tert-butyl peroxyneodecanoate

Biodegradation in soil

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in soil: simulation testing

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because the substance is readily biodegradable

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 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.

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 readily 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. Furthermore, the test item is readily biodegradable, therefore simulation testing for biodegradation in soil was considered not scientifically justified.