2,2,6,6-Tetramethylpiperidin-4-yl dodecanoate

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

0.001 mg/L

Assessment factor:

500

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

0.003 mg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0 mg/L

Assessment factor:

10 000

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

9.5 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

1.03 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

0.051 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 mg/kg soil dw

Assessment factor:

1 000

Extrapolation method:

assessment factor

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Additional information

According to ECHA’s Guidance on information requirements and chemical safety assessment, Chapter R.10: Characterisation of dose [concentration]-response for environment, an assessment factor of 1000 is the standard value to derive the PNEC-aquatic when at least one short-term L(E)C50 from each of three trophic levels (fish, invertebrates (preferred Daphnia) and algae) is available. Furthermore, the guidance document states that the use of a factor of 1000 assumes that each of the identified uncertainties makes a significant contribution to the overall uncertainty. For any given substance there may be evidence that this is not so, or that one particular component of the uncertainty is more important than any other. In these circumstances it may be necessary to vary this factor. This variation may lead to a raised or lowered assessment factor depending on the available evidence.

In case of the present compound the regular short-term toxicity tests on fish, daphnids and algae are available according to the OECD guidelines 203, 202 and 201 and corresponding L(E)C50 values were determined. Additionally, a toxicity study on Lemna gibba (OECD 221) and a screening study on Daphnia in the presence of low concentrations of humic acid were conducted. Table 1 gives on overview of the results.

Table 1: Overview of the toxicity tests on fish, daphnids and algae as well as the additional tests on Lemna gibba and Daphnia magna with humic acid.

Test system	L(E)C50
Short-term toxicity to fish (OECD 203)	0.26 mg/L
Short-term toxicity to Daphnia (OECD 202)	0.383 mg/L
Toxicity to algae (OECD 201)	0.626 mg/L
Toxicity to duckweed (OECD 221)	>1.02 mg/L
Short-term toxicity to Daphnia with humic acid - screening	>1.90 mg/L

 

Lemna gibba represents a member of aquatic plants other than algae and delivers further information on the toxic potential of the compound towards a wider range of organisms. This study revealed EC50 and EC10 values of greater than 1.02 mg/L (measured value) and a NOEC value of 0.17 mg/L. The non-GLP but well documented screening study towards Daphnia magna in the presence of low concentrations of humic acid investigated the effect of the test substance on the immobilization of Daphnia magna according also to OECD guideline 202. Under environmental conditions the compound is present in its cationic form and expected to bind to humic acid, suspended particles and the solid soil phase which reduces its bioavailability and its toxic effects towards aquatic organisms. Therefore, the more realistic approach of a test with low concentrations of humic acid was chosen to have a better approximation of the compound’s environmental behavior and subsequent toxic potential. The M4 test medium used in this study was amended with a low level of humic acid equivalent to 1 mg/L total organic carbon in order to better approximate a natural surface water. The EC50 value was determined to be greater than 1.9 mg/L and the NOEC value as 0.95 mg/L. The mitigating effect of humic acid as demonstrated in the Daphnia magna screening study is critical for a proper assessment of the toxic behavior of the compound in the environment.

In light of the available data an assessment factor of 1000 seems to be overly protective. On the one hand additional information on a further species (Lemna gibba) is available and on the other hand the more realistic behavior of the compound under environmental conditions was investigated. According to ECHA’s Guidance on information requirements and chemical safety assessment, Chapter R.10 the assessment factor can be lowered depending on the available evidence. Both the study on Lemna gibba and the screening study towards Daphnia magna clearly reduce the overall uncertainty in the derivation of the PNEC-aquatic. The study towards Lemna gibba reduces the interspecies variation and the study towards Daphnia magna with humic acid is clear proof that the cationic properties of the compound mitigate the toxic potential. Furthermore, in the available regular OECD 201, 202 and 203 studies the lowest L(E)C 50 was determined in the fish study with a LC50 of 0.26 mg/L. The study was conducted without humic acid. Subsequently, this value was used for the derivation of the PNEC-aquatic and thus represents a worst case condition as the mitigating effect of humic acid and other suspended particles is not even taken into account. Therefore, it was decided to use an assessment factor of 500 for the derivation of the PNEC-aquatic. Against the background of the available data a factor of 500 still seems to be a conservative and protective factor and it still ensures that possible adverse effects are identified in the hazard assessment.