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Sediment toxicity

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Description of key information

Ziegler Bottoms are characterised according to two primary constituents; icosan-1-ol and docosan-1-ol. The REACH requirement in Annexes XI for studies on sediment organisms is waived based on technical difficulties associated with conducting studies, the ready biodegradability of the test substance, and the low to no toxicity in aquatic organisms.  No reliable measured ecotoxicity data are available for sediment organisms.

Key value for chemical safety assessment

Additional information

Ziegler Bottoms are characterized as comprising of two primary constituents; icosan-1-ol and docosan-1-ol. Together these constituents represent a structural class of components (alcohols) that constitute approximately 82% of the composition of Ziegler Bottoms. Study data, where available, for each of these primary constituents has been evaluated and considered together. In a conservative approach the most sensitive study result from across the two primary constituents has been identified and used to adequately address the Ziegler Bottoms endpoint in question. 

In accordance with Annex XI, section 2, the long-term toxicity effects studies to sediment dwelling organisms (required in Section 9.5.1) do not need to be conducted as the study is technically not possible, readily biodegradable and exerts low to no toxicity to aquatic organisms. The technical infeasibility is due to the very short sediment half-life once desorbed (see CSR for further details), which do not allow for the studies to be conducted. No reliable predicted or measured toxicity to sediment organism¿s data are available for Ziegler Bottoms. The requirement to conduct sediment studies for this substance is being waived based on technical infeasibility, ready biodegradation and low toxicity to aquatic organisms as detailed below.

Study not technically feasible

The requirement to conduct long-term sediment toxicity studies for icosan-1-ol and docosan-1-ol is waived due to anticipated technical difficulties in performing such a test. The requirement to conduct long-term toxicity studies for icosan-1-ol and docosan-1-ol is waived due to anticipated technical difficulties in performing such a test. Guideline (standard) studies for long-term toxicity testing would be confounded by the technical difficulties of maintaining the test alcohols (icosan-1-ol and docosan-1-ol) in solution, as was demonstrated in long-term invertebrate studies reported in the OECD SIDS Report for Long Chain Alcohols (2006). Severe difficulties were encountered when studies were conducted with ¿C15 alcohols, which are similar to constituents of the Ziegler Bottoms, as biodegradation in the test system was almost complete within the 24-hr test media renewal period. It is reasonable to assume that similar biodegradation would occur in sediment.


Icosan-1-ol and docosan-1-ol are both readily biodegradable. The most recent reliable study (OECD 301B) using icosan-1-ol reported results of 87.9% (CO2) in 28 days confirming the readily biodegradable (P&G, 2009). The finding is consistent with very high levels of removal in other types of test systems where very fast degradation and metabolism in microorganisms and a range of trophic levels has been identified for alcohols in the range C6-24. Ready biodegradability means that the test substance will rapidly be unavailable for uptake and bioaccumulation in biological organisms.

Toxicity to Aquatic Organisms

Generally the short-term aquatic toxicity of the two constituent substances (icosan-1-ol and docosan-1-ol) is low and long-term toxicity is considered to be below the limit of solubility (LoS) for alcohols > C15 in chain length. In addition, the ready biodegradability of the test substance means long-term exposure to aquatic organisms is unlikely. It is reasonable to assume that similarly low toxicities would be seen in sediment organisms.

In summary, the data requirement for sediment studies is waived on the evidence of technical difficulties, ready biodegradability and the absence of toxicity to aquatic organisms.