Isopentyl acetate

Endpoint summary

Additional information

Summary and discussion of the data:

Phototransformation:

For isoamyl acetate, a half-life of about 64 hours at an atmospheric concentration of 5X10 +5 hydroxyl radicals per cu cm was estimated (*Meyland and Howard, SRC); From HSDB, original data sources: SRC and *Meylan WM, Howard PH; Chemosphere 26: 2293-99 (1993)

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Hydrolysis / Environmental Abiotic Degradation:

A base-catalyzed second-order hydrolysis rate constant of 0.10 L/mol-sec (SRC) was estimated using a structure estimation method (Mill et al.); this corresponds to half-lives of 2 years and 78 days at pH 7 and 8 respectively (Mill et al., SRC).

Info stated in HSDB database under "isoamyl acetate" entry. Original data referred to: SRC database ; Mill et al. (1987): Environmental Fate and Exposure Studies Development of a PC-SAR for Hydrolysis: Esters, Alkyl Halides and Epoxides. EPA Contract No. 68-02-4254. Menlo Park,CA: SRI International (1987)

The substance appears to be relatively stable and does not appear to easily degrade on non-biotic pathways.

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Biodegradation:

Isopentyl acetate is regarded as readily biodegradable (see discussions under IUCLID endpoints 5.2 and 5.2.1) based on the evaluation of two OECD test guideline studies on ready biodegradability.

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Bioaccumulation:

Under "4.1.3.2.3.3 Bioaccumulation", in "Guidance on the application of the CLP criteria (Version 3.0, ECHA, Nov 2012)" is stated:

"Annex I: 4.1.2.8.1

... Using a cut-off value of log Kow≥4 is intended to identify only those substances with a real potential to bioconcentrate. While this represents a potential to bioaccumulate, an experimentally determined BCF provides a better measure and shall be used in preference if available. A BCF in fish of ≥ 500 is indicative of the potential to bioconcentrate for classification purposes. ..."

The log Kow was experimentally determined to be 2.7 and the estimated BCF (derived from log Kow ) as 28.1 L/kg wet-wt. These data point to a low potential for bioaccumulation of isopentyl acetate.

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Transport and distribution:

Adsorption/desorption:

In "Guidance on information requirements and chemical safety assessment Chapter R.7b: Endpoint specific guidance" (Version 1.2, ECHA, Nov 2012) is stated:

"R.7.8.7 Introduction to sediment organisms’ toxicity:

Substances that are potentially capable of depositing on or sorbing to sediments to a significant extent have to be assessed for toxicity to sediment-dwelling organisms. In addition, marine sediment effects assessment is necessary for substances that are known to be persistent in marine waters and may accumulate in sediments over time. In general substances with a Koc < 500 – 1000l/kg are not likely sorbed to sediment (SETAC 1993). According to this, a log Koc or log Kow of ≥3 is used as a trigger value for sediment effects assessment."

Koc and log Koc values were estimated based on the experimental log Kow of 2.7.

The values are Koc = 225.4 L/kg and Log Koc = 2.35. The estimated Koc is below the trigger value of 500.

The log Koc value is below the trigger value of 3 for sediment effects assessment.

The log Kow value is below the trigger value of 3 for sediment effects assessment.

Nevetheless for completeness reasons, the PNECsediment was calculated with EPM and used in the risk assessment.

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Transport and distribution:

Volatilisation probably leads to a limited exposure to isopentyl acetate and therefore a low potential for bioaccumulation:

Henry's Law constant:

The Henry's Law constant for isoamyl acetate was measured as 5.9X10-4 atm-cu m/mole at 25 deg C (Hine and Mookerjee). This value indicates that isoamyl acetate will volatilize from water surfaces (Lyman et al., SRC). Based on this Henry's Law constant, the volatilization half-life from a model river (1 m deep, flowing 1 m/sec, wind velocity of 3 m/sec) is estimated as approximately 5 hours (Lyman et al., SRC). The volatilization half-life from a model lake (1 m deep, flowing 0.05 m/sec, wind velocity of 0.5 m/sec) is estimated as approximately 121 hours (Lyman et al., SRC). Isoamyl acetate's Henry's Law constant (Hine and Mokerjee) indicates that volatilization from moist soil surfaces is expected (SRC).

Volatilisation from dry soil:

Isoamyl acetate is expected to volatilize from dry soil surfaces based on a vapor pressure of 5.6 mm Hg at 25 deg C (Daubert and Danner).

Reference:

HSDB database: http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?HSDB) under the entry of "isoamyl acetate", under "Volatilization from Water/Soil". (see also IUCLID 5.2.2 for details of the references of the original data sources)