Glycerides, C16-18 and C18-unsatd. mono- and di-, citrates

Endpoint summary

Description of key information

There is one experimental study according to OECD 222 available for Glycerides, C16-18 and C18-unsatd. mono- and di-, citrates (CAS 91052-16-3). Exposure of the soil compartment is generally considered to be low. Even if exposed to the soil the target substance is readily biodegradable indicating that it will not be persistent in the environment. Indirect exposure via irrigation or atmospheric transport is considered to be negligible based on the physico-chemical properties of the target substance (water solubility: 1.86E-37 to 1.2721 mg/L; vapour pressure: < 0.001 Pa).

In absence of a clear indication of selective toxicity towards a specific group of organisms, terrestrial toxicity was tested on the earthworm Eisenia fetida for the target substance itself, as recommended by the “Guidance on information requirements and chemical safety assessment Chapter R.7c: Endpoint specific guidance” (ECHA, 2014). No studies are available for terrestrial arthropods, terrestrial plants or soil microorganisms. However, since the substance is poorly soluble (1.86E-37 to 1.2721 mg/L) in water and has potential to adsorb to solid soil particles, a soil dwelling organism, such as the earthworm, which is exposed to the complete soil system via both dermal and oral uptake, is the most relevant test organism to evaluate the terrestrial toxicity.

The available study was conducted according to OECD 222 (GLP; Kamper, 2016). No inhibition of reproduction was recorded after 56 d of exposure up to a nominal concentration of 1000 mg/kg soil dw (NOEC (56 d) ≥ 1000 mg/kg soil dw). The earthworm study shows that the toxicity to terrestrial organisms is very low.

After absorption, Glycerides, C16-18 and C18-unsatd. mono- and di-, citrates is expected to be enzymatically hydrolyzed by carboxylesterases yielding the corresponding alcohol and fatty acid. QSAR estimations using BCFBAF v3.01 support the expected rapid biotransformation of this substance. When including biotransformation, BCF and BAF values of 0.89 - 34.81 L/kg, respectively were obtained (Arnot-Gobas estimate, including biotransformation, upper trophic). The metabolism of the hydrolysis products is well established and not of concern in terms of bioaccumulation (for further information see chapter 5.3 of the technical dossier). Summarizing, Glycerides, C16-18 and C18-unsatd. mono- and di-, citrates is expected to be rapidly hydrolyzed to the respective fatty acid and fatty alcohol. Therefore, the overall potential for bioaccumulation is low.

Furthermore, experimental data for aquatic toxicity are available indicating a low toxicity to aquatic organisms. Aquatic data can be used as an indicator for potential effects on soil organisms (ECHA, 2014). These results support the assumption that the target substance is of low toxicity to terrestrial organisms.

The available data for toxicity to activated sludge microorganisms support the determination of a lack of toxicity to soil microorganisms. No inhibition of respiration rate of activated sludge microorganisms was observed in the available experimental study. The Guidance Document (ECHA, 2014, page 136) states that a test on soil microbial activity will only be additionally necessary for a valid PNEC derivation if inhibition of sewage sludge microbial activity has occurred and this is clearly not the case. This is supported by further evidence from literature data. These data show that soil microorganism communities are well capable of degrading fatty acid esters (Hita et al., 1996 and Cecutti et al., 2002) and use them as energy source (Banchio & Gramajo, 1997). Based on the available information, effects on soil microorganisms are not expected to be of concern, and consequently, no further testing is required.

In conclusion the target substance is of low toxicity to terrestrial organisms based on all available data.