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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Description of key information

BCF < 500

Key value for chemical safety assessment

BCF (aquatic species):
260 dimensionless

Additional information

Assessment of the parent compound Benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-,C7-9-branched alkyl esters (CAS: 125643 -61 -0)

In an OECD 305 flow through test on Rainbow trout, a low bioaccumulation potential of Benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-,C7-9-branched alkyl esters was established with a maximum BCF(whole fish) of 260. Fish were exposed to 0.05 or 0.25 μg/L of [ring-U-14C] Benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-,C7-9-branched alkyl esters (cited as TK11014 or Irganox L135/1135) during 35 days (CIBA 2006, Huntington Life Sciences No: CBG0865/063570).

The exposure was followed by a depuration period of 28 days. At the low exposure concentration, the bioconcentration factor was determined as 112 in the edible fraction, as 361 in the non-edible fraction and as 258 in the whole fish based on the total radioactivity. After 18 days, 90% of the radioactivity was eliminated from the fish. At the high concentration the bioconcentration factor was determined as 112 in the edible fraction, as 371 in the non-edible fraction and as 260 in the whole fish. Chromatographic analysis of the fish extracts showed that TK 11014 accounted for 25 – 40% of the radioactive dose.

Corresponding bioconcentration factors for the parent substance were low and mean values were in the range 50 - 201, the lowest values related to tihe edible portion of fish.

During exposure 58 – 82 % of the radioactivity was the test substance, and Metilox acid was identified as the major metabolite. Its content was highest on day 35, when it accounted for 35% of the radioactive dose.

As a worst case the BCF(whole fish) based on total radioactivity of 260 was used.

Supporting assessment of the major degradation product Metilox acid (CAS: 20170-32-5)

The bioconcentration of Metilox acid was tested in a study on the uvcb substance CAS 179986 -09 -5. One constituent of this substance is Metilox (CAS 6386 -38 -5). Metilox acid (CAS: 20170-32 -5) was identified as relevant transformation product.

The study was conducted according to OECD guideline 305 C. At 50 ug/l, the bioconcentration factor was determined to be 60-223 and 121-532 at 5 ug/l, respectively, after 8 weeks of exposure. The exposure concentration is well below the solubility limit of Metilox acid in water.