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Synthesis of highly brominated diphenyl ethers and aspects on photolysis and indoor spreading
Stockholm University, Faculty of Science, Department of Environmental Chemistry.
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Adding chemicals to materials to decrease flammability can be dated back to as early as 450 BC when the Egyptians used alum to reduce flammability of wood. Almost 2500 years later brominated flame retardants (BFRs) are used to prevent ignition of textiles, electronics and polymers. BFRs in major use today are polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCDD) and tetrabromobisphenol A (TBBPA), including derivatives. There have been three industrial PBDE mixtures produced. Extensive scientific reporting has shown increasing concentrations of PBDEs in wildlife and in humans. This in combination with reports on their physico-chemical characteristics and chemical reactivity have led to that two of the PBDE products have been classified as being persistent, bioaccumulative and toxic, which has led to legislative measures, in e.g. EU, Norway and the USA.

The availability of pure reference standards is a prerequisite for much toxicologically related research. Hence the main objective of this thesis was to develop additional methods for synthesis of highly brominated diphenyl ethers. Further, to quantify and identify photolysis products of decabromodiphenyl ether (decaBDE) and to perform a case study regarding PBDE exposure in aircrafts.

Synthesis of highly brominated BDE congeners by perbromination of mono- or diaminodiphenyl ethers followed by diazotization of the amino group(s) and introduction of hydrogen(s) in the molecules is a convenient route for synthesis of some octaBDEs and all nonaBDEs. Selective bromination of diaminodiphenyl ether, followed by diazotization of the amino groups and substitution with bromines yielded a hexaBDE or a heptaBDE which were then further brominated to octaBDE congeners.

Even though several studies have been performed on photolysis of decaBDE a new study with a more quantitative approach was performed as part of this thesis. Debrominated PBDE products were identified and quantified and a marker PBDE for UV degradation of DecaBDE was identified i.e., 2,2’,3,3’,5,5’,6,6-octabromodiphenyl ether (BDE-202). Polybrominated dibenzofuranes, methoxlated brominated dibenzofuranes, pentabromophenol and hydroxylated bromobenzenes were also detected. The PBDEs accounted for approximately 90% of the total amount of substances in each sample and the PBDFs for about 10%. Also, a case study on potential exposure to PBDEs in humans travelling long distances by aircraft was done. It was shown that PBDE concentrations in dust onboard aircrafts may be high and increased PBDE serum levels were indicated in a majority of the travellers.

The present thesis has contributed to make higher brominated diphenyl ethers available as reference standards, allowing better quantitative assessments possible regarding both abiotic studies and exposure assessments. New toxicological testing can also be pursued.

Place, publisher, year, edition, pages
Stockholm: Institutionen för miljökemi , 2008. , 81 p.
National Category
Environmental Sciences
Research subject
Environmental Chemistry
Identifiers
URN: urn:nbn:se:su:diva-7519ISBN: 978-91-7155-579-3 (print)OAI: oai:DiVA.org:su-7519DiVA: diva2:198484
Public defence
2008-05-23, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 12 A, Stockholm, 13:00
Opponent
Supervisors
Available from: 2008-04-23 Created: 2008-04-23Bibliographically approved
List of papers
1. Methods for synthesis of nonabromodiphenyl ethers and a chloro-nonabromodiphenyl ether
Open this publication in new window or tab >>Methods for synthesis of nonabromodiphenyl ethers and a chloro-nonabromodiphenyl ether
Show others...
2006 (English)In: Chemosphere, Vol. 63, no 4, 562-569 p.Article in journal (Refereed) Published
Abstract [en]

Polybrominated diphenyl ethers (PBDEs) have been used extensively as brominated flame retardants (BFRs) in textiles, upholstery and electronics. They are ubiquitous contaminants in wildlife and humans. A low concentration of nonabrominated diphenyl ethers (nonaBDEs) is present in commercial DecaBDE and they are also abiotic and biotic debromination products of decabromodiphenyl ether (BDE-209). The objective of the present work was to develop methods for synthesis of the three nonaBDEs, 2,2',3,3',4,4',5,5',6-nonabromodiphenyl ether (BDE-206), 2,2',3,3',4,4',5,6,6'-nonabromodiphenyl ether (BDE-207) and 2,2',3,3',4,5,5',6,6'-nonabromodiphenyl ether (BDE-208), with the intention of making them available as authentic standards for analytical, toxicological and stability studies, as well as studies regarding physical-chemical properties. Two methods were developed, one based on perbromination of phenoxyanilines and the other via reductive debromination of BDE-209 by sodium borohydride followed by chromatographic separation of the three nonaBDE isomers formed. An additional nonabrominated compound, 4'-chloro-2,2',3,3',4,5,5',6,6'-nonabromodiphenyl ether (Cl-BDE-208), was also synthesized in the present work. Cl-BDE-208, prepared by the perbromination of 4-chlorodiphenyl ether, may be used as an internal standard in analysis of highly brominated diphenyl ethers. BDE-206, BDE-207, BDE-208 and Cl-BDE-208 were characterized by 1H NMR, 13C NMR, electron ionization mass spectra and by their melting points. The structures of all three nonaBDEs have been characterized previously by X-ray crystallography.

Research subject
Environmental Chemistry
Identifiers
urn:nbn:se:su:diva-24889 (URN)16297962 (PubMedID)
Note
Part of urn:nbn:se:su:diva-7519Available from: 2008-04-23 Created: 2008-04-23 Last updated: 2010-01-25Bibliographically approved
2. Synthesis of octabrominated diphenyl ethers from aminodiphenyl ethers
Open this publication in new window or tab >>Synthesis of octabrominated diphenyl ethers from aminodiphenyl ethers
2007 (English)In: Environmental Science and Technology, Vol. 41, no 21, 7459-7463 p.Article in journal (Refereed) Published
Abstract [en]

Polybrominated diphenyl ethers (PBDEs) are additive brominated flame retardants (BFRs), which have become widespread pollutants in abiotic and biotic environments including man. Tetra- to hexaBDEs and decaBDE are the most common environmental PBDE contaminants. Congeners of octabromodiphenyl ethers (octaBDEs) originate from used industrial OctaBDE mixtures and from transformation products of the high-volume industrial BFR mixture "DecaBDE", which most exclusively consists of perbrominated diphenyl ether (BDE-209). The objective of the present work was to develop methods for the synthesis of authentic octaBDE congeners in order to make them available as standards for analytical, toxicological, and stability studies, as well as studies concerning physical-chemical properties. The syntheses of six octaBDEs, 2,2',3,3',4,4',5,5'-octabromodiphenyl ether (BDE-194), 2,2',3,3',4,4',5,6'-octabromodiphenyl ether (BDE-196), 2,2',3,3',4,5,5',6-octabromodiphenyl ether (BDE-198), 2,2',3,3',4,5',6,6'-octabromodiphenyl ether (BDE-201), 2,2',3,3',5,5',6,6'-octabromodiphenyl ether (BDE-202), and 2,2',3,4,4',5,6,6'-octabromdipheny ether (BDE-204), are described, of which BDE-204 was prepared via two different pathways. Syntheses of BDE-198, BDE-201, BDE-202, and BDE-204 are based on octabromination of mono- or diaminodiphenyl ethers followed by diazotization and reduction of the amino group(s). BDE-194 and BDE-196 were prepared by bromination of 3,3',4,4',5,5'-hexabromodiphenyl ether (BDE-169) and 2,3,3',4,4',5',6-heptabromodiphenyl ether (BDE-191), respectively, and BDE-169 and BDE-191 were prepared from 4,4'-diaminodiphenyl ether and 3,4'-diamiodiphenyl ether, respectively. The synthesized PBDE congeners are described by 1H NMR, 13C NMR, electron ionization mass spectra, and their melting points.

Research subject
Environmental Chemistry
Identifiers
urn:nbn:se:su:diva-24890 (URN)18044526 (PubMedID)
Note
Part of urn:nbn:se:su:diva-7519Available from: 2008-04-23 Created: 2008-04-23 Last updated: 2010-01-25Bibliographically approved
3. Identification and quantification of products formed via photolysis of decabromodiphenyl ether
Open this publication in new window or tab >>Identification and quantification of products formed via photolysis of decabromodiphenyl ether
2009 (English)In: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 16, no 3, 312-321 p.Article in journal (Refereed) Published
Abstract [en]

BACKGROUND, AIM, AND SCOPE: Decabromodiphenyl ether (DecaBDE) is used as an additive flame retardant in polymers. It has become a ubiquitous environmental contaminant, particularly abundant in abiotic media, such as sediments, air, and dust, and also present in wildlife and in humans. The main DecaBDE constituent, perbrominated diphenyl ether (BDE-209), is susceptible to transformations as observed in experimental work. This work is aimed at identifying and assessing the relative amounts of products formed after UV irradiation of BDE-209. MATERIALS AND METHODS: BDE-209, dissolved in tetrahydrofuran (THF), methanol, or combinations of methanol/water, was exposed to UV light for 100 or 200 min. Samples were analyzed by gas chromatography/mass spectrometry (electron ionization) for polybrominated diphenyl ethers (PBDEs), dibenzofurans (PBDFs), methoxylated PBDEs, and phenolic PBDE products. RESULTS: The products formed were hexaBDEs to nonaBDEs, monoBDFs to pentaBDFs, and methoxylated tetraBDFs to pentaBDFs. The products found in the fraction containing halogenated phenols were assigned to be pentabromophenol, dihydroxytetrabromobenzene, dihydroxydibromodibenzofuran, dihydroxytribromodibenzofuran, and dihydroxytetrabromodibenzofuran. The PBDEs accounted for approximately 90% of the total amount of substances in each sample and the PBDFs for about 10%. DISCUSSION: BDE-209 is a source of PBDEs primarily present in OctaBDEs but also to some extent in PentaBDEs, both being commercial products now banned within the EU and in several states within the USA. It is notable that OH-PBDFs have not been identified or indicated in any of the photolysis studies performed to date. Formation of OH-PBDFs, however, may occur as pure radical reactions in the atmosphere. CONCLUSIONS: Photolysis of decaBDE yields a wide span of products, from nonaBDEs to hydroxylated bromobenzenes. It is evident that irradiation of decaBDE in water and methanol yields OH-PBDFs and MeO-PBDFs, respectively. BDE-202 (2,2',3,3',5,5',6,6'-octabromodiphenyl ether) is identified as a marker of BDE-209 photolysis. RECOMMENDATIONS AND PERSPECTIVES: BDE-209, the main constituent of DecaBDE, is primarily forming debrominated diphenyl ethers with higher persistence which are more bioaccumulative than the starting material when subjected to UV light. Hence, DecaBDE should be considered as a source of these PBDE congeners in the environment

Keyword
Chemical reactivity - Photolysis - Polybrominated dibenzofurans - PBDFs - Polybrominated diphenyl ethers - PBDEs - UV degradation
National Category
Environmental Sciences
Research subject
Environmental Chemistry
Identifiers
urn:nbn:se:su:diva-24891 (URN)10.1007/s11356-009-0150-4 (DOI)000265880600011 ()19360447 (PubMedID)
Note
Part of urn:nbn:se:su:diva-7519Available from: 2008-04-23 Created: 2008-04-23 Last updated: 2017-12-13Bibliographically approved
4. Polybrominated diphenyl ethers in aircraft cabins – a source of human exposure?
Open this publication in new window or tab >>Polybrominated diphenyl ethers in aircraft cabins – a source of human exposure?
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2008 (English)In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 73, no 10, 1654-1660 p.Article in journal (Refereed) Published
Abstract [en]

Commercial aircrafts need a high degree of fire protection for passenger safety. Brominated flame retardants (BFRs), including polybrominated diphenyl ethers (PBDEs), may be used for this purpose. Because PBDEs readily absorb to dust particles, aircraft crew and passengers may receive significant PBDEs exposure via inhalation. The aims of this work were to assess whether PBDEs could be found in aircraft cabin dust and whether serum levels of PBDEs increased in passengers after long-distance flights. Hence nine subjects on intercontinental flights collected cabin dust samples, as well as donated blood samples before departure and after return to Sweden. Two subjects who were domestic frequent flyers were also investigated. The levels of PBDEs in dust and serum were determined by GC/MS in electron capture negative ionization (ECNI) mode. Authentic reference substances were used for identification and quantitation. PBDEs were found in all aircraft dust samples at high concentrations, higher than in common household dust. Congener patterns indicated that the technical products PentaBDE, OctaBDE and DecaBDE were used in the aircrafts. Serum concentrations in the travellers were similar to those observed in Swedish residents in general. Post-travel serum levels of BDE-28, BDE-99, BDE-100, BDE-153, and BDE-154 were significantly higher (p < 0.05) than concentrations prior to travel. The findings from this pilot study call for investigations of occupational exposures to PBDEs in cabin and cockpit crews.

Keyword
Analysis; BFR; Dust; Human serum; PBDEs; Human levels
National Category
Chemical Sciences
Research subject
Environmental Chemistry
Identifiers
urn:nbn:se:su:diva-24892 (URN)10.1016/j.chemosphere.2008.07.071 (DOI)000261561600012 ()18786695 (PubMedID)
Note
Part of urn:nbn:se:su:diva-7519Available from: 2008-04-23 Created: 2008-04-23 Last updated: 2017-12-13Bibliographically approved

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Output format
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