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 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, 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.

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 is considered not scientifically justified. REACH Regulation No. 1907/2006, Annex IX, Sect. 9.1., Col. 2, states that: “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 based on exposure and stability considerations.

1) The test item is readily biodegradable. Further, exposure to the water compartment is considered unlikely.

2) The bioaccumulation factor (BCF) for the test item was estimated to be BCF = 925 L/kgwwt by QSAR calculation. Therefore, the test item is of no concern regarding bioaccumulation.

In summary, long-term toxicity testing is considered not scientifically justified and not in line with animal welfare.