 269 ppm.
Duration of treatment / exposure:
Males: 2 weeks prior to mating and after post-mating to give a minimum 28 day exposure period.Females: 2 weeks prior to mating and post-mating for an additional 4 weeks
Frequency of treatment:
6 hours/day, 7 days/week
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:0, 900, 3000 and 9000 ppm Basis:other: target concentration
Remarks:
Doses / Concentrations:0.0 ± 0.0, 930.6 ± 28.1, 3022 ± 58, 9157 ± 269 ppm Basis:analytical conc.
No. of animals per sex per dose:
12
Control animals:
yes, sham-exposed

Examinations

Observations and clinical examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes- Time schedule: twice daily (mortality and clinical condition)DETAILED CLINICAL OBSERVATIONS: Yes- Time schedule: All animals examined prior to randomisation and once weekly throughout the study.BODY WEIGHT: Yes- Time schedule for examinations: Once weekly throughout the study. Animals were fasted prior to the recording of terminal bodyweights.FOOD CONSUMPTION: Yes- Time schedule for examinations: Once weekly throughout the study.WATER CONSUMPTION: NoOPHTHALMOSCOPIC EXAMINATION: NoHAEMATOLOGY: Yes. Haematology in control and high dose animals- Time schedule for collection of blood: at study termination.- Anaesthetic used for blood collection: Yes (CO2/O2)- Animals fasted: Yes, overnight prior to blood collection- How many animals: 12/sex/group- Parameters examined: haemoglobin concentration, haematocrit, erythrocyte count, platelet count, mean corpuscular volume, mean corpuscular haemoglobin, mean corpuscular haemoglobin concentration, total leukocyte count, reticulocyte count, differential leukocyte count. Erythrocyte and platelet morphology examined (from peripheral blood smear).CLINICAL CHEMISTRY: Yes. Clinical pathology in control and high dose animals- Time schedule for collection of blood: at study termination.- Anaesthetic used for blood collection: Yes (CO2/O2)- Animals fasted: Yes, overnight prior to blood collection- How many animals: 12/sex/group- Parameters examined: Prothrombin time, activated partial thromboplastin time, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, blood urea nitrogen, creatinine, glucose, cholesterol, total protein, triglycerides, albumin, total bilirubin, sodium, potassium, chloride, calcium, inorganic phosphorus, gamma-glutamyl transpeptidase, globulin and albumin/globulin ratio.URINALYSIS: NoNEUROBEHAVIOURAL EXAMINATION: Yes- Time schedule for examinations: during the last week of exposure- Dose groups that were examined: all main study animals- Battery of functions tested: sensory observations, neuromuscular observations, physical observations and motor activity assessments
Specific biochemical examinations:
NEUROPATHY TARGET ESTERASE (NTE) ACTIVITY: NoCHOLINESTERASE ACTIVITY: No
Neurobehavioural examinations performed and frequency:
FUNCTIONAL OBSERVATIONAL BATTERY: Yes - Parameters examined: Sensory observations, neuromuscular observations, physical observations - Description of procedures: Startle response to auditory stimuli, tail pinch response; grip strength - hindlimb and forelimb; rectal temperature- Minimization of bias: Yes- Same technicians used throughout testing: No data- Technicians were blind to treatment status of animals: Yes - Site of testing: No data- Time schedule for examinations: During last week of exposure (animals were not exposed on the day of evaluations). Testing was staggered over several sessions. Each session consisted of approximately equal numbers of animals/sex/group.- Environmental conditions:- Noise level: 54.5-63.2 decibels by a white noise generator- Other: Temperature 20-21°C, Relative humidity 26-51%, illumination <54.5-63.9 footcandles- Scoring criteria (if any): No data- The functional observational battery was performed for all animals before evaluation of motor activityLOCOMOTOR ACTIVITY: Yes- Replicates used: No data- Type of equipment used: automated Photobeam Activity System (San Diego Instruments, Inc)- Length of session, number and length of subsessions: 60 minutes, sub-divided into 12 five-minute intervals. Time of testing balanced across groups.- Parameters measured: Mean motor activity (number of beam breaks per interval).- Environmental conditions:- Noise level: 50.7-61.6 decibels by a white noise generator- Other: Temperature 20-21°C, Relative humidity 25-54%, illumination <52.1-61.4 footcandlesAUDITORY STARTLE REFLEX HABITUATION: NoLEARNING AND MEMORY TESTING: No
Sacrifice and (histo)pathology:
- Time point of sacrifice: After at least 28 days of exposure- Number of animals sacrificed: 12/sex/groupGROSS PATHOLOGY: Yes (all animals)ORGAN WEIGHTS: Yes (all animals). Adrenal glands, brain, epididymides, heart, kidneys, liver, lungs, ovaries, spleen, testes, thymus and uterus with vagina.HISTOPATHOLOGY: Yes (control and high dose group only). Tissues examined: adrenal glands, bone (sternum/femur), bone marrow, brain (medulla/pons, cerebrum and cerebellum), epididymides, heart, kidneys, caecum, colon, rectum, larynx, liver, lungs (with mainstem bronchi), lymph nodes (mesenteric and mediastinal), mammary glands (with adjacent skin), nasopharynx, ovaries (with oviducts), prostate, seminal vesicles, duodenum, ileum, jejunum, spinal cord (cervical, thoracic and lumbar), spleen, stomach, testes, thymus, thyroid with parathyroids, tibial nerve, trachea, urinary bladder, uterus with vagina and all macroscopic lesions and tissue masses.During the microscopic examination of the testes, special emphasis was placed on the stages of spermatogenesis and the histopathology of interstitial testicular cell structure.
Statistics:
Group mean values of parameters for all the exposure groups were compared to the control group mean values at each time interval, using appropriate statistical methods.

Results and discussion

Results of examinations

Clinical signs:
no effects observed
Mortality:
no mortality observed
Body weight and weight changes:
no effects observed
Food consumption and compound intake (if feeding study):
no effects observed
Ophthalmological findings:
not examined
Behaviour (functional findings):
no effects observed
Gross pathological findings:
no effects observed
Neuropathological findings:
no effects observed
Other effects:
no effects observed
Details on results:
No neurological effects (as measured by clinical observations, functional observational battery, and motor activity) were observed. No effects on survival, haematological or clinical chemistry parameters, feed consumption, body weight, organ weight, and histopathology.

Effect levels

open allclose all
Dose descriptor:
NOAEC
Remarks:
neurotoxicity
Effect level:
9 000 ppm
Sex:
male/female
Remarks on result:
other:
Dose descriptor:
NOAEC
Remarks:
neurotoxicity
Effect level:
21 394 mg/m³ air
Sex:
male/female
Remarks on result:
other:

Applicant's summary and conclusion

Conclusions:
No neurological effects (as measured by clinical observations, functional observational battery, and motor activity) were observed. No effects on survival, haematological or clinical chemistry parameters, feed consumption, body weight, organ weight, and histopathology were observed.The no observed adverse effect concentration (NOAEC) for neurotoxicity of butane was 9000 ppm. Equivalent to 21394 mg/m3
Executive summary:

The study assessed the potential toxicity, including neurotoxicity and reproductive performance in male and female rats following butane exposure at 900, 3000 and9000 ppm. It also was designed to investigate effects inboth sexes on mating behavior and on gonadal function, as well as effects on conception, development, parturition and pup survival to lactation day 4.

Male and female rats were exposedfor 6 hours/day, 7 days/week for 2 weeks prior to mating initiation. Main study males and females were then evaluated for subchronic effects and were exposed once daily (6 hours/day), seven days/week for 4 weeks (28 days).

There was no effect on survival. There were no exposure-related clinical effects or effects on body weight, food consumption, FOB or motor activity parameters for either sex. Furthermore there were no exposure-related differences in haematology, clinical chemistry and no macroscopic or microscopic changes at post-mortem.

Exposure of male and female rats to target concentrations of 900, 3000 and 9000 ppm of butane resulted in no general systemic effects, no effects on fertility and reproductive performance and no effects on pup survival and development to postnatal Day4.               

A no observed adverse effect concentration (NOAEC) of 9000 ppm was determined for this study's systemic, reproductive, and neonatal endpoints. Equivalent to 21394 mg/m3 (MW 58.12g/mol).