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Environmental fate & pathways

Endpoint summary

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The environmental fate of isononyl benzoate is determined by its low water solubility and its ready biodegradability under aerobic conditions as well as its biodegradability under anaerobic conditions. Studies on hydrolysis and bioaccumulation either yielded no result or were aborted prematurely due to the low water solubility and the fast degradation of the test item. In sewage treatment plants and surface waters rapid degradation is expected, since the test item was readily biodegradable in an OECD 301 screening test.

The adsorption coefficient on soil (KOC) of the test item was determined according to OECD guideline no. 121 [adopted on 22 January 2001] and EU test method C.19 [Directive 2001/59/EC, Official Journal L 225 2001]. The Adsorption coefficient on soil (KOC) was determined as KOC = 5000 to 6300 / log KOC = 3.7 to 3.8 (upper and lower limits of the test item mixture). The result indicate some potential of the test substance to adsorb to soil particles. As isononyl benzoate is readily biodegradable under aerobic conditions and will also be rapidly degraded under unaerobic conditions, a significant transfer of the test item to sediment and soil is considered to be highly unlikely.

The hydrolysis as a function of pH of the test item was determined according to DECD guideline no. 111 [adopted on 12 May 1981] and EU test method C.7 [Directive 92J69JEEC, Official Joumal L 383 A 1992]. The hydrolysis as a function of pH was not measurable because of poor solubility in aqueous buffer solutions.

Isononyl benzoate is readily biodegradable under aerobic conditions and also biodegradable under anaerobic conditions. Isononyl benzoate was tested in an OECD 301B study (modified Sturm test / CO2 evolution test) for ready biodegradability. The test item studied reached a degree of degradation of 89 % in the course of 28 days. Since the test substance was degraded by > 60 % in the course of 10 days after the time when biodegradation had achieved 10 %, Isononyl benzoate is considered to be "readily biodegradable".

Isononyl benzoate was tested in a DIN EN ISO 11734 (1998) study (comparable to OECD 311) for biodegradability under anaerobic conditions. Washed digested sludge, containing very low amounts of inorganic carbon, is diluted to total soids concentration of 1 g/L and incubated an 35 +- 2 °C in sealed vessels with a test chemical at an organic carbon concentration of 20 mg/L to 100mg/L for up to about 60 days.

The increase in headspace pressure in the test vessels resulting from the gas production of carbon dioxid and methane is measured. A considerable amount of carbon dioxine will be dissolved in water or transfomed to hydrogen carbonate or carbonate under the conditions of the test. This inorganic carbon is measured at the end of the test.

The test item isononyl benzoate studied reached a degree of degradation from headspace gas of 41% in the course of 60 days (mean of the test item batches). The degree of the total biodegradation (biodegradation from biogas and TIC-analyses) reached 55%. So, the test item can be considered as biodegradable under anaerobic conditions.

Isononyl benzoate was tested in a bioaccumulations study with fish (Cyprinus carpio) under flow-through conditions according to OECD 305. The study was aborted during the pre-exposure period, because the measured content of the test item in the test water was not stable and significantly lower than the nominal concentrations. Besides this, strong microbial growth (control: 15 cfu´s/mL; 10 µg/L nominal :1190 cfu´s/mL cfu = colony forming unit) could be observed in the test containers. These observations were clearly due to the ready biodegradability of the test item.

Therefore, it has to be concluded, that the test item was not suitable for the examination in the actual test system for technical reasons. In consequence, it seems highly unlikely that the test item isononyl benzoate will bioaccumulate to a high degree.