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Environmental fate & pathways

Biodegradation in water: screening tests

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Administrative data

Endpoint:
biodegradation in water: ready biodegradability
Data waiving:
study technically not feasible
Justification for data waiving:
the study does not need to be conducted because the substance is inorganic
Justification for type of information:
In accordance with column 2 of REACH Annex VII, the ready biodegradability test (required in section 9.2.1.1) does not need to be conducted as Activated Carbon - Low Density Skeleton (AC-LDS) is a refractory material and not amenable to break down by any natural chemical or enzymatic processes. AC-LDS is only broken down under extreme conditions - such as heating under reflux with concentrated sulphuric acid/nitric acid mixtures - when the carbon will eventually oxidise to CO2. AC-LDS cannot be rendered into a soluble form capable of being absorbed. Therefore AC-LDS cannot find its way to any cell site where it could conceivably be biodegraded. Moreover, testing is not feasible because the substance is not soluble in water.

Data source

Materials and methods

Results and discussion

Applicant's summary and conclusion

Conclusions:
In accordance with column 2 of REACH Annex VII, the ready biodegradability test (required in section 9.2.1.1) does not need to be conducted as 'Activated carbon' is a glassy material. It is not soluble in water and has a particle size between 0.5 to 250.0 µm. Therefore it is not expected to pass cell membranes to become accessible for enzymatic attack and thus enzymatic oxidation. But furthermore, the oxidation (mineralisation) of organic substances is accomplished by electron transfer from the electron donor (substance) to the electron acceptor. During biological substrate oxidation, mostly two electrons are transferred at the time, and two protons (H+) are split from the substrate (dehydrogenation). The hydrogen is transferred to NAD or NADP (acceptor) as part of the respiration chain (e.g., citric acid cycle). The substance activated carbon does not contain any hydrogen available for dehydrogenation; thus there is no energy gain by enzymatic dehydrogenation, so further biodegradation of this molecule will not occur. Therefore a test on the ready biodegradability is scientifically not justified.
Executive summary:

In accordance with column 2 of REACH Annex VII, the ready biodegradability test (required in section 9.2.1.1) does not need to be conducted as 'Activated carbon' is a glassy material. It is not soluble in water and has a particle size between 0.5 to 250.0 µm. Therefore it is not expected to pass cell membranes to become accessible for enzymatic attack and thus enzymatic oxidation. But furthermore, the oxidation (mineralisation) of organic substances is accomplished by electron transfer from the electron donor (substance) to the electron acceptor. During biological substrate oxidation, mostly two electrons are transferred at the time, and two protons (H+) are split from the substrate (dehydrogenation). The hydrogen is transferred to NAD or NADP (acceptor) as part of the respiration chain (e.g., citric acid cycle). The substance activated carbon does not contain any hydrogen available for dehydrogenation; thus there is no energy gain by enzymatic dehydrogenation, so further biodegradation of this molecule will not occur. Therefore a test on the ready biodegradability is scientifically not justified.

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