Nitric acid

Carcinogenicity

Description of key information

Two unreliable studies were identified for nitric acid carcinogenicity. These studies were of limited value for addressing the carcinogenic potential of the test substance due to the short duration of exposure and the inadequate reporting of the study design and results. 
Sodium nitrate is no complete carcinogen in rats, but did increase the incidence of urinary bladder cancer in rats when it was given after administration of a carcinogen.
A 2-year study in rats and a lifespan mice study showed no increased tumour incidence.

Key value for chemical safety assessment

Carcinogenicity: via oral route

Endpoint conclusion

Quality of whole database:

The studies have klimisch code 2.

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 the above information nitric acid is not expected to have full carcinogenic properties. Nitric acid does not have to be classified according to Regulation 1272/2008 and amendments.

Additional information

As nitric acid is a strong acid, nitric acid is corrosive to skin (Cat. 1A) and eyes. Based on the studies available concentrations as low as 150 µg/m³nitric acid show indications of local irritation. Moreover, nitric acid as soon as entering the body dissociates into nitrate and H⁺. Nitrate is distributed widely, and is an essential element to organisms and its fate in the human body is regulated. The H⁺ions are only expected to give local irritating/corrosive effects and at low concentrations will also be internally buffered/regulated. Upon exposure to nitric acid local effects are considered to appear far before systemic effects due to its corrosive nature.

No reliable data on nitric acid is available. In a 2-year carcinogenicity study with 2.5 or 5% sodium nitrate administered to rats in the diet, no increased incidence of any tumour was found. Animals were killed after 123 weeks and almost all of the animals had tumours in the control as well as the nitrate groups. In a 9-month study in which rats were exposed via the drinking water to sodium nitrate no hyperplastic changes in the urothelium or carcinomas were found.

Fromin vitrogenotoxicity studies on nitric acid, potassium nitrate and sodium nitrate andin vivostudies with sodium nitrate nitric acid is not considered to be genotoxic (see also EFSA, , Nitrate in vegetables. Scientific opinion of the panel on contaminants in the food chain, 2008). The ADI determined by JECFA and confirmed by EFSA was based on a 2-y study in rats with a NOEL of 500 mg sodium nitrate/kg bw/ (= 370 mg/kg bw/d nitrate) and a subchronic study with sodium nitrate in dogs with a NOEL of 370 mg/kg bw/d for nitrate. The 2-year study with sodium nitrate in this dossier has a NOAEL of 5% in the diet (= 2000 mg/kg bw/d *) which is equivalent to 62/101.1 x 2000 = 1227 mg nitrate/kg bw/d, which is higher than the study on which the ADI was based. As the exposure assessment using this value indicates safe use for humans, it is also considered safe for carcinogenicity. Moreover, nitrates have been used in fertilizers for over decades without an identifiable relation to carcinogenic effects.

* rats eat min. 40 g/kg/d (TNO V98.390, Default values in occupational risk assessment).

Based on the above information, it is concluded that it is not scientifically justified to perform a carcinogenicity study.

Justification for selection of carcinogenicity via oral route endpoint:
Reliable studies with the read-across substance sodium nitrate are available. The read-across rationale can be found in the CSR.