tert-butyl peroxyneodecanoate

Biodegradation in soil

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in soil: simulation testing

Data waiving:

exposure considerations

Justification for data waiving:

the study does not need to be conducted because direct and indirect exposure of soil is unlikely

Justification for type of information:

The performance of a study on biodegradation in soil was considered scientifically not justified.

REACH Regulation No. 1907/2006, Annex IX, Sect. 9.2.1.3, Col. 2, states as follows: “9.2.1.3: The study need not to be conducted: - if the substance is readily biodegradable, or - if direct and indirect exposure of soil is unlikely. ”

Direct and indirect exposure of the test item to soil 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. Hydrolysis half-life of TBPND was determined to be < 24 or even 12 h at 20 °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 a simulation test.
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.


Further, Environmental Risk Assessment revealed safe use of the substance throughout its whole life cycle due to very low exposure of the soil compartment which is especially based on the following facts:
Chemicals can reach the soil via several routes:

1. Application of sewage sludge in agriculture. 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. So it is expected that organic peroxides are not present in sludge. 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 soil is not exposed to organic peroxides via use of sludge. As a consequence, soil is not exposed to organic peroxides via the application of sewage sludge in agriculture.

2. Direct application of chemicals. Based on the uses inventoried for organic peroxides there is no direct application of these substances on the soil compartment. Indeed, all uses are within industrial settings.

3. Deposition from the atmosphere. Deposition from the atmospheric compartment involves volatilization, vaporization or direct release of a considered substance into the atmosphere. Due to their dangerous intrinsic physico-chemical properties, organic peroxides are carefully handled in (semi-)closed systems and their transport, production and use are ruled by several regulations. This is also in line with the release factor to atmosphere for curing agents from ESD n°3. Based on organic peroxides uses, deposition on soil from the atmosphere is also not expected.

Based on these arguments exposure to the soil compartment is considered highly unlikely.

In conclusion, biodegradation testing in soil is considered not scientifically justified since exposure to this compartment is considered unlikely as outlined above according to REACH Regulation No. 1907/2006, Annex IX, Sect. 9.2.1.3, Col. 2. Further, the chemical safety assessment does not indicate the need to further investigate the degradation properties of the substance since the substance is inherently biodegradable and thus not considered to be P or vP. Therefore, further testing on P or vP properties in regards to PBT or vPvB assessment is also not applicable.

Description of key information

The performance of tests for biodegradation in soil is scientifically unjustified.

REACH Regulation No. 1907/2006, Annex IX, Sect. 9.2.1.3, Col. 2, states as follows:

“9.2.1.3: The study need not to be conducted:

-if the substance is readily biodegradable, or

-if direct and indirect exposure of soil is unlikely. ”

Direct and indirect exposure of the test item to soil is highly unlikely. Due to the unstable nature of organic peroxides, it can be assumed that upon contact with soil and organic matter, the test item undergoes rapid degradation resulting in the formation of respective alcohols and acids. Furthermore, TBPND was considered to be inherently biodegradable, therefore simulation testing for biodegradation in sediment was considered not scientifically justified.

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