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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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bioaccumulation in aquatic species: fish
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
the study does not need to be conducted because direct and indirect exposure of the aquatic compartment to the substance is unlikely
Justification for type of information:
The performance of a study on bioaccumulation in fish was considered scientifically not justified.

REACH Regulation No. 1907/2006, Annex IX, Sect. 9.3.2, Col. 2, states as follows: “9.3.2: The study need not to be conducted: - if the substance has a low potential for bioaccumulation (for instance a log Kow ≤ 3) and/or a low potential to cross biological membranes, or direct and indirect exposure of the aquatic compartment is unlikely. ”

Direct and indirect exposure of the test item to surface water is highly unlikely. Due to the unstable nature of organic peroxides, it can be assumed that upon contact with water and organic matter, the test item undergoes degradation resulting in the formation of respective alcohols and acids. Hydrolysis half-life of TBPIN was determined to be 213.2 hrs (ca. 9 days) at 12 °C, reflecting the worst case half-life determined with TBPIN in this study. Therefore, an abiotic degradation of the test item in the environment is expected.

In addition, TBPIN was investigated in three screening studies on ready (OECD 301 D) and inherent (OECD 302 A) biodegradation (Laus, 2010; Akzo, 1994; Pharmaco-LSR, 1993). Biodegradation was observed to be 4 % or 22 % in the OECD 301D Tests. Based on these findings, TBPIN cannot be considered as readily biodegradable. However, in the semi-continuous activated sludge (SCAS) Test 58 % biodegradation were recorded based on O2 consumption. Consequently, TBPIN and/or its hydrolysis products are considered to be inherently biodegradable. According to ECHA Guidance on Information Requirements and Chemical Safety Assessment Chapter R11: PBT/vPvB Assessment inherent biodegradability of a substance is proof enough for considering the substance as not P or vP.

The very low exposure of the water compartment is further based on the following facts:
Organic peroxides, when released into the sewage of a plant production or a downstream user’s plant, are treated with other substances in dedicated sewage treatment plants. The activated sludge stemmed from these sewage treatment plants are then extracted and treated as chemical waste. From the production plant, the release of organic peroxide into the sewage is very limited, not to say completely negligible. The waste water from production plant can be treated on site (at least a physical/chemical treatment, which will neutralize potential residual organic peroxide), which is usually followed by a biological treatment. Regarding the rest of the lifecycle, organic peroxides are mainly used as cross-linking agent/polymerization initiator for the production of resins/rubbers/polymers. Based upon the fact that organic peroxides are totally consumed during the process (>99%, which is confirmed by the release factor to sewage for curing agents from ESD n°3), the surface water is not exposed to organic peroxides via the waste water system. As a consequence, the surface water is not considered to be significantly exposed by the test item.

In addition, bioaccumulation potential was estimated by QSAR calculation for the parent compound. The substance was within the applicability domain of the model and thus fulfilling validity criteria of the QSAR calculation. A calculated BCF value of 372 L/kg was obtained, being way smaller than the threshold value of 2000 L/kg for the B criterion. This further indicates no concern in regards to bioaccumulating potential of TBPIN. Further, results of a BCF study with 3,5,5-Trimethylhexanoic acid (CAS 3302-10-1), one of both hydrolysis products of TBPIN, reveal even lower BCF values in the range of 0.5 to 7 (please refer to disseminated information of REACH Registration Dossier of 3,5,5-Trimethylhexanoic acid). The other hydrolysis product, tert-butanol (CAS 75-65-0), was not investigated for its bioaccumulating potential. However, its logPow was determined to be 0.3. Tert-butanol is therefore not considered of concern in regards to bioaccumulation (logPow < 4.5, please also refer to disseminated information of REACH Registration Dossier of tert-butanol).

In conclusion, according to REACH Annex IX, Sect. 9.3.2, Col. 2 the study does not need to be conducted as exposure to the aquatic environment is unlikely, as outlined above. Further, the substance is readily biodegradable and thus not considered to be P or vP. Therefore, testing on bioaccumulation properties in regards to PBT or vPvB assessment is also not applicable. In addition, QSAR calculation of the parent compound as well as experimental data of the hydrolysis products indicate no concerns in regards to bioaccumulation potential.
Based on these points testing for bioaccumulation is considered neither scientifically justified nor reasonable. And for animal welfare reasons no test is proposed for bioaccumulation in fish.

Description of key information

A study does not need to be conducted according to REACH Annex IX Section 9.3.2 Column 2.

Key value for chemical safety assessment

Additional information