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Environ Sci Technol 47, 2013, 6063 6064 .pdf


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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.

I

© 2013 American Chemical Society

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*



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:
sierra.rayne@live.co.uk..
Notes

The authors declare no competing financial interest.



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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