Reaction products from the esterification of neopentylglycol with fatty acids, C16-18 (even numbered) and C18-unsatd. and fatty acids, C18-unsaturated, dimers

Sediment toxicity

Description of key information

The chemical safety assessment according to Annex I of Regulation (EC) No 1907/2006 does not indicate the need to investigate further the effects on sediment organisms. Based on the presented information, toxicity to sediment organisms is not expected to be of concern.

Additional information

Reaction products from the esterification of neopentylglycol with fatty acids, C16-18 (even numbered) and C18-unsatd. and fatty acids, C18-unsaturated, dimers is readily biodegradable therefore chronic exposure of sediment organisms is unlikely. Furthermore, the substance is not toxic to aquatic organisms up to the limit of water solubility. In addition, Reaction products from the esterification of neopentylglycol with fatty acids, C16-18 (even numbered) and C18-unsatd. and fatty acids, C18-unsaturated, dimers is not expected to bioaccumulate, due to rapid metabolism.

Distribution to the environmental compartments, intrinsic properties and fate

A direct release of Reaction products from the esterification of neopentylglycol with fatty acids, C16-18 (even numbered) and C18-unsatd. and fatty acids, C18-unsaturated, dimers to the aquatic system is not anticipated, thus release to the aquatic compartment might only occur via sewage treatment plants.

According to the Guidance on information requirements and chemical safety assessment, Chapter R.7b (ECHA, 2014) once insoluble chemicals enter a standard STP, they will be extensively removed in the primary settling tank and fat trap and thus, only limited amounts will get in contact with activated sludge organisms. Nevertheless, once this contact takes place, these substances are expected to be removed from the water column to a significant degree by adsorption to sewage sludge (Guidance on information requirements and chemical safety assessment, Chapter R.7b, (ECHA, 2014). The target substance is characterized by a log Koc value of > 5 (KOCWIN v2.00) and is poorly soluble in water (< 0.05 mg/L at 20 °C) and thus will undergo the same fate as stated in the Guidance document. Furthermore, Reaction products from the esterification of neopentylglycol with fatty acids, C16-18 (even numbered) and C18-unsatd. and fatty acids, C18-unsaturated, dimers is readily biodegradable (95.6% CO2 evolution after 28 days; Häner, 2007) and according to the Guidance on information requirements and chemical safety assessment, Chapter R.7b, readily biodegradable substances can be expected to undergo rapid and ultimate degradation in most environments, including biological Sewage Treatment Plants (STPs) (ECHA, 2014). Therefore, after passing through conventional STPs, release of the substance into the aqueous/sediment compartment are likely to be negligible.

Aquatic ecotoxicity data

Acute aquatic toxicity tests for the suitable source substance neopentylglycol dioleate (CAS 42222-50-4) to fish, invertebrates and algae showed no adverse effects in the range of the water solubility of the substance (< 0.05 mg/L at 20°C). The second structurally related source substance heptanoic acid, ester with 2,2-dimethyl-1,3-propanediol (CAS 68855-18-5) showed no toxicity to activated sludge microorganisms. Additionally, no effects occurred in the long-term toxicity tests with Daphnia magna (OECD 211) with source substance neopentylglycol dioleate at the tested loading rate of 1 mg/L, which is far above the water solubility of the substance (< 0.05 mg/L at 20 °C). The obtained results indicate that the target substance neopentylglycol dioleate is also not likely to show toxicity to sediment organisms.

Metabolism/Bioaccumulation

The test substance has a log Kow of > 10 (KOWWIN v1.67) indicating a potential for bioaccumulation. But due to the low water solubility, rapid environmental biodegradation and metabolisation via enzymatic hydrolysis, a relevant uptake and bioaccumulation in aquatic organisms is not expected. After absorption, Reaction products from the esterification of neopentylglycol with fatty acids, C16-18 (even numbered) and C18-unsatd. and fatty acids, C18-unsaturated, dimers is expected to be enzymatically hydrolyzed by carboxylesterases to the free fatty acid (oleic acid) and the free alcohol (neopentyl glycol). From literature it is well known, that these hydrolysis products will be metabolized and excreted in fish effectively (Heymann, 1980; Lech & Bend, 1980; Lech & Melancon, 1980; Murphy & Lutenske, 1990). This is supported by a low calculated BCF value of 0.893 L/kg ww (BCFBAF v3.01, Arnot-Gobas, including biotransformation, upper trophic). Please refer to IUCLID Section 5.3 for a detailed overview on bioaccumulation of the substance. Thus, taking all information into account, the bioaccumulation of the substance is assumed to be low.

Conclusion

Due to its readily biodegradable nature, extensive degradation of this substance in conventional STPs will take place and only low concentrations are expected to be released (if at all) into the environment. Once present in the aquatic compartment, further biodegradation will occur and, due to the high log Kow, low water solubility and high adsorption potential, the test substance will be bioavailable to sediment organisms mainly via food and contact with suspended organic particles. After uptake by sediment species, extensive and fast biotransformation of the substance by carboxylesterases into fatty acids acid and neopentyl glycol is expected. The supporting BCF/BAF values estimated with the BCFBAF v3.01 program, Arnot-Gobas model including biotransformation, also indicate that this substance will not be bioaccumulative (all well below 2000 L/kg). Furthermore, aquatic toxicity data show that no effects occur up to the limit of water solubility. Therefore, the substance is unlikely to pose a risk for sediment organisms, hence toxicity to sediment organisms is not expected to be of concern and thus there is no need to investigate further the effects on sediment organisms.