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The largest BCF modeled for Dimeric constituents of MTDID 18990 was 42. This is based on an estimated log Kow of 12.1. The smallest calculated average of maximum diameters was 36.4 angstroms. Trimeric and polyamide constituents are of molecular weight too large to model, but given increasing molecular size and the negative relationship between hydrophobicity and bioaccumulation for substances with log Kow >>6, the trimeric constituents (approximate molecular weight 1470) and polyamide fractions (approximate molecular weight >1710) would be too large (average maximum diameter >>17 angstroms) and too hydrophobic (log Kow >>10) to meaninfully bioconcentrate. Monomeric constituents, i.e. C18 fatty amides of 3,3'-[oxybis(ethane-2,1-diyloxy)]dipropan-1-amine, are expected to be surfactants similar to fatty amide ethoxylates, and would not be expected to bioconcentrate because of charge at physiological pH. Residual amines are not expected to bioaccumulate based on a log Kow of -1.25.

Additional information

Bioaccumulation endpoints are not required at this annual volume. QSAR modeling of bioconcentration factors (BCFs) was done in support of the PBT assessment. Two models were used: BCFBAF v.3.01 (within EPISUITE 4.11) and BCF baseline model v.02.09 (within Catalogic v.5.11.17). These models are both considered valid and applicable to the structures modeled. Reaction products of fatty acids, C18-unsaturated, dimers and trimers with 3,3'-[oxybis(ethane-2,1-diyloxy)]dipropan-1-amine have multiple components. Approximately 62.7% of compounds are identified as dimers, and 31.5% of compounds are identified as trimers. Among the identified dimers and trimers, two dimers have ≥ 10% of composition and no trimers has ≥ 10% composition. The two most prevalent dimers, having molecular weights 967.5 and 969.5, were selected as representative. No trimers were modeled due to excessive molecular weight (ca. 1470). The modeled dimers have estimated log Kow values of 11.7 and 12.1, and estimated log BCF values of 7.4 to 42. In addition, the dimers have calculated average of maximum diameters (Dmax aver) values of 36.4 and 38.3 angstroms, or 3.6 and 3.8 nm. Based on consideration of log Kow, BCF, and Dmax aver, the dimers would not be considered bioaccumulative. While trimeric and potential polyamide constituents were not modeled, these would have larger log Kow and Dmax aver values, lower estimated BCF due to the inverse relationship between log Kow and log BCF for substances with log Kow >>6, and further have molecular weights of ca. 1470 and >1710, respectively. These molecular weights are greater than the limiting value for bioaccumulation set forth in chapter R11 of the Guidance on information requirements. Based on trend in log Kow, estimated log BCF, Dmax aver, and molecular weight, the trimeric and potential polyamide constituents of MTDID 18990 would also not be considered bioaccumulative.

Monomeric constituents of MTDID 18990, i.e. fatty amides of 3,3'-[oxybis(ethane-2,1-diyloxy)]dipropan-1-amine, are expected to act similarly to the ethoxylated fatty acid amides surfactants (e.g., PEG-4 stearamide, CAS# 31886-11-0, PEG-3 cocamide, CAS# 61791-08-0) differing in that they terminate in an aminopropyl rather than hydroxyethyl group. The free amine group is expected to be ionized at physiological pH based on the pKa of the residual amine (see below). Based on charged terminus on a polar head group, the monomeric constituents would not be expected to bioconcentrate.

Residual amine 3,3'-[oxybis(ethane-2,1-diyloxy)]dipropan-1-amine would not bioconcentrate based on a log Kow of -1.25. The diamine has a reported pKa of 10 with no reported distinction between the first and second ionization of amine nitrogen groups.