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Toxicity to microorganisms

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Description of key information

The toxicity of Guanidine hydrochloride to microorganisms was monitored in Pseudomonas putida.  A 16-h-EC10 of 7125 mg/L was determined.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
7 125 mg/L

Additional information

In an 18 h acute toxicity study, the cultures of the microorganism Pseudomonas putida were exposed to Guanidine hydrochloride at nominal concentrations of 1.7 - 456000 mg/L under static conditions in accordance with the guideline of Umweltbundesamt (1979) and slightly modified to DEV DIN 38412 part 8 (1991). Bacterial growth was determined by measurement of the turbidity at 436 nm. The study is in accordance with standard guidelines with some restrictions. The 18-h-EC10 was 7125 mg/L.

This result is supported by a study conducted with the read-across substance Guanidine nitrate: The toxicity of Guanidine nitrate to microorganisms was studied in an 18-h-cell multiplication inhibition test using Pseudomonas putida as test organism. Bacterial growth inhibtion was determined by measurement of the turbidity of the bacterial culture. The 18-h-EC10 was 831.8

mg/L.

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.