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Long-term toxicity to fish

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Description of key information

Ziegler Bottoms are characterized as comprising of two primary constituents; icosan-1-ol and docosan-1-ol.  In accordance with REACH Annex XI, section 1, testing does not appear scientifically necessary for Annex endpoint 9.1.6.  Sufficient information is available to predict an absence of toxicity at the limit of solubility for linear alcohols with carbon chain lengths >C15.  Moreover, from experience gained in tests that have been conducted with substances in this category, considerable technical difficulties would be expected in the conduct of such a test, due to the very rapid biotic removal of the substance from the test system.  Therefore, long-term toxicity to fish requirements are waived based on technical testing difficulties, ready biodegradation and low to no short-term toxicity to aquatic organisms at the limit of solubility.  No reliable measured or predicted long-term toxicity data to fish for constituents of Ziegler Bottoms is available.

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 primary 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 constituents has been identified and used to adequately address the Ziegler Bottoms endpoint in question. 

In accordance with REACH Annex XI, section 1, testing does not appear scientifically necessary for Annex endpoint 9.1.6. Sufficient information is available to predict an absence of toxicity at the limit of solubility for linear alcohols with carbon chain lengths ¿C15. Moreover, from experience gained in tests that have been conducted with substances in this category, considerable technical difficulties would be expected in conducting such a test, due to the low solubility of the test substance and its very rapid biotic removal from the test system. Therefore, long-term toxicity to fish requirements are waived based on technical testing difficulties, ready biodegradation and low to no short-term toxicity to aquatic organisms at the limit of solubility. No reliable measured or predicted long-term toxicity data to fish for constituents of Ziegler Bottoms is available.

Study not technically feasible

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.

Biodegradation

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) degradation 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.

Therefore, long-term toxicity to fish requirements are waived based on technical testing difficulties, ready biodegradation and low to no short-term toxicity to aquatic organisms at the limit of solubility.

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