Fluorine

Repeated dose toxicity: oral

Administrative data

Endpoint:

short-term repeated dose toxicity: oral

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: NTP study

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference Type:

publication

Title:

Technical Report on the Toxicology and Carcinogenesis Studies of Sodium Fluoride in F344/N Rats and B6C3F, Mice.

Author:

NTP

Year:

1990

Bibliographic source:

U.S Department of Health and Human Services. NTP TR 393, NIH Publication No. 91-2848, December 1990

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: NTP protocol

Principles of method if other than guideline:

6-month repeated dose study.

GLP compliance:

not specified

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Sodium fluoride

EC Number:

231-667-8

EC Name:

Sodium fluoride

Cas Number:

7681-49-4

Molecular formula:

FNa

IUPAC Name:

sodium fluoride

Details on test material:

No further details

Test animals

Species:

mouse

Strain:

B6C3F1

Sex:

male/female

Details on test animals or test system and environmental conditions:

Progeny of C57BL/N6 female and C3H/HeN male mice, obtained from Charles River Laboratories, Wilmington, DE, were used in this study. Mice were 4 to 6 weeks old when placed on study. Their diet consisted of a semisynthetic low fluoride diet. The mice were kept in groups of ten in cages set at a temperture of 22-24 degC and of relative humidity 40-60%. The fluorescent light was 12 hours per day.

Administration / exposure

Route of administration:

oral: drinking water

Vehicle:

water

Details on oral exposure:

Groups of 8-12 mice of each sex received 0, 10, 30, 100, 200, 300 or 600 ppm sodium fluoride in deionised water ad libitum for 6 months.

Analytical verification of doses or concentrations:

no

Details on analytical verification of doses or concentrations:

The concentrations are nominal concentrations.

Duration of treatment / exposure:

0, 10, 30, 100, 200, 300 or 600 ppm sodium fluoride in deionised water

Frequency of treatment:

Continous (ad libitum, in drinking water)

Doses / concentrations

Remarks:

Doses / Concentrations:
0, 10, 30, 100, 200, 300 or 600 ppm
Basis:
nominal in water

No. of animals per sex per dose:

The method stated ten mice of each sex per dose group. However, some of the test animals were incorrectly sexed, resullting in 8-12 mice per sex per dose group.

Control animals:

other: One control group received de-ionised water and a low fluoride diet. One control group received sodium chloride and a low fluoride diet. An additional control group received standard diet.

Details on study design:

Groups of 8-12 mice of each sex received 0, 10, 30, 100, 200, 300 or 600 ppm sodium fluoride in deionised water ad libitum for 6 months. All test animals receiving water supplemented with sodium fluroide were provided with a low fluoride (<2.1 ppm) semisynthetic diet throughout the study. Three control groups were included in the studies of male and female mice; one received deionised drinking water and a low fluoride, semisynthetic diet, the second received sodium chloride supplemented deionized drinking water and a low fluoride, semisynthetic diet and the third received deionized water and a standard NIH-07 diet. At termination of the studies, the fluoride concentrations in urine, blood and bone were determined from samples collected from all surviving mice. Necropsy was performed on all animals, with histopathology at 300 and 600 ppm.

Positive control:

Not relevant

Examinations

Observations and examinations performed and frequency:

Animals were observed twice daily for mortality and morbidity, weighed initially, once weekly and at termination. Clinical observations recorded daily. Food consumption recorded every other week for the first 13 weeks and for 1 week during each of the last 3 months. Water consumption was recorded daily.

Sacrifice and pathology:

Necropsy was performed on all animals, with histopathological investigation of animals at 300 and 600 ppm.

Other examinations:

Fluoride concentrations in bone, blood and urine measured prior to necropsy

Statistics:

Not reported.

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Food efficiency:

not examined

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

effects observed, treatment-related

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

no effects observed

Details on results:

CLINICAL SIGNS AND MORTALITY

Deaths occurred at 600 ppm (4 males, 9 females) and at 300 ppm (1 male). Signs of toxiicity (weakness, thin appearance, hunched posture) were seen at 600 ppm. Mice at 100, 200m 300 and 600 ppm had chalky white teeth; the lower incisors were more affected and were also chipped at higher dose levels.

BODY WEIGHT AND WEIGHT GAIN

Reduced weight gain was seen at 200, 300 and 600 ppm; food consumption was reduced in males at 600 ppm. Water consumption was unaffected by treatment.

GROSS PATHOLOGY

None

HISTOPATHOLOGY

Treatment-related findings were noted in the kidney, liver, testes and myocardium of decedents. Acute nephrosis was characterised by extensive multifocal degeneration and tubular necrosis and was diagnosed as the cause of death in these animals. Multifocal myocardial degeneration was also seen in two 600 ppm females. Liver changes consisted of scattered heptocellular hypertrophy and megalocytosis. The effects on the testes (degeneration/necrosis of the seminiferous tunules) were not considered to be directly related to treatment, but occur frequently in moribund mice. Effects were also noted on teh femur and (to a lesser extent) the tibia of mice at 50 ppm and greater. Changes are considered to be indicative of altered rates of bone deposition and remodelling. Effects on the teeth were seen at 300 and 600 ppm.


OTHER FINDINGS

The fluoride content of plasma, bone and urine increased with dose level.

Effect levels

1

Dose descriptor:

NOEL

Effect level:

< 50 ppm

Sex:

male

Basis for effect level:

other: Effects on bone

2

Dose descriptor:

LOEL

Effect level:

50 ppm

Sex:

male

Basis for effect level:

other: Effects on bone

3

Dose descriptor:

NOEL

Effect level:

50 ppm

Sex:

female

Basis for effect level:

other: Effects on bone

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

Dose (ppm)	Survival	Mean Body Weight			Final Weight relative to control (%)
		Initial	Final	Change
Male
Control^a	9/9	16.9±0.4	40.2±1.0	23.3±1.1	100
Control^b	10/10	18.6±0.4*	41.6±0.6	23.0±0.7	103
Control^c	11/11	17.8±0.4	39.2±1.0	21.4±1.0	97
10	9/9	17.3±0.5	43.1±1.5	25.8±1.8	107
50	10/10	18.0±0.6	41.1±1.1	23.1±1.3	102
100	10/10	19.2±0.8	41.5±1.1	22.3±1.3	103
200	10/10	17.9±0.7	36.5±1.2	18.6±1.4*	91
300	7/8	18.8±0.7	38.1±1.1	19.0±1.4*	95
600	5/9	17.4±0.4	32.0±1.6**	14.8±1.9**	80
Female
Control^a	11/11	16.9±0.6	30.2±1.4	13.3±1.6	100
Control^b	10/10	18.6±0.4	31.5±1.0	12.9±1.1	104
Control^c	9/9	16.6±0.2	28.7±0.9	12.1±0.8	95
10	11/11	17.1±0.4	29.6±1.1	12.5±1.1	98
50	10/10	16.4±0.3	32.2±1.1	15.8±1.2	107
100	10/10	17.2±0.4	30.6±1.5	13.4±1.4	101
200	10/10	17.2±0.4	25.3±0.6**	8.1±0.7*	84
300	12/12	16.9±0.3	26.2±0.8*	9.3±0.7*	87
600	2/11	16.6±0.4	24.5±1.5	9.0±1.0	81

*Significantly different (P=0.05) from the control group by Dunn’s or Shirley’s test

**P<0.01

^a         Control group receiving semisynthetic, low fluoride diet and deionised water.

^b      Control group receiving semisynthetic, low fluoride diet and sodium chloride supplemented deionised water

^c      Control group receiving standard NIH-07 diet and deionised water.

Organs and Diagnoses	300 ppm	600 ppm
Male Animals initially in study Early deaths   Kidney Nephrosis, multifocal   Liver Megalocytosis, multifocal Syncytial alteration, multifocal   Myocardium Mineralization, multifocal   Testis Necrosis Tubule, degeneration, multifocal Tubule, multinucleated giant cells, multifocal   Female   Animals initially in study Early deaths   Kidney Nephrosis, multifocal   Liver Megalocytosis, multifocal Syncytial alteration, multifocal   Myocardium Degeneration, multifocal Mineralization, multifocal	8 1     1     1 1     1     1   1       12 0     0     0 0     0 0	9 4     2     4 4     4     3 2 1       11 9     2     7 7     2 4

Applicant's summary and conclusion

Conclusions:

Skeletal effects of fluoride were seen at all dose levels in this study.

Executive summary:

In the 6 month studies in mice, 4/9 males and 9/11 females receiving 600 ppm sodium fluoride and 1/8 male given water containing 600 ppm died.

The fluoride content of urine and bone increased with the concentration of sodium fluoride in the drinking water in both sexes of mice. Bone fluoride concentration were as high as 14.8 µg/mg of ashed bone in male mice receiving 600 ppm sodium fluoride in water. The bone fluoride content found in mice was somewhat greater than that found in rats given comparable sodium fluoride content. This maybe due to a greater water intake on a body weight basis by mice than by rats resulting in higher exposures. Plasma fluoride concentrations in mice showed a good dose relationship and appeared increased in groups receiving water concentrations of 50 ppm of sodium fluoride or higher.

Histopathologic findings for mice are consistent with previously recognised toxic effects. The acute nephrosis observed in the kidneys was probably the most likely cause of death. Lesions were also observed on the incisor teeth, femur and tibia of mice