Diguanidinium carbonate

Long-term toxicity to fish

Description of key information

No long-term toxicity in the classifiable range of CLP

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

133.6 mg/L

Additional information

The long-term toxicity of Guanidine nitrate (CAS 506-93-4) to fish was investigated in a study (van der Schalie 1985) using early life stage of Fathead minnow (Pimephales promelas) comparable to the OPPTS 850.1400 (1996) and OECD TG 210 (1992) protocols. GLP is not stated. The experiment is deemed valid, conclusive and thus suitable for assessment with restrictions.

Two replicates of 45 less than 24 h old fertilized eggs were exposed to control and six treatments during 35 days under flow through conditions in well water. The test item concentrations were nominal 400, 200, 100, 50, 25and 0 mg/L corresponding to measured concentrations of 424, 181, 98.1, 52.7, 27.3 and < 0.5 mg/L, to which the results were related. The test system was maintained at 24.7-25.8 °C, 5.2-8.5 mg dissolved oxygen/L and a pH of 8.2 to 8.6. The hardness of the test media were 169-197 mg CaCO3/L, which corresponds to more than ca. 101-118 mg carbonate/L.

The effect parameters measured were time to hatch (i.e. number of days from the start of the test required for hatching of at least 50 percent of the eggs), egg hatching success (egg cups removed, examined and dead eggs removed daily), fry survival, overall survival (i.e. both embryo survival and fry survival) and growth (measured at the end of the test including standard length and weight).

The most sensitive end point was the overall survival (mortality), which was significantly different to control at the highest tested level. Accordingly the 35-d NOEC values and LOEC-values, based on mortality were 181 and 424 mg test item/ L respectively.

The NOEC corresponds to 1.483 µmol Guanidinium kation/L or considering equimolar conversion to this species 133.6 mg Guanidine carbonate (CAS 593-85-1)/L.

In conclusion the test item (source chemical) was found not being toxic to fish up to the relevant levels considered for long-term exposure of the aquatic life (i.e. 1 mg/L according to CLP, Regulation (EC) No 1272/2008)) and no indication for aquatic hazard classification is given by the results of this study. This conclusion can be read-across to the target chemical Guanidine carbonate according to the following justification.

Justification for read-across: Guanidine carbonate and guanidine nitrate dissociate in aqueous media to yield the Guanidinium kation and the respective anions. The carbonate toxicity is considered negligible for the environmental assessment as it is known to be generally not toxic to the standard test organisms used for hazard evaluation. Carbonates are a standard constituent of the OECD test media for aquatic organisms, e.g. OECD TG 203 (1992) states that waters with total hardness of between 10 and 250 mg CaCO3/L (i.e. 6 to 150 mg carbonate/L) were preferable. Nitrate may be more toxic mainly due to its conversion to Nitrite as shown in the effect data overview of Camargo et al (2005). Therefore a read-across from a nitrate salt to the corresponding carbonate salt constitutes an additional safely margin. A slight overestimation of the carbonate salt effects rather than underestimation can be expected. Therefore read-across from guanidine nitrate to the equimolar guanidine concentration derived from guanidine carbonate is suitable to define a reliable ecotoxicological threshold concentration.

This approach is further justified by the comparable short-term toxicity to aquatic invertebrates, for which data from both, the source and the target chemical are presented in the respective section.

• Camargo JA, Alonso A, Salamanca A (2005). Nitrate toxicity to aquatic animals: a review with new data for freshwater invertebrates. PMID 15667845 DOI 10.1016/j.chemosphere.2004.10.044 Chemosphere 58:1255–67