Dibutyltin oxide

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

2 µg/L

Assessment factor:

1 000

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

20 µg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.2 µg/L

Assessment factor:

10 000

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

4.4 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

5.247 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

0.525 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:

3.4 mg/kg soil dw

Extrapolation method:

assessment factor

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

PNEC oral

PNEC value:

0.67 mg/kg food

Assessment factor:

30

Additional information

For derivation of the PNECaqua (freshwater), PNECaqua (marine water) and PNECaqua (intermittent release), the results of the Steger-Hartmann and Schmidt (1998) study were used. The value quoted for algae (>1.6 mg/L), although lower, was a greater than value set at the limit of solubility in the test; at this concentration, there was only 13% inhibition of growth rate and 26% inhibition of biomass indicating that the EC50 value for algae is above the saturation concentration. Steger-Hartmann and Schmidt is a reliable study (rated 2 according to the criteria set out by Klimisch, 1997) and gives the lowest actual EC/LC50 value observed in the key information for any of the ecotoxicology endpoints. The study examined toxicity of the test substance to Daphnia magna over a 48-hour exposure period and was conducted in accordance with OECD guideline for testing number 202. The standard assessment factors given in the European Chemicals Agency guidance document (R.10: Characterisation of dose [concentration]-response for environment) have been used to predict the above PNEC values from the results.

PNECstp has been derived based upon the Clarke (2010) study which provided an EC50 result of >1000 mg/L and a NOEC of 44 mg/L. The PNEC value has been derived from the NOEC. The standard assessment factors given in the European Chemicals Agency guidance document (R.10: Characterisation of dose [concentration]-response for environment) have been used to predict the PNEC values from the results.

PNECsoil has been derived based uponm the Sindermann (2015) earthworm reproduction study, which provided an NOEC of 170 mg/kg dwt (converted to 3.4% organic matter content). The standard assessment factors given in the European Chemicals Agency guidance document (R.10: Characterisation of dose [concentration]-response for environment) have been used to predict the PNEC values from the results.

PNECsediment has been estimated using the equilibrium partitioning method, in the absence of measured physico-chemical data, based on physico-chemical properties determined by expert judgement.

Conclusion on classification

Classification and labelling has been based upon the key information for the ecotoxicity endpoints. The results of these studies are as follows:

72 hour LOEC (fish): 3.1 mg/L (Steger-Hartmann T and Wendt B 1998)

48 hour EC50 (Daphnia): 2 mg/L (Steger-Hartmann, T. & Schmidt, M. 1998)

72 hour EC50 (algae): >1.6 mg/L (Steger-Hartmann T 1999)

It should also be considered that the substance does not meet the definition of a readily biodegradable substance (Hanstveit 2003).

The lowest of these results is the 72 hour EC50 for algae (Steger-Hartmann 1999), however this is a greater than the limit of solubility value set in the test and is therefore not suitable for classification and labelling. The 48 -hour EC50 (Daphnia) value presented by Steger-Hartmann and Schmidt (1998), of 2 mg/L is suitable for use for classification and labelling and this meets the criteria under Regulation (EC) No 1272/2008 as follows:

Hazardous to the aquatic environment, Aquatic Chronic: Category 2 (H411)