tert-butyl peroxyneodecanoate

Long-term toxicity to fish

Link to relevant study record(s)

Reference

Endpoint:

fish early-life stage toxicity

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Justification for type of information:

The performance of a test for long-term toxicity to fish was considered not scientifically justified. REACH Regulation No. 1907/2006, Annex IX, Sect. 9.1., Col. 2, states as follows: “9.1.: Long-term toxicity testing shall be proposed by the registrant if the chemical safety assessment according to Annex I indicates the need to investigate further the effects on aquatic organisms.”

The chemical safety assessment does not indicate the need to further investigate the effects on aquatic organisms for the following reasons:

Exposure and stability considerations:
TBPND is not stable in the aquatic environment. 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. Hydrolysis half-life of TBPND was determined to be < 24 or even 12 h at 25 °C. Therefore, an abiotic degradation of the test item in the environment is expected.

In addition, TBPND is considered as inherently biodegradable based on a Closed Bottle Test according to OECD 301 D (26 % degradation after 28 days, 53 % after 140 days, please refer to IUCLID section 5.2.1). New data for other peroxyesters were recently generated. Those revealed that surface water does not change the degradation products or behavior compared to hydrolysis studies in water/buffer. It is therefore proposed to first invest more in clarifying the biodegradation potential of the compound before considering long-term toxicity testing in aquatic vertebrates.
For this reason a new prolonged closed bottle test was initiated. Preliminary results of a non-GLP enhanced closed bottle test revealed 65 % degradation after 28 days. 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 tert-butanol and 7,7-dimethyloctanoic acid 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 new data on biodegradation will be included in the dossier as soon as the GLP compliant study is concluded and study report is available. A second test with the respective hydrolysis product (neo¬decanoate, UVCB) will be performed depending on the outcome of the first test, as the data for the registered mono-constituent neodecanoic acid are not applicable and sufficient data for tert-butanol are available. Depending on the outcome in a second step a Zahn-Wellens test is foreseen as positive results for other organic peroxides were noted. 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. Based on preliminary results, TBPND could even be considered as readily biodegradable.


Based on the points outline above, long-term toxicity testing is considered scientifically not justified since the test item is not stable in the aquatic environment.
Further, Environmental Risk Assessment revealed safe use of the substance throughout its whole life cycle due to very low exposure of the water compartment which is especially 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 and with this aquatic organisms are not considered to be significantly exposed by the test item.

Furthermore, based on available data on acute and long-term toxicity to aquatic organisms, daphnia was considered to be the most sensitive species with the test item. This is in line with QSAR calculations. Chronic toxicity effect concentrations were estimated with ECOSAR v1.11 for algae, daphnia and fish (For more details please refer to IUCLID Section 6.1.2). The test item was within the applicability domain of the model thus reliability of the results is not affected. ChV values were estimated to be 0.041, 0.085 and 0.030 mg/L for fish, daphnia, and algae, respectively, being in well accordance with experimental data for long-term toxicity in algae and daphnia. Based on calculated values, again fish was predicted to be not the most sensitive species.

Therefore, and for animal welfare reasons, long-term toxicity testing with fish is considered to not improve the chemical safety assessment.
In summary, long-term toxicity testing in an aquatic vertebrate species is considered not scientifically justified according to REACH Regulation No. 1907/2006, Annex IX, Sect. 9.1., Col. 2 and not in line with animal welfare.

Description of key information

The performance of a test for long-term toxicity to fish was considered not scientifically justified. REACH Regulation No. 1907/2006, Annex VIII, Sect. 9.1.3, Col. 2, states as follows: “9.1.3: The study (long-term toxicity to fish) does not need to be conducted if:

- there are mitigating factors indicating that aquatic toxicity is unlikely to occur, for instance if the substance is highly insoluble in water or the substance is unlikely to cross biological membranes”

TBPND is not stable in aquatic environment. 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. In addition, the substance is not poorly water soluble and is not expected to have potential for bioaccumulation (calculated BCF = 925 L/kgwwt). Thus, the CSA does not show a need for an additional long-term aquatic test. Risk assessment is based on the long-term daphnia study.

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