Bismuth tris(2-ethylhexanoate)

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

0.522 mg/L

Assessment factor:

50

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

0.714 mg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.052 mg/L

Assessment factor:

500

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

52.24 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

9.23 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

0.92 mg/kg sediment dw

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:

1.536 mg/kg soil dw

Extrapolation method:

equilibrium partitioning method

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Additional information

Read-across approach

Metal carboxylates are substances consisting of a metal cation and a carboxylic acid anion. Based on the solubility of bismuthtris (2 -ethylhexanoate) in water, a dissociation resulting in bismuth cations and2-ethylhexanoateanions may be assumed under environmental conditions. Bismuth carboxylates were analysed for the presence of covalent and ionic bonds between bismuth and the oxygen of the carboxylate group. It was confirmed that bismuth carboxylate bonds are ionic (Mehrotra and Bohra 1983). The equilibrium equation of the dissociation products does not indicate any pH dependency of the dissociation. The dissociation of bismuthtris(2-ethylhexanoate)is in principle reversible and the ratio of the salt /dissociated ions is dependent on the metal-ligand complexation constant of the salt, the composition of the solution and its pH.

A metal-ligand complexation constant of bismuthtris(2-ethylhexanoate)could not be identified. Data for bismuth appear to be generally limited. However, bismuth cations tend to form complexes with ionic character as a result of their low electronegativity. Further, the ionic bonding of bismuth is typically described as resulting from electrostatic attractive forces between opposite charges, which increase with decreasing separation distance between ions. Bi3+ cations are acidic and have a strong tendency to form insoluble salts (hydroxides) in water reducing its bioavailability (reference given in HSDB, 2008; Thomas et al. 1984; Thomas, 1991). Further insoluble bismuth salts include oxides, sulphides and oxychlorides, salts of inorganic oxoacids (carbonate, nitrate, sulfate) and organic acids (triglycollate, trialkylates) (Fowler and Vouk, 1979). However, uncertainties regarding the behaviour of bismuth species in aqueous solutions remain (Slikkerveer and De Wolff, 1996 and references therein). Upon dissolution of bismuth tris(2-ethylhexanoate), bismuth (3+) ions are expected to form insoluble salts that reduce its bioavailability whereas 2-ethylhexanoate anions remain dissolved in the water column.

Thus, read-across to bismuth cations and 2 -ethylhexanoate anions is applied since the dissociation products of bismuth 2-ethylhexanoate behave differently in the environment regarding their fate and toxicity. A separate assessment of each assessment entity is performed. Please refer to the data as submitted for each individual assessment entity.

In order to evaluate the environmental fate and toxicity of bismuth tris(2-ethylhexanoate), information on the assessment entities bismuth cations and 2-ethylhexanoateanions were considered. For a documentation and justification of that approach, please refer to the separate document attached to section 13, namely Read Across Assessment Report for bismuth tris(2-ethylhexanoate).

References:

Mehrotra, R. C. and Bohra R. (1983): Metal Carboxylates. Academic Press

HSDB (2008). Hazardous substances data bank (HSDB), a database of the national library of medicine’s TOXNET system.

Fowler, B. A. and Vouk, V. (1979). Chapter 20, Bismuth, in Handbook on the Toxicology of Metals, Friberg et al. (Edt), Elsevier, North-Holland Biomedical Press.

Slikkerveer, A. and De Wolff, F. (1996). Chapter 27, Toxicity of Bismuth and Its Compounds, CRC Press, Inc., p. 439-454.

Thomas, D.W., Hartley, T. F. and Coyle, P. (1984), II.5 Bismut, Met. Umwelt, Adelaide, p. 343-350. Krieger, R. (Ed.) (2001). Bismuth, Handbook of pesticide toxicology, p. 1389-1390.

Thomas, D. W. (1991). II.5 Bismuth, Met. Their Comp. Environ., p. 789-801.

Conclusion on classification

Aquatic toxicity studies with bismuth tris(2-ethylhexanoate) are not available. For the assessment of the aquatic hazard potential, read-across of existing aquatic toxicity data of the dissociation products bismuth cations and 2 -ethylhexanoate anions is applied.

Acute (short-term) toxicity: EC/LC50 values of 3 trophic levels (algae, invertebrates and fish) for bismuth and 2 -ethylhexanoate are > 100 and 10 mg/L, respectively and thus well above the classification cut-off value for acute (short-term) aquatic hazard category 1 of 1 mg/L. In accordance with Regulation (EC) No 1272/2008, Table 4.1.0 (a), classification for acute (short-term) aquatic hazard is not required for bismuth tris(2-ethylhexanoate). Therefore, bismuth tris (2-ethylhexanoate) does not meet classification criteria as short-term hazard to the aquatic environment under Regulation (EC) No 1272/2008 and its subsequent adaptations.

Chronic (long-term) toxicity: Bismuth appears to have a very low potential for chronic toxicity based on the NOEC value of ≥100mg bismuth/L for algae. Based on its very low acute toxicity (all EC/LC50 values are > 100 mg/L) and its tendency to form insoluble and non-bioavailable salts in aquatic systems, a low potential for chronic toxicity to other trophic levels may be expected for bismuth. Based on the surrogate approach (Table 4.1.0 (b) (iii)) of Regulation (EC) No 1272/2008, bismuth would also not meet chronic classification criteria since the EC50 for crustacea and fish are > 100 mg/L. Criteria for the "Safety net" classification in Category Chronic 4 are also not met.

Reliable chronic aquatic toxicity of 2-ethylhexanoate are available from guideline studies for algae and daphnia. The lowest respective EC10/NOEC values are 32 mg/L and 18 mg/L, respectively, and well above the classification cut-off values for long-term aquatic hazard category 1 -3. Since long-term data are not available for fish, the surrogate approach is applied. Based on classification criteria for substances for which adequate chronic toxicity are not available in Table 4.1.0 (b) (III), Figure 4.1.1 and adequate acute toxicity data of fish with LC50 values > 100 mg/L, 2-ethylhexanoate does not classify as long-term aquatic hazard category 1 -3. Criteria for classification in category 4 are also not met.

Therefore, bismuth tris(2-ethylhexanoate) does not meet classification criteria as long-term hazard to the aquatic environment under Regulation (EC) No 1272/2008 and its subsequent adaptations.

 

In sum, based on read-across of toxicity data available for bismuth and 2 -ethylhexanoate, bismuth tris(2 -ethylhexanoate) does not meet acute or long-term aquatic hazard criteria ofRegulation (EC) No 1272/2008.