Tris[oxalato(2-)]digadolinium

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

The substance is an organic metal salt, the persistent part of the molecule (gadolinium) being inorganic. PBT assessment does not apply to the inorganic part of the molecule.

The organic part of the salt is oxalate, i.e. a dianion and the conjugate base of oxalic acid.

This organic part is not considered to have potential P or vP properties because it is readily biodegradable (Young et al., 1968) based on the results of a series of BOD tests showing high percentages of degradation within 5 days, with the onset of degradation occurring without any delay. Ready biodegradability is, in the absence of data allowing assessment against the REACH Annex XIII criteria for PBT assessment, considered as a screening criterium for drawing conclusions on potential persistency.

Oxalic acid is also not considered to have potential B or vB properties based on its log Pow, which is predicted to be -1.74 (Kowwin v1.67). In the absence of data allowing assessment against the REACH Annex XIII criteria for PBT assessment, substances with a log Pow > 4.5 (screening criterium) are considered to have potential B/vB properties, which is clearly not the case for oxalic acid.

Finally, according to the PBT screening criterium (i.e., substances with acute EC50 or LC50 values >= 0.01 mg/L are considered to have potential T properties), oxalic acid should not be considered as having potential T properties either. Bringmann and Kuhn (1978) reported an 8-d "toxic threshold" of 80 mg/L for the freshwater cyanobacteria Microcystis aeruginosa. Median effect concentrations for fish and aquatic invertebrates are also available from scientific literature: the 48-h LC50 for the freshwater fish Leuciscus idus melanotus was reported to be 160 mg/L (Juhnke and Luedemann, 1978), and the 48-h EC50 for Daphnia magna was reported to be 136.9 mg/L (Randall and Knopp, 1980).

Based on these data, oxalic acid, and consequently the substance gadolinium oxalate, should not be considered as potential PBT or vPvB substance.

References:

- Bringmann G, Kuhn R, 1978. Testing of substances for their toxicity threshold: model organisms Microcystis (Diplocystis) aeruginosa and Scenedesmus quadricauda. Mitteilungen – Internationale Vereinigung für Limnologie 21, 275-284.

- Juhnke I, Luedemann D, 1978. Ergebnisse der Untersuchung von 200 chemischen Verbindingen auf akute Fischtoxizität mit dem Goldorfentest.Zeitschrift für Wasser und Abwasser Forschung 11, 161-164.

- Randall TL, Knopp PV, 1980. Detoxification of specific organic substances by wet oxidation. Journal of the Water Pollution Control Federation 52, 2117-2130.

- Young RHF, Ryckman DW, Buzzel Jr JC, 1968. An improved tool for measuring biodegradability. J Water Pollut Contr Fed 40: R354-R368.