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Toxicological information

Repeated dose toxicity: oral

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Administrative data

Endpoint:
sub-chronic toxicity: oral
Adequacy of study:
supporting study
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
documentation insufficient for assessment

Data source

Reference
Reference Type:
publication
Title:
Comparative Toxicity of Fluorine Compounds
Author:
Smith MC & Leverton RM
Year:
1934
Bibliographic source:
Industrial & Engineering Chemistry July 1934. 791-797

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
The authors investigated the comparative toxicity of various forms of fluorine including calcium difluoride when administered to rats in the drinking water for 6 weeks. Investigations focussed on mortality, weight gain and dental effects.
GLP compliance:
no
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
not specified
Details on test material:
Various fluorides, including calcium difluoride

Test animals

Species:
rat
Strain:
not specified
Sex:
male
Details on test animals and environmental conditions:
The albino rats used were taken at 4 weeks of age from the stock colony and raised on Shierman's Diet B, composed of one-third whole milk powder, two-thirds ground whole Kansas red wheat, and salt equal to 2 per cent of the weight of the wheat. Only male rats weighing from 50-65 g at the time of weaning were used.

Administration / exposure

Route of administration:
oral: feed
Vehicle:
unchanged (no vehicle)
Details on oral exposure:
Rats were administered various inorganic fluorides in the diet at equivalent concentrations for a 6-week exposure period. Sodium fluoride was incorporated into the diet at Ievels of 0.05% or multiples or fractions of this amount. All of the other compounds of fluorine were compared with sodium fluoride at the same percentage level of fluoride.
Analytical verification of doses or concentrations:
not specified
Duration of treatment / exposure:
6 weeks
Frequency of treatment:
Continuous / daily (dietary admixture)
Doses / concentrationsopen allclose all
Dose / conc.:
0 mg/kg bw/day (actual dose received)
Dose / conc.:
2.66 mg/kg bw/day (actual dose received)
Remarks:
Approximate actual dose of fluoride (F-) received; dosed as 0.00282% F- in the diet.
Dose / conc.:
5.178 mg/kg bw/day (actual dose received)
Remarks:
Approximate actual dose of fluoride (F-) received; dosed as 0.00565% F- in the diet.
Dose / conc.:
9.74 mg/kg bw/day (actual dose received)
Remarks:
Approximate actual dose of fluoride (F-) received; dosed as 0.0133% F- in the diet.
Dose / conc.:
18.62 mg/kg bw/day (actual dose received)
Remarks:
Approximate actual dose of fluoride (F-) received; dosed as 0.0226% F- in the diet.
Dose / conc.:
38.82 mg/kg bw/day (actual dose received)
Remarks:
Approximate actual dose of fluoride (F-) received; dosed as 0.0452% F- in the diet.
Dose / conc.:
206 mg/kg bw/day (actual dose received)
Remarks:
Approximate actual dose of fluoride (F-) received; dosed as 0.226% F- in the diet.
Dose / conc.:
384.3 mg/kg bw/day (actual dose received)
Remarks:
Approximate actual dose of fluoride (F-) received; dosed as 0.452% F- in the diet.
Dose / conc.:
769.2 mg/kg bw/day (actual dose received)
Remarks:
Approximate actual dose of fluoride (F-) received; dosed as 0.904% F- in the diet.
Dose / conc.:
1 204 mg/kg bw/day (actual dose received)
Remarks:
Approximate actual dose of fluoride (F-) received; dosed as 1.356% F- in the diet.
Dose / conc.:
1 476 mg/kg bw/day (actual dose received)
Remarks:
Approximate actual dose of fluoride (F-) received; dosed as 1.808% F- in the diet.
Remarks:
For the test group dosed with 3.616% F- in the diet, no actual received doses could be calculated due to mortality.
No. of animals per sex per dose:
0% F-: 40 males
0.00282 and 0.00565% F-: 1 male each
0.0113% F-: 5 males
0.0226 and 0.0452% F-: 8 males each
0.2260 and 0.9040% F-: 6 males each
0.4520% F-: 10 males
1.3560, 1.8080 and 3.6160% F-: 4 males each

Control animals:
yes, plain diet
Details on study design:
No information
Positive control:
No information

Examinations

Observations and examinations performed and frequency:
Animals were observed for general health, growth and food consumption. The appearance of the teeth was recorded.
Sacrifice and pathology:
No information
Other examinations:
No information
Statistics:
No information

Results and discussion

Results of examinations

Clinical signs:
effects observed, treatment-related
Description (incidence and severity):
No details available.
Mortality:
mortality observed, treatment-related
Description (incidence):
Mortality was observed in the highest dose group receiving 3.6% of fluoride. This dose caused death in 3-4 weeks.
In contrast, mortaility was seen at levels of >0.0452% of more soluble salts.
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
Animals receiving a diet containing 0.452% of fluoride (F-) or more were found to have a stunted growth (ca. 10% reduction of body weight as compared to the control group). The actual received daily dose in this dose group is 384 mg/kg bw/d.

The authors note that this level is approximately 20 times higher than the level of sodium fluoride causing similar effects and ten times higher than highest non-lethal concentration of sodium fluoride.
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Description (incidence and severity):
Food consumption decreased with increasing fluoride concentration in the diet.
Food efficiency:
effects observed, treatment-related
Description (incidence and severity):
Average weight gain per gram of food consumed decreased with increasing fluoride concentration in the diet.
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
not examined
Gross pathological findings:
effects observed, treatment-related
Description (incidence and severity):
Dental fluorosis. The severity of the dammage to the teeth was proportional to the fluoride intake.

A decrease in the amount of pigment in the lower incisors was observed as of the lowest dose concentrations. At higher dose levels, the teeth had a ringed or lined appearance, with alternating light and orange lines. Further increasing the dose concentration lead to the appearance of small pits in the death, and enamel chipping off, and severe dental corrosion.

Dental effects were noted with all sources of fluorine at comparable concentrations, however more severe effects were only seen at comparatively very high levels of calcium difluoride (20-40 times equivalent levels of sodium fluoride).
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
not examined
Histopathological findings: neoplastic:
not examined
Other effects:
not specified

Effect levels

open allclose all
Dose descriptor:
NOAEL
Effect level:
206 mg/kg bw/day (actual dose received)
Based on:
element
Remarks:
fluoride
Sex:
male
Basis for effect level:
body weight and weight gain
Remarks on result:
other: Corresponding fluoride content in diet: 0.226% F-
Dose descriptor:
NOAEL
Effect level:
423.1 mg/kg bw/day (actual dose received)
Based on:
test mat.
Remarks:
Calcium difluoride
Sex:
male
Basis for effect level:
body weight and weight gain

Target system / organ toxicity

Critical effects observed:
not specified

Any other information on results incl. tables

Fluoride level

n

Weight gain (g)

Food intake (g)

0

40

158

466

0.00282

1

194

612

0.00565

1

176

560

0.0113

5

158

494

0.0226

8

152

462

0.0452

8

155

487

0.226

6

142

492

0.452

10

132

441

0.904

6

115

411

1.356

4

77

358

1.808

4

32

252

3.616

4

-

-

Additional information: daily received dose values as calculated by the registrant.

Fluoride content in diet Food intake
Av. over 6 wks
Food intake
Av. per day
Daily fluoride intake Av. rat body weight Daily received dose
% F- grams grams mg/rat grams mg/kg bw/d
0 466 11.1 0.000 136.5 0
0.00282 612 14.6 0.411 154.5 2.660
0.00565 560 13.3 0,753 145.5 5.178
0.0113 494 11.8 1.329 136.5 9.74
0.0226 462 11.0 2.486 133.5 18.62
0.0452 487 11.6 5.241 135 38.82
0.226 492 11.7 26.474 128.5 206.0
0.452 441 10.5 47.460 123.5 384.3
0.904 411 9.8 88.463 115 769.2
1.356 358 8.5 115.583 96 1204
1.808 252 6.0 108.480 73.5 1476
3.616 death

Applicant's summary and conclusion

Conclusions:
The results of the study indicate that the toxicity of calcium difluoride is markedly influenced by its low water solubiliy.
Executive summary:

The authors investigated the comparative toxicity of various forms of inorganic fluoride in a 6 -week feeding study in male rats. They noted that overt effects of calcium difluoride toxicity (bodyweight reduction, mortality) were seen only at very high concentrations compared to other, water-soluble fluorides. In contrast, mild dental effects were seen at comparable fluoride levels for all of the compounds investigated, however the more severe effects were only seen at comparatively much higher concentrations of calcium difluoride. The results of the study therefore indicate that the toxicity of calcium difluoride is markedly influenced by its low water solubiliy.

From the observations reported in the publication, the registrants deducted an NOAEL of 0.266% fluoride content in the diet. This corresponds to an NOAEL of 206.0 mg F-/kg bw/d and 423.1 mg CaF2/kg bw/d.