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The biodegradability potential of the members of Dimerised fatty acids and sub-category 2 members is evaluated based on standard biodegradation studies. These experimental results revealed a limited biodegradability potential for the members of the sub-category 2. As summarized in the category justification, the members of the fatty acids are divided into two sub-categories on the basis of their environmental fate properties. The first sub-category covers three monomeric (by-)products of the dimerization process, which are readily biodegradable. The second sub-category covers the predominately oligomers (dimeric and trimeric products) of dimerization based on their lack of ready biodegradability and other environmental fate characteristics.

For Fatty acids, C18-unsaturated, dimers (CAS No. 61788-89-4) four guideline studies investigating the ready biodegradability are available. In all four studies the biodegradation of the test substance was < 10 % at test termination after 28 days. Thus, Fatty acids, C18-unsaturated, dimers is not readily biodegradable under conditions tested according to the OECD criteria.

This result is consistent with the complete data set for the sub-category 2 members of the Dimerised Fatty Acids and its derivatives as all available study reports for biodegradation in water (screening tests) for the sub-category 2 members, i.e Fatty acids, C18-unsaturated, dimers (CAS No. 61788-89-4), Fatty acids, C18-unsaturated, dimers, hydrogenated (CAS No. 68783-41-5), Fatty acids, C18-unsaturated, trimers (CAS No. 68937-90-6) and Fatty acids, C16-18 and C18-unsaturated, dimerized (CAS No 71808-39-4), observed a degradation of < 10 % within 28 days for the first three substances and 29.3 % within 28 days for the last mentioned substance, respectively.