6-[(1-oxomethyloctyl)amino]hexanoic acid

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:

11.44 mg/L

Assessment factor:

100

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

no hazard identified

Sediment (marine water)

Hazard assessment conclusion:

no hazard identified

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

no hazard identified

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Additional information

The submission substance - or by read across its supporting substances - was tested at high concentrations of 100 mg/L or higher. No effects were observed in reliable (RL 1 or RL 2) acute toxicity tests with freshwater organisms of three trophic levels and in a reliable (RL 2) test on a marine fish species (turbot). Other tests on marine species are available, however judged to be not reliable. Consequently, no LOEC, NOEC, or ECx - value can be calculated. Since these data are a prerequisite to estimate a PNEC_freshwater and further on by equilibrium partitioning a PNEC_sediment or PNEC_soil, it is not possible to derive these values.

Sediment or soil are not anticipated to be relevant compartments for the submission substance: It has a low potential for adsorption to sediment or soil. Its log Pow is < 3.0, and calculated log Koc-values for the neutral, non-dissociated molecule using KOCWIN v2.00 (US-EPA EPI Suite v. 4.11) are between 1.50 (estimate based on experimentally determined log Kow of 2.47 for the free acid) and 2.44 (estimate according to molecular connectivity index based method). Actual adsorption potential will still be considerably lower: due to being an organic acid with an estimated pKa of 4.69, at pH 7.0, 99.5% will be negatively charged (dissociated). Negatively charged compounds are known to have a lower tendency to sorb compared to non-charged analogues. Furthermore, the submission substance is readily biodegradable and environmental concentrations will be very low.

Two reliable (RL1 and RL2) studies on STP microorganism toxicity (activated sludge respiration inhibition tests according to OECD 209 and compliant to GLP) are available for the submission substance and by read across its supporting substances with following results:

For 6-(isononanoylamino)hexanoic acid, compound with 2,2’,2’’-nitrilotriethanol no respiration inhibition was observed up to the highest tested concentration of 10000 mg/L (reliability category 1).

In the test on 6-(isononanoylamino)hexanoic acid Tween 80 was used to enhance solubility of the otherwise poorly soluble test item far above the level of water solubility, which renders the study reliable with restrictions (RL 2). In spite of artificially high concentration levels due to the solubilizer, observed respiration inhibition was comparably low with an observed EC20 (3h) of 386 mg/L and an EC50 (3h) of 1144 mg/L (key value for safety assessment). Thus, under natural conditions taking the poor solubility of 6-(isononanoylamino)hexanoic acid into account, no toxicity towards sewage treatment plant microorganisms is expected also for this compound.

Secondary poisoning is highly unlikely: As pointed out above, the submission substance being an organic acid with an estimated pKa of 4.69 is under environmentally relevant conditions almost completely present in its dissociated form, i.e. negatively charged. Experimentally determined log Kow values are therefore low, i.e. between 2.47 (free acid) down to -0.04 (salt). It is known that ionic compounds have a low potential to cross membranes and to bio-accumulate. Therefore, it is highly unlikely that the submission substance would present any relevant bioaccumulation potential. Log Kow is far below the screening criterion on B of 4.5. In addition, the submission substance is readily biodegradable. Thus environmental concentrations will be very low. In accordance with ECHA Guidance on Information Requirements and CSA, Part B, assessment of secondary poisoning is not necessary.

Conclusion on classification

The submission substance - or by read across its supporting substances - was tested at high concentrations of 100 mg/L or higher. No effects were observed in reliable (RL 1 or RL 2) acute toxicity tests with freshwater organisms of three trophic levels and in a reliable (RL 2) test on a marine fish species (turbot). In addition, due to being readily biodegradable, long term effects in the environment can be excluded for the submission substance. In conclusion, no environmental classification is proposed.