2-ethyl-2-[[(1-oxononyl)oxy]methyl]propane-1,3-diyl dinonan-1-oate

Endpoint summary

Description of key information

No hazard identified.

Additional information

In accordance with column 2 of REACH Annexes IX and X, terrestrial studies do not need to be conducted if direct and indirect exposure of the soil compartment is unlikely. Direct exposure to soil is not likely, since the substance is not intentionally applied to soil. Indirect exposure of soil organisms is also not likely since the substance is readily biodegradable(OECD 301B: 76% biodegradation within 28 days; biodegradation rate/level comparable to reference compound cellulose) and as such will largely be degraded in STPs. Based on substance properties, sludge adsorption may be an issue. However, biodegradation in soil was confirmed to be rapid for trimethylolpropane trinonanoate: At an initial concentration of 3 g test item /kg soil (n=2), the test item was shown to be degraded (mineralized to CO2) by 78.8% (+/- 6.1) within 63 days, with a DegT50 of only 7 days (Tosin, 2013). From this it may be deduced that biodegradation is effective even in the adsorbed state. As a consequence, deviating from the default assumption that biodegradation within the STP is limited to the freely dissolved fraction it can be concluded that for trimethylolpropane trinonanoate also the fraction adsorbed to sewage sludge will effectively be mineralized, making a relevant soil exposure via the sludge to soil pathway improbable. But even if a minor fraction escaped biodegradation in the surplus sludge phase and would reach agricultural soils, based on the determined DegT50 of only 7 days it is expected to be rapidly mineralized. As such, any accumulation within soils over time can be excluded with high certainty.

With regard to toxicity, based on a well-founded aquatic toxicity data-set the innocuousness of trimethylolpropane trinonanoate could be demonstrated without doubt: reliable acute as well as chronic studies on aquatic toxicity are available for all three trophic levels, i.e. algae, aquatic invertebrates (Daphnia) as well as fish (Danio rerio). For more details, please see endpoint summary on sediment toxicity, IUCLID section 6.2. As a result from these reliable studies with analytical verification of test item concentrations, neither short term hazard for aquatic organisms of three trophic levels at exposure concentrations a factor >55000 above the true solubility in water nor long-term hazard (OECD 310 and 311) at exposure concentrations equaling the saturation level in water could be identified.

According to ECHA guidance document R.7c, section R.7.11.5.3, “The absence of chronic or long-term effects in aquatic organisms up to the substance solubility limit, or of acute effects within the solubility range above 10 mg/l can be used as part of a Weight-of-Evidence argument to modify/waive the data requirements of Annex IX and X.” Based on the reliably demonstrated innocuousness of the submission substance to aquatic organisms, toxicity towards soil macroorganisms is highly unlikely: The equilibrium partitioning method for deriving a PNEC_soil from a PNEC_aquatic is accepted for a screening hazard assessment for soil macroorganisms. Key assumption in equilibrium partitioning is an equivalent toxicity of the test item towards aquatic and soil organisms, being modified only due to the bioavailable fraction, which may be reduced in soil due to adsorption of the test item to the solids fraction. As such, if no toxicity is observed at and even above the solubility limit in long-term and acute aquatic toxicity tests, respectively, based on the EPM theory toxicity towards soil organisms must be negated as well.

In conclusion, direct exposure to soil is highly unlikely (not intentionally applied to soil) and indirect exposure concluded to be negligible due to the biodegradability properties of the submission substance. Due to absence of any aquatic toxicity, soil macroorganism toxicity is highly unlikely and chronic soil toxicity testing is not expected to result in any relevant knowledge gain. Base on the available data, with regard to soil macroorgansims no hazard is identified.

Soil microorganism toxicity cannot be waived by EPM considerations based on aquatic toxicity towards three trophic levels. Rather, any observed toxicity towards STP microorganism indicates a potential for soil microorganism toxicity. For the submission substance, no microorganism toxicity was observed in the available test on ready biodegradability at an initial concentration of 79.2 mg/L. Further, from the study on biodegradability in soil performed with the submission substance (Tosin, 2013), at an initially applied concentration of 3 g test item /kg soil dry weight equally no soil microorganism toxicity became obvious. Rather, biodegradation started substantially faster as compared to the reference item cellulose used in this study. Based on these data, also soil microorganism toxicity can be excluded with high certainty.