Correspondence/Rebuttal pubs.acs.org/est
Comment on “Screening Criteria for Long-Range Transport Potential of Organic Substances in Water”
I
n their article,1 the authors state that they conducted “[s]imulations of nonionic organic substances selected from the Canadian Domestic Substance List [DSL]” and that “the DSL contains 4069 nonionic organic compounds.” The authors do not provide this list of 4069 purportedly nonionic organic compounds in their Supporting Information. The authors do provide a short sublisting of compounds in Supporting Information Table S1 with the following heading: “Table S1: Organic, non-ionic compounds contained in the Canadian Domestic Substance List, which are not persistent in water but are mainly transported within the water compartment (i.e. the characteristic travel distance in water (CTDW) exceeds the one in air (CTDA) by more than one order of magnitude).” There appear to be ionizable compounds in Table S1. For example, 2H-1-benzopyran-2-one, 7-(diethylamino)-4-methyl-, sulfate (1:1) (CAS-RN 67210666) is a salt. As well, 1,3-benzenediamine, 4-methyl- (CAS-RN 95807) appears to be basic with a SPARC (http://archemcalc.com/sparc/; October 2011 release w4.6.1691-s4.6.1687) estimated pKa of 5.35 that will likely render it at least partially ionized in near neutral waters. The full list of “4069 nonionic organic compounds” should be provided to readers so they may confirm whether any additional compounds are ionizable. The authors conduct modeling exercises on n-perfluorooctane sulfonic acid (PFOS), which is acidic with an estimated pKa of
