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Ecotoxicological information

Long-term toxicity to fish

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Description of key information

A 73-day NOEC value of 0.014 mg unionised NH3/l (measured concentration) has been determined for the effects of ammonia on mortality of Oncorhynchus mykiss.

Key value for chemical safety assessment

Additional information

Testing for long-term toxicity to fish is not considered necessary because:

- Short-term toxicity of the silanol hydrolysis product, trimethylsilanol, to fish is low.

- The risk characterisation ratio (RCR) based on PNECfreshwater derived from the short-term data is <1 (see Section 10 of the CSR).

- For the hydrolysis by-product, ammonia, reliable chronic data are available.

- The substance is used under highly controlled conditions and, therefore, exposure of the aquatic environment is low (see Section 9 for further details).

Ammonia Long-Term Toxicity to Fish:

Reliable long-term data are available sourced from the Environment Agency Proposed EQS for Water Framework Directive Annex VIII Substances: Ammonia (unionised) 2007.

The lowest credible concentration of unionised ammonia at which long-term effects were found is 0.022 mg/l of nitrogen present as NH3 (0.027 mg NH3/l) when a cumulative mortality of 71 per cent was observed for eggs, larvae and fry of rainbow trout (Oncorhynchus mykiss) over 73 days exposure (Solbe et al, 1989). No NOEC value was derived in the study since effects were observed at the lowest exposure concentration. However, data on the concentration–response curve for similar effects in other fish have been evaluated, and these indicate 2–3 times difference in exposure concentration for a 50 per cent reduction in survival (from the controls) in such an early life stage test (EA 2007). A factor of 2 is applied to the LOEC result to estimate a NOEC, giving a long-term toxicity to fish result of 0.014 mg unionised NH3/l.