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Environmental fate & pathways

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In a standard hydrolysis study according to OECD guideline 111 half-lives of 14 -19h were found at 12 °C.

As ECHA advised in its notes for consideration the registrant performed a hydrolysis study according to OECD guideline 111, at 12 °C in natural surface water (containing 2-3 mg/L DOC and 15 mg/L TSS) and in deionized water with humic acid (containing 2-3 mg/L DOC). In this study half-lives decreased to 11.5h and 11.9h, respectively. Because half-lives are <12h under environmental conditions hydrolysis products have been identified in a separate study according to OECD guideline 111 tier 3.

2-Ethylhexanoic acid (CAS 149-57-5, log Kow = 2.64), Neopentyl alcohol (CAS 75-84-3, log Kow = 1.31) and Acetone (CAS 67-64-1, log Kow = -0.24) were formed in natural surface water, deionized water as well as standard pH 7 buffer. The presence of organic material did not affect formation of hydrolysis products.

On molar basis all three would be formed in equal amounts in theory. On mass basis 2-ethylhexanoic acid would be the main degradation product. From the hydrolysis study (van Dam, 2017) it can be concluded that 2-ethylhexanoic acid was indeed the main degradation product (largest mass) in most cases.

 

Due to the hydrolysis half-lives being < 12h, the hydrolytically degraded mixture was tested in a ready biodegradability test. The chemically converted test item was biodegraded by 69% at day 28 in the OECD 301 Closed Bottle test and should therefore be classified as readily biodegradable.

The log Kow of 6.2 would indicate that bioaccumulation should be determined. However the hydrolysis results show that half-lives of the parent material are < 12h under environmental realistic conditions. Hence, the likelihood of bioaccumulation is greatly reduced (REACH guidance document R.7c, section R.7.10.3.4, p. 26) focus should therefore be on the readily biodegradable hydrolysis products instead of the parent substance.

The Log Kow values of the hydrolysis products are 2.64, 1.22 and -0.24 (see aquatic summary information on degradation products) and therefore bioaccumulation is not expected.

Because 2-ethylhexanoic acid is identified as the main degradation product with equal toxicity to neopentyl alcohol, 2-ethylhexanoic acid is used in the exposure and risk assessment.

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