tert-butyl peroxyneodecanoate

Bioaccumulation: aquatic / sediment

Link to relevant study record(s)

Reference

Endpoint:

bioaccumulation in aquatic species: fish

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

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 TBPND was determined to be < 24 or even 12 h at different pH values and 25 °C. Therefore, an abiotic degradation of the test item in the environment is expected.

In addition, TBPND is considered as readily biodegradable based on a Closed Bottle Test according to OECD 301 D (63 % degradation after 28 days, please refer to IUCLID section 5.2.1).

In ready biodegradability tests, the time window concept has been introduced as a simple alternative to quantify the rate of biodegradation. However, this concept is only applicable and valid for single water-soluble chemical substances. TBPND is a chemical in which two moieties are linked together. Upon hydrolysis the degradation products require the concerted action of at least two microorganisms as a single organism usually lacks the full complement of enzymatic capabilities. It can be expected that those two moieties usually do not have identical lag periods. Instead, sequential degradation is the case. Biodegradation curves of peroxyesters, such as TBPND, should therefore not be used to assess a 10- or 14- day effect.

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 925 L/kg was obtained, being well below the threshold value of 2000 L/kg for the B criterion. This further indicates no concern in regards to bioaccumulating potential of TBPND. The first 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). A BCF study is available for 7,7-dimethyloctanoic acid, the other hydrolysis product, stating a BCF of < 225. Therefore, no bioaccumulating potential is expected for both hydrolysis products.

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 available 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

The performance of a test for bioaccumulation in aquatic species, preferably fish, is scientifically unjustified. REACH Regulation No. 1907/2006, Annex IX, Sect. 9.3.2, Col. 2, states as follows: “9.3.2 The study need not be conducted if:

- the substance has a low potential for bioaccumulation (for instance a logKow<= 3) and/or a low potential to cross biological membranes, or

- direct and indirect exposure of the aquatic environment is unlikely. ” Direct and indirect exposure of the test item to 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 rapid degradation resulting in the formation of respective alcohols and acids. Therefore, TBPND was considered to have no bioaccumulation potential. Using EPIWIN 4.1 a BCF of 925 L/Kgwwtwas calculated indicating no potential for bioaccumulation.