Ferric ammonium citrate

Carcinogenicity

Description of key information

No data for carcinogenicity is available for the reaction mass of ammonium iron (III) citrate and ammonium sulfate, however a combined chronic toxicity/carcinogenicity study was available for its constiuent ammonium sulfate, which has been included for completeness (Ota et al., 2006).

A reliable study, conducted according to a protocol equivalent to current guideline but not compliant with GLP  found no carcinogenic potential of ammonium sulfate in a 2 year rat study (Ota et al., 2006).

Key value for chemical safety assessment

Carcinogenicity: via oral route

Link to relevant study records

Reference

Endpoint:

carcinogenicity: oral

Type of information:

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

Adequacy of study:

key study

Study period:

2006

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The study was conducted according to a test protocol equivalent to current guideline, but not in compliance with GLP.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 451 (Carcinogenicity Studies)

GLP compliance:

not specified

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Japan
- Age at study initiation: 5 weeks
- Housing: 3/4 rats per plastic cage
- Acclimation period: 1 week

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 24 +/- 1
- Humidity (%): 55 +/- 5
- Air changes (per hr): 18
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Details on exposure:

PREPARATION OF DOSING SOLUTIONS: Ammonium sulfate was mixed at concentration of 0, 0.1, 0.6, 1.5 and 3% into powdered basal diet and then pelleted (chronic toxicity study). Carcinogenicity study doses of 0%, 1.5% and 3% were used.

Analytical verification of doses or concentrations:

not specified

Details on analytical verification of doses or concentrations:

Recapture rates for ammonium sulfate from the admixed diet at each concetration level were confirmed to be 95.4-98.7%. Stability of ammonium sulfate in the solid pellet diet was evaluated and no decomposition was confirmed after storage under refrigeration or at room temperature for 2 weeks.

Duration of treatment / exposure:

104 weeks

Frequency of treatment:

No data available.

Post exposure period:

No data available.

Remarks:

Doses / Concentrations:
0, 1.5, 3%
Basis:
nominal in diet

No. of animals per sex per dose:

50 animals/sex/dose

Control animals:

yes

Details on study design:

- Dose selection rationale: A chronic (52 week) toxicity study was conducted before carcinogenicity study.

Positive control:

No data available.

Observations and examinations performed and frequency:

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Daily

BODY WEIGHT: Yes
- Time schedule for examinations: Every two weeks until week 10 and every 5 weeks thereafter.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes, every two weeks until week 10 and every 5 weeks thereafter.
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: Yes


HAEMATOLOGY: Yes
- Parameters checked: red blood cell count, haemoglobin concentration, hematocrit, mean corpuscular volume, mean corpuscular haemoglobin concentration, platelet count, white blood cell count, differential leukocyte and reticulocyte count.

CLINICAL CHEMISTRY: Yes
- Parameters checked: total protein, albumin, albumin/globulin ratio, total bilirubin, total cholesterol, triglyceride, blood urea nitrogen, creatinine, calcium, inorganic phosphorus, sodium, potassium, chloride, aspartate transaminase, alanine transaminase, alkaline phosphatase, gamma-glutamyl transpeptidase

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes

Other examinations:

Brain, lungs, heart spleen, liver, adrenals, kidneys and testes were weighed. For adrenals, kidneys and testes, the weights of each side were recorded separately and the total of both sides was used for calculation of group mean and SD values. The nasal cavity, trachea, aorta, pituitary, thyroids, parathyroids, salivary glands, tongue, oesophagus, stomach, duodenum, jejunum, ileum, cecum, colon, rectum, pancreas, urinary bladder, epidydimes, prostrate, seminal vesicles, ovaries, uterus, vagina, mammary glands, skin, mesenteric and submandibular lymph nodes, thymus, sternum, femur including bone marrow, sciatic nerve, trigeminal nerve, spinal cord, eye, Harderian gland an thigh muscle were excised and specimens from all these organs or tissues were fixed in 10% buffered formalin for paraffin embedding sectioning and staining with hematoxylin and eosin for histopathologival examination. All organs and tissues in the control and 3% group animals were histopathologcially examined in both chronic toxicity and carcinogenicity study. Additionally, macroscopically abnormal sites in the 0.1% and 0.6% group animals in the chronic study and all organs and tissues of the 1.5% animals in the carcinogenicity study were also histopathologically examined.

Statistics:

Variance in data for body weights, hematology, serum biochemistry and organ weights was checked for homogeneity by the Bartlett test. When data were homogenous, one way analysis of variance (ANOVA) was used. In the heterogenous cases, the Kruskal-Wallis test was applied. When statistically significant differences were indicated, Dunnett's multiple test was employed in comparison between control and treated groups. Final survival rates and the incidences of tumours and non-neoplastic lesions were cmpared with the Fisher's exact probability test or the Mann-Whitney's U- test.

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

not examined

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:

effects observed, treatment-related

Details on results:

CLINICAL SIGNS AND MORTALITY
Survival rate of control, 1.5% and 3% groups were 88%, 78% and 76%, respectively for males and 76%, 80% and 80% respectively, for females. No significant difference was observed between the groups. No obvious findings were observed in any group in either the chronic toxicity or carcinogenic studies.

BODY WEIGHT AND WEIGHT GAIN
No test substance related change in body weight was found.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study)
No test substance related change in food intake was found, except for a tendency for increase of food intake in male 3% group in the chronic toxicity study.

HAEMATOLOGY
No dose-related changes.

CLINICAL CHEMISTRY
No dose-related changes.

ORGAN WEIGHTS
Absolute and relative kidney weights were increased, or showed a tendency for increase at 3% in both sexes in the chronic toxicity study. Absolute spleen weights were decreased and relative liver weights increased in the 3% male dose group. No dose related changes were found in the other organs.

GROSS PATHOLOGY
There were no obvious findings in any group in either the chronic toxicity or carcinogenicity studies, except for massive nodular or focal lesions suggesting neoplastic change in the carcinogenicity study.

HISTOPATHOLOGY: NON-NEOPLASTIC
In the chronic toxicity study, several non-neoplastic lesions such as bile duct proliferation in the liver and focal myocarditis in the heart were noted in the control and 3% group and there were no significant differences in their incidences between the groups in either sex.
In the carcinogenicity study, incidence of chronic nephropathy in the kidney was significantly increased in the male 1.5% group. As for other lesions such as altered hepatocellular foci and bile duct proliferation in the liver and retinal atrophy in the eye were noted in the control and treatment groups, with no significant inter-group difference in their incidence or severity.

HISTOPATHOLOGY: NEOPLASTIC
Malignant pheochromocytoma of the adrenal in the male 3% group, two adenomas in the anterior pituitary in females of the 3% group, and uterine endometrial stromal polyp in a female control rat were noted.
Neoplastic lesions such as C-cell adenomas/adenocarcinomas in the thyroids, fibroadenomas/adenomas/adenocarcinomas in the mammary glands, adenomas/adenocarcinomas in the pituitary glands, interstitial cell tumours in the testes and endometrial stromal polyps in the uteri were noted in all groups, but these are all known to occur spontaneously in this strain, and neither increases in their incidences nor specific types of lesions were observed in the test substance administered groups.

Relevance of carcinogenic effects / potential:

Not carcinogenic.

Dose descriptor:

NOAEL

Effect level:

256 mg/kg bw/day

Sex:

male

Basis for effect level:

other: In the carcinogenicity study, incidence of chronic nephropathy in the kidney was significantly increased in the male 1.5% group. The NOAEL was therefore based on the chronic toxicity study (52 weeks), 0.6% dose level.

Remarks on result:

other: Effect type: toxicity (migrated information)

Dose descriptor:

NOAEL

Effect level:

284 mg/kg bw/day

Sex:

female

Basis for effect level:

other: In the carcinogenicity study, incidence of chronic nephropathy in the kidney was significantly increased in the male 1.5% group. The NOAEL was therefore based on the chronic toxicity study (52 weeks), 0.6% dose level.

Remarks on result:

other: Effect type: toxicity (migrated information)

In the chronic toxicity study, no mortality was found in any groups throughout the treatment period.

Conclusions:

The NOAEL for ammonium sulfate was estimated from the chronic toxicity study of F344 rats to be 0.6% in both sexes, which is equbvalent to 256 and 284 mg/kg/day in males and females, respectively, and no evidence of long term carcinogenic activity was found in the carcinogenicity study.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Justification for classification or non-classification

Based on the available information, no classification is required for carcinogenicity in accordance with Regulation (EC) No. 1272/2008.

Additional information

A reliable chronic toxicity and carcinogenicity study, conducted acording to a protocol equivalent to current guideline but not in compliance with GLP was available for ammonium sulfate (CAS 7783-20-2) (Ota et al., 2006).

The chronic toxicity study with 10 animals/sex/dose was carried out before the main study for the duration of 52 weeks. The animals were administered 0. 0.1, 0.6 or 3% ammonium sulfate in the diet. The main carcinogenicity study was conducted with 50 animals/sex/dose, for a duration of 104 weeks at 0, 1.5 and 3% dose levels.

While several tumours were noted, there were no significant intergroup differences in their incidence or histological types, all being spontaneous tumours described previously in the same strain. Although some neoplastic lesions were observed in the 3% group in the chronic toxicity study, no induction of such tumours was evident in the carcinogenicity study. In the carcinogenicity study, incidence of chronic nephropathy in the kidney was significantly increased in the male 1.5% group. The NOAEL for ammonium sulfate was therefore estimated from the chronic toxicity study of F344 rats to be 0.6% in both sexes, which is equivalent to 256 and 284 mg/kg/day in males and females, respectively, and no evidence of long term carcinogenic activity was found in the carcinogenicity study.

Due to the ubiquitous nature of citrate and iron in living organisms and the environment, and the important role of the constituents in biological processes, there is no concern over the potential carcinogenicity of the registered substance.