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Environmental fate & pathways

Phototransformation in air

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The assessment entity “Ol” is a mixture of naturally occurring C14-18 saturated and C16-18 unsaturated 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 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 can enter air (particulate and vapour phases) but would breakdown very quickly by hydroxyl radical reaction and/or be removed by wet and dry deposition (e.g. particulate-phase fatty acids) (Health Canada, 2017). Based on the hydroxyl radical reaction at 25°C (AOPWin v1.92; EPI Suite v4.1; 12-hr day; 1.5E6 OH/cm3), half-live times of 7.63, 6.53, 5.71, 1.77, ≤1.70 (cis/trans), ≤1.0 (cis/trans) and ≤0.71 (cis/trans) hours were estimated for tetradecanoic acid (C14), hexadecanoic acid (C16), octadecanoic acid (C18), cis-9-hexadecenoic acid (C16 unsatd.), 9-octadecenoic acid (C18 unsatd.), 9,12-octadecadienoic acid (C18 unsatd.) and 9,12,15-octadecatrienoic acid (C18 unsatd.), respectively. In addition, half-live times of 2.12, ≤2.12 (cis/trans), ≤1.06 (cis/trans), and ≤0.71 (cis/trans) hours were determined based on the ozone reaction at 25°C (AOPWin v1.92; EPI Suite v4.1; at 7E11 mol/cm3) for cis-9-hexadecenoic acid (C16 unsatd.), 9-octadecenoic acid (C18 unsatd.), 9,12-octadecadienoic acid (C18 unsatd.) and 9,12,15-octadecatrienoic acid (C18 unsatd.), respectively. Estimates were not provided for the ozone reaction at 25°C for tetradecanoic, hexadecanoic and octadecanoic acid. However, previous QSAR-based estimations with C8 to C18 fatty acids generally pointed to an increased stability with decreasing alkyl chain length with half-life values ranging from 0.6 to 17.5 hours for e.g. C18 and C8 fatty acids, respectively (OECD SIDS, 2014).

 

(III) Level III fugacity modelling (EPI Suite v4.10) indicates that “aliphatic acids will distribute primarily to soil and water, with lesser amounts to air and sediment. With increasing chain length, the percent distributions to soil and sediment generally increase and the percent distributions to water and air generally decrease” (OECD SIDS, 2014). In summary, available data point to a fast photodegradation of C14-18 saturated and C16-18-unsatd. fatty acids with half-live times in air of < 1 day. Taking into account that C14-18 saturated and C16-18-unsatd. fatty acids are expected to be readily biodegradable under aerobic conditions, further tests on the photodegradation of C14-18 saturated and C16-18-unsatd. fatty acids are not considered to be scientifically necessary.

 

References:

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

OECD SIDS initial assessment profile- aliphatic acids (2014), CoCAM 6 September 30-October 3, Italy/ICCA, p. 41

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

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