2-phosphonobutane-1,2,4-tricarboxylic acid

Endpoint summary

Additional information

Soil macroorganisms (earthworm)

Different concentrations (1 -1000 mg) of the 39.7% aqueous solution of 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC), thoroughly mixed in artificial soil, were tested for toxicity of earthworms. After 14 days of exposure to the test material, no significant difference was observed in mortality rate and in weight in any of the different concentration groups that were examined compare to the control group. The LC50 (14 days) was determined for the 39.7% water solution of PBTC as > 1000 mg/kg dry weight substrate. Thus, the no-observed-effect concentration (NOEC) was 1000 mg/kg dry weight substrate, the lowest-observed-effect concentration (LOEC) and the lowest tested concentration with mortality (LLC) was > 1000 mg/kg dry weight substrate (Heimbach, 1994). Referring the results to the purity of PBTC in the anhydrous form of the substance, the highest nominal test concentration showing no effect is converted based upon the water content resulting in a 14d-LC50 and LLC > 397 mg/kg dry weight substrate and a NOEC of 397 mg/kg dry weight substrate.The substance is not harmful to earthworms at concentration lower or equal to 397 mg/kg dry weight substrate.

Terrestrial arthropods, plants, and soil micro-organisms

The substance cannot be regarded as adsorptive with a log Kow of -1.66 (logKow < 3) and is not toxic to aquatic organisms with an LC50 >1042 mg/L (LC50 > 0.1 mg/L). It falls into Soil Hazard Category 1. Moreover, 2-phosphonatobutane-1,2,4-tricarboxylic acid is moderately degradable and is thoroughly metabolised to CO2 in soil, as shown in biodegradation studies in soil. Risk to soil organisms exposed to the substance is acceptable based on the PNECsoil calculated using the Equilibrium Partitioning Method, with additional support by a confirmatory short-term terrestrial toxicity study. The derivation from the study results in a PNECsoil of 0.397 mg/kg dwt. The equilibrium method results in the lowest PNECsoil of 0.08856 mg/kg dwt. Therefore, the PNECsoil derived by the Equilibrium Partitioning Method represents a worst-case approach. As the CSA demonstrates PEC/PNEC values of < 1 towards the environment in all cases, no hazard towards the environment is indicated. In conclusion, according to ECHA Guidance R.7c (Figure R.7.11—3 Scheme B: Integrated testing strategy (Annex IX and Annex X substances)) no further testing is required.

Birds

No experimental study on birds is available. The study does not need to be conducted as avian toxicity data are used in the assessment of secondary poisoning which is required for substances indicating a bioaccumulation potential. 2-Phosphanobutane-1,2,4-tricarboxylic acid has a low potential for bioaccumulation (log Kow = - 1.66) and no adverse effects to birds due to bioaccumulation in food chains would be expected. Furthermore, 2-phosphanobutane-1,2,4-tricarboxylic acid was assessed as moderately degradable and is thoroughly metabolised to CO2 in soil, it is generally assumed that the substance will not enter the terrestrial environment. Moreover, the results of toxicity studies in mammals, i.e. studies on acute, repeated dose and reproductive toxicity in mammals as well as genetic toxicity (in-vitro) have shown that the toxicity of 2-phosphanobutane-1,2,4-tricarboxylic acid is very low. No further testing is considered necessary with respect to animal welfare.