Formamide

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Formamide was not mutagenic in 3 independent valid Ames Tests (S. typhimurium TA100, TA97, TA 98, TA1535, and TA1537; E. coli WP uvrA pKM101) both with and without metabolic activation up to 10000 µg/plate (Key 1 study).

There are different results from in vitro cell transformation assays. Formamide was negative in a cell transformation assay using rat embryo cells at test concentrations of 0.01 to 100 µg/mL (Key 3 study) whereas a statistically significant and dose-related increase in the number of transformed colonies was obtained with metabolically competent Syrian hamster embryo cells which were exposed to formamide in the range 200 to 550 µg/mL (Key 2 study).

Further tests were not considered reliable.

Based on the available in vitro studies while also considering the availabe in vivo studies, the registered substance formamide is not considered to be mutagenic or clastogenic.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Genetic toxicity in vivo

Description of key information

Formamide was negative in the mouse peripheral blood micronucleus assay (Key 1 study).

In another in vivo study, formamide was tested positive at high dose levels (225 – 1800 mg/kg bw, i.p. injection) for its potential to induce chromosome damage in vivo in a Mouse Micronucleus according to OECD test guideline No. 474 and GLP conditions (Key 2 study). The registrants consider that this positive result is a result of secondary toxicity but does not indicate a genotoxic mode of action, due to the effect of formamide on the hematopoietic system, which was also observed in several repeated dose toxicity studies (e.g. 2- week range finder and 90-d gavage study in rat and mouse: see key study and the range finding studies under "repeated dose toxicity: oral" and 28-d gavage study in rat).

Formamide was tested negative in a Rodent Dominant Lethal test similar to OECD test guideline No. 478 assay (Key 3 study).

Furthermore, Formamide was mot mutagenic in two independent Sex-linked Recessive Lethal Test in Drosophila melanogaster conducted similar to OECD guideline No. 477 (Key 4 and 5 studies).

Further tests were not considered reliable.

Based on the available studies, the registered substance formamide is not considered to be mutagenic or clastogenic in vivo.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (positive)

Mode of Action Analysis / Human Relevance Framework

Based on the available studies, the registered substance formamide is not considered to be mutagenic or clastogenic.

Additional information

Genetic toxicity in vitro

Bacterial cell mutagenicity

Formamide was tested for its genotoxic potential in three independent bacterial test systems using S. typhimurium and E.coli.

Formamide was negative in two valid Ames Tests usingS. typhimurium strains TA97, TA 98, TA1535, and TA1537, both with and without metabolic activation. The doses ranged from 0 to 10,000 µg/plate. Bacteriotoxicity was not observed. The test was conducted by the NTP, and the test conditions were closely related to OECD TG 471. Positive and negative controls were included and performed as expected(Mortelmans et al., 1986).

Formamide was also negative in a test usingE. coliWP uvrA pK101, with and without metabolic activation. The doses ranged from 0 to 10,000 µg/plate. Bacteriotoxicity was not observed. The test was conducted by the NTP, and the test conditions were closely related to OECD TG 472. Positive and negative controls were included and performed as expected (NTP, 2008).

Mammalian cell mutagenicity

No valid in-vitro test was located, however, valid in-vivo data are available.

Mammalian cell cytogenetic studies

Formamide (300 -550 µg/mL) was tested in a Syrian hamster embryo cell (SHE) transformation test according to a draft OECD test guideline which is essentially equivalent to the EU Method B.21 (In Vitro Mammalian Cell Transformation Test) in the dose range 300 – 550 µg/mL. Formamide caused a statistically significant, biologically relevant and dose-dependent increase in morphologically transformed colonies after an exposure time of 7 days in two independent experiments in the dose range 350 - 450 µg/mL in the first experiment, and in the range 350 - 450 µg/mL in the second experiment. The morphological transformation frequencies were up to 1.08 and 1.38%, respectively. The negative controls gave transformation frequencies within the range expected for the SHE cell line. The positive control substance (benzo(a)pyrene) led to the expected increase in morphologically transformed colonies (BASF, 2003).

Formamide (0.01, 0.1, 0.5, 1, 10 und 100 µg/mL) did not induce cell transformation when it was tested in a valid pre-guideline cell transformation study using rat embryo cells in two independent experiments (Freeman, 1973).

Thus, there are different results from in vitro cell transformation assays. Formamide was negative in a cell transformation assay using rat embryo cells at test concentrations of 0.01 to 100 µg/mL whereas a statistically significant and dose-related increase in the number of transformed colonies was obtained with metabolically competent Syrian hamster embryo cells which were exposed to formamide in the range 200 to 550 µg/mL.

Genetic toxicity in vivo

Mouse micronucleus test

Formamide was negative in the mouse peripheral blood micronucleus assay when blood cells from male and female mice (10/dose/sex) of the 13-week repeated dose toxicity tests were examined at termination of the subchronic oral gavage study (NTP, 2008). The method is valid and comparable to OECD TG 474. The dose levels used were 0, 10, 20, 40, 80, and 160 mg/kg bw/day. The incidence of polychromatic erythrocytes was not significantly changed in males or females at any dose level, indicating the absence of formamide-induced bone marrow toxicity (NTP, 2008).

In another study, formamide had been tested at high dose levels (225 – 1800 mg/kg bw, i.p. injection) for its potential to induce chromosome damage in vivo in a Mouse Micronucleus study that was conducted according to OECD test guideline No. 474 and under GLP conditions. Five male NMRI mice were used in three individual experiments. At high doses (900 -1800 mg/kg bw) a statistically significant increase of micronuclei was detected. At these dose levels evident toxicity and inhibition of erythropoiesis was also seen. There was no increase of cells with large micronuclei.

Therefore, formamide is considered to be a clastogenic agent in vivo in bone marrow cells in mice under the experimental conditions of this study. The observation of chromosomal fragmentation (small micronuclei) in the absence of large micronuclei suggests that formamide under test condition induces chromosome-breakage rather than aneuploidy (i.e. spindle poison effect) (BASF, 2001).

Rodent Dominant Lethal test

Formamide (412 mg/kg bw) was examined in a pre-guideline study similar to an OECD test guideline No. 478 assay (Genetic Toxicology: Rodent Dominant Lethal Test). 20 male NMRI mice were used in the treatment group and in both the negative and positive control groups. Each male was mated with 3 females in a total of 8 mating cycles, i.e. in total 480 females were used per male test group. The uterine contents were examined on day 18 post mating.

There were no signs of toxicity in treated males or findings at the terminal necropsy. There was no effect of formamide on conception, average number of implants, or percentage of dead implants noted in the females from all 8 mating weeks, whereas the positive control showed expected effects. Thus, formamide was negative as there was no evidence of a mutagenic effect of formamide at any stage of germ cell maturation (BASF, 1974).

Sex-linked Recessive Lethal Test in Drosophila melanogaster

In a study that was conducted similar to OECD guideline No. 477, adult Drosophila melanogaster Canton-S males were fed formamide test solutions (0, 2500, and 5000ppm; in 5% sucrose) for 72 hours. The solutions were renewed at 24 and 48 hours. Each surviving male was mated to Basc females for a total of 3 broods. The percentage of lethal mutations was 0.15% (7/4576) and 0% (0/691) in the 2500 and 5000 ppm group, respectively, compared to 0.11% (9/7935) and 0.12% (1/847) in the corresponding control groups. Formamide did not significantly increase SLRL mutations (p=0.377), and was therefore not mutagenic in this test (NTP, 2008).

As no response was obtained in the above SLRL feeding experiment, a second experiment was conducted. Adult Drosophila melanogaster Canton-S males were injected with 0.7% sodium chloride solution containing the test substance at 21570 ppm (n= 5,166 animals). Controls (n= 7,349) received saline only. At 24 h post injection, toxicity was noted and survivors were mated. Each surviving male was mated to Basc females for a total of 3 broods. The percentage of lethal mutations was 0.04% (2/5166) in the formamide treatment group, compared to 0.11% (8/7349) in the vehicle control group. Formamide did not increase the number of mutations and was therefore not mutagenic in the injection experiment. The negative result of the feeding experiment was confirmed (NTP, 2008). Thus, formamide was not genotoxic in germ cells of male Drosophila melanogaster in this study (NTP, 2008).

Short description of key information:
Formamide was not mutagenic in 3 independent valid Ames Tests (S. typhimurium TA100, TA97, TA 98, TA1535, and TA1537; E. coli WP uvrA pKM101) both with and without metabolic activation up to 10000 µg/plate.
There are different results from in vitro cell transformation assays. Formamide was negative in a cell transformation assay using rat embryo cells at test concentrations of 0.01 to 100 µg/mL whereas a statistically significant and dose-related increase in the number of transformed colonies was obtained with metabolically competent Syrian hamster embryo cells which were exposed to formamide in the range 200 to 550 µg/mL.
The incidence of micronuclei was not increased in mice treated with formamide in a 90-day study (comparable to OECD TG 474); at very high doses following i.p. injection clastogenicity was seen in an OECD TG 474 study.

).The registrants consider that this positive result is a result of secondary toxicity but does not indicate a genotoxic mode of action, due to the effect of formamide on the hematopoietic system, which was also observed in several repeated dose toxicity studies (e.g. 2- week range finder and 90-d gavage study in rat and mouse: NTP 2008; 28-d gavage study in rat: BASF 1978). Therefore, the registered substance is classified with STOT RE 2 (target organ: blood, oral).
No male germ cell mutation was seen in a Rodent Dominat Lethal test using mice (OECD TG 478) and in Drosophila melanogaster (OECD TG 477).

Conclusion: Based on the available studies, the registered substance formamide is not considered to be mutagenic or clastogenic.

Justification for classification or non-classification

Considering the available studies, the registered substance is not classified for genetic toxicity according Regulation (EC) No 1272/2008 (CLP).