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Carcinogenicity

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Description of key information

For the sodium sulfide as well as for sodium hydrogensulfide, no adequate data from carcinogenicity studies are available, and therefore, information from other substances related to sulfides is considered for evaluation of the carcinogenic hazard. 
The evaluation report is attached to the technical dossier and the CSR. No carcinogenicity studies are available for sodium hydroxide and sodium carbonate. However, sodium, hydroxide and bicarbonate ions as well as hydrogen sulfide are present in the body under normal physiological conditions, and their concentrations are physiologically regulated. It is unlikely that the Reaction mass would have a carcinogenic effect.

Key value for chemical safety assessment

Justification for classification or non-classification

There is no evidence for carcinogenic potential of H2S in the public domain, and the compound has a physiological role in the body as a signal molecule and cytoprotecant. Upon systemic availability, sulfides are rapidly oxidised and excreted renally as sulfates. Regarding sulfur and sulfates, there is a general opinion that these compounds are essential for life and do not pose a risk for humans.

Thus, in the absence of any conclusive human or animal evidence for any carcinogenic effect, the complete lack of genotoxicity of sulfides, and given the metabolic profile and natural geogenic ubiquitous presence of the constituents of the Reaction mass, there is no need for the conduct of a carcinogenicity study, and this data requirement should therefore be waived.

Additional information

An extensive literature search and evaluation programme on animal and human repeated dose toxicity data of sodium sulfide, sodium hydrogensulfide and dihydrogen sulfide has recently been conducted. However, no adequate data from carcinogenicity studies are available. Therefore, information from other substances related to sulfides is considered for evaluation of the carcinogenic hazard.

The evaluation report is attached to the technical dossier (IUCLID section 7.7) and included in the CSR.

It is important to note that hydrogen sulfide is not only a xenobiotic but it has also a physiological role as a signal molecule and cytoprotectant in the body (reviewed by Kimura, 2010. Hydrogen sulfide has been shown to protect the nervous system and the cardiovascular system from oxidative stress. Therefore the body has the ability to deal with small amounts of hydrogen sulfide, and at low exposure levels a carcinogenic effect is unlikely.

No carcinogenicity studies are available for sodium hydroxide and sodium carbonate. Sodium, hydroxide and bicarbonate ions are normal constituents of the body and their concentrations are physiologically regulated. Also, their physical and chemical properties do not favour toxicologically relevant systemic exposure, and no carcinogenic effects are expected. Based on these facts and the lack of genotoxicity, it is unlikely that the Reaction mass would have a carcinogenic effect.