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Biodegradation in water and sediment: simulation tests

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biodegradation in water: simulation testing on ultimate degradation in surface water
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:
A study does not need to be conducted according to REACH Annex IX Sect. 9.2 Col. 2.
The performance of simulation test on biodegradation in surface water was considered scientifically not justified.

REACH Regulation No. 1907/2006, Annex IX, Sect. 9.2 Col. 2, states as follows: “9.2. Further biotic degradation testing shall be proposed by the registrant if the chemical safety assessment according to Annex I indicates the need to investigate further the degradation of the substance and its degradation products."

The chemical safety assessment does not indicate the need to further investigate the biodegradation of the substance for the following reasons:

Direct and indirect exposure of the test item to surface water 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 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 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 the 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 hydrolysis study, t1/2 at pH4 and pH7 is 8 and 9 h at 25°C, respectively. Thus at the relevant temperature and pH values of aquatic toxicity tests the t1/2 is below 12 h.

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 is not considered to be significantly exposed by the test item.

In conclusion, simulation testing on ultimate degradation in surface water is considered not scientifically justified since the chemical safety assessment does not indicate the need to further investigate the degradation properties of the substance according to REACH Regulation No. 1907/2006, Annex IX, Sect. 9.2 Col. 2. Further, the test item is found to be readily biodegradable.

Description of key information

The performance of simulation tests for biodegradation in water and sediment is scientifically unjustified.

REACH Regulation No. 1907/2006, Annex IX, Sect., Col. 2, states as follows: “ The study need not to be conducted:

- if the substance is readily biodegradable, or

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

Direct and indirect exposure of the test item to water and sediment is highly unlikely. Furthermore, the test item is considered to be readily biodegradable, therefore simulation testing for biodegradation in water is scientifically not justified.

Key value for chemical safety assessment

Additional information