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Environmental fate & pathways

Phototransformation in water

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Administrative data

Endpoint:
phototransformation in water
Type of information:
experimental study
Adequacy of study:
disregarded due to major methodological deficiencies
Study period:
2012
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Nonguideline/nonGLP study using uncharacterized test article with no information on identity or purity. Essential information (wavelength of light source, etc) pertaining to the study's conduct was not including in the publcation. Positive and negative controls not included.

Data source

Reference
Reference Type:
publication
Title:
Photolytic degradation of decabromodiphenyl ethane (DBDPE)
Author:
Wang et al.
Year:
2012
Bibliographic source:
Chemosphere http://.dx.doi.org/10.1016/j.chemosphere.2012.05.006

Materials and methods

Study type:
other: photolysis in hexane, tetrahydrofuran, methanol/water, humic acid/water, slica gel
Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
Exposed DBDPEthane to UV light in hexane, tetrahydrofuran, methona/water, humic acid, or silica gel for varying periods of time. DBDP-Ethane in hexane also exposed to natural sunlight. Calculated half-lives of dissaperance of DBDP-Ethane and rate constants. Analyzed UV-hexane solutions for lower brominated diphenyl ethanes.
GLP compliance:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
other: DBDPEthane in hexane, tetrahydrofuran, methonal/water, humic acid, or silica gel
Details on test material:
No information on purity of test article provided. Obtained from "Chemical Market of Guangzhou, China". Test material not characterized prior to use.

Study design

Radiolabelling:
no
Analytical method:
other: GC-MS in ECNI and EI modes
Light source:
other: mercury lamp or sunlight
Details on light source:
GGZ-125 125 W high-pressure mercury lamp (Yaming Lighting, Shanghai, China). Further information not provided.
Natural sunlight.

Results and discussion

Spectrum of substance
Parameter:
not specified

Any other information on results incl. tables

Under the conditions of the study, the following half-lives were reported: hexane-UV (16.6 min), tetrahydrofuran-UV (6.0 min), methanol/water-UV (>240 min), Humic acid/water-UV (>30, < 60 min), sliica gel-UV (75.9 min), hexane-sunlight (>20, < 40 min). The half-lives were based on the concentrations of DBDPEthane detected in the various matrixes at each time point. The half-lives were not based on detection and quantification of degradants. The authors speculated the low solubility of DBDPEthane in methanol/water resulted in ts adsorption to the glass wall of the reaction vessel, which could reduce its reaction rate.

Rate constants could not be calculated for methanol/water-UV, humic acid/water-UV, and hexane-sunlight, because the dissapearance of the test material did not follow first order kinetics. The rate constant in silica gel-UV was reported to be 9.13 x 10-3 min.

With respect to degradation products, results were presented for hexane-UV exposures only. The hexane-UV results were presented as graphs (Fig 4 and 6). No tabluated data was presented. Either a chromatogram (Fig 4) or results reported as % of the DBDPEthane molecule (Fig 6) were provided. Actual measured concentrations of degradants were not presented in the text. Fig 6, page 5, indicates detection of 3 nonabromodiphenyl ethanes, 2 octabromodiphenyl ethanes, and 2 heptabromodiphenyl ethanes. By extracting data from the graph, the sum of these lower brominated diphenyl ethanes at the end of the exposure (70 min) represented ca. 0.865% of the amount of the parent molecule at time zero. Fig 6 indicates relative amounts of all presumed degradants were declining with the exception of Octa-1. Thus, although the authors claim that the parent molecule was degraded to lower brominated diphenyl ethanes, the formation of these congeners was negligble and the majority of the disappearance of the parent molecule was not accounted for. Further, interpretation of this data is complicated by differences in the solubility of lower brominated diphenyl ethanes in solvents relative to the DBDPEthane molecule. The lower brominated diphenyl ethanes likely have different solubilities in the same solvent, and different solubilites between solvents. This means that their relative extraction will differ from each other and importantly from DBDPEthane. DBDPEthane is expected, in general, to be less soluble than lower brominated diphenyl ethanes. Thus, lower bromianted diphenyl ethanes may be disproportionately represented depending on the solvents used for extraction.

The authors concluded "The current photolytic degradation experiments were performed on DBDPE in solvents and on silica gel. Large difference in the photolytic degradation behaviors of DBDPE may exist between lab matriaxes and the natural envirnmental media such as atmospheric particles, soli, wan dwater as suggested previously for deca-BDEs (Raff and Hites, 2007).".

These results cannot be used to predict DBDPEthane's potential for photolysis in the environment. The conditions of exposure were not described in proper detail such that extrapolation to the environment can be made, the identity and purity of the test material was not provided, and the test matrixes do not correspond to the manner in which DBDPEthane would be exposed to natural sunlight.

Note that the Y axis was not specified in Fig 4 that reported the GC-MS chromatograms at t0 to t70 minutes. This critical given the difference in scale observed in a similar figure of chromatograms in Wang et al. 2010. The changes in peak size with time illustrated in Fig 4 are dependent on the Y scale.

Applicant's summary and conclusion

Validity criteria fulfilled:
no
Conclusions:
This study was disregarded. It was not conducted according to GLPs or an established guideline, did not provide information on the identity and purity of the test article, and did not provide sufficient details of the exposure conditions such that it utility in predicting environmental photolysis is minimal. Although hepta- to nonabromodiphenyl ethanes were claiimed as photolysis products, their amounts totalled ca. 0.865% of the parent substance at time 0.
Executive summary:

This study was disregarded. It was not conducted according to GLPs or an established guideline, did not provide information on the identity and purity of the test article, and did not provide sufficient details of the exposure conditions such that it utility in predicting environmental photolysis is minimal. Although hepta- to nonabromodiphenyl ethanes were claiimed as photolysis products, their amounts totalled ca. 0.865% of the parent substance at time 0.

Under the conditions of the study, the following half-lives were reported: hexane-UV (16.6 min), tetrahydrofuran-UV (6.0 min), methanol/water-UV (>240 min), Human acid/water-UV (>30, < 60 min), sliica gel-UV (75.9 min), hexane-sunlight (>20, < 40 min). Rate constants could not be calculated for methanol/water-UV, humic acid/water-UV, and hexane-sunlight, because the dissapearance of the test material did not follow first order kinetics. The rate constant in silica gel-UV was reported to be 9.13 x 10-3 min.

With respect to degradation products, results were presented for hexane-UV exposures only. The hexane-UV results were presented as a graph; no tabluated data was presented. Information on the purity and composition of the test material were not provided. Fig 6, page 5, indicates detection of 3 nonabromodiphenyl ethanes, 2 octabromodiphenyl ethanes, and 2 heptabromodiphenyl ethanes. By extracting data from the graph, the sum of these lower brominated diphenyl ethanes at the end of the exposure (70 min) represented ca. 0.865% of the amount of the parent molecule at time zero. Thus, although the authors claim that the parent molecule was degraded to lower brominated diphenyl ethanes, the formation of these congeners was negligble and the majority of the disappearance of the parent molecule was not accounted for.

These results cannot be used to predict DBDPEthane's potential for photolysis in the environment. The conditions of exposure were not described in proper detail such that extrapolation to the environment can be made, the identity and purity of the test material was not provided, and the test matrixes do not correspond to the manner in which DBDPEthane would be exposed to natural sunlight.