Registration Dossier

Administrative data

Description of key information

No potassium formate repeated dose study is known to exist for any route of exposure, but read across to other formate salts can be made. Regarding the most relevant oral route, the systemic toxicity of potassium diformate was low in a subchronic study (NOAEL 3000 mg/kg bw/day). Taking formula weights and stoichiometry into account, the subchronic NOAEL was 3877 mg/kg bw/day for the systemic toxicity of sodium formate in the rat. There was no target organ except the stomach which showed local irritation. 

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Referenceopen allclose all

Endpoint:
chronic toxicity: oral
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
comparable to guideline study
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 453 (Combined Chronic Toxicity / Carcinogenicity Studies)
Deviations:
no
GLP compliance:
yes
Limit test:
no
Specific details on test material used for the study:
- Name of test material (as cited in study report): "Formi LHS-Super"
- Substance type: salt
- Physical state: powder
- Analytical purity: 98.44 and 99%.
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


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:
104 weeks
52 weeks: interim report
104 weeks: final report
Frequency of treatment:
7 days/week
Dose / conc.:
50 mg/kg bw/day (nominal)
Remarks:
Based on amount in the diet
Dose / conc.:
400 mg/kg bw/day (nominal)
Remarks:
Based on amount in the diet
Dose / conc.:
2 000 mg/kg bw/day (nominal)
Remarks:
Based on amount in the diet
No. of animals per sex per dose:
Main study: 50
Interim kill: 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
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
- 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.
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
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
no effects observed
Gross pathological findings:
effects observed, treatment-related
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Histopathological findings: neoplastic:
no effects observed
Other effects:
not specified
Details on results:
CLINICAL SIGNS AND MORTALITY
Clinical signs: There were no clinical signs related to treatment.
Mortalities: 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.
The distribution of deaths at the end of Week 52 is tabulated below.

==============================
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)
==============================

The distribution of deaths at the end of Week 104 is tabulated below.
==============================
Dose level Males Females
(mg/kg bw/d) [number of deaths (% survival)]
----------------------------------------------
0 8 (84) 11 (78)
50 12 (76) 9 (82)
400 11 (78) 13 (74)
2000 7 (86) 12 (76)
==============================
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, with a tendency of an approx. 5% reduction in the high dose 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. This was attributable to local irritation. The NOAEL was 50 mg/kg bw/day in teh 104-week study.

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 "Any other infromation 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.
Dose descriptor:
NOAEL
Remarks:
; systemic toxicity; potassium formate
Effect level:
2 585 other: mg/kg/day (calculated)
Sex:
male/female
Basis for effect level:
other: Read across from potassium diformate. Absence of systemic toxicity.
Dose descriptor:
NOAEL
Remarks:
; systemic toxicity; potassium diformate
Effect level:
2 000 mg/kg bw/day (actual dose received)
Sex:
male/female
Basis for effect level:
other: Absence of systemic toxicity or target organ.
Dose descriptor:
NOAEL
Remarks:
; local irritation toxicity; potassium diformate
Effect level:
400 mg/kg bw/day (actual dose received)
Sex:
male/female
Basis for effect level:
other: Changes in stomach at 2000 mg/kg bw/day: increased incidences of foveolar epithelium and sqamous cell hyperplasia.
Critical effects observed:
not specified

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
                     


Conclusions:
Local effects were seen in the stomach in both sexes at 2000 mg/kg bw/day. Systemic toxicity was not seen at any dose, including 2000 mg/kg bw/day, the highest dose tested. The NOAEL for systemic toxicity was therefore 2000 mg potassium diformate/kg bw/day in the rat, equivalent to 2585 mg potassium formate/kg bw/day.
Executive summary:

The repeated dose toxicity and oncogenicity of potassium diformate(1:2) was examined in a combined chronic toxicity and 104-week oral feed oncogenicity study in the rat similar to the OECD guideline 453 and under GLP conditions.

 

A read across from potassium diformate is justified because potassium diformate decomposes in aqueous solution into one molecule of each formate and formic acid, and the potassium ion. Thus, potassium diformate gives two formate anions on a molar basis. Local effects are attributable to the formic acid formed and can be neglected because these are not expected with neutral salts (sodium, potassium, ammonium, calcium formate). Read across can therefore be limited to systemic effects.

 

The oral dietary administration of potassium formate (1:2) in a combined chronic toxicity/carcinogenicity study (equivalent to OECD guideline No. 453 and under GLP) to male and female Wistar rats (50 animals/dose/sex) for 104 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 (lower by 27% in males and 19% in females; no effect at the low and intermediate dose levels) 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 (Covance, 2002).

Overall, the local toxicity NOAEL for 52 and 104 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. As no signs of systemic effects were noted, the NOAEL (rat, 104 week) for systemic toxicity is considered to be 2000 mg potassium diformate /kg bw/day.

Taking stoichiometry and formula weights into consideration, this is equivalent to 1385 mg formate anion/kg bw/day, or systemic toxicity NOAEL(rat, oral, 104-week) 2585 mg potassium formate/kg bw/day.

 

This study in the rat is acceptable and satisfies the guideline requirement for a chronic oral study (OECD 453).

Endpoint:
sub-chronic toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Justification of test substance: potassium diformate decomposes into one molecule of each formate and formic acid. Thus, potassium diformate gives two formate anions on a molar basis. Local effects of the formic acid formed can be neglected because these are not expected with neutral salts (sodium, potassium, ammonium, calcium formate). Read across can therefore be limited to systemic effects.
Justification for type of information:
Justification of test substance: potassium diformate decomposes into one molecule of each formate and formic acid. Thus, potassium diformate gives two formate anions on a molar basis. Local effects of the formic acid formed can be neglected because these are not expected with neutral salts (sodium, potassium, ammonium, calcium formate). Read across can therefore be limited to systemic effects.
Qualifier:
according to guideline
Guideline:
OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)
Deviations:
yes
Remarks:
; absorption of TS and  reversibility of effects  over a 4 week treatment-free period.
GLP compliance:
yes (incl. QA statement)
Limit test:
no
Specific details on test material used for the study:
- Name of test material (as cited in study report): Formi-LHS; Formi LHS-Super
- Molecular formula (if other than submission substance): C2H3O4 K
- Molecular weight (if other than submission substance): 130.14
- Substance type: double salt
- Physical state: white powder
- Analytical purity: not reported; information available at the sponsor
- Impurities (identity and concentrations):
- Storage condition of test material: in sealed container at room temperature (10-30°C) in the dark
Species:
rat
Strain:
other: Crl:CDBR
Sex:
male/female
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Age at study initiation: 6 weeks
- Weight at study initiation: males: 166 to 208 g; females; 136 to 173 g.
- Housing: groups of 5 rats per cage
- Diet: ad libitum
- Water: ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature (°C):  routinely 19 to 25°C
- Humidity (%): 40 to 70%
- Air changes (per hr): minimum 15/hour
- Photoperiod (hrs dark / hrs light): 12/12
Route of administration:
oral: feed
Vehicle:
unchanged (no vehicle)
Details on oral exposure:
- Dosing: test substance was mixed into the diet.
- Diet: ground SQC Rat and Mouse Maintenance Diet No. 1, free access to diet and to tap water.
- Stability of TS in diet: at least 2 weeks
- Replacement of diet: regularly within 2 weeks
- Dose levels:
- Main study: 0, 600, 1200, 3000 mg/kg bw/day.
- Recovery study: 0 and 3000 mg/kg bw/day.
- Absorption study: 3000 mg/kg bw/day.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
The enzymatic method "Formic Acid" by Boehringen Mannheim was used
Duration of treatment / exposure:
13 weeks
Frequency of treatment:
7 days/week
Dose / conc.:
600 mg/kg bw/day (nominal)
Dose / conc.:
1 200 mg/kg bw/day (nominal)
Dose / conc.:
3 000 mg/kg bw/day (nominal)
No. of animals per sex per dose:
Main study: 10 per sex and dose group.
Recovery study: 10 per sex of the control and the high dose groups.
Absorption study: 10 per sex of the high dose group.
Control animals:
yes, concurrent no treatment
Details on study design:
Post-exposure period: Satellite group: 4 weeks
Positive control:
Not required
Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
Mortality, clinical signs: observed at least daily.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: weekly

BODY WEIGHT: Yes
- Time schedule for examinations: recorded before first treatment, at weekly intervals 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
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: Yes

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: before treatment and in week 12
- Dose groups that were examined: all main-study animals were examined before treatment and  all control and high dose animals in week 12.

HAEMATOLOGY: Yes
- Time schedule for collection of blood: week 13 in main study, week 17 in recovery study
- How many animals: all animals

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: week 13 in main study, week 17 in recovery study
- How many animals: week 13 in main study, week 17 in recovery study

URINALYSIS: Yes
- Time schedule for collection of urine: week 13 in main study, week 17 in recovery study
- Metabolism cages used for collection of urine: yes


OTHER:

ABSORPTION
0.5 ml blood samples were taken on Day 1 of feeding and during weeks 13  and 17 by tail vein  puncture. Plasma was separated and stored at below  -10°C until analysis of formate using the Formic Acid method by  Boehringer Mannheim.

GROSS PATHOLOGY

- All animals except those of the absorption study  were subjected to terminal necropsy after sacrifice. 
- Organ weights: adrenals, kidneys, liver, testes and epididymides were  weighed before fixation.

HISTOPATHOLOGY
Histopathology: samples of the following tissues were fixed in 10%  buffered formalin. Eyes were fixed in Davidson's fluid.

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, mammary  (females)#, mandibular lymph nodes, mesenteric lymph nodes, muscle  quadriceps#, 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 an  parathyroids, tongue#, urinary bladder, uterus, nasal turbinates#*,  nasopharynx#*, vagina#, Zymbal glands*#.

# = tissue retained in fixative but not examined. * = retained in situ with the head

All organs and tissues in the control and high dose group animals were  histopathologically examined following hematoxylin and eosin staining.  Additionally, kidneys, lungs and gross lesions from the intermediate  groups were examined. Following observations in the stomachs of high dose animals, the stomachs  of the low and intermediate dose group animals were also examined,  together with the stomachs from the animals at the end of the recovery  period.

Sacrifice and pathology:
GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes
Other examinations:
Absorption and recovery within 4 weeks
Statistics:
Body weight gains, necropsy body weight, hematology and clinical  chemistry 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. Organ weights were analyzed using ANCOVA and Dunnett's test. 
All recovery study data were analyzed using ANCOVA.
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:
effects observed, treatment-related
Clinical biochemistry findings:
effects observed, treatment-related
Urinalysis findings:
effects observed, treatment-related
Behaviour (functional findings):
not examined
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
effects observed, treatment-related
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Histopathological findings: neoplastic:
not specified
Details on results:
CLINICAL SIGNS AND MORTALITY
There were no treatment-related clinical observations or mortalities. Of the 3 mortalities observed (2 controls, 1 high dose female), necropsy  confirmed that all were associated with the orbital sinus blood sampling.

BODY WEIGHT AND WEIGHT GAIN
In males, there was a significant and dose-related reduction of body  weight gain. The overall difference from the controls (Weeks 0-13) was  statistically significant in all three groups (p<0.05, <0.01, and <0.001  in the low, intermediate, and high dose, resp.). In females, body weight gain was also reduced. Significance  was gained  only in the high dose group (p<0.01). 

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study)
A slight dose-related reduction of food intake was noted in all male  groups. In females, a reduction was seen only in the high dose group. No  level of statistical significance was reached in any group. In the treatment-free recovery groups food intake was comparable to the  control rats.
For details of resulting doses see "Remarks on results". The authors argued that reduced body weight gain and food intake were probabl relate to reduced palability of the test diets.

OPHTHALMOSCOPIC EXAMINATION
No treatment related effects noted.

HAEMATOLOGY
There were small but statistically significant differences from the  controls (cf. table in "Remarks on results"). Clotting times were unchanged. Fluctuations in  white blood cell counts were noted for both sexes in all groups with no  clear dose-relation or significant trends. Observed changes were not regarded to be of biological or toxicological relevance.

CLINICAL CHEMISTRY
There were small but statistically significant differences from the  controls  (cf. table in "Remarks on results"). Clotting times were unchanged. Fluctuations in  white blood cell counts were noted for both sexes in all groups with no  clear dose-relation or significant trends. Observed changes were not regarded to be of biological or toxicological relevance.

URINALYSIS
Urinary parameters were similar to the controls in all groups except pH.  There was a trend towards an increased urinary pH (pH 8 or 9) in the  intermediate and high dose groups of both sexes at the end of the  treatment period. 

After the 4-wk treatment-free period the majority of the high dose rats  had a urine pH of 6.0 or 7.0.


ORGAN WEIGHTS
At the end of the treatment period, group mean adjusted kidney, liver,  testes and epididymides weights in males were similar to the controls, as  were the mean weights of kidneys and liver in females. Reduced adrenal  weights compared to controls were noted in males (not significant) and in  females (p<0.05).

At the end of the treatment-free period, the mean liver weight of the  high dose males was slightly higher (p<0.01) than in controls.

GROSS PATHOLOGY
No remarkable findings, except thickening of the stomach, usually  involving the limiting ridge, at the end of the 13-week treatment period.  The effect was more pronounced in males, probably due to the higher  concentration of the TS in the diet (cf. table in "Remarks on results").

The effect subsided within the 4-week recovery period.


HISTOPATHOLOGY: NON-NEOPLASTIC
There was no other finding than a dose-related increase in the severity  and incidence of squamous cell hyperplasia in the stomach. No squamous  cell hyperplasia was noted in any of the male and female controls. The  histopathological finding correlated with the thick stomach findings  during necropsy.

The effect was largely reversible within the 4-week treatment-free period.


OTHER FINDINGS

Absorption study
Formate plasma levels following 3000 mg/kg bw/day were below the LOD  (Level of Detection, i.e. 62.54 µg/ml) in all but few animals on Day 1.  In Week 13, mean plasma levels were increased and slightly above the LOD  in animals from both sexes in the early morning, consistent with the  nocturnal feeding habit, but decreased within few hours to below the LOD. 

In Week 17, formate levels were below  the LOD at the end of the 4-week  recovery period.  Thus, there was no accumulation of formate detectable in plasma over  time. 

======================================================
Examination      LOD          Males         Females              
at (time) (µg/ml)       (µg/ml)        (µg/ml) 
--------------------------------------------------------------------------------              
 62.54 
Day 1          
18:00 h                     < LOD           < LOD     
24:00 h                max. 88.3       
Day 2 
06:00 h                max. 114.4
15:00 h                    < LOD           < LOD 

Week 13 18:00 h                    < LOD           < LOD 
next day, 06:00 h      mean: 158         mean: 96.6
next day, 15:00 h          < LOD          < LOD

End of 4-week recovery period            < LOD           < LOD 
======================================================
Dose descriptor:
NOAEL
Remarks:
systemic toxicity; potassium formate
Effect level:
3 877 other: mg/kg/day (calculated)
Sex:
male/female
Basis for effect level:
other: Read across from potassium diformate (1:2). No systemic toxicity or target organ
Dose descriptor:
NOAEL
Remarks:
systemic toxicity; potassium diformate
Effect level:
3 000 mg/kg bw/day (actual dose received)
Sex:
male/female
Basis for effect level:
other: No systemic toxicity or target organ
Dose descriptor:
NOAEL
Remarks:
local irritation; potassium diformate
Effect level:
< 600 mg/kg bw/day (actual dose received)
Sex:
male/female
Basis for effect level:
other: Local irritation. Squamous cell hyperplasia in the forestomach of male and female rats seen at all tested dose levels.
Critical effects observed:
not specified


Consumption of test substance:
The consumption of test substance was close to the nominal dose levels.

Dose group

Nominal dose

(mg/kg/day

Males

Females

Low

600

591

589

Intermediate

1200

1177

1178

High

3000

2879

2951

 


Hematology:

At Week 13: There were small but statistically significant differences from the controls (cf. table). Clotting times were unchanged.

Fluctuations in white blood cell counts were noted for both sexes in all groups with no clear dose-relation or significant trends.

 

Males

Females

 

Low

Intermediate

High

Low

Intermediate

High

RBC

 

 

Incr*

 

 

 

MCV

 

 

Decr***

 

Decr*

Decr***

MCH

 

 

Decr**

 

 

Decr*

MCHC

 

 

 

 

 

Incr**

Platelet

 

 

Incr***

 

 

 

WBC

 

 

Incr**

 

 

 


Levels of statistical significance:
 * = p<0.05; ** = p<0.01; *** = p<0.001


RBC
   = red blood cell count                         MCV   = mean cell volume
MCH
   = mean cell hemoglobin                   MCHC = mean cell hemoglobin concentration
WBC
  = white blood cell count                     

Incr      = increase                                           Decr    = decrease


At Week 17: At the end of the 4-week recovery significant changes were only noted in females as tabulated below.

 

 

Males

Females

 

Low

Intermediate

High

Low

Intermediate

High

Hb

 

 

 

 

 

Incr*

RBC

 

 

 

 

 

Incr*

HK

 

 

 

 

 

Incr*

 

Hb      = hemoglobin             HK = hematocrit

Clinical chemistry:
Isolated fluctuations were noted among all groups without a clear trend. Statistically significant findings are listed below.

At week 13:

 

 

Males

Females

 

Low

Intermediate

High

Low

Intermediate

High

AST

 

 

Incrtrend

 

 

 

AP

 

 

Incrtrend

 

 

 

Total bilirubin

 

 

 

 

 

Decr*

Total protein

 

 

 

 

 

Decr*

 

 

 

 

 

 

 

K

 

 

Decr***

 

 

 

Ca

 

 

 

 

 

Decr*

 

 

 

 

 

 

 

Creatinine

 

 

Decr***

Incr.*

 

Decr*

Urea

 

 

 

Incr.*

Incr.*

 

Total cholesterol

 

 

 

Incr.*

Incr.*

 

 

 

 

 

 

 

 

Globulin

 

 

 

 

 

Decr*

Albumin/globulin ratio

 

 

 

 

 

Decr*


Levels of statistical significance:        * = p<0.05;     ** = p<0.01;     *** = p<0.001
AST
                = aspartate aminotransferase
AP
                 = alkaline phosphatase
Tot
bilirub       = total bilirubin
A/G ratio
        = albumin/globulinratio

At Week 17 

At the end of the 4-week recovery significant changes were as tabulated below.

 

 

Males

Females

 

Low

Intermediate

High

Low

Intermediate

High

AST

 

 

Incr**

 

 

 

AP

 

 

Incr***

 

 

Incr**

 

 

 

 

 

 

 

Glucose

 

 

Decr**

 

 

Decr**

 


Urinalysis:
Urinary parameters were similar to the controls in all groups except
pH. There was a trend towards an increased urinary pH (pH 8 or 9) in the intermediate and high dose groups of both sexes at the end of the treatment period. 

After the 4-wk treatment-free period the majority of the high dose rats had a urine pH of 6.0 or 7.0.

 

Necropsy
Table: local effects: incidences of thickening of the stomach

 

 

Males

Females

 

Low

Intermediate

High

Low

Intermediate

High

Week 13

1/10

3/10

7/10

0/10

2/10

5/10

 

 

 

 

 

 

 

Week 17

0/10

0/10

2/10

0/10

0/10

0/10

 

Organ weights
At the end of the treatment period, group mean adjusted kidney, liver, testes and epididymides weights in males were similar to the controls, as were the mean weights of kidneys and liver in females. Reduced adrenal weights compared to controls were noted in males (not significant) and in females (p<0.05).

At the end of the treatment-free period, the mean liver weight of
the high dose males was slightly higher (p<0.01) than in controls.


Histopathology


Table: Incidence of squamous cell hyperplasia in the forestomach (local effect)

 

 

Males

Females

 

Low

Intermediate

High

Low

Intermediate

High

Week 13

 

n

10

10

10

10

10

10

Grade 0

6

1

0

6

2

0

Grade 1

2

6

4

4

6

5

Grade 2

2

3

5

0

2

3

Grade 3

0

0

1

0

0

2

 

Week 17

 

n

 

 

10

 

 

10

Grade 0

 

 

6

 

 

7

Grade 1

 

 

4

 

 

3

Grade 2

 

 

0

 

 

 

Grade 3

 

 

0

 

 

0

 

 

Conclusions:
Local effects were seen in the stomach in both sexes in a dose-dependent manner at 1200 and at 3000 mg/kg bw/day. Clear systemic toxicity was not seen at any dose, including 3000 mg/kg bw/day, the highest dose tested. The NOAEL for systemic toxicity was therefore 3000 mg potassium diformate/kg bw/day in the rat, equivalent to 3877 mg potassium formate/kg bw/day.
Executive summary:

The repeated dose of potassium diformate(1:2) was examined in a subchronic rat study according to the OECD guideline 408 and under GLP conditions. The guideline requirements were exceeded in that an absorption study and a recovery study were also included.

 A read across from potassium diformate is justified because potassium diformate decomposes in aqueous solution into one molecule of each formate and formic acid, and the potassium ion. Thus, potassium diformate gives two formate anions on a molar basis. Local effects of the formic acid formed can be neglected because these are not expected with neutral salts (sodium, potassium, ammonium, calcium formate). Read across can therefore be limited to systemic effects.

 

In the 13-week oral fed study potassium diformate (1:2) was administered in the diet at dose levels of 0, 600, 1200, and 3000 mg/kg bw/day to 10 rats/sex/dose. The doses were selected based on the results of a 7 day range finding study. Additional animals were used in satellite studies, i.e. a 4-week recovery study (0 and 3000 mg/kg bw/day, 10 rats/sex/dose), and in an absorption study (3000 mg/kg bw/day, 10 rats/sex/dose).

 

In the absorption study, formate blood levels were below the level of detection (LOD; 62.54 µg/mL) in most instances. Slightly increased levels in the range 66 to 158 µg/mL were occasionally seen in some animals few hours after the nocturnal food uptake, but these declined to below the detection limit within few hours. Blood levels were also below the LOD at the end of the 4-week recovery period.

These findings indicate that formate is rapidly metabolised in the rat, and that there was no accumulation over the 13-week treatment period.

 

Main study: no mortality or clinical signs of toxicity were seen. Male body weight gain was significantly decreased in all treated groups, whereas in females body weight reduction gained a level of significance only in the high dose group animals. A slightly reduced food consumption was seen in groups with reduced body weights. Test substance consumption was close to the nominal doses, i.e. 0, 590, 1180, and 2880 (males) and 2950 (females) mg/kg bw/day, respectively. Reduced body weight gain and food consumption resulted possibly from a reduced palability of the diet, and from the local irritation.

 

There were no effects in ophthalmology. No clear effects were seen in hematology and clinical chemistry. Some parameters gained a level of statistical significance, but this was of no biological or toxicological relevance. Organ weights of male and female rats were similar to those of the controls.

 

Pathology revealed no remarkable finding except from local irritation, evidenced by the observation of a thickening of the limiting ridge in the stomach in all male groups and in the female high dose group at the end of the 13-week period. Histopathology revealed a dose-related increase in the incidence and severity of squamous cell hyperplasia in the forestomach of male and female rats. This effect was largely reversible in the 4-week recovery group.

 

Overall, there was no overt systemic toxicity or target organ in this study. A dose-related body weight decrease was seen in all treated males and in the high dose female group, possibly as a result of the reduced palability of the diet. The small but statistically significant changes in hematology and clinical chemistry parameters in the high dose animals were not of toxicological significance, due to the small changes and the lack of target organ toxicity.

A specific target organ was the stomach, based on local  irritation in the forestomach which caused a dose-related thickening of the stomach at all dose levels, and was confirmed to be squamous cell hyperplasia. This was considered to be a response to minor irritation by the test substance, rather than a toxic effect (Covance, 1998).

 

 

Conclusion:

Overall, dietary administration of potassium diformate (1:2) to rats at 600, 1200, and 3000 mg/kg bw and day for 13 weeks did not produce any overt systemic toxicity. Minor local irritation had occurred in the forestomach of both sexes, with effects being seen in the males at all dose levels. Recovery was not complete in all animals after the 4-week treatment-free period.

 

The authors did not derive NOAEL values, but they may be considered as follows:

 

 

Local irritation: NOAEL below 600 mg/kg bw/day, based on the irritation of the forestomach and the squamous cell hyperplasia seen at 600 mg/kg bw and day in both sexes.

Systemic toxicity: NOAEL(rat, 90 day study) 3000 mg Formi LHS/kg bw/day, as no adverse effect was seen at the highest dose tested. Taking stoichiometry and formula weights into consideration, this is equivalent to 2077 mg formate anion/kg bw/day, or 3877 mg potassium formate/kg bw/day.

 

This subchronic toxicity study in the rat is acceptable and satisfies the guideline requirement for a subchronic oral study (OECD 408).

 

Endpoint conclusion
Dose descriptor:
NOAEL
3 877 mg/kg bw/day
Study duration:
subchronic
Species:
rat

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

No repeated dose study on potassium formate was located, but the results from an analogue formate salt may be used as outlined below.

Subchronic oral feed rat study

The repeated dose potassium diformate(1:2) was examined in a subchronic rat study according to the OECD guideline 408 and under GLP conditions. The guideline requirements were exceeded in that an absorption study and a recovery study were also included.

A read across from potassium diformate is justified because potassium diformate decomposes in aqueous solution into one molecule of each formate and formic acid, and the potassium ion. Thus, potassium diformate gives two formate anions on a molar basis. Local effects of the formic acid formed can be neglected because these are not expected with neutral salts (sodium, potassium, ammonium, calcium formate). Read across can therefore be limited to systemic effects.

 

In the 13-week oral fed study potassium diformate (1:2) was administered in the diet at dose levels of 0, 600, 1200, and 3000 mg/kg bw/day to 10 rats/sex/dose. The doses were selected based on the results of a 7 day range finding study. Additional animals were used in satellite studies, i.e. a 4-week recovery study (0 and 3000 mg/kg bw/day, 10 rats/sex/dose), and in an absorption study (3000 mg/kg bw/day, 10 rats/sex/dose).

 

In the absorption study, formate blood levels were below the level of detection (LOD; 62.54 µg/mL) in most instances. Slightly increased levels in the range 66 to 158 µg/mL were occasionally seen in some animals few hours after the nocturnal food uptake, but these declined to below the detection limit within few hours. Blood levels were also below the LOD at the end of the 4-week recovery period.

These findings indicate that formate is rapidly metabolised in the rat, and that there was no accumulation over the 13-week treatment period.

 

Main study: no mortality or clinical signs of toxicity were seen. Male body weight gain was significantly decreased in all treated groups, whereas in females body weight reduction gained a level of significance only in the high dose group animals. A slightly reduced food consumption was seen groups with reduced body weights. Test substance consumption was close to the nominal doses, i.e. 0, 590, 1180, and 2880 (males) and 2950 (females) mg/kg bw/day, respectively. Reduced body weight gain and food consumption resulted possibly from a reduced palability of the diet, and from the local irritation.

 

There were no effects in ophthalmology. No clear effects were seen in hematology and clinical chemistry. Some parameters gained a level of statistical significance, but this was of no biological or toxicological relevance. Organ weights of male and female rats were similar to those of the controls.

 

Pathology revealed no remarkable finding except from local irritation, evidenced by the observation of a thickening of the limiting ridge in the stomach in all male groups and in the female high dose group at the end of the 13-week period. Histopathology revealed a dose-related increase in the incidence and severity of squamous cell hyperplasia ain the forestomach of male and female rats. This effect was largely reversible in the 4-week recovery group.

 

Overall, there was no overt systemic toxicity or target organ in this study. A dose-related body weight decrease was seen in all treated males and in the high dose female group, possibly as a result of the reduced palability of the diet. The small but statistically significant changes in hematology and clinical chemistry parameters in the high dose animals were not of toxicological significance, due to the small changes and the lack of target organ toxicity.

A specific target organ was the stomach, based on local  irritation in the forestomach which caused a dose-related thickening of the stomach at all dose levels, and was confirmed to be squamous cell hyperplasia. This was considered to be a response to minor irritation by the test substance, rather than a toxic effect (Covance, 1998).

 

Conclusion:

Overall, dietary administration of potassium diformate (1:2) to rats at 600, 1200, and 3000 mg/kg bw and day for 13 weeks did not produce any overt systemic toxicity. Minor local irritation had occurred in the forestomach of both sexes, with effects being seen in the males at all dose levels. Recovery was not complete in all animals after the 4-week treatment-free period.

NOAEL values:

The authors did not derive NOAEL values, but they may be considered as follows:

Local irritation: NOAEL below 600 mg/kg bw/day, based on the irritation of the forestomach and the squamous cell hyperplasia seen at 600 mg/kg bw and day in both sexes.

Systemic toxicity: NOAEL(rat, 90 day study) 3000 mg Formi LHS/kg bw/day, as no adverse effect was seen at the highest dose tested. Taking stoichiometry and formula weights into consideration, this is equivalent to 2077 mg formate anion/kg bw/day, or 3877 mg potassium formate/kg bw/day.

 

This subchronic toxicity study in the rat is acceptable and satisfies the guideline requirement for a subchronic oral study (OECD 408).

 

Chronic oral feed rat study

The repeated dose toxicity and oncogenicity of potassium diformate(1:2) was examined in a combined chronic toxicity and 104-week oral feed oncogenicity study in the rat similar to the OECD guideline 453 and under GLP conditions.

 

A read across from potassium diformate is justified because potassium diformate decomposes in aqueous solution into one molecule of each formate and formic acid, and the potassium ion. Thus, potassium diformate gives two formate anions on a molar basis. Local effects are attributable to the formic acid formed and can be neglected because these are not expected with neutral salts (sodium, potassium, ammonium, calcium formate). Read across can therefore be limited to systemic effects.

 

The oral dietary administration of potassium formate (1:2) in a combined chronic toxicity/carcinogenicity study (equivalent to OECD guideline No. 453 and under GLP) to male and female Wistar rats (50 animals/dose/sex) for 104 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 (lower by 27% in males and 19% in females; no effect at the low and intermediate dose levels) 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 (Covance, 2002).

Overall, the local toxicity NOAEL for 52 and 104 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. As no signs of systemic effects were noted, the NOAEL (rat, 104 week) for systemic toxicity is considered to be 2000 mg potassium diformate /kg bw/day.

Taking stoichiometry and formula weights into consideration, this is equivalent to 1385 mg formate anion/kg bw/day, or systemic toxicity NOAEL(rat, oral, 104-week) 2585 mg potassium formate/kg bw/day. No target organ was identified.

 

This study in the rat is acceptable and satisfies the guideline requirement for a chronic oral study (OECD 453).



Repeated dose toxicity: via oral route - systemic effects (target organ) digestive: stomach

Justification for classification or non-classification

No classification. Criteria of regulations 67/548/EC and 1272/2008/EC are not met.