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Long-term toxicity to fish

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Description of key information

In water (including soil or sediment pore water), NaOH is present as the sodium ion (Na+) and hydroxyl ion (OH-), as solid NaOH rapidly dissolves and subsequently dissociates in water (EU RAR, 2007; section 3.1.3, page 24).

Key value for chemical safety assessment

Additional information

No valid long-term toxicity studies to fish are available. Despite of this, there is no need for further toxicity testing with NaOH, as all available tests resulted in a rather small range of toxicity values (chronic toxicity test > or = 25 mg/L) and there are sufficient data on pH ranges that are tolerated by major taxonomic groups (EU RAR, 2007, section, page 30).

The OECD SIDS (2002) assigned a low code of reliability ('invalid' or 'not assignable') to all available tests, as in general the tests were not conducted according to the current test guidelines (EU RAR, 2007; section, page 30). Furthermore, in many tests reports there were no data on pH, buffer capacity and/or test medium composition, although this is essential information for toxicity tests with NaOH. This is the most important reason why most of the tests were considered 'invalid'.