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Environmental fate & pathways

Biodegradation in soil

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Description of key information

Guanidine  was rapidly and extensively mineralized in soil with a  half-live of 2.5-8 days for guanidine concentrations of 2.5-100mg/kg soil.

Key value for chemical safety assessment

Half-life in soil:
8 d
at the temperature of:
25 °C

Additional information

14-C Guanidinium in aerated soil is biodegraded with a half live of 2.5 - 8 days for guanidine concentrations of 2.5 – 100 mg/kg dw. The degradation rate is dependent on the concentration of guanidinium with a lower degradation rate at high concentrations, on the type of soil used and on the availability of carbon sources (Glucose or Cellulose) which enhance mineralization rate. Nitrogen in form of Ammonium, Nitrate, Nitroguanidine only slightly inhibit guanidinium mineralization. Also other studies of Praveen-Kumar and Brumme (1999) and Williams et al (1989) supports the conclusion that Guanidine Nitrate was rapidly and extensively mineralized in soil although the values differ depending on the soil and method used and there are some different findings concerning the dependence of mineralization on availability of carbon source.

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.