Borate(1-), tris(acetato-.kappa.O)hydro-, sodium, (T-4)-

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

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

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Acceptable, well documented publication of a study performed equivalent to OECD guideline with the decomposition product boric acid

Data source

Reference

Reference 1

Reference Type:

publication

Title:

The Developmental Toxicity of Boric Acid in Rabbits

Author:

Price, C.J. et al.

Year:

1996

Bibliographic source:

Fundam. Appl. Toxicol. 34,176-187

Reference 2

Reference Type:

study report

Title:

Unnamed

Year:

1991

Reference 3

Reference Type:

publication

Title:

The developmental toxicity of boric acid in mice, rats and rabbits

Author:

Heindel, J.J. et al.

Year:

1994

Bibliographic source:

Environ Health Perspect 102(Suppl 7):107-112

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

not specified

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Boric acid

EC Number:

233-139-2

EC Name:

Boric acid

Cas Number:

10043-35-3

Molecular formula:

BH3O3

IUPAC Name:

Boric acid

Details on test material:

- Name of test material: Boric acid
- Analytical purity: > 99%
- Stability under test conditions: Stable at room temperature for at least 28 days
- Lot/batch No.: 872703
- Supplier: Fisher Scientific Co.

Test animals

Species:

rabbit

Strain:

New Zealand White

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Hazleton Research Products inc., Denver, PA, USA
- Age at study initiation: approx. 5 months
- Weight at study initiation: 2690 - 4380 g
- Housing: individually in stainless steel cages with mesh flooring
- Diet (e.g. ad libitum): Purina Certified Rabbit Chow (No. 5322), Ralston Purina Co., St. Louis, MO, USA; ad libitum
- Acclimation period: 14 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 17.8 - 26.1
- Humidity (%): 47 - 89
- Photoperiod (hrs dark / hrs light): 12 / 12 (females), 10 / 14 (males)

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

water

Remarks:

distilled/deionized

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
dose volume was adjusted daily.


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

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Assays (UVNIS spectroaxtry) conducted prior to dosing indicated that all formulations were within a range of 94-106% of the theoretinl concentrationa Formulations were used within the period of demcostrued stability.

Details on mating procedure:

- Impregnation procedure: artificial insemination
- Any other deviations from standard protocol: The study was performed in two replicates with two consecutive breeding days within each replicate
and 34 days between replicates.

Duration of treatment / exposure:

Treatment: on gestational days 6 - 19
Termination: at day 30 of gestation

Frequency of treatment:

Once daily on the mornings, 7 d/weeks

Duration of test:

30 days (gestation days 0 - 30)

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
62.5, 125 or 250 mg/kg bw
Basis:
actual ingested
Boric acid

Doses / concentrations 2

Remarks:

Doses / Concentrations:
10.9, 21.8 and 43.5 mg/kg bw
Basis:
actual ingested
Element Boron

No. of animals per sex per dose:

30

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: Based on reults of preliminary toxicity study where nonpregnant female rabbits (2/group) were dosed with BA (0 or 275 mg/kg bw/day, po) using a dose volume of 5 mL/kg in distilled/deionized water.

Examinations

Maternal examinations:

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Daily

BODY WEIGHT: Yes
- Time schedule for examinations: Days 0, 6-19, 25 and 30

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes, at 2-3 days intervals
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: No

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 30
- Organs examined: liver, kidneys,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 resorptions: Yes

Fetal examinations:

- External examinations: Yes: All per litter, including cleft palate
- Soft tissue examinations: Yes: All per litter, including sex determination
- Skeletal examinations: Yes: All per litter
- Head examinations: Yes: Half per litter

Litter size, number of dead foetuses and foetal weight were assessed.

Statistics:

The doe or litter was considered the experimental unit for all statistical analyses . General Linear Models (GLM) procedures were applied for the analyses of variance (ANOVA) of maternal and fetal parameters . Prior to GLM analysis, an arcsinesquare root transformation was performed on all litter-derived percentage data and Bartlett's test for homogeneity of variance was performed on all data to be analysed by ANOVA . GLM analysis 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 multiple comparison test compared exposed groups to control groups. One-tailed tests were used for all pairwise comparisons except maternal body and organ weights and fetal body weight. Nominal scale measures were analyzed by x² test for independence and by a test for linear trend on proportions. When a x² test showed significant groupwise differences, a one-tailed Fisher's exact probability test was used for pairwise comparisons of control and BA 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 treatment-related clinical signs of toxicity were observed during the study, except for vaginal bleeding noted in 2-11 does/day on gd 19-30 at the high dose; these does had no live fetuses on day 30. Vaginal bleeding was also observed in one female in the low-dose group and in one in the mid-dose group. Two maternal deaths occurred (one each at the low- and mid-dose), but were not treatment-related. Food intake was decreased relative to that of controls on treatment days 6-15 at the high dose, and was increased after treatment ceased on days 25-30 at the mid and high doses. Body weight on gd 9-30, weight gain on gd 6-19, gravid uterine weight, and number of corpora lutea per dam were each decreased in the high-dose group. After correction for gravid uterine weights, however, maternal body-weight gain was increased at both the mid-and high- doses. Treatment with boric acid did not affect absolute or relative liver weight. Relative, but not absolute kidney weight increased at the high dose; kidney histopathology was unremarkable.

Effect levels (maternal animals)

1

Dose descriptor:

NOAEL

Effect level:

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

Based on:

test mat.

Remarks:

Boric acid

Basis for effect level:

other: maternal toxicity

2

Dose descriptor:

NOAEL

Effect level:

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

Based on:

element

Remarks:

Boron

Basis for effect level:

other: maternal toxicity

3

Dose descriptor:

NOAEL

Effect level:

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

Based on:

test mat.

Remarks:

Boric acid

Basis for effect level:

other: developmental toxicity

4

Dose descriptor:

NOAEL

Effect level:

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

Based on:

element

Remarks:

Boron

Basis for effect level:

other: developmental toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:yes

Details on embryotoxic / teratogenic effects:
Developmental effects were noted in the high dose group which consisted of a high rate of prenatal mortality (90% of implants/litter were reabsorbed compared with 6% in controls). Also, the percentage of pregnant females with no live fetuses was greatly increased (73% compared with 0% in controls), whereas the number of live fetuses per litter on day 30 was significantly reduced (2.3/litter compared with 8.8/litter in controls). Malformed live fetuses per litter increased significantly at the high dose, primarily due to the incidence of fetuses with cardiovascular defects, the most prevalent of which was interventricular septal defect (8/14 at high dose compared with 1/159 in controls). The incidence of skeletal malformations was comparable among groups. Relative to controls, the percentage of fetuses with variations (all types combined) was not significantly increased in any treated group, but the percentage with cardiovascular variations was significantly increased from 11% in controls to 64% in the high-dose group. Fetal body weights per litter at the high dose were depressed relative to control, but the difference was not statistically significant; however, this could have been due to the small sample size in the high-dose group. No developmental effects were found in the low- and mid-dose groups.

Effect levels (fetuses)

Dose descriptor:

NOAEL

Effect level:

125 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Based on increased resorptions and CVS malformations in surviving fetuses at 250 mg/kg bw/day

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Any other information on results incl. tables

Maternal toxicity:

		Boric acid (mg/kg bw/d)
		0	62.5	125	250
No. pregnant at euthanization		18	23	20	22
No. of live litters		18	23	20	6
No. of live fetuses		159	175	153	14
Maternal weight change (g)	Treatment period (GD 6 to 19)	93 ± 30*	132 ± 40	97 ± 51	-137 ± 42**
	Gestation period (GD 0 to 30)	357 ± 69*	493 ± 51	543 ± 63**	226 ± 35
	Corrected gestation wt. gain	-205 ± 78*	-52 ± 63	40 ± 57**	165 ± 40**
	Gravid uterine wa (g)a	562 ± 40*	504 ± 26	502 ± 28	62 ± 18**
Maternal liver weight (% bw)		2.56 ± 0.13	2.8 ± 0.09	2.78 ± 0.08	2.87 ± 0.09
Maternal kidney weight (% bw)		0.46 ± 0.02	0.46 ± 0.01	0.47 ± 0.01	0.51 ± 0.01**
Renal pathology		0/18	2/23	0/20	1/22
Relative food consumption (g/kg/day)	Pretreatment period  (GD 0 to 6)	48.1 ± 1.7	48.0 ± 1.8	48.9 ± 2.4	46.4 ± 1.5
	Treatment period (GD 6 to 19)	38.8 ± 1.7*	40.0 ± 2.0	38.7 ± 2.3	26.6 ± 2.2**
	Posttreament (GD 19-25)	36.9 ± 2.5*	37.0 ± 2.6	40.0 ± 3.1	44.9 ± 2.2
	Posttreament (GD 25-30)	24.5 ± 3.0	30.9 ± 2.1	33.9 ± 1.9**	41.9 ± 1.6**

* p < 0.05, linear trend. .

** p < 0.05, Dunnett's teat.

Developmental effects:

		Boric acid (mg/kg bw/d)
		0	62.5	125	250
No. implantation sites per litter (a)		9.5 ± 0.8	26.1 ± 3.8	8.3 ± 0.5	8.6 ± 0.7
% Resorptions per litter (a)		6.3 ± 2.4*	5.9 ± 1.9	7.7 ± 2.1	89.9 ± 5.0**
% Litters with one or more resorptions		39	39	45	95***
% Litters with 100% resorptions		0	0	0	73***
No. live fetuses per litter (b)		8.8 ± 0.8*	7.6 ± 0.6	7.7 ± 0.5	2.3 ± 0.8**
Average fetal body wt (g) per litter (b)		44.8 ± 1.5	46.5 ± 1.4	45.7 ± 1.2	41.1 ± 2.7
All malformations	% Fetuses per litter (b)	25.5 ± 5.8*	26.1 ± 3.8	30.4 ± 6.3	80.6 ± 16.3**
	%Litters	72	78	75	83
External malformations	% Fetuses per litter (b)	0.8 ± 0.8*	1.4 ± 1.0	1.0 ± 1.0	11.1 v 8.2**
	%Litters	6	9	5	33
Skeletal malformations	% Fetuses per litter (b)	19.9 ± 5.4	19.9 ± 4.0	24.3 ± 6.4	38.9 ± 20.0
	%Litters	61	65	55	50
Visceral malformations	% Fetuses per litter (b)	7.3 ± 1.9*	5.9 ± 2.0	7.4 ± 2.0	80.6 ± 16.3**
	%Litters	50	35	45	83
Cardiovascular malformations	% Fetuses per litter (b)	2.7 ± 1.6*	3.1 ± 1.5	4.2 ± 1.3	72.2 ± 16.5**
	%Litters	17*	22	35	83***
All variations	% Fetuses per litter (b)	67.7 ± 7.2	54.8 ± 5.1	40.4 ± 5.2	86.1 ± 9.0
	%Litters	94	100	90	100
Cardiovascular variations	% Fetuses per litter (b)	10.6 ± 5.5*	5.7 ± 1.8	7.2 ± 2.5	63.9 ± 17.4**
	%Litters	44	35	35	83

a) Includes all dams pregnant at euthanization; litter size is number of implantation sites per dam; mean ± SEM.

b) Includes only dams with live fetuses; litter size is number of live fetuses per dam; mean ± SEM.

* p < 0.05, linear trend. .

** p < 0.05, Dunnett's teat.

*** p< 0.05, Fisher’s exact test.

Applicant's summary and conclusion

Conclusions:

Due to observed maternal and developmental effects at 125 mg/kg bw/d Boric acid, this dose corresponding to 21.8 mg/kg bw/d Boron was determined to be the NOAEL.

Executive summary:

Developmental toxicity of Boric acid was evaluated in a GLP study performed equivalent to OECD guideline 414, where groups of 30 New Zealand White) rabbits were administered boric acid once daily by gavage at doses corresponding to 0, 10.9, 21.9 and 43.8 mg boron/kg bw/day during major organogenesis on GD 6-19. The rabbits exposed to 43.8 mg boron/kg bw/day on gestation day 6-19 revealed decreased food intake during treatment, relative but not absolute kidney weight increase and vaginal bleeding. At the highest dose, prenatal mortality was increased (90% resorption/litter versus 6% in controls). In this dose group the number of live fetuses available for evaluation where dramaticall decreased compared to live fetuses in the other groups. Additionally, the resorption rate was disproportionally high (95%) and an increased incidente of malformed live foetuses/litter was observed primarily due to cardiovascular effects. Based on these results, the NOAEL for maternal and developmental toxicity was 125 mg/kg bw/d boric acid corresponding to 21.8 mg/kg bw/d Boron, respectively.