tert-dodecanethiol

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

no hazard identified

Marine water

Hazard assessment conclusion:

no hazard identified

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

1 000 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

3 mg/kg sediment dw

Assessment factor:

100

Extrapolation method:

assessment factor

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

0.3 mg/kg sediment dw

Assessment factor:

1 000

Extrapolation method:

assessment factor

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

no exposure of soil expected

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

PNEC oral

PNEC value:

5.55 mg/kg food

Assessment factor:

90

Additional information

Fate

The substance is not expected to hydrolyse. Biodegradation data shows tert-dodecanethiol not to be readily biodegradable in an OECD 301 D test and therefore may be expected to persist in the environment (Jenkins 1990).

The bioconcentration factor (BCF) of this substance lies between 500 and 1950 L/kg. These values were derived from an OECD 305 study and other approaches under a WoE approach performed by Comber & Thomas (2013) and the full review is attached in chapter 5.3.1.

an adsorption study on soil/ sewage sludge by Mollandin (2010), using high performance liquid chromatography, gives a log Koc of 3.6, which indicates a strongly potential to adsorb on soil/sediment particles.

Ecotoxicity

A total of 14 ecotoxicity studies have been evaluated (review by Thomas & Comber, 2013 attached to chapter 13) and are considered fit for use in hazard assessment; 9 aquatic acute studies, 2 ASRIT studies; 1 chronic study on daphnids; one sediment chronic test on chironomids and an earthworm reprotoxicity test.

Of these, due to methodological problems, only 5 of these studies were considered valid by the reviewers: The 2 ASRIT studies, one acute study on daphnids, the chronic daphnid study and the chronic sediment study. Nevertheless, several other studies were classified Klimisch 4 and can be used in a weight of evidence approach notably an acute study on trout and the chronic study on worms.

For aquatic studies, no effects were observed at concentrations at or close to the solubility limit in any study. In certain cases effects were observed at intermediate concentrations but not at higher or lower concentrations. These effects are believed to be physical, due to the preparation methods used and should not be taken into account in the hazard assessment. In the worm study no effects were observed at the highest concentration tested of 100 mg/Kg dry weight however, no analysis of this volatile test substance was undertaken and the highest test concentration was only 100 mg/Kg dw.

In the sediment study a series of concentrations were used up to 926 mg/Kg dw measured and no effect on any parameter was observed up to 300 mg/Kg dw measured. This study has therefore been used as the key study for sediment effects. It is possible to use a reverse EP method to determine an equivalent NOEC for the aquatic compartment. The NOEC aquatic determined in this fashion is 0.75 mg/L confirming that the toxicity limit is far greater (a factor of 2000) than the solubility limit.

Conclusion on classification

As no toxicity has been found leading to the application of acute or chronic toxicity classification and taking into account that the substance is not readily/rapidly biodegradable and has a BCF confirmed experimentally at >500, tert-dodecanethiol can be classified only as Category Chronic 4 under CLP (regulation 1272/2008 and 286/2011), with the hazard statement H413: May cause long lasting harmful effects to aquatic life.