Formamide

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: GLP guideline study

Data source

Reference

Reference 1

Reference Type:

publication

Title:

Evaluation of the developmental toxicity of formamide in Sprague-Dawley (CD) rats.

Author:

George JD, Price CJ, Marr MC, Myers CB and Jahnke GD

Year:

2000

Bibliographic source:

Toxicol. Sci. 57, 284-291.

Reference 2

Reference Type:

publication

Title:

Developmental toxicity evaluation of formamide administered to rats on gestational days (gd) 6 through 19.

Author:

Price CJ, Marr MC, Myers CB and Jahnke GD

Year:

1999

Bibliographic source:

Teratology 59 (6), 412; abstract no. P49.

Reference 3

Reference Type:

study report

Title:

Unnamed

Year:

1998

Report date:

1998

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

no

Principles of method if other than guideline:

Method: in accordance with US FDA, CFR 56 FR 12300 (March 21, 1994)

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Formamide

EC Number:

200-842-0

EC Name:

Formamide

Cas Number:

75-12-7

Molecular formula:

CH3NO

IUPAC Name:

formamide

Details on test material:

- Name of test material (as cited in study report): FORM
- Analytical purity: purity >99%
- source: Aldrich Chemical

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: 222-273 g on GD0
- Housing: singly
- Diet: Purina Certified Rodent Chow® (#5002; PMI, St. Louis, MO) and tap water were available ad libitum
- Water: ad libitum
- Acclimation period: 10 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21-23°C
- Humidity (%): 48-59%
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

oral: gavage

Details on exposure:

Formamide was dissolved in water.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Dose fonnu1ations were stored under refrigeration and administered within the period of proven stability (35 days). One set of dose formulations were prepared, and aliquots were submitted for verification of concentration before and after the period of use. Measured concentrations were within 97.9-100.3% of the theoretical concentration (NTP (1998), Tables 4 and A4-1).

Details on mating procedure:

- Impregnation procedure: purchased timed pregnant
- Proof of pregnancy: sperm in vaginal smear; referred to asday 0 of pregnancy (GD0)

Duration of treatment / exposure:

days 6 through 19 of gestation

Frequency of treatment:

daily

Duration of test:

entire gestation from GD0 to GD 20

Doses / concentrations

Remarks:

Doses / Concentrations:
50, 100, 200 mg/kg bw/d
Basis:
actual ingested

No. of animals per sex per dose:

25 females per dose

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: based on results of a preceding range finding study

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily



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


BODY WEIGHT: Yes / No / No data
- Time schedule for examinations:


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


WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): Yes / No / No data
- Time schedule for examinations:


POST-MORTEM EXAMINATIONS: Yes / No / No data
- Sacrifice on gestation day #
- Organs examined:


OTHER:
CAGE SIDE OBSERVATIONS: Yes / No / No data
- Time schedule:
- Cage side observations checked in table [No.?] were included.

DETAILED CLINICAL OBSERVATIONS: No

BODY WEIGHT: Yes
- Time schedule for examinations: body weight (g) was recorded on the mornings of gd 0, 6 through 20, and immediately following sacrifice
on gd 20.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes (no feeding study)
- 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

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day # 20
- Organs examined: uterus, liver
-other: the body, liver, and gravid uterus of each timed-mated female were weighed. Thoracic and abdominal cavities were examined.

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: half per litter
- Skeletal examinations: Yes: all per litter
- Head examinations: Yes: half per litter

Statistics:

Statistical evaluation was extensive; cf. attached publication for details

Indices:

No

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:yes

Details on maternal toxic effects:
Statistically significantly reduced maternal body weigt gain during gestation (GD6 - GD20). The maternal body weight corrected for the gravid uterine weight was not changed. Clinical signs of toxicity or mortality were not seen.

Effect levels (maternal animals)

Dose descriptor:

NOAEL

Effect level:

100 mg/kg bw/day

Basis for effect level:

other: maternal toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:yes

Details on embryotoxic / teratogenic effects:
Statistically significantly reduced fetal body weights at 100 and 200 mg/kg bw/day.Number of fetuses/litter and viability were not affeted. the incidence of malformations or variations was not increased at any doose.

Effect levels (fetuses)

1

Dose descriptor:

NOAEL

Effect level:

50 mg/kg bw/day

Basis for effect level:

other: fetotoxicity

2

Dose descriptor:

NOAEL

Effect level:

200 mg/kg bw/day

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

MATERNAL TOXICITY: 

Maternal food and water intake were not different from control. 

There were no substance-related clinical signs of toxicity. 

No maternal deaths or morbidity occurred. 

Maternal body weight exhibited a dose-related decreasing trend; reductions were significant at 200 mg/kg bw/d on gd 18 to 20. 

Body weight gain was significantly reduced at the top dose during gestation days 6 -20.

However, maternal gestational weight gain was not affected when corrected for gravid uterine weight. 

Mean uterine weight wasdecreased in a dose-related manner (-0, -6, and -13%, respectively; statistically significant at 200 mg/kg bw/d).
Maternal liver weight was not affected.

Overall, maternal toxicity was minimal, a NOAEL of 100 mg/kg bw/d was established, based on a decrease in gravid uterine
weight at the top dose.

FETAL TOXICITY:
Treatment-related effects were limited to a decreasing trend in the average fetal body weight (-0, -7, and -15%), with
significant reductions at >= 100 mg/kg bw/d). 
[Note: In the 100-mg group, one animal was treated as an outlier because of comparatively high fetal weights (p. 15).
The reduction in fetal body weight reduction at this dose level became statistically significant after removal of this
animal from the study]

All other parameters failed to show any difference from control values:  Number of corpora lutea/dam ranged from 15.6 to 16.1 and largely corresponded the number of implantations
in all groups, with preimplantation losses from about 4 to 6.5% throughout. Mean percentage of resorptions ranged from
1.4 and 1.6 (control and low-dose group, resp.) to 3.0 and 4.1% in the mid- and high-dose group with no statistical
significance for the latter apparent increases.
Late fetal deaths were absent in all groups.
Sex ratios were not affected by exposure.

No statistical significant differences were observed in the incidences of fetal morphological anomalies, the overall
incidences were approximately 1.3 (control), 2.2, 0.6, and 1.3% for the respective groups. A NOAEL of 50 mg/kg bw/d was established, based on decreases in fetal body weight.

Applicant's summary and conclusion

Conclusions:

Fetal toxicity (decrease in fetal weight) was noted in rats at a dose (100 mg/kg bw/day) which was not evidently toxic to the dams.
There was no evidence of an increase in structural anomalies related to formamide at 50, 100, or 200 mg/kg bw.

Executive summary:

In a developmental toxicity study conducted similar to OECD guideline 414 and under GLP conditions, time-pregnant Sprague-Dawley (25 females/dose) were dosed by gavage with formamide (0, 50, 100 or 200 mg/kgbwandday; dose selection based on results of a range finding study) on GD 6 through 19. Maternal toxicity was low and limited to statistically significant body weight gain reduction during gestation (GD 6-19), reduced body weight on GD 18-20, and reduced gravid uterine weight at 200 mg/kgbwand day. The body weight corrected for the gravid uterus weight was not affected and comparable between all groups. Liver weight (absolute and relative) was unaffected by treatment with formamide.

The average male and female fetal weight was statistically significantly reduced at 100 and 200 mg/kgbwand day. The number of fetuses per litter and fetal viability were not affected. The sex distribution was not changed. The incidence of external, skeletal or visceral malformations and variations was not increased at any dose. In this study, the ratconceptuswas more sensitive than the adult to the adverse effects of formamide administered orally throughout the embryo/fetal period of gestation.

 

 

Overall, the maternal toxicity NOAEL was 100 mg/kg bw/day in this study, based on a decrease in gravid uterine weight at the top dose. The developmental NOAEL was 50 mg/kg bw/d was established, based on decreases in fetal body weight. Teratogenicity was not seen, the NOAEL was therefore 200 mg/kg bw/day (NTP, 1998).