Naphthalene

Repeated dose toxicity: oral

Administrative data

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1980

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study following accepted scientific standards; although no guideline provided, acceptable for assessment.

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1980

Report date:

1980

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)

Deviations:

yes

Remarks:

no documentation of organ weights

GLP compliance:

no

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Naphthalene

EC Number:

202-049-5

EC Name:

Naphthalene

Cas Number:

91-20-3

Molecular formula:

C10H8

IUPAC Name:

naphthalene

Test material form:

solid: crystalline

Details on test material:

- Name of test material (as cited in study report): naphthalene
- Physical state: solid (white crystalline)
- Analytical purity: 99.6 %
- Impurities (identity and concentrations): 0.23 % water; two further impurities (0.13 % and 0.02 %) not further identified
- Lot/batch No.: C 52904
- Stability under test conditions: at least 24 weeks at room temperature (25°C)

Test animals

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River, Portage, Michigan
- Age at study initiation: 6 weeks
- Weight at study initiation: Males: 170 - 215 g; females: 135-155 g
- Fasting period before study: no data
- Housing: groups of 5 animals per polycarbonate cages
- Diet (e.g. ad libitum): yes (added as needed)
- Water (e.g. ad libitum): yes (via automatic watering devices)
- Acclimation period: 15 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21 - 23 °C
- Humidity (%): 40 - 60 % relative humidity
- Air changes (per hr): 15
- Photoperiod (hrs dark / hrs light): 12 / 12

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS:
Stock solution was prepared by placing a weighed portion of naphthalene into a mixing graduated cylinder and adding corn oil to make up the proper volume. Selected doses of 400, 200, 100, 50 and 25 mg/kg were achieved by preparing a stock solution of the highest concentration and sequential dilution in order to reach the appropriate dose level. The respective mixture quantities were prepared on a weekly basis.

VEHICLE
- Justification for use and choice of vehicle (if other than water): no justification provided
- Concentration in vehicle: 400, 200, 100, 50, 25 mg/5 mL solution
- Amount of vehicle (if gavage): 0.5 mL solution per 100 g body weight

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

One analysis for the accuracy of the dose was performed: results were within +/- 10% of the concentrations for all dose levels, except 200 mg/kg which had a deviation of 1.76 % from this range.

Duration of treatment / exposure:

13 weeks

Frequency of treatment:

1x/d, five consecutive days per week.

Doses / concentrations

Remarks:

Doses / Concentrations:
25, 50, 100, 200, 400 mg/kg bw
Basis:
actual ingested

No. of animals per sex per dose:

Ten animals of each sex per dose level.

Control animals:

yes, concurrent no treatment

Details on study design:

- Dose selection rationale: Dose selection was performed in order to determine maximum tolerated doses for a subsequent 104-week chronic toxicity study. Dose selections for this sub-chronic study were based on clinical and pathological findings which were observed during a prior two-week repeated dose study.

- Other: Animals were administered 5 ml/kg bw with the respective mixture.

Positive control:

no

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice each day (with at least six hours between observation)

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: twice each day (with at least six hours between observation)

BODY WEIGHT: Yes
- Time schedule for examinations: weekly

Sacrifice and pathology:

Detailed necropsy examinations were performed on all rats in this study. The following tissues were examined: mandibular lymph node, salivary gland, femur, thyroid, parathyroid, small intestine, colon, liver, prostate, testes, ovaries, lungs and mainstem brochi, mammary gland, eyes, heart, oesophagus, stomach, uterus, brain (3 sections), thymus, trachea, pancreas, spleen, kidneys, adrenals, urinary bladder, pituitary gland.

For histopathology, the tissues obtained from the highest dosage groups and from the control group were examined in a routine manner: they were sectioned at 5 µm, stained with haematoxylin and eosin and examined microscopically.
Since lesions had been observed in the highest dosage groups, which may have been substance-specific, kidneys from males and thymus glands from females were examined from the 200 mg/kg dosage groups.

Other examinations:

Haematology

Statistics:

Yes (in regard of body weight and haematology)

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Signs of discomfort and disorder observed in the highest dosage groups of both sexes. 2/10 males died during the last week of the study.

Mortality:

mortality observed, treatment-related

Description (incidence):

Signs of discomfort and disorder observed in the highest dosage groups of both sexes. 2/10 males died during the last week of the study.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Dose-related trend especially at the two highest doses.

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not specified

Water consumption and compound intake (if drinking water study):

no effects observed

Ophthalmological findings:

not specified

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

Marginal decrease in haemoglobin and haematocrit at 400 mg/kg bw in the male and female group.

Clinical biochemistry findings:

not specified

Urinalysis findings:

not specified

Behaviour (functional findings):

not specified

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Lesions in kidneys (male rats) and thymus glands (female rats) were observed at highest dosage groups.

Histopathological findings: neoplastic:

no effects observed

Details on results:

CLINICAL SIGNS AND MORTALITY:
Diarrhoea, lethargy, hunched posture and roughened haircoats were observed in animals of both sexes of the highest dosage groups. Mortality was noted for two male rats in the highest dose groups in the last week of the experiment. In one of the dead animals, renal lesions were found.

BODY WEIGHT AND FOOD CONSUMPTION:
Effects on body weights were observed at the 400 mg/kg and 200 mg/kg dose groups: in male rats significant decreases in body weight of -60% and -24% were seen in the 400 mg/kg and 200 mg/kg dose groups, respectively. In female rats, both doses caused a decrease in body weight of -69% and -15%, respectively. No substance-specific trends in diet consumption were evident.

HAEMATOLOGY
Marginal decrease in haemoglobin and haematocrit in the male and female group of 400 mg/kg bw. Considerable effects on lymphocyte and neutrophil values were observed in males of the highest dosage groups (400 mg/kg bw).

HISTOPATHOLOGY:
Lesions in kidneys from male animals (score 3 = moderate) and thymus glands from female animals (score 3 = moderate) have been observed in the highest dosage groups (400 mg/kg bw).

Effect levels

1

Dose descriptor:

NOEL

Effect level:

100 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: based on decrease in body-weight gain

2

Dose descriptor:

NOAEL

Effect level:

200 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: based on clinical signs, mortality (males), haematological effect, and some evidence of histological changes (kidney, thymus).

3

Dose descriptor:

LOAEL

Effect level:

400 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

Table 1: Summary of necropsy data by group and sex  Note: Only organs that exhibited anomalies in any group have been documented. Organ and Observation Dose Group 0 mg/kg 25 mg/kg 50 mg/kg 100 mg/kg 200 mg/kg 400 mg/kg Sex M F M F M F M F M F M F Number in Group 10 10 10 10 10 10 10 10 10 10 10 10 Anus, inflamed 1 Eye, left, yellow material in anterior chamber or on lens 1 Heart, enlarged 1 Liver, middle lobe, small nodule at diaphragmatic hiatal area 1 1 1 Liver, middle lobe, nodular protrusion into hiatus of diaphragm 1 Lung, all lobes haemorrhagic 1 Ovarian sac, left, red, small amount of fluid 2 Ovary, left, small amount of fluid in parovarian sac 1 Ovary, right, small parovarian cyst 1 Periovarian fat, 5 mm red nodule on fibrous stalk 1 Seminal vesicles, small 3 Testes, two-thirds normal size 1 Uterine horns filled with clear fluid (estrus) 3 3 3 2 Uterine horns, slightly reddened and slightly enlarged (estrus) 1

Table 2: Summary of histopathology data by group and sex  Note: Only organs that exhibited anomalies in any group have been documented. Organ and Observation Dose Group 0 mg/kg 200 mg/kg^# 400 mg/kg Sex M F M F M F Number in Group 10 10 10 10 10 10 Adrenal glands, congestion 1 Bone narrow, reticulum cell hyperplasia, focal 2 Colon, parasitosis 1 2 Eye, retina, retinal rosette 1 Eye, retina, focus of vacuolated cells 1 Heart, papillary muscle, histiocytic infiltrate, focal 1 Heart, left ventricle, myocardium, myocarditis, fibrosis, focal 1 Heart, myocarditis, subacute, multifocal 1 Heart, myocardium, myocarditis, multifocal 1 Kidney, cortex, lymphocytic infiltrate, focal 1 Kidney, cortex, tubular degeneration, diffuse 1 Kidney, tubular, regeneration, focal 1 Liver, centrilobular areas, vacuolization, diffuse 3 Liver, centrilobular areas, hepatocellular vacuolization, multifocal or diffuse 1 1 Liver, subcapsular area, fibrosis, focal 1 Lung, pneumonia, granulomatous, focal, gavage induced 1 Lung, pneumonia, histiocytic, focal or multifocal, gavage induced 2 Lung, pneumonia, subacute, focal 1 Parathymic adipose tissue, congestion and haemorrhage 1 Pleural cavity, mast cell and neutrophil accumulation 1 Pleural cavity, inflammation, fibrinous 1 Thymus, lymphoid depletion 2 Thyroid gland, lymphocytic infiltrate, focal 1 Trachea, tracheitis, acute 1 ^#200 mg/kg bw: Unscheduled histopathology only of kidney (males) and thymus (females) examined due to increased effect at 400 mg/kg bw.

Applicant's summary and conclusion

Conclusions:

After 13 weeks of oral exposure by gavage, unspecific adverse effects, predominantly loss in body-weight gain, considered to be substance-related were noted from 200 mg/kg bw/d onwards.

Executive summary:

Doses of 0, 25, 50, 100, 200, and 400 mg naphthalene/kg bw/d were administered orally in corn oil to Fischer 344 rats (60 rats per sex) for five days a week for 13 weeks. Up to 200 mg/kg bw/d, the only signs - obviously substance-related - were decrease in body weight of >10 % in both sexes. At 400 mg/kg bw/d, in addition, clear clinical signs of discomfort and disorder (lethargy, roughened haircoats, hunched posture, and diarrhoea) emerged, but also mortality was slightly increased (2/10 males during the last week of the study, one with renal lesion), shifts in the lymphocyte count and apparently an increasing trend in organ damage (kidney in males and there noted, and the thymus) were observed.