Tetrasodium hydrogen 2-phosphonatobutane-1,2,4-tricarboxylate

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

0.666 mg/L

Assessment factor:

50

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

10.42 mg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.067 mg/L

Assessment factor:

500

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

50.4 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

2.398 mg/kg sediment dw

Assessment factor:

1

Extrapolation method:

equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

0.24 mg/kg sediment dw

Assessment factor:

1

Extrapolation method:

equilibrium partitioning method

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

PNEC soil

PNEC value:

0.089 mg/kg soil dw

Extrapolation method:

equilibrium partitioning method

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Additional information

Based on the absence of data for tetrasodium hydrogen 2-phosphonatobutane-1,2,4-tricarboxylate a read-across approach with the corresponding parent acid 2-phosphonobutane-1,2,4-tricarboxylic acid is proposed.

In aqueous media, tetrasodium hydrogen 2-phosphonatobutane-tricarboxylate and 2-phosphonobutane-1,2,4-tricarboxylic acid dissociate into the corresponding anion (2-phosphonatobutane-tricarboxylate ion) and the sodium ion and hydrogen ion (proton), respectively. Fate, behavior and the ecotoxicological properties of 2-phosphonobutane-1,2,4-tricarboxylic acid and its tetrasodium salt are thought to be an effect of the phosphonato-carboxylate ion rather than of the sodium ion or the hydrogen ion (proton), which are normal constituents in environmental systems and have no relevant ecotoxic properties in low concentrations.

Therefore a read-across between tetrasodium hydrogen 2-phosphonatobutane-tricarboxylate and 2-phosphonobutane-1,2,4-tricarboxylic acid is justified.

The PNEC´s were derived from the most sensitive study available for each compartment.

For calculation of the PNECwater the ErC10 of 33.3 mg/L value of the Algal Growth Inhibition Test was used to reflect a worst case scenario.

As recommended in REACH guidance document R.10, an EC10 for a long-term test which is obtained using an appropriate statistical method (usually regression analysis) will be used preferentially. The NOEC is defined as “the highest concentration tested at which the substance is observed to have no statistically significant effect (p< 0.05) when compared with the control, within a stated exposure period” (OECD 211, 1998b) or the test concentration immediately below the LOEC, which when compared with the control has no statistically significant effect (p< 0.05) within a stated period (OECD 211, 1998b). There has to be a concentration-effect relationship. In the past, the NOEC was mainly derived on the basis of ANOVA (analysis of variance) and a subordinate test (e.g. Dunett's) or determined directly from the concentration-effect curve by consideration of the deviation of the control (e.g. 10%). In older investigations, it may be difficult to find out how the NOEC was generated unless test reports or raw data are available. There has been a recommendation within OECD in 1996 to phase out the use of the NOEC, in particular as it can correspond to large and potentially biologically important magnitudes of effect. The preconditions for the use of ANOVA have to be fulfilled (normal distribution, homogeneous variances). The advantage of regression method for the estimation of ECx is that information from the whole concentration-effect relationship is taken into account and that confidence intervals can be calculated. These methods result in an ECx, where x is a low effect percentile (e.g. 5-20%).

In conclusion, it is not entirely clear as to whether the EC10 or NOEC from the algal study should be used as the main result, in the context of PNEC derivation. In this case, due to the shallow dose-response relationship seen in the study with Desmodesmus subspicatus, it is considered appropriate to use ErC10 as the primary result of the study.

Conclusion on classification

According to the information summarized in this chapter, the substance should not be classified with the following reasons:

- The acute toxicity values are all above 100 mg/l representing three trophic levels obtained in short-term toxicity tests towards algae and fish, and concluded from a long-term toxicity test towards Daphnia.

- The most sensitive long-term toxicity is to algae with a 72h-ErC10 of 33.3 mg/l, where the 21d-NOEC obtained from the reproduction test with Daphnia magna is 104 mg/l.

- Not readily and inherently biodegradable, but moderately degradable under environmental conditions.

- The bioaccumulation potential is expected to be very low, based on its logKow of -5.45 for the dissociated form of the substance and -1.66 for the non-water based parent acid.

With the data listed above, the substance should not be classified according to  GHS (Regulation EC 1272/2008 including Commission Regulation EU-286/2011).