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Toxicity to terrestrial arthropods

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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 Annex IX for studies on soil arthropods is waived on the basis of direct or indirect exposure of the soil compartment being unlikely.

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. 

The REACH requirement in Annexes IX and X for studies on terrestrial organisms is waived if direct or indirect exposure of the soil compartment is unlikely. In particular, substances that are unlikely to be persistent in the environment do not require long-term terrestrial testing.

Terrestrial testing is waived based on the unlikely direct or indirect exposure to soils, the technical difficulties associated with conducting studies, the ready biodegradability of the test substance and the low toxicity in aquatic organisms resulting in the unlikely direct or indirect exposure of terrestrial organisms to the test substance, as presented in more detail below:

Exposure to soils

It is unlikely that soil organisms will be exposed to the test substance as there is no intended use involving the direct application of Ziegler Bottoms to soil. In addition, it is unlikely that indirect exposure will occur, via the application of sewage sludge to land, as the test substance is expected to biodegrade through the sewage treatment process.

Study not technically feasible

The requirement to conduct terrestrial 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 soils.

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. It is reasonable to assume that similarly low toxicities would be seen in terrestrial organisms.

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