Formic acid

Repeated dose toxicity: oral

Administrative data

Endpoint:

chronic toxicity: oral

Type of information:

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

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Comparable to GLP guideline study.

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

1999

Report date:

1999

Reference 2

Reference Type:

study report

Title:

Unnamed

Year:

2002

Report date:

2002

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 453 (Combined Chronic Toxicity / Carcinogenicity Studies)

Deviations:

no

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Potassium formate(1:2)

EC Number:

243-934-6

EC Name:

Potassium formate(1:2)

Cas Number:

20642-05-1

Molecular formula:

CH2O2.1/2K

IUPAC Name:

potassium formate(1:2)

Test material form:

solid

Details on test material:

- Name of test material (as cited in study report): "Formi LHS-Super"
- Substance type: salt
- Physical state: powder
- Analytical purity: 98.44 and 99%.

Test animals

Species:

rat

Strain:

other: Crl:HanWist(Glx:BRL)BR

Sex:

male/female

Details on test animals or test system and environmental conditions:

Test animals
- Species: rat.
- Strain: Crl:HanWist(Glx:BRL)BR.
- Sex: male and female.
- Age: approx. 8 weeks at commencement of the experiment.
- Body weight: males: 186 to 275 g; females: 132 to 200 g.
- Number of animals: 20 per sex and dose group in the chronic toxicity study
- Housing: in groups of 5, in stainless steel mesh cages.
- Environment: routinely 19 to 25°C, relative humidity 40 to 70%, 
- Air changes: 15 air  changes/hour. 
- Photo period: 12-h light/dark cycle.

Treatment
- Dosing:  TS mixed into the diet.
- Diet: ground diet SQC Rat and Mouse Maintenance Diet No. 1, free access  to feed and tap water.
- Stability of TS in diet: examined; at least 7 days. 
- Dose levels: 0, 50, 400, 2000 mg/kg bw/day.
- Dose selection: based on results from preliminary studies including a  13-week study in rats

Administration / exposure

Route of administration:

oral: feed

Vehicle:

other: feed

Details on oral exposure:

PREPARATION OF DOSING FEED:


DIET PREPARATION
- Rate of preparation of diet (frequency): weekly
- Mixing appropriate amounts with (Type of food): ground diet; mixed with TS in a mortar to give a premix, to which further diet was added as required and mixed in a blendor for five minutes.
- Storage temperature of food: at room temperatur ein sealed containers

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Analysis was performed in week 1, and at 12 or 13 week intervals thereafter

Duration of treatment / exposure:

52 weeks

Frequency of treatment:

7 days/week

Doses / concentrations

Remarks:

Doses / Concentrations:
0, 50, 400, and 2000 mg/kg bw/day
Basis:
actual ingested

No. of animals per sex per dose:

20

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: based on the results of a 13-week study

Positive control:

not required

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Mortality: recorded twice daily. Clinical signs: observed daily.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Detailed physical examination of each animal was performed at weekly intervals.


BODY WEIGHT: Yes
- Time schedule for examinations: recorded before first treatment, at weekly intervals for 16 weeks, once every 4 weeks thereafter and before necropsy.


FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Food consumption for each animal group determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes. Determined weekly for the first 16 weeks, then one week in every 4 weeks thereafter.
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: Yes

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: investigation in all animals pre-treatment and in all control and high dose animals in Week 50
- Dose groups that were examined: investigation in all animals pre-treatment and in all control and high dose animals in Week 50


HAEMATOLOGY: Yes
- Time schedule for collection of blood: weeks 26, 52 and 103
- Method: 0.5 ml samples were withdrawn from 10 animals per group and sex in Weeks 26 and 52. Blood was taken from the lateral caudal vein of fasted animals and from decedents where possible.
- Anaesthetic used for blood collection: No data
- Animals fasted: Yes
- How many animals: 10/sex/dose; all at termination
- Parameters examined: hemoglobin concentration, packed cell volume, mean cell volume, mean cell hemoglobin concentration, red blood cell count, total and differential white blood cell count, mean cell hemoglobin, and platelet count was performed and clotting times were determined.


CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: weeks 26 and 52, and 103
- Animals fasted: Yes
- How many animals: 10/sex/dose; all at termination
- Parameters examined: aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, sodium, potassium, calcium, chloride, inorganic phosphorus, total protein, albumin, globulin, albumin/globulin ratio, total cholesterol, glucose, urea, total bilirubin, creatinine.


URINALYSIS: Yes / No / No data
- Time schedule for collection of urine: samples were collected from 10 animals per group and sex in Weeks 25, 51 and 102. Where possible, urine and blood samples were taken from the same animals.
- Metabolism cages used for collection of urine: Yes
- Animals fasted: Yes
- Parameters examined: microscopy of sediment, volume, specific gravity, urobilinogen. Semi-quantitatively: pH, protein, glucose, ketones, bilirubin, blood, reducing substances.


NEUROBEHAVIOURAL EXAMINATION: No


OTHER:

PATHOLOGY:
all animals killed at termination in Week 52 or found dead during the scheduled terminal necropsy period were considered to have completed the study, and any data collected was treated as such. All animals including decedents were necropsied. Animals were weighed and tissues were preserved:

------------------------------------------------------------
Adrenals#, aorta, brain#, cecum#, colon#, duodenum#, eyes#, femur with marrow and articular surface, gross lesions#, Harderian glands*, head, heart#, ileum#, jejunum#, kidneys#, lacrimal glands*, larynx, liver#, lungs with mainstem bronchi#, mammary (females)#, mandibular lymph nodes#, mesenteric lymph nodes#, muscle quadriceps, nasal turbinates*, nasopharynx*, esophagus#, optic nerves#, ovaries#, pancreas#, pituitary#, prostate#, rectum, salivary glands#, sciatic nerves#, seminal vesicles, skin#, spinal cord (cervical, lumbar, thoracic)#, spleen#, sternum with bone marrow#, stomach#, testes and epididymides#, thymus#, thyroids and parathyroids#, tissue masses#, tongue, trachea#, urinary bladder#, uterus#, vagina#, Zymbal glands*.
------------------------------------------------------------
(# = microscopically examined; * = retained in situ with the head)


HISTOPATHOLOGY:
Histopathology was performed on gross lesions, tissue masses and stomach from all animals and tissues denoted by (#) in the tissue list from control and high dose animals, and decedents from all groups.

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes

Statistics:

Data from treated animals were compared with control data. In-life data: body weight gains, organ weights, food consumption and hematology variables were analyzed using ANOVA, separately for each sex. Dunnett's multiple test was used for comparison between control and treated group. A regression test was performed to determine whether there was a linear relationship between increasing dose and response.

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Food efficiency:

not specified

Water consumption and compound intake (if drinking water study):

not specified

Ophthalmological findings:

no effects observed

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

no effects observed

Details on results:

CLINICAL SIGNS AND MORTALITY
Clinical signs: There were no clinical signs related to treatment.
Mortalities: The distribution of deaths at the end of Week 52 is tabulated below. There was no pattern to indicate that the test substance had any effect on survival. Also, the incidence and pattern of morbidity observed in this strain was not changed by the test substance.

==============================
Dose level Males Females
(mg/kg bw/d) [number of deaths (% survival)]
----------------------------------------------
0 1 (95) 2 (90)
50 0 (100) 0 (100)
400 1 (95) 3 (85)
2000 0 (100) 1 (95)
==============================

BODY WEIGHT AND WEIGHT GAIN
Body weight ands body weight gain for low and intermediate dose animals were comparable with that of the controls. High dose animals had significantly reduced body weights at week 52, and at week 104 (lower by 27% in males, lower by 19% in females; up to p
FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study)
Food consumption was comparable between all groups.


OPHTHALMOSCOPIC EXAMINATION
There was no effect on the eye noted.

HAEMATOLOGY
There was no consistent pattern of variation to indicate an effect of treatment.

CLINICAL CHEMISTRY
There was no consistent pattern of variation to indicate an effect of treatment.

URINALYSIS
There was no consistent pattern of variation to indicate an effect of treatment.

ORGAN WEIGHTS
There was no consistent pattern of variation to indicate an effect of treatment.

GROSS PATHOLOGY
The only treatment-related finding was an increase in the number of high dose animals with thick stomach when compared with the controls.

Group incidence of findings in the stomach, Week 52
======================================
Males Females
Group 1M 2M 3M 4M 1F 2F 3F 4F
mg/kg/day 0 50 400 2000 0 50 400 2000
---------------------------------------------------------
n 20 20 19 20 20 20 18 20

Thick 4 2 2 16 0 0 1 13
stomach
======================================
n = number of animals examined


HISTOPATHOLOGY:

NON-NEOPLASTIC
The spectrum of microscopic findings was generally consistent with that expected for rats of this strain.
Treatment-related changes were noted in the stomach and the salivary gland of high dose animals. For details see table under "Remarks on results".

In the stomach, basal cell hyperplasia was restricted to the squamous epithelium of the limiting ridge and appeared to correlate with the necropsy finding of thick stomach. Foveolar epithelial hyperplasia was seen in both high dose animal groups, as were slightly increased incidences of hyperkeratosis.
Acinar cell hypertrophy of the salivary gland was considered to be a minor cytological change and as a physiological response with no toxicological significance.
Increased incidences of pancreas lobular atrophy were noted in the high dose groups; however, the incidences were comparable between the controls and the high dose groups in the 104 Week study.

The incidence of non-neoplastic histopathology findings in other tissues was generally comparable with the control group and did not indicate a systemic target organ toxicity.

NEOPLASTIC LESIONS:
The spectrum of tumors was generally consistent with that expected in rats of this strain. There were no tumors of unusual nature or incidence indicative of specific target organ carcinogenicity in the stomach or any other tissue.

Effect levels

1

Dose descriptor:

NOAEL

Remarks:

; local and systemic

Effect level:

400 mg/kg bw/day (nominal)

Sex:

male/female

Basis for effect level:

other: absence of systemic and local adverse effects

2

Dose descriptor:

LOAEL

Remarks:

; local and systemic

Effect level:

2 000 mg/kg bw/day (actual dose received)

Sex:

male/female

Basis for effect level:

other: Statistically reduced body weight at 52 weeks. At 104 weeks, lowered by 27% (males) an d19% (females). Increased incidences of foveolar epithelium and sqaumous cell hyperplasia in the stomach.

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

Analysis of formulations: the target homogeneity of the test substance in the diet (85 to 115%) was sufficiently met (within +10 and -15% of nominal concentrations). Formulations were stable for up to 7 days at room temperature in the dark.

Test substance consumption:  
TS consumption for the first 52 weeks was generally close (within 1%) to the nominal target dose level:

 

Target dose (mg/kg bw/d)	Consumption of TS (mg/kg bw/d)
	males	females
50	50.1	50.2
400	401.1	402.1
2000	2013.3	2015.3

Histopathology:  

Group incidences of selected microscopic findings at Week 52

	Males				Females
Dose group (mg/kg bw/day)	0	50	400	2000	0	50	400	2000
Stomach         n	20	20	19	20	20	20	18	20
Basal/squamous cell hyperplasia	0	0	1	12	0	0	0	12
Foveolar epithelium hyperplasia	0	1	0	14	0	0	0	11
Erosion /ulcer	1	0	1	1	0	0	0	0
parakeratosis	1	0	1	2	0	0	0	0
Salivary gland    n	20	0	0	20	20	0	0	20
Acinar cell hypertrophy	0			7	0			3
Pancreas        n	20	0	0	20	20	0	0	20
Lobular atrophy	5			10	0			2

n= number of animals examined
                     

Applicant's summary and conclusion

Executive summary:

The oral administration of potassium formate (1:2) in a combined chronic toxicity/carcinogenicity study (equivalent to OECD guideline No. 453 and under GLP) for 52 weeks to rats at dose levels of 50, 400, and 2000 mg/kg bw/day was well tolerated without effects on clinical condition or survival. Treatment related findings were noted at 2000 mg/kg bw/day and included a statistically significant depression of body weight gain and, at terminal kill, a thickening of the stomach confirmed as basal cell hyperplasia or foveolar epithelium hyperplasia in the majority of the high dose animals. These changes were less pronounced than in a previous 90-day rat study. There was no evidence of systemic target organ toxicity due to test substance administration, including the eyes.

The spectrum of tumors was generally consistent with that expected in rats of this strain. There were no tumors of unusual nature or incidence indicative of specific target organ carcinogenicity in the stomach or any other tissue.

 

The local and the systemic toxicity NOAEL for 52 weeks of treatment was considered to be 400 mg potassium diformate/kg bw/day, based on the local effects in the stomach and reduced body weight of the high dose rats.