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Please see IUCLID section "Additional information" below.

Additional information

3,5,5 -trimethylhexanoic acid is not expected to hydrolyse in the aqueous compartment at ambient conditions due to its chemical structure (GUBDH, 2008).

In accordance with column 2 of Annex IX, the study does not need to be conducted if the substance is readily biodegradable. 3,5,5-Trimethylhexanoic acid is readily biodegradable (Harlan, 2010).

 

The ready biodegradability of 3,5,5 -trimethylhexanoic acid was studied in a DOC Die-Away Test according to OECD 301A (Harlan, 2010). The biodegradation reached 96% after 21 d based on DOC removal. The 10 -d window was passed. In conclusion, 3,5,5 -trimethylhexanoic is readily biodegradable.

 

The Koc for 3,5,5-trimethylhexanoic acid was estimated by calculation as a function of soil pH using the method of Franco, Fu and Trapp (2009) (OXEA, 2019). Input parameters logPn (Kow for the neutral molecule) and pKa were determined in reliable experimental guideline studies. For environmental exposure and risk assessment, the value of (rounded) 123 L/kg obtained for Koc at soil pH 6.5 is regarded to be most relevant, because European soils are predominantly of neutral to slightly acidic pH. The low Koc indicates high mobility in soil and low potential for adsorption.

No significant bioaccumulation potential is expected for 3,5,5-trimethylhexanoic acid based on a measured BCF according to the MITI protocol, which corresponds to OECD 305 C (NITE, 2008). The BCF at the lower test concentration (0.1 mg/L) was < 3.1-7.0, while the BCF at the higher test concentration (1 mg/L) was lower (0.5-1.7).

Henry's law constant was calculated from water solubility and vapour pressure to be 0.104 Pa*m³/mol (20 °C; ECT, 2008). Hence, 3,5,5 -trimethylhexanoic acid is expected to have a low potential to volatilise from aqueous solutions.

 

In conclusion, it can be stated that 3,5,5 -trimethylhexanoic acid is not persistent in water and will be rapidly degraded (readily biodegradable), and no significant potential for bioaccumulation is expected. Its mobility in soil is high in the alkaline to slightly acidic range, and moderate in the acidic pH range. Volatility from aqueous solutions is low.