Formic acid, manufacture of, by-products from

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

2008

Report date:

2008

Reference 2

Reference Type:

study report

Title:

Unnamed

Year:

2007

Report date:

2007

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Test guideline 2

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Sodium formate

EC Number:

205-488-0

EC Name:

Sodium formate

Cas Number:

141-53-7

Molecular formula:

CHO2Na

IUPAC Name:

sodium formate

Details on test material:

- Name of test material (as cited in study report): Sodium formate
- Analytical purity: 100%

Specific details on test material used for the study:

- Name of test material (as cited in study report): Sodium formate
- Analytical purity: 100%

Test animals

Species:

rabbit

Strain:

Himalayan

Details on test animals or test system and environmental conditions:

- Species:  rabbit
- Strain:   Himalayan
- Source:  Charles River Laboratories, Research Models and Services, Germany GmbH (former Charles River Laboratories, Germany)
- Sex: female
- Number: 25 per group
- Age: 13-21 weeks at study initiation
- Body weight (group mean): 2560 g
- Mating: Insemination; day of insemination designated day 0 of the study

Administration / exposure

Route of administration:

oral: gavage

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
For the preparation of the solutions, an appropriate amount of the test substance was weighed in a graduated measuring flask depending
on the dose group, topped up with doubly distilled water and subsequently thoroughly mixed until it was completely dissolved.


VEHICLE
- Amount of vehicle (if gavage): dose volume: 10 mL/kg bw

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

HPLC with external calibration. Column Synergi 4µ Hydro-RP 80 A, 250 x 3 mm. Eluant: phsophate buffer pH 2.9. UV-detection at 200 nm (report, page 229 onwards).

Details on mating procedure:

Artificial insemination:
After an acclimatization period of at least 5 days, the does were fertilized by means of artificial insemination.
This implied that 0.2 ml of a synthetic hormone which releases LH and FSH from the anterior pituitary lobe (Receptal®) were
injected intramuscularly to the female rabbits about 1 hour before insemination. The ejaculate samples used for the artificial insemination
were derived from male Himalayan rabbits of the same breed as the females. Each female was inseminated with the sperm of a defined male donor as documented in the raw data. The male donors were kept under conditions (air conditioning, diet, water) comparable to those of
the females participating in this study.
The day of insemination was designated as day 0 (beginning of the study) and the following day as day 1 post insemination (p.i.).

Duration of treatment / exposure:

days 6-28 post implantation

Frequency of treatment:

daily

Duration of test:

22 days

No. of animals per sex per dose:

25 females

Control animals:

yes, concurrent vehicle

Details on study design:

Sex: female

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Clinical signs: checked each day
- Mortality: checked twice daily on working days, once on Saturday, Sunday, at public holidays


DETAILED CLINICAL OBSERVATIONS: Yes / No / No data
- Time schedule:


BODY WEIGHT: Yes
- Time schedule for examinations: recorded regularly throughout the entire study period, i.e. on days 0, 2, 4, 6, 9, 11, 14, 16, 19, 21, 23, 25, 28 and 29 p.i.


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.
Food consumption was recorded daily throughout the entire study period.


POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day # 29
- Organs examined: all females were sacrificed and assessed by gross pathology (including weight determinations of the unopened uterus and the placentae). For each doe, corpora lutea were counted and number and distribution of implantation sites (differentiated by resorptions, live and dead fetuses) were determined. Number and distribution of implantations sites were classified as live fetuses and dead implantations. Dead implantations comprised early resorptions, late resorptions and dead fetuses.

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: Yes
- Placenta 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:

Simultaneous comparison of all dose groups with the control group using the DUNNETT-test (twosided) for the hypothesis of equal means * for p < 0.05, ** for p < 0.01: Food consumption, body weight, body weight change, corrected, body weight gain (net maternal, body weight change), carcass, weight, weight of unopened, uterus, number of corpora lutea, number of implantations, number of resorptions, number of live fetuses, proportions of preimplantation loss, proportions of postimplantation loss, proportions of resorptions, proportion of live fetuses in each litter, litter mean fetal body weight, litter mean placental weight. 
Pairwise comparison of each dose group with the control group using FISHER'S EXACT test (one-sided) for the hypothesis of equal proportions * for p < 0.05, ** for p < 0.01: Female mortality, females pregnant at terminal sacrifice, number of litters with fetal findings.
Pairwise comparison of each dose group with the control group using the WILCOXON-test (onesided) for the hypothesis of equal medians * for p < 0.05, ** for p < 0.01: Proportions of fetuses with malformations, variations and/or unclassified observations in each litter.

Indices:

Conception rate, pre- and postimplantation loss

Historical control data:

Included in Part III of the report

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:no effects

Details on maternal toxic effects:
No clinical signs of toxicity, no treatement-related mortalities. Food consumption, body weights, necropsy findings not affected.

Effect levels (maternal animals)

1

Dose descriptor:

NOAEL

Effect level:

1 000 mg/kg bw/day (actual dose received)

Basis for effect level:

other: maternal toxicity

2

Dose descriptor:

NOAEL

Effect level:

1 000 mg/kg bw/day (actual dose received)

Basis for effect level:

other: developmental toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
Fetal weight, sex distribution, placenta weight not affected. Pre- and postimplantation loss not affected. External, soft tissue and skeletal malformations not affected by treatment.

Effect levels (fetuses)

1

Dose descriptor:

NOAEL

Effect level:

1 000 mg/kg bw/day (actual dose received)

Basis for effect level:

other: embryotoxicity

2

Dose descriptor:

NOAEL

Effect level:

1 000 mg/kg bw/day (actual dose received)

Basis for effect level:

other: teratogenicity

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Any other information on results incl. tables

Analysis of Test Substance
By various analyses, the stability of the test substance solutions over a period of 13 days at room temperature was
demonstrated, and the correctness of the prepared concentrations was shown.

EFFECTS
1 - Parental animals

Mortalities: none in any of the groups.
Clinical signs: none in any of the groups (Report, p. 34)
Food consumption: comparable across all groups, no relevant difference in treated groups compared to the control group
(Report, p. 35).
Body weights: comparable across all groups, no difference in treated groups compared to the control group ((Report p. 36).
Corrected body weight gain: did not reveal statistically significant differences between the test substance-treated groups and the control group (Report p. 36)
Uterus weight: no effect; the mean uterus weights were comparable between all groups (Report p. 37)
Necropsy findings: no test-substance related effect noted (Report p. 37)

Table1: Selected results for does in test groups 0 - 3,  i.e. at 0, 100, 300, or 1000 mg/kg bw per day

===========================================================
Parameter        Group 0     Group 1    Group 2     Group 3
-----------------------------------------------------------
Females mated/   
pregnant/       25/24/24   25/23/23    25/22/22   25/23/23
with viable 
fetuses

Food con-
sumtion (g)      100.5       97.8         94.5       94.6
day 0-29                    (97%)         (94%)      (94%)

Body weight      306.0      323.5        260.5      297.7 
gain (g)                    (106%)       (85%)      (97%)
day 0-29

Necropsy         - - No treatment-related findings  - -        
findings 
in dams 

Conception         96          92          88         92
rate (%)

Abortions           0           0           0          0

Corpora lutea    201/24     196/23        193/22    185/23
total/number 
of dams                

Implantations    176/24     185/23        156/22    161/23
total/number 
of dams
        
Resorptions       13/24     16/23          19/22     22/23
total/number 
of dams

total number      163        169            137       139
of fetuses                

total number       24         23             22        23
of litters                

pre-implantation 12.5(19.1) 6.7(11.9)   18.4(24.9) 13.3(16.1)
loss (+/- SD) %                

post-implantation 7.3(10.1) 7.9(9.3)  13.0(16.4) 13.9(16.2)
loss (+/- SD) %

fetuses/litter  6.8(2.25)  7.3(1.7)  6.2(2.5)  6.0(2.0)
(+/- SD)
live fetuses/   92.7(10.1)  92.1(9.3) 87.0(16.4) 86.1(16.2)
litter (+/- SD) %                

placenta weight   4.7        4.5          4.6          4.3
(mean) [g]                  (96%)        (98%)       (92%)

fetus weight     37.8        36.4        36.7        35.2
(mean) [g]                  (96%)        (97%)       (93%)
 
Fetal sex ratio 38.7:61.3  50.9:49.1   54.0:46.0   51.1:48.9        
[ratio m : f]
===========================================================
SD = Standard Deviation


2 - Fetuses
There were no test substance-related effects in any of the test groups at 100, 300, and 1000 mg/kg bw/day. 

Table 2: Selected results for fetuses in test groups 0 - 3,  i.e. from does at 0, 100, 300, or 1000 mg/kg bw per day:

===========================================================
Parameter        Group 0     Group 1    Group 2     Group 3
-----------------------------------------------------------
Total external malformations [%]
Fetuses           0.0         0.0        0.7         0.7
Litter            0.0         0.0        4.5         4.3 
Affect. fetuses   0.0         0.0        0.6         0.5
per litter

Total external variations [%]
Fetuses           4.3         0.6        2.2         1.4
Litter            13          4.3        9.1         8.7
Affect. fetuses   2.3         0.9        2.0         1.4
per litter

Skeletal malformations [%]
Fetuses           1.8         1.8        1.5         3.6
Litter            13          13         9.1         22 
Affect. fetuses   2.3         2.0        1.0         3.4
per litter

Skeletal variations [%]
Fetuses           52          65         60          65
Litter           100          91         95          96
Affect. fetuses   53.5        61.8       62.2        65.7
per litter

Soft tissue malformations [%]
Fetuses           1.2         0.6       2.2         4.3
Litter            8.3         4.3       14          26
Affect. fetuses   1.5         0.5       2.1         4.5
per litter

Soft tissue variations [%]
Fetuses           4.3         11        11          10
Litter            21          48        41          39
Affect. fetuses   4.2        10.9       9.4         8.9
per litter
===========================================================

Applicant's summary and conclusion

Conclusions:

Result: negative; no maternal and prenatal developmental toxicity, no  teratogenicity at any tested dose level.

Executive summary:

In a developmental toxicity study sodium formate was administered to 25 female Himalayan rabbits in water by gavage at dose levels of 0, 100, 300, and 1000 mg/kg bw/day from days 6 through 28 of gestation.

 

There were no treatment-related effects in mortality, clinical signs, body weight, food consumption,cesareanparameters, and terminal necropsy in the does. The maternal NOAEL is therefore 1000 mg sodium formate/kg bw/day.

There were no treatment-related effects in developmental parameters.Fetal weight at birth, sex distribution, placenta weight, pre- and postimplantation loss was not affected. There were no unusual or increased incidences of external, soft tissue or skeletal malformations attributable to the treatment. The developmental NOAEL is therefore 1000 sodium formate mg/kg bw/day.The NOAEL for teratogenicity is also 1000 sodium formate mg/kg bw/day, the highest dose tested.

 

The developmental toxicity study in the rabbit is classified acceptableand satisfies the guideline requirement for a developmental toxicity study (OECD 414) in rabbits.

 

Generally, formate salts are used as test material in studies requiring repeated dosing, due to the corrosivity of formic acid. NOAEL values obtained in such studies may be used to calculate the NOAEL for the formate anion which may be read across to other salts or formic acid, taking into account stoichiometry and formula weights. For the ease of the reader, this is tabulated below (calculation in brackets).

Table: calculation of NOAEL values

 

	Formula weight	NOAEL maternal toxicity	NOAEL developmental toxicity	NOAEL teratogenicity
		(mg/kg bw/day)
Sodium formate	69	1000	1000	1000
Formate anion	45	652 (1000/69x45)	652 (1000/69x45)	652 (1000/69x45)
Formic acid	46	667 (1000/69x46)	667 (1000/69x46)	667 (1000/69x46)