1-chlorobutane

Carcinogenicity

Description of key information

oral NOAEL (rat): 120 mg/kg bw/day (NTP, 1986)
oral NOAEL (female mouse): 500 mg/kg bw/day (NTP, 1986)
oral NOAEL (male mouse): 1000 mg/kg bw/day (NTP, 1986)

Key value for chemical safety assessment

Carcinogenicity: via oral route

Link to relevant study records

Reference

Endpoint:

carcinogenicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Feb. 1980 - March 1982

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: comparable to guideline study with acceptable restrictions

Reason / purpose for cross-reference:

reference to same study

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 451 (Carcinogenicity Studies)

Deviations:

yes

Remarks:

only two dose levels were used; only necropsy and histologic examination were performed, other observations (e.g. food consumption and efficiency, haematology, clinical chemistry) are not regarded

GLP compliance:

yes

Species:

rat

Strain:

other: Fisher 344/N

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories, Portage, USA
- Age at study initiation: 7 weeks
- Weight at study initiation: males: 159-167 g; females: 120-124 g
- Housing: five per cage in polycarbonate cages (Lab Products, Rochelle Park, NJ, USA); Bedding: Aspen bed hardwood chips (American Exelsior Co., Baltimore,MD, USA)
- Diet: ad libitum NIH 07 Rat and Mouse Ration (Zeigler Bros., Gardners, PA, USA)
- Water: ad libitum (Automatic watering system; Edstrom Industries, Waterford, WI, USA)
- Acclimation period: 3 weeks


ENVIRONMENTAL CONDITIONs
- Temperature: mean 23 °C
- Humidity: 95% - 78% (mean 41%)
- Air changes (per hr): 12
- Photoperiod: 12 hrs dark / 12 hrs light (fluorescent light)

IN-LIFE DATES: Feb 1980 - April 1982

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

VEHICLE
- Amount of vehicle (if gavage): 5 mL/kg bw/d

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Periodic analyses for n-butyl chloride in corn oil were performed by the testing and analytical chemistry laboratories. Duplicate 1 mL samples were extracted with methanol containing 2 mg/mL of n-amyl alcohol as an internal standard. Samples were analyzed by GC-FID. Individually spiked portions of undosed corn oil (5 or 6 concentrations bracketing the specified concentration range of the referee sample) were used to obtain standard data. The samples were determined from the linear regression equation computed from the standard data (peak area analysis).
Analyzed mixtures were within +/- 10% of the target concentration.

Duration of treatment / exposure:

2 years (103 weeks)

Frequency of treatment:

5 d/w

Remarks:

Doses / Concentrations:
0, 60 and 120 mg/kg bw/d
Basis:
other: nominal concentration

No. of animals per sex per dose:

50

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: Because of weight gain depression and convulsion observed at 250 mg/kg bw/d in the 13 week study, doses selected for rats in the 2-year study were 60 and 120 mg/kg bw/d n-butyl-chloride.

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice per day

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: clinical signs were recorded once per week

BODY WEIGHT: Yes
- Time schedule for examinations: once per week for the first 12 weeks of the study and once per month thereafter

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: No
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: No

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: No

CLINICAL CHEMISTRY: No

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes

The following tissues were examined: tissue masses, abnormal regional lymph nodes, skin, mandibular lymph nodes, mammary gland, salivary gland, bone marrow, costochondral junction, thymus, larynx, trachea, lungs and bronchi, heart, thyroid gland, parathyroids, esophagus, stomach, duodenum, jejunum, ileum, colon, mesenteric lymph nodes, liver, pancreas, spleen, kidneys, adrendal glands, seminal vesicles/prostata/testes or ovaries/uterus, brain and pituitary gland.
Tissues were preserved in 10% neutral buffered formalin, embedded in paraffin, sectioned and stained with hematoxylin and eosin.
After completion of the pathology examination, the slides, individual animal data records and summary tables were sent to an independent quality assurance laboratory for evaluation.

Statistics:

Data recording:
Data were recorded in the Cacinogenesis Bioassay Data System (Linhart et al., 1974). The data elements include the recommendations by the International Union Against Cancer (Berenblum, 1969)

Survival analyses:
The probability of survival was estimated by the product-limit procedure of Kaplan and Meier (1985) and is presented in the form of graphs. Statistical analyses for a possible dose-related effect on survival used the method of Cox (1972) for testing two groups for equality and Tarone's (1975) life table test for a dose-related trend. All reported P values for the survival analysis are two-sided.

Analysis of Tumor Incidence:
Three statistical methods are used to analyze tumor incidence data. The two that adjust for intercurrent mortality employ the classical method for combining contingency tabled developed by Mantel and Haenszel (1959). Tests of significance included pairwise comparisons of high dose and low dose groups with vehicle controls and tests for overall dose-response trends.

Historical control data:
Control tumor incidences from the NTP historical control data base are included for those tumors appearing to show compound-related effects.

Details on results:

CLINICAL SIGNS AND MORTALITY
Many dosed rats had convulsions and tremors after being gavaged. Convulsion after dosing especially in high dose animals were common throughout the studies.
Statistically significant decrease of survival was observed in the high dose male (after week 59: 120 mg/kg bw/d 9/50; vehicle control 1/50) and female (after week 41: 120 mg/kg bw/d 7/50; vehicle control 0/50) animals due to n-butyl chloride related toxicity and not due to errors in gavage administration. Based on the survival in the 13-week studies (NTP, 1986), the high mortality in both the 60 and 120 mg/kg bw/d groups were unexpected. Some animals showed hyperactivity, leading to tremors and convulsions, before they died.


BODY WEIGHT AND WEIGHT GAIN
No compound-related reductions in weight gain occured. The initial mean body weights of the dosed males were lower than that of the vehicle controls and the mean body weights of the 120 mg/kg bw/d group remained slightly lower throughout the studies. Mean body weights of all females were comparable throughout the studies.


GROSS PATHOLOGY/HISTOPATHOLOGY
Neither gross observations nor histopathological evaluations revealed toxic morphologic lesions directly attributable to administration of n-butyl chloride, but there were incidences of small, usually perivascular hemorrhages in the brain which were consistent with rats dying suddenly from convulsions. In addition, agonal or terminal congestion, edema and hemorrhage of the lung were common in these animals. The actual cause of death could not be determined. Similiar histopathological findings were examined in animals dying later in the study but not in those killed after 2 years.


HISTOPATHOLOGY: NON-NEOPLASTIC
In male rats, there was a positive trend in the incidence of cytoplasmic vacuolization in the adrenal cortex (vehicle control 5/50; low dose 10/50; high dose 20/50). In female rats, the incidences were lower and not different among the groups (vehicle control 4/50; low dose 5/50; high dose 3/49). The biological significance of this compound-related effect in male rats is not clear. There were no further compound-related nonneoplastic lesions in the adrenal cortex.

Several nonneoplastic effects were observed primarily in high dose rats as a probable result of chemical-related toxicity. Lymphoid depletion of the spleen and splenic hemosiderosis were examined in high dose animals dying from convulsion , as well as the mentioned hemorrhage of brain and alveoli. Hemorrhage of the brain and lung are often observed in animals dying from convulsions. In addition, lymphoid depletion of the spleen is consistent with a stressed state of the animals. The observed splenic hemosiderosis could not be explained.

In female rats nephropathy was observed (vehicle control 13/50; low dose 25/50; high dose 20/50), but no further non-neoplastic kidney effects (congestion, inflammation, nephrosis) were revealed. Although there were higher incidences in dosed animals, the significance of this lesion is not clear.


HISTOPATHOLOGY: NEOPLASTIC
There was a marginally (P=0.04) increased incidence of pheochromocytomas of the adrenal gland in low dose female rats (vehicle control 1/50; low dose 6/50; high dose 1/49). No supporting increase could be observed in the high dose group and most of these tumours were examined at the end of the study. The incidence of hyperplasia of the adrenal medulla was not strongly supportive (vehicle control 3/50; low dose 7/50; high dose 4/49).If these lesions were compound-related, higher incidences of hyperplasia and tumours would have been expected. A negative trend was seen in males (vehicle control 15/50; low dose 11/50; high dose 4/50). This marginal increase is considered unlikely to be the result of n-butyl chloride administration.

Transitional cell papillomas were examined in one low dose male rat and in one high dose female rat. The overall historical incidence of this tumour (NTP program) is 0% and 0.3% in male and female rats, respectively and none has been observed previously in the testing laboratory (EG&G Mason Research Institute). The significance of this lesion is not clear.

OTHER:
Antibodies to Sendai virus and RC virus were detected in sentinel animals throughout the studies.

Dose descriptor:

NOAEL

Effect level:

120 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: No effects at highest dose tested.

Remarks on result:

other: Effect type: carcinogenicity (migrated information)

Dose descriptor:

NOAEL

Effect level:

60 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Remarks on result:

other: Effect type: toxicity (migrated information)

Dose descriptor:

LOAEL

Effect level:

120 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: clinical signs; mortality;

Remarks on result:

other: Effect type: toxicity (migrated information)

As cited by the authors:

Based on the findings in the 13-weeks studies, high mortality in the 120 mg/kg bw/d high dose groups was not expected and reduced the sensitivity for determining carcinogenic response in these groups. In retrospect, it might have been desirable to have conducted additional studies at a dose lower than 60 mg/kg bw/d. Despite the low survival of high dose male and female rats, the present studies are considered adequat because survival of male and female rats in the 60 mg/kg bw/d dose groups was sufficient to permit evaluation and interpretation of the data.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

120 mg/kg bw/day

Study duration:

chronic

Species:

rat

Justification for classification or non-classification

The available data is conclusive but not sufficient for classification according to DSD (67/548/EEC) and CLP (1272/2008/EC).

Additional information

NTP performed 2-year gavage studies with 1-chlorobutane. There was no evidence of carcinogenicity for male and female F344/N rats at doses of 60 and 120 mg/kg bw/day, for male B6C3F1 mice at doses of 250, 500 or 1000 mg/kg bw/day or for female B6C3F1 mice at doses of 250 or 500 mg/kg bw/day.

Poirier et al. (1975) examined pulmonary tumour response in A/Heston mice. Male and female mice were administered 1-chlorobutane (in tricaprylin) weekly by intraperitonal injections of 24 weeks with a total dose of 1.2, 3.0 or 6 g/kg bw/day. No significant increase in lung tumour incidence was observed.