Fatty acids, C14-18 and C16-18-unsatd., zinc salts

Biodegradation in soil

Description of key information

The assessment entity “Ol” is a mixture of naturally occurring saturated and unsaturated fatty acids with an alkyl chain length ranging from C14-C18 (C14-18 saturated and C16-18-unsatd. fatty acids). Therefore, the endpoint is addressed with publicly available data on fatty acids with the same or similar structure, including conservatively fatty acids with a shorter chain if relevant and appropriate in accordance with previously applied read-across approaches (U.S. EPA Fact Sheet, 2008).

A registration dossier shall contain information on the environmental hazard assessment (Regulation 1907/2006, Article 10). For the environmental hazard assessment of C14-18 saturated and C16-18-unsatd. fatty acids, the standard testing regime set out in Annexes VII to IX is adapted in accordance with Section 1.2 and 1.3 of Annex XI so that “testing does not appear to be scientifically necessary” as follows:

(I) The ecotoxic potential of C14-18 saturated and C16-18-unsatd. fatty acids is assumed to be negligible. Fatty acids are generally not considered to represent a risk to the environment, which is reflected in their exemption from the obligation to register (Annex V, Section 9 and Regulation (EC) No 987/2008). Non-branched aliphatic fatty acids (C5-24) “are expected to be of low toxicity by their nature”, i.e. they “are not considered PBT/vPvB, […] degrade rapidly and have a low potential for bioaccumulation” (ECHA, 2020: Integrated Regulatory Strategy Annual Report May 2020)

(II) Fatty acids are not persistent in soil and are broken down quickly by soil microorganisms (Health Canada, 2017). Half-live times of C8- C18 fatty acids in soil were determined with < 3 days (U.S. EPA Fact Sheet, 2008, Health Canada, 2017). Hypothetically, the degradation pathway of fatty acids constitutes a sequential elimination of C2 fragments, meaning that the major soil metabolites of a given fatty acid would be other fatty acids with shorter chains (U.S. EPA Fact Sheet, 2008). Zinc salts of C8 fatty acids (Simon, 2012) and C16-18 fatty acid, zinc salts are readily biodegradable (>80% in 28 days, Simon, 2012; 93% in 28 days, TÜV Bayern, 1992; 71% in 28d, Rudolf, 1992). The EU RA on zinc stearate (2008) also concluded: Fatty acids are rapidly degraded in soil and water via the β-oxidation pathway and are thus not expected to accumulate in the environment. Fatty acids are “not expected to be persistent in the environment” (Health Canada, 2017).

 

In summary, fatty acids are readily biodegradable, not expected to be persistent in soil and are indistinguishable from naturally occurring fatty acids present in soil as a result of plant, animal and microbial metabolism. Thus, performing further soil simulation tests of C14-18 saturated and C16-18-unsatd. fatty acids in soil is from a scientific point of view not expected to provide more insight and is not considered scientifically necessary for the environmental hazard assessment.

References:

European Chemicals Agency (ECHA, 2020). Grouping speeds up regulatory action. Integrated Regulatory Strategy Annual Report May 2020.

Health Canada’s PMRA, Pest Management Regulatory Agency (2017). Ammonium Salt of Fatty Acid Proposed Registration Decision PRD2017-04, p. 36

HERA (2003). Human & Environmental Risk Assessment on ingredients of European household cleaning products. Fatty Acid Salts (Soap) Environmental Risk Assessment

Rudolf, A. (1992): Study report following OECD 301B: Biodegradability of Zink-12-Hydroxystearat

TÜV Bayern Sachsen E.V. (1992): Untersuchungsbericht Zinkstearat

U.S. Environmental Protection Agency, U.S. EPA (2008). Ammonium nonanoate (031802) Fact Sheet, OPP Chemical Code: 031802, p. 2