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Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Stability :

Two key studies evaluating the hydrolysis of Trigonox 101 are available. The first study was the preliminary study and the second study was the definitive study. In the preliminary study (Vos, 2010), two sets of results are available (Dupont and AkzoNobel) but were included in the same report. The tests were both performed under GLP and following OECD guideline 111, and in both case significant decomposition of Trigonox 101 occurred within 24 hours at pH4, 7 and 9. As the possible hydrolysis product TBA (tertiary-butyl alcohol) could not be detected no confirmation of the increase of this product in 24 hours could be given. Unfortunately, only the screening studies performed at 50°C have been conducted, however, as the results are consistent the test substance is expected to decompose rapidly in aqueous samples but the hydrolysis route is not yet known. These results can be considered as hydrolysis of the test substance. The half-life can be tentatively determined as between 4 and 13 hours at 50°C and extrapolated to 44.1 -143 hours at all three pHs at 20°C using the Arrhenius equation. In the definitive study (Habeck, 2011), performed under GLP and following OECD Guideline 111 and EU Method C.7, the results showed a half-life time comprised between 3.8 and 4.4 hours for all pHs (4, 7 and 9) at 20°C. To consider the worst case, a half-life for hydrolysis of 4.4 hours at 20°C is used as key value for chemical safety assessment.

Biodegradation:

One key study was available on the biodegradation of Trigonox 101. This study was performed according to modified OECD Test Guidelines to permit prolonged measurements with no GLP statement. In the SCAS test, Trigonox 101 was exposed to activated sludge maintained by daily addition of primary settled sewage for a period of 8 weeks. The test substance caused no reduction of the biodegradation of the organic compounds present in primary settled sewage. Therefore the test substance is considered to be non-inhibitory to the activated sludge.Trigonox 101 was not degraded in prolonged Closed Bottle tests inoculated with unacclimated and acclimated sludge from the SCAS unit. This result demonstrates that microorganisms do not have the ability to grow on this organic peroxide under aerobic conditions. Potential decomposition products of the test substance i.e. tert butanol and 2,5-dimethyl-2,5-hexanediol were degraded in Closed Bottle tests with both acclimated and unacclimated sludge (> 80% within 56 days).The length of the lag period found with 2,5-dimethyl-2,5-hexanediol with acclimated sludge was short compared to the period obtained with unacclimated sludge. This result suggests that the peroxide bond of Trigonox 101 is cleaved in the SCAS unit.

Bioaccumulation:

Two studies on bioaccumulation were available on TRIGONOX 101.

The first study (Erhardt, 2008) was evaluated as the key study. This study assessed the bioaccumulation of TRIGONOX 101 using the in vitro trout liver S9 metabolism assay (no standard guideline followed). The BCF value was determined with and without metabolism being taken into account. The calculation is based on the Arnot Gobas BCF mass balance model run with and without metabolism. When metabolic rate (Kmet) is set to 0, the model calculates a BCF ot 46097. When Kmet is experimentally determined using two methods: arterial hepatic and arterial hepatic and portal, blood flow extrapolation further to a trout hepatocyte in vitro study, BCFs are calculated as 766 and 443 L/Kg respectively. The in vitro rate of metabolism was determined for this organic peroxide. The substance dissipated rapidly under biologically active conditions. A half- life for metabolism was 210 min or 3.5 hours. These data were used to extrapolate in vivo rate constants of metabolism or Kmet of 0.116 day-1or 0.189 day-1using hepatic portal blood flow or hepatic portal and arterial blood flow, respectively. The use of these kMET values in conjunction with the Gobas model dropped the calculated BCF from 31,819.51(assuming no metabolism) to 521 or 839.

The second study (author unknown, 2004) was evaluated as the weight of evidence. This study assessed the bioconcentration of TRIGONOX 101 on Cyprinus carpio, following "Methods concerning the testing of new chemical substances" (Kanpo n°. 5, Yakuhattsu n°.615, 49th Unit, n°.392, 1974, partially revised in 1998), which is similar to OECD Guideline 305. Results demonstrated that a BCF steady-state of 3690 and 2250 L/Kg (for primary and secondary concentration areas respectively).

As the experimental BCF study was incomplete missing numerous details allowing it to be validated, the BCF and as further experimental data are available from an in vitro study which is deamed to be valid, it is concluded that the BCF is between 521 and 839.

Transport and distribution:

The adsorption coefficient of the substance in soil and sludge using an HPLC method was estimated in a reliable GLP study following OECD 121. Based on two measurements of the substance, and by comparison with reference substances, the Koc of the substance was calculated as 52600 at 30°C.

The Log Koc of the test substance was therefore approximately 4.72.