Ammonium dihydrogen citrate

Endpoint summary

Description of key information

As discussed in the read across rationale attached in section 13, the citrate part of ammonium dihydrogen citrate is not considered relevant for repeated dose toxicity, as little or no effects are expected after repeated exposure up to high doses. For the ammonium part, a chronic feeding study with ammonium sulfate is used as key study. Based on this chronic toxicity study, the NOAEL was found to be 0.1% in feed, which was calculated to correlate to 256 mg/kg bw/day (males) and 284 mg/kg bw/day (females). The corresponding NOAEL was calculated to be 1255 mg/kg bw/day for ammonium dihydrogen citrate in water (≤ 55% ammonium dihydrogen citrate and ≥ 45% water).

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

chronic toxicity: oral

Type of information:

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

Adequacy of study:

key study

Justification for type of information:

The rationale to read across the data is attached in Section 13.

Reason / purpose for cross-reference:

read-across source

Clinical signs:

no effects observed

Description (incidence and severity):

No obvious findings were observed.

Mortality:

no mortality observed

Description (incidence):

No mortality was found in any groups throughout the treatment period.

Body weight and weight changes:

no effects observed

Description (incidence and severity):

No test substance-related change in the body weights was found.

Food consumption and compound intake (if feeding study):

no effects observed

Description (incidence and severity):

No significant test substance-related change in the food intake was found. A tendency for increased food intake was noted in high dose males.

Food efficiency:

no effects observed

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

effects observed, non-treatment-related

Description (incidence and severity):

No significant variation was found in erythrocytic parameters and platelet count among the groups. Some slight changes were found in white blood cell count parameters (reticulocyte count was increased compared to control with -62.5% and 29.1% for the groups exposed to 0.1 and 0.6, respectively (high dose group was unaltered compared to control), white blood cell count decreased with -13.7%, -11% and -4.2% for the groups exposed to 0.1, 0.6 and 3.0%, respectively). Since there was no dose-relation these effects were considered to be incidental.

Clinical biochemistry findings:

effects observed, non-treatment-related

Description (incidence and severity):

No dose-related alteration was found in any of the serum biochemical parameters. A slight increase was seen for T-Bil for the groups exposed to 0.1 and 0.6% (from 0.1 mg/dL (controls) to 0.2 (0.1% group) and 0.3 mg/dL (0.6% group)), however the high dose group had the same level as the controls. Similar pattern was seen for aspartate transaminase, alanine transaminase and alkaline phosphatase (aspartate transaminase: +23.9% and +52.3%; alanine transaminase: +43.6% and +76.4%; alkaline phosphatase: 10.5% and 18.1% for the groups exposed to 0.1% and 0.6%, respectivley). Also for these parameters, the high dose group showed same levels as the controls. In anbsence of a dose-relationship of the effects these results were considered non-adverse.

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

Kidney weights were increased at 3.0% in both sexes (in males: +11.2% (absolute) and +10% (relative); females: 10.5% (relative)). No changes compared to controls were found in the other organs of exposed animals.

Gross pathological findings:

no effects observed

Description (incidence and severity):

There were no obvious macroscopic findings in any of the groups.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

In the high dose group, 4/10 males were found to have focal necrosis in the liver (1/10 in conrols). In females, bile duct prolifereation was seen in 3/10 high dose rats (not seen in controls, and 9/10 high dose rats had altered hepatocellular foci (also seen in 7/10 control females).

Histopathological findings: neoplastic:

effects observed, non-treatment-related

Description (incidence and severity):

A malignant pheochromocytoma of the adrenal in the male 3.0% group, two adenomas in the anterior pituitary in females of the 3.0% group (none found in control groups). These were considered coincidental findings.

Dose descriptor:

NOAEL

Effect level:

810 mg/kg bw/day (actual dose received)

Based on:

test mat.

Remarks:

ammonium dihydrogen citrate (recalculated value; pure substance)

Sex:

male/female

Basis for effect level:

histopathology: non-neoplastic

Key result

Dose descriptor:

NOAEL

Effect level:

>= 1 255 mg/kg bw/day (actual dose received)

Based on:

test mat.

Remarks:

ammonium dihydrogen citrate in water (recalculated value; ≤ 55% ammonium dihydrogen citrate and ≥ 45% water)

Sex:

male/female

Basis for effect level:

histopathology: non-neoplastic

Key result

Critical effects observed:

yes

Lowest effective dose / conc.:

3 other: %

System:

hepatobiliary

Organ:

liver

Treatment related:

yes

Dose response relationship:

yes

The actual daily intake of the test substance (ammonium sulfate) was calculated to be 42, 256 and 1527 mg/kg bw/day for males and 48, 284 and 1490 mg/kg bw/day for females.

In order to adjust this value from the source chemical (ammonium sulfate) to the target chemical, the following calculation is used:

Based on a molecular weight of ammonium sulfate (MW=132.14), the ammonium part (2 NH4+, MW=36.08) has a weight percentage of 27.3%. Therefore, the adjusted NOAEL for the ammonium ion (NH4+) is calculated to be 69.9 mg/kg bw/day (256 mg/kg bw/day * 0.273)

Based on a molecular weight of the ammonium dihydrogen citrate (MW=209.15), the ammonium ion (MW=18.04) has a weight percentage of 8.63%. Therefore, the adjusted NOAEL for ammonium dihydrogen citrate is calculated to be 810 mg/kg bw/day ((69.9 mg/kg bw/day/ 8.63)*100).

Conclusions:

Based on a chronic toxicity study in rats with ammonium sulphate, the NOAEL was found to be 0.1% in feed, which was calculated to correlate to 256 mg/kg bw/day (males) and 284 mg/kg bw/day (females). This value is read across to ammonium dihydrogen citrate in water (see rationale section 13). The corresponding NOAEL was calculated to be 1255 mg/kg bw/day for ammonium dihydrogen citrate in water (≤ 55% ammonium dihydrogen citrate and ≥ 45% water).

Executive summary:

A chronic toxicity study was performed with ammonium sulphate in male and female rats (10/sex/group), with exposure through feed at 0%, 0.1%, 0.6% and 3.0%. During the treatment period, clinical signs and mortality were observed daily, and body weight and food consumption were recorded every 2 weeks until week 10 and every 5 weeks thereafter. After sacrifice, hematological examinations and serum biochemistry were performed. Full necropsy was done (including organ weights) and histopathology was performed on controls and high dose groups. No effects were found on survival rate, body weights, and hematological, serum biochemical or histopathological parameters at any dose levels in the chronic toxicity study. Kidney weights were increased at 3.0% in both sexes (in males: +11.2% (absolute) and +10% (relative); females: 10.5% (relative)). No changes compared to controls were found in the other organs of exposed animals. In the high dose group, 4/10 males were found to have focal necrosis in the liver (1/10 in conrols). In females, bile duct prolifereation was seen in 3/10 high dose rats (not seen in controls, and 9/10 high dose rats had altered hepatocellular foci (also seen in 7/10 control females). Based on these results, the NOAEL was found to be 0.1% in feed, which was calculated to correlate to 256 mg/kg bw/day (males) and 284 mg/kg bw/day (females). This value is read across to ammonium dihydrogen citrate in water (see rationale section 13). The corresponding NOAEL was calculated to be 1255 mg/kg bw/day for ammonium dihydrogen citrate in water (≤ 55% ammonium dihydrogen citrate and ≥ 45% water).

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

1 255 mg/kg bw/day

Study duration:

chronic

Species:

rat

Quality of whole database:

The study used is considered reliable (Klimisch 2).

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

Justification for classification or non-classification

Based on the current data-set, the substance is not classified for adverse effects after repeated exposure according to Regulation (EC) No. 1272/2008 and its amendments.