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Ecotoxicological information

Toxicity to soil microorganisms

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Endpoint:
toxicity to soil microorganisms
Data waiving:
exposure considerations
Justification for data waiving:
the study does not need to be conducted because direct and indirect exposure of the soil compartment is unlikely
Justification for type of information:
Direct and indirect exposure of OO-t-butyl-O-(2-ethylhexyl)monoperoxycarbonate to soil is highly unlikely. Due to the unstable nature of the 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 the respective alcohols and acids. Thus, toxicity to soil organisms was considered scientifically not justified. Furthermore, according to the Guidance on information requirements and chemical safety assessment R.7, Chapter R.7.11.5.3, the PEC and PNEC for the terrestrial compartment do not have to be calculated if exposure to soil is negligible. Based on the examples given this is applicable if e. g. potential land spreading or aerial deposition of the substance and other pathways such as irrigation or contact with contaminated waste can be considered unlikely. Taking the complete life cycle of this substance into careful consideration including the risk management measures in place, these qualifications are fulfilled. This is confirmed by the following argumentation when looking at the several routes chemicals can reach the soil:
1. Application of sewage sludge in agriculture
- Organic peroxides, when released into the sewage of a plant production or of a downstream user 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 wastewater from production plants is usually treated: at least a physical/chemical treatment, which will neutralize potential residual organic peroxide and that can be followed by a biological treatment. So it is expected that organic peroxides won’t be present in the 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 %) and that those processes are water-free (no production of sewage sludge), it is assumed that soil is not exposed to organic peroxides via the use of sludge. As a consequence, exposure of soil to organic peroxides via the application of sewage sludge in agriculture can be excluded.
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 via other pathways such as irrigation or contact with contaminated waste
- Contact with contaminated waste or deposition via e.g. irrigation processes is negligible. Any waste from production plants is treated on site and the organic peroxides are totally consumed during the industrial end uses. In addition, there are risk management measures in place to control the deposition via any other pathways such as irrigation. In case contamination takes place, the wastewater is disposed e. g. via STP with high efficiency or incineration (see also 1. above).
4. Deposition from the atmosphere / aerial deposition of the substance
- 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 OECD Emission Scenario Document n°3 on Plastic Additives. Based on organic peroxides uses, deposition on soil from the atmosphere is also not expected. In addition, dedicated equipment with high efficiency requiring only minor cleaning processes is implemented to prevent aerial deposition of the substance (e. g. adsorption units, off-gas cleaning, air-filtration using high efficiency air filter, waste gas membrane separation, biological treatment, thermal treatment, etc.).
Based on these arguments any exposure to soil is highly unlikely and is considered negligible. Therefore, no test is proposed for the soil compartment. As a worst case a PNEC soil was derived with the equilibrium partitioning method to cover cases in which accidential release ever occurs.

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