Ammonia, anhydrous

Carcinogenicity

Description of key information

No evidence of carcinogenicity was seen in a study with read-across substance ammonium sulphate. An investigative study suggests that long-term exposure to drinking water containing ammonia (aqueous ammonia) may cause irritant gastritis which in turn may promote gastric carcinogenesis initiated by MNNG ( N-methyl-N'-nitro-N-nitrosoguanidine). However there is no evidence that ammonia is carcinogenic.

Key value for chemical safety assessment

Carcinogenicity: via oral route

Link to relevant study records

Reference

Endpoint:

carcinogenicity: oral

Type of information:

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

Adequacy of study:

key study

Justification for type of information:

See attached read-across justification

Reason / purpose for cross-reference:

read-across source

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

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

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:

No mortality was recorded in the 52 week chronic toxicity study. In the 104 week carcinogenicity study, the survival rate of control, 1.5% and 3.0% groups were 88%, 78% and 76%, respectively for males, and 76%, 80% and 80%, respectively for females.
There were no obvious clinical signs in any group of either the chronic or the carcinogenicity study. Diarrhoea was not seen in this study, despite being noted at 3% in the preliminary 13 week study. There were no significant effects on body weight or food intake. There was a tendency towards increased food intake in the male 3% group in the chronic study.
There were no significant effects of treatment on haematology or serum chemistry in the 52 week chronic study. Some slight changes were observed in WBC paramters, but there was no dose-response relationship and the findings were therefore considered to be incidental.
Absolute and relative kidney weights were increased, or showed a tendency to increase, at 3% in both sexes in the chronic study. Absolute spleen weights were decreased and relative liver weights were increased in the 3% male dose group in the chronic study. Tables 1 and 2 show the organ weights for males and females, respectively.
The only macroscopic finding at necropsy in the carcinogenicity study was massive, nodular or focal lesions suggesting neoplastic change. There were no macroscopic findings in the chronic study.
Chronic study histopathology: several non-neoplastic lesions, such as bile duct proliferation in the liver and focal myocarditis in the heart were noted in both the control and the 3% group. There were no significant differences in incidence between the groups. Neoplastic lesions observed were 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.
Carcinogenicity study histopathology: The incidence of chronic nephropathy in the kidney was significantly increased in the 1.5% males. 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 incidences or severity. 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 were not thought to be treatment related as they are all known to occur spontaneously in rats of this strain and age, and neither increases in incidence nor specific types of lesions were observed in the treated groups.

Relevance of carcinogenic effects / potential:

There was no evidence of carcinogenicity.

Dose descriptor:

NOAEL

Remarks:

toxicity

Effect level:

256 mg/kg bw/day (nominal)

Based on:

other: Ammonium sulfate

Sex:

male

Basis for effect level:

other: 0.6% dietary concentration

Dose descriptor:

NOAEL

Remarks:

toxicity

Effect level:

284 mg/kg bw/day (nominal)

Based on:

other: Ammonium sulfate

Sex:

female

Basis for effect level:

other: 0.6% dietary concentration

Dose descriptor:

NOAEL

Remarks:

carcinogenicity

Effect level:

3 other: %

Based on:

other: Ammonium sulfate

Sex:

male/female

Calculated actual doses based on final body weight and average food consumption in the chronic toxicity study were: 42, 256 and 1527 mg/kg bw/day for the 0.1%, 0.6% and 3% males, respectively; and 48, 284 and 1490 mg/kg bw/day for the 0.1%, 0.6% and 3% females, respectively.

Calculated actual doses based on final body weight and average food consumption in the carcinogenicity study were: 564.1 and 1288.2 mg/kg bw/day for the 1.5% and 3% males, respectively, and 649.9 and 1371.4 mg/kg bw/day for the 1.5% and 3% females, respectively.

Table 1. Organ weights of male rats exposed to dietary ammonium sulfate for 52 weeks.

	Dose level (%)
	0 (Control)	0.1	0.6	3.0
Body weight (g)	410.9±12.3	428.6±17.6	416.7±23.7	400.5±15.1
Absolute (g)
Brain	2.04±0.05	2.03±0.07	2.05±0.05	2.04±0.05
Lungs	1.20±0.09	1.23±0.21	1.16±0.07	1.13±0.06
Heart	1.09±0.08	1.10±0.07	1.08±0.05	1.08±0.07
Spleen	0.73±0.05	0.72±0.04	0.83±0.36	0.68±0.04*
Liver	9.62±0.58	9.92±0.73	10.26±0.63	10.0±0.85
Adrenals	0.03±0.01	0.04±0.01	0.04±0.00	0.04±0.00
Kidneys	2.35±0.25	2.32±0.11	2.42±0.11	2.51±.011*
Testes	3.38±0.17	3.27±0.11	3.25±0.25	3.29±0.14
Relative (g/100 g bw)
Brain	0.50±0.02	0.47±0.02	0.49±0.04	0.51±0.02
Lungs	0.29±0.02	0.29±0.04	0.28±0.02	0.28±0.01
Heart	0.26±0.02	0.26±0.02	0.26±0.02	0.27±0.01
Spleen	0.18±0.01	0.17±0.01	0.20±0.08	0.17±0.01
Liver	2.34±0.13	2.31±0.09	2.46±0.10	2.50±0.16*
Adrenals	0.01±0.00	0.01±0.00	0.01±0.00	0.01±0.00
Kidneys	0.57±0.07	0.54±0.02	0.58±0.04	0.63±0.04*
Testes	0.83±0.04	0.76±0.03*	0.78±0.07	0.82±0.04

Each value representts the mean ± SD. n = 10 per group.

* Significantly different from the control at p < 0.05

Table 2. Organ weights of female rats exposed to dietary ammonium sulfate for 52 weeks.

	Dose level (%)
	0 (Control)	0.1	0.6	3.0
Body weight (g)	207.4±13.49	220.3±8.68	219.2±13.62	212.7±24.39
Absolute (g)
Brain	1.86±0.04	1.83±0.04	1.83±0.05	1.82±0.05
Lungs	0.82±0.06	0.79±0.10	0.83±0.12	0.79±0.05
Heart	0.65±0.05	0.67±0.05	0.70±0.03	0.67±0.05
Spleen	0.44±0.04	0.44±0.02	0.45±0.03	0.45±0.07
Liver	4.44±0.26	4.66±0.35	4.69±0.40	4.89±0.42
Adrenals	0.04±0.00	0.04±0.01	0.04±0.01	0.04±0.01
Kidneys	1.25±0.07	1.35±0.08*	1.35±0.09	1.39±0.08**
Relative (g/100 g bw)
Brain	0.90±0.05	0.83±0.04	0.84±0.05	0.86±0.09
Lungs	0.39±0.04	0.36±0.05	0.38±0.06	0.37±0.04
Heart	0.31±0.02	0.31±0.03	0.32±0.03	0.32±0.02
Spleen	0.21±0.03	0.20±0.01	0.21±0.02	0.21±0.03
Liver	2.15±0.17	2.11±0.13	2.14±0.18	2.31±0.18
Adrenals	0.02±0.00	0.02±0.00	0.02±0.00	0.02±0.00
Kidneys	0.60±0.01	0.61±0.04	0.61±0.06	0.66±0.05

Each value representts the mean ± SD. n = 10 per group.

* Significantly different from the control at p < 0.05.

** Significantly different from the control at p < 0.01.

Conclusions:

There was no evidence of carcinogencity for read-across substance ammonium sulfate..

Executive summary:

Chronic toxicity and carcinogenicity studies of ammonium sulfate, used as a food additive in fermentation, were performed in male and female Fisher 344 rats at dietary concentrations of 0%, 0.1%, 0.6% and 3.0% in a 52-week toxicity study and 0%, 1.5% and 3.0% in a 104-week carcinogenicity study. Treatment with read-across substance ammonium sulfate caused significant increase in kidney and/or liver weights in males and females of the 3.0% diet group, but 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. Regarding carcinogenicity, read-across substance ammonium sulfate did not exert any significant influence on the incidences of tumors in any of the organs and tissues examined. It was concluded that the no observed adverse effect level of ammonium sulfate was the 0.6% diet, which is equivalent to 256 and 284 mg/kg b.w./day in males and females, respectively, and the compound is non-carcinogenic under the conditions of the study.The NOAEL of anhydrous ammonia was considered to be 67 and 74 mg/kg b.w./day in males and females (based on ammonia equivalents of ammonium sulfate), and the target compound was considered non-carcinogenic under the conditions of this study.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

350 mg/kg bw/day

Study duration:

chronic

Species:

rat

Quality of whole database:

Three published studies are available.

Carcinogenicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no study available

Carcinogenicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

Based on read-across to available carcinogenicity studies using diammonium sulphate, ammonia is not considered to have any carcinogenic potential. Classification of the substance for carcinogenicity according to CLP Regulation 1272/2008/EC is not therefore warranted.

Additional information

Key chronic toxicity and carcinogenicity studies using ammonium sulphate have been performed in male and female Fisher 344 rats at dietary concentrations of 0%, 0.1%, 0.6% and 3% in a 52 week toxicity study (OECD Test Guideline 452; Ota et al, 2006)) and at 0%, 1.5% and 3% in a 104 week carcinogenicity study (OECD Test Guideline 453; Ota et al, 2006).

No evidence of carcinogenicity was seen at any of the dose levels tested. From these studies, the NOAEL for general toxicity was determined to be 0.6% (dietary level) equivalent to 256 and 284 mg/kg bw/day in males and females respectively [67 and 74 mg/kg bw/d ammonia equivalents], based on significant increases in kidney and/or liver weights at the highest dose tested. No tumors were observed up to 3% in the diet (NOAEL for carcinogenicity, which approximates 1330 mg/kg ammonium sulphate or ‘target’ NOAEL of 0.258 x 1330 = 350 mg/kg bw).

 

In a non-standard supporting mechanistic assay, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-initiated rats were exposed for 24 months to a 0.01% ammonia solution via drinking water (Tsuji et al, 1992). Gastritis was seen in all animals, indicating a local irritant effect. The incidence of gastric tumours was increased in treated animals, suggesting that ammonia may be acting as a promoter of carcinogenesis.

 

In another supporting non-standard study, solutions of hydrazine as 0.001%, methylhydrazine as 0.01%, methylhydrazine sulfate as 0.001%, and ammonium hydroxide as 0.3, 0.2 and 0.1% were administered continuously in the drinking water of 5- and 6-week-old randomly bred Swiss mice for their entire lifetime (Toth, 1972). Similarly ammonium hydroxide as a 0.1% solution was given to 7-week-old inbred C3H mice. Hydrazine and methylhydrazine sulfate significantly increased the incidence of lung tumors in Swiss mice, while methylhydrazine enhanced the development of this neoplasm by shortening its latent period. The ammonium hydroxide treatments in Swiss and C3H mice were, however, without carcinogenic effect, and did not inhibit the development of breast adenocarcinomas in C3H females, which are characteristic of these animals. The study provided evidence for the carcinogenicity of methylhydrazine and further evidence of the tumor-inducing capability of hydrazine alone and negated the possibility that the metabolite of hydrazine; ammonium hydroxide, could interfere in the development of neoplasia.