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Long-term toxicity to aquatic invertebrates

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Description of key information

The long-term toxicity of the read-across substance Guanidine Nitrate to Daphnia magna was tested in a 21-day flow-through test. The lowest concentration with an effect on reproduction (LOEC) was monitored at a concentration 4.2mg/L in a first chronic test of van der Schalie, 1985 and  6.09mg/L in a second chronic test. The highest concentration of the test item without an effect (NOEC) was found at 2.90mg/L.

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater invertebrates:
2.9 mg/L

Additional information

The toxic effect of the read-across substance Guanidine Nitrate was monitored in a 21-day toxicity test. 2.9 mg/L of the test substance was the highest concentration where no toxic effect was monitored. Because in a first chronic toxicity test of van der Schalie, 1985 an toxic effect was monitored at the lowest concentration tested (4.2mg/L), a second test was performed with lower concentrations tested. In this second test the lowest effect concentration was reported at 6.09 mg/L. In another study of Cooney et al. (1985) the LOEC was higher. Therefore the van der Schalie study can serve as the key study. It is interesting to mention that Guaninine Nitrate is 10 to 20 times more toxic in a chronic 21-day toxicity test compared to an acute 48h toxicity test which is reported in the same study of van der Schalie, 1985.

Justification for read-across:

Guanidine hydrochloride and guanidine nitrate dissociate in aqueous media to yield the guanidine ion and the respective anion. Therefore it is reasonable to discuss the effects of the ions separately. The chloride ion is a naturally occurring essential ion in human beings with well-known metabolism and mechanisms of action as described in standard textbooks on pharmacology and physiology. As well it is found as salt in the Earth´s crust and is dissolved in seawater. Effects of guanidine hydrochloride are expected to be based primarily on the guanidine ion. The physiological processing of the guanidine ion is expected to be independent of the individual source. Therefore read-across from guanidine hydrochloride for effects of guanidine dissociated from guanidine nitrate is considered valid. This strategy is supported by a quite similar toxicological profile of both substances, as shown in acute toxicity, irritation, sensitization and genotoxic studies.

A more detailed justification is attached and outlined in CSR chapter 1.1.2 as well.

Justification for non-classification:

GuCl is fast degradable (and inherently biodegradable) following criteria of GHS regulation (legal stand October 2012). Therefore there is no need for environmental classification (GHS legal stand October 2012).