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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Link to relevant study record(s)

Description of key information

A waiver is proposed to cover this endpoint, and consequently a study on potassium nitrate (Admiraal, 1977) is provided as supporting evidence. The read-across rationale can be found in the category approach document attached in Section 13 of IUCLID and is fully incorporated in the CSR. 

Key value for chemical safety assessment

Additional information

According to REACH Annex XI section 1.5, the study can be waived when it can be covered by a structural analogue. Nitric acid will dissociate in the environment into its ions: H+ ions and nitrate ions. The H+ ions will cause a pH decrease, but in the aquatic environment the net pH decrease will be limited due to buffering. Regulatory aquatic ecotoxicity studies should be conducted at relevant environmental pH (i.e. pH 6 -9). At this pH, exposure to nitric acid comes down to exposure to nitrate ions. Therefore this endpoint can be covered by a study conducted with potassium nitrate (Admiraal, 1970), which also dissociates in the environment into its ions. In this study, several marine benthic diatoms were exposed to potassium nitrate. The derived NOEC = 6.75 mmol/L (i.e. 419 mg nitrate/L).