Correspondence/Rebuttal pubs.acs.org/est
Comment on Screening for PBT Chemicals among the “Existing” and “New” Chemicals of the EU n their article, Strempel et al.1 “present a PBT [persistence, bioaccumulation potential, and toxicity] screening of approximately 95 000 chemicals based on a comparison of estimated P, B, and T properties of each chemical with the P, B, and T thresholds defined under REACH [European chemicals regulation on the registration, evaluation, authorization, and restriction of chemicals].” Some of the compounds predicted to be potential PBT chemicals in the Supporting Information of ref 1 are incorrectly drawn and include aromatic rings where none exist. The corrected structures for these five compounds are shown below: 1,3,5-tris(2,3-dibromopropyl)-1,3,5-triazinane-2,4,6-trione (CAS RN 52434-90-9); dibenzo def,mno chrysene-6,12-dione, 4,10-dibromo- (CAS RN 4378-61-4); pimozide (CAS RN 2062-78-4); perylo 3,4-cd:9,10-c′d′ dipyran-1,3,8,10-tetrone (CAS RN 128-69-8); and 1,3,5tris(3-isocyanato-4-methylphenyl)-1,3,5-triazinane-2,4,6-trione (CAS RN 26603-40-7). Such issues are not trivial, as expert judgment on chemical reactivity in environmental systems generally functions via the visual assessment of various functional groups on a compound. If those functional groups are incorrectly represented in a two- or three-dimensional molecular representation, erroneous assessments can result. Similarly, quantitative structure−activity/property modeling (QSA/PR) work often begins by converting a compound from SMILES, CAS RN, or other alphanumeric codes into a two- or three-dimensional molecular representation from which various molecular descriptors (e.g., the number and location of aromatic rings, etc.) are calculated and regressed against activity/property data sets. If software is employed that inaccurately converts molecular codes to structures, erroneous QSA/PR models will result. The list of compounds predicted to be potential PBT chemicals in ref 1 also includes the following anhydrides: 4,5,6,7-tetrabromo-1,3-isobenzofurandione [tetrabromophthalic anhydride] (CAS RN 632-79-1); 1,3-isobenzofurandione, 4,5,6,7-tetraiodo- [tetraiodophthalic anhydride] (CAS RN 632-80-4); 1,3-isobenzofurandione, 5,5′- 2,2,2-trifluoro-1(trifluoromethyl)ethylidene bis- (CAS RN 1107-00-2); 1,3isobenzofurandione, 5,5′-[[1,1′-biphenyl]-4,4′-diylbis(oxy)]bis(CAS RN 26177-82-2); 1,3-isobenzofurandione, 4,4′-(1methylethylidene)bis(4,1-phenyleneoxy) bis-(CAS RN 5225680-1); 1,3-isobenzofurandione, 4-4-1- 4-(1,3-dihydro-1,3-dioxo5-isobenzofuranyl)oxy phenyl-1-methylethyl phenoxy-(CAS RN 53196-94-4); bis[1]benzothieno[3,2-e:2′,3′-g]isobenzofuran-5,7-dione (CAS RN 65689-55-6); bis(1)benzothieno(2,3-e:2,3-g)isobenzofuran-6,8-dione (CAS RN 65689-56-7); and perylo 3,4-cd:9,10-c′d′ dipyran-1,3,8,10tetrone (CAS RN 128-69-8). Anhydrides such as these are well-known to have rapid hydrolysis rates in aqueous solution (half-lives often measured in seconds) and to be extremely sensitive to even trace amounts of atmospheric moisture (see, e.g., refs 2 and 3 and the general experience in synthetic organic chemistry). It is highly unlikely that these anhydrides will be persistent and/or bioaccumulative.
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The list of compounds predicted to be potential PBT chemicals in ref 1 also includes the following isocyanates: 1,3bis[(5-isocyanato-1,3,3-trimethylcyclohexyl)methyl]urea (CAS RN 55525-54-7); 1,3,5-tris(3-isocyanato-4-methylphenyl)1,3,5-triazinane-2,4,6-trione (CAS RN 26603-40-7); 1,3-bis[4[(4-isocyanatophenyl)methyl]phenyl]-1,3-diazetidine-2,4-dione (CAS RN 17589-24-1); [1-[[3-(isocyanatomethyl)phenyl]carbamoyloxy]-3-[[4-(isocyanatomethyl)phenyl]carbamoyloxy]propan-2-yl] N-[3(isocyanatomethyl)phenyl]carbamate (CAS RN 28470-82-8); 7-isocyanatobenzo[a]anthracene (CAS RN 63018-56-4); benzene, 1,3diisocyanatomethyl-, reaction products with 1,6-diisocyanatohexane (CAS RN 68411-41-6); carbamic acid, (5-isocyanato1,3,3-trimethylcyclohexyl)methyl-, oxidi-2,1-ethanediyl ester (CAS RN 68975-84-8); carbamic acid, 4- (4isocyanatophenyl)methyl phenyl-, oxidi-2,1-ethanediyl ester (CAS RN 71832-70-7); ureylenebis(p-phenylenemethylene-pphenylene) diisocyanate (CAS RN 93805-48-2); and benzenamine, N,N-methanetetraylbis[4-[(4-isocyanatophenyl)methyl]- (CAS RN 79864-11-2). As with anhydrides, isocyanates are well-known to have rapid hydrolysis rates in aqueous solution (half-lives often measured in seconds, minutes, and up to a few hours) and to generally be extremely sensitive to even trace amounts of atmospheric moisture (see, Published: May 1, 2013 6063
dx.doi.org/10.1021/es401204q | Environ. Sci. Technol. 2013, 47, 6063−6064
Environmental Science & Technology
Correspondence/Rebuttal
e.g., refs 4−6). It is highly unlikely that these isocyanates will be persistent and/or bioaccumulative. The list of compounds predicted to be potential PBT chemicals in ref 1 also includes the following acyl fluorides: propanoyl fluoride, 2,3,3,3-tetrafluoro-2- 1,1,2,3,3,3-hexafluoro2- 1,1,2,2-tetrafluoro-2-(fluorosulfonyl)ethoxy prop (CAS RN 4089-58-1); decanoyl fluoride, octadecafluoro-9-(trifluoromethyl)- (CAS RN 15720-98-6); and dodecanoyl fluoride, docosafluoro-11-(trifluoromethyl)- (CAS RN 15811-52-6). Acyl fluorides are known to hydrolyze rapidly (see, e.g., refs 7−9). As such, it is highly unlikely that these acyl fluorides will be persistent and/or bioaccumulative.
Sierra Rayne*
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Chemologica Research, PO Box 74, 318 Rose Street, Mortlach, Saskatchewan S0H 3E0, Canada
AUTHOR INFORMATION
Corresponding Author
*Phone: + (1) 306 690 0573; fax: + (1) 306 690 0573; e-mail:
[email protected].. Notes
The authors declare no competing financial interest.
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REFERENCES
(1) Strempel, S.; Scheringer, M.; Ng, C. A.; Hungerbuhler, K. Screening for PBT chemicals among the “existing” and “new” chemicals of the EU. Environ. Sci. Technol. 2012, 46, 5680−5687. (2) SIDS Initial Assessment Report for Phthalic Anhydride; Organisation for Economic Co-operation and Development: Paris, France, 2005. (3) Tice, R. Tetrabromophthalic Anhydride [CASRN 632-79-1]: Review of Toxicological Literature; Integrated Laboratory Systems: Research Triangle Park, NC, 1999. (4) Sekizawa, J.; Greenberg, M. M. Concise International Chemical Assessment Document 27: Diphenylmethane Diisocyanate (MDI); World Health Organization: Geneva, Switzerland, 2000. (5) SIDS Initial Assessment Report for 4,4′-Methylenedicyclohexyl Diisocyanate; Organisation for Economic Co-operation and Development: Paris, France, 2005. (6) Toxicological Profile for Hexamethylene Diisocyanate (HDI); Agency for Toxic Substances and Disease Registry: Atlanta, GA, 1998. (7) Bunton, C. A.; Fendler, J. H. The hydrolysis of acetyl fluoride. J. Org. Chem. 1966, 31, 2307−2312. (8) Motie, R. E.; Satchell, D. P. N.; Wassef, W. N. The Bronsted acidcatalysed hydrolysis of acyl fluorides in aqueous media; Evidence for two mechanisms. J. Chem. Soc. Perkin Trans. 2 1992, 859−860. (9) Motie, R. E.; Satchell, D. P. N.; Wassef, W. N. The Bronsted acidcatalysed hydrolysis of acyl fluorides in aqueous media. J. Chem. Soc. Perkin Trans. 2 1993, 1087−1090.
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