Zinc fluoride

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: The study was conducted according to generally vaild procedures and accordinig to GLP guidelines. All parameters described are closely related or comparable to guideline methods.

Data source

Reference

Reference 1

Reference Type:

publication

Title:

Developmental toxicity evaluation of sodium fluoride administered to rats and rabbits in drinking water

Author:

Heindel, J.J. et al.

Year:

1996

Bibliographic source:

Fundamental and Applied Toxicology 30: 162-177.

Reference 2

Reference Type:

study report

Title:

Unnamed

Year:

1994

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

EPA OPPTS 870.3700 (Prenatal Developmental Toxicity Study)

GLP compliance:

yes

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

IUPAC Name:

sodium fluoride

Details on test material:

- Name of test material (as cited in study report): sodium fluoride
- Analytical purity: >99%

Test animals

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Inc., Raleigh, NC
- Weight at study initiation: mean body weights/group ranged from 248 to 253 g
- Fasting period before study: no
- Diet (e.g. ad libitum): ad libitium
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 7 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22.2 (average)
- Humidity (%): 55% (average)
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

oral: drinking water

Vehicle:

water

Details on exposure:

Animals were exposed to 0, 50, 150 or 300 ppm sodium fluoride in drinking water

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Preexposure analysis of drinking water solutions demontrated the concentrations of sodium fluoride to be within a range of 104-107% of target concentrations.

Details on mating procedure:

- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1:1
- Length of cohabitation: overnight
- Any other deviations from standard protocol: The morning on which sperm were found in a vaginal lavage was designated as GD 0.

Duration of treatment / exposure:

Gestation days 6 through 15

Frequency of treatment:

ad libitum - drinking water

Duration of test:

Terminated on Gestation day 20

Doses / concentrations

Remarks:

Doses / Concentrations:
0, 50, 150 or 300 ppm sodium fluoride
Basis:
nominal in water

No. of animals per sex per dose:

26

Control animals:

yes

Details on study design:

- Dose selection rationale: The sodium fluoride concentrations tested were 50, 150 and 300 ppm which corresponded to approximately 7.5, 22.5, and 45 mg/kg/day based on an estimated water consumption of 150 mL/kg body weight/day. The LD50 for sodium fluoride in rats is at least 52 mg/kg/day or approximately 350 ppm if administered in drinking water. The concentrations were chosen after consideration of data from the NTP 14-day study in which female rats given 400 ppm sodium fluoride in drinking water showed decreasesd body weight and water consumption and clinical signs of toxicity (dehydration , lethargy, and hunched posture) while 800 ppm killed all the animals. The high dose (300 ppm) was chosen in an effort to induc e some maternal toxicity while avaoiding the potentially confounding effects of dehydration seen at the 400 ppm level in the 14-day study. The 300 ppm level was anticipated to be a nonlethal exposure based on the lack of lethality among rats exposed to 300 ppm sodium fluoride in the NTP 6-month drinking water studty and 50 ppm low level was expected to produce no maternal toxicity based on a lack of effects related to sodium fluoride consumption in the NTP 2-year toxicity study at exposures up to 100 ppm.

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily


DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: daily beginning on gestation day 6


BODY WEIGHT: Yes
- Time schedule for examinations: 0, 2, 4, 6, 8, 10, 12, 14, 16, 18 and 20


FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes


WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): Yes
- Time schedule for examinations:0, 2, 4, 6, 8, 10, 12, 14, 16, 18 and 20


POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day # 20
- Organs examined: liver, kidney and uterus

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes

Fetal examinations:

- External examinations: Yes: [all per litter]
- Soft tissue examinations: Yes: [all per litter]
- Skeletal examinations: Yes: [all per litter]
- Head examinations: Yes: [half per litter]

Statistics:

General linear model (GLM) procedures were applied for the analyses of varience (ANOVA) of maternal and fetal parameters. Prior to GLM-ANOVA analysis, an arcsine-square root transformation was performed on all litter-derived percentage data to normalize the means and Bartlett's test for homogeneity of variance was performed on all data to be analyzed by ANOVA. GLM-ANOVA anyalysis determined the significance of dose-response relationships and the significance of dose effects, replicate effects, and dose x replicate interactions. When ANOVA revealed a significant (p<0.05) dose effect, Dunnett's test and Williams' test were used to compare treated to control groups. One-tailed tests wre used for all pairwise comparisons except maternal body and organ weeights, food and water consuumption , fetal body weight, and percentage of males per litter. If a significant (p<0.05) dose x replicate interaction occurred, then the data for that endpoint were analyzed separately for dose effects witnin each replicate in the study, as well as for all replicates combined. Nominal scale measures were analyzed by a X2 test for independence and by a test for linear trend on proportions. When a X2 test showed significant experinent-wise differences, a one-tailed Fisher's exact test was used for pairwise comparisons of treatment and control groups.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:yes

Details on maternal toxic effects:
No animals died during the course of the study. No treatment-related clinical signs were observed in confirmed-pregnant animlsa during or after administration of sodium fluoride. Maternal body weight gain during the first 2 days of exposure (GD 6 to 8) was significantly reduced at 300 ppm relative to controls. Maternal water consumption of rats given 300 ppm sodium fluoride was significantly decreased for each period of observation from GD 6 to 15. Maternal food consumption was also decreased in the animals given 300 ppm sodium fluoride from GD 8 to 10, but did not differ from controls for any other period of measurement. Maternal liver and kidney weights on GD 20 were not differenct from control . Examination of uteri demonstrated that 100% (26/26), 96% (25/26), 89% (23/26), and 96% (25/26) of the mated animals in the control throught high-dose groups were pregnant.

Effect levels (maternal animals)

1

Dose descriptor:

NOAEC

Effect level:

ca. 150 ppm

Based on:

test mat.

Basis for effect level:

other: maternal toxicity

2

Dose descriptor:

LOAEC

Effect level:

ca. 300 ppm

Based on:

test mat.

Basis for effect level:

other: maternal toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
No embryotoxic or teratogenic effects related to exposure to sodium fluoride in drinking water was observed at any dose concentration.

Effect levels (fetuses)

Dose descriptor:

NOAEC

Effect level:

> 300 ppm

Based on:

test mat.

Basis for effect level:

other: developmental effects

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

Maternal exposure to sodium fluoride at conentrations up to 300 ppm (approximately 27 mg/kg/day) during organogenesis (gestation days 6 to 15) did not significantly affect the frequency of postimplantation loss, mean fetal body weight/litter, or external, visceral or skeletal malformations in the rat.