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Ssh tunnel 16 07. For extraction optimization there were considered two of the most commonly applied methodologies in this research field, namely: classical Soxhlet extraction and ultrasonic/vortex extraction. In order to choose the suitable technique for this study, the extraction solvents were also considered for the optimization process, later being decided to use a mixture of n-hexane:dichloromethane (1:1, v/v). Therefore, all dust samples were processed through a combination of vortex and ultrasonication: three cycles of 2 minutes vortex (Velp, Italy, 1200 rpm) combined with 30 minutes room temperature ultrasonication (ISOLAB, 6 L, 40 KHz, 180W) followed by centrifugation of the extracts (5000 rpm) after each cycle and transferring of the extracts after each extraction in a separate tube with combining of the organic phase together for each sample. The total extraction volume after following this extraction procedure was initially reduced by the use of a rota-evaporator and later using a concentrator/evaporator under a gentle nitrogen flow (Thermo Scientific, Reacti-Vap™ Evaporator) operated at 25 degrees Celsius. Thus, the extract was reduced to below 3 mL, the target analytes being concentrated at this stage in n-hexane.

c) Clean-up of the extracts

Due to the non-polar nature of the extraction solvents, other compounds might also be co-extracted from collected samples contributing to the increasing of the S/N ratio and interfering with the target analytes for this study. Therefore, there was applied a clean-up step on the obtained extracts from previous stage of the analysis protocol. The clean-up of the extracts was based on using column chromatography (3 mL, propylene, Supelco) filled with a layer of acidified silicagel (44% sulphuric acid, Merck), inferior layer, and anhydrous sodium sulphate on top. The extracts were applied on the clean-up cartridges and later analytes were eluted with 10 mL mixture of n-hexane:dichloromethane (1:1, v/v). Later the obtained extracts were again concentrated to near dryness and redissolved in 100 μL iso-octane. Prior to instrumental analysis, the extracts were filtered on Eppendorf filtration cartridges (20 μm pore-size) followed by centrifugation, 7000 rpm. The final extracts were transferred to injection vials in limited volume inserts of 250 μL.

Image 1. Columns prepared for clean-up of the obtained extracts.

Image 2. Vacuum manifold system used for extracts clean-up and filtration.

d) Instrumental analysis

Both standard solutions and final extracts obtained after sample preparation procedures were injected under optimized conditions in two gas-chromatographic systems with mass spectrometer detection. The instrumental characteristics and operation parameters used for analysis are given in Tables 5 and 6.

Table 5. Characteristics of the instruments used for identification/quantification of BDE 209 and PCB 143

Table 6. Gas chromatograph operating conditions for identification/quantification of BDE 209 and PCB 143

Standard solutions of each tested analyte, namely BDE 209 (concentration of 1.25 ng/μL), ε-HCH (50 pg/µL), PCB 143 (100 pg/µL) where injected in GC systems with detector operated in full-scan in order to select the proper retention time, identification/quantification ions for each compound. Standard solution of BDE 209 were prepared starting with solid analyte of 99.9% purity (Dr. Ehrenstorfer Laboratories, Augsburg, Germany) and later consequently diluted up to the required concentration level. In order to quantify the target analyte from extracted dust samples, a calibration set of solutions were prepared based on data presented in Table 7.

Table 7. Standard solutions used for preparing the calibration curve (internal calibration based on PCB 143)

Calibration solutions and final extracts of the dust samples were injected into GC-MS system operated accordingly with conditions included in Table 6 and later the peaks were manually integrated in order to extract the areas of each signal associated with target analytes and later by the use of the internal calibration equation the analyte mass was calculated. Using the processed sample mass there could be obtained the analyte concentrations expressed in ng/g of sample.

Method applicability for determination of BDE 209 from dust samples Adobe dreamweaver 2020 20 12.

The above described protocol was applied for all extracts obtained after preparation of the collected dust samples, but in order to quantify the BDE 209 there were applied two different approaches: with and without considering the presence of PCB 143 with role of internal standard and thus with and without corrections for the analyte loss during sample preparations procedures.

The obtained results on the BDE 209 levels (ng/g sample) are given in Table 8.

Table 8. BDE 209 concentrations (ng/g sample) from dust samples collected from working stations (computers) sampled from the Department of Chemistry, UAIC, Romania

Estimation of the human exposure to BDE 209 through dust ingestion

In order to estimate the human exposure to various contaminants through dust ingestion, the existing exposure models are based on some assumptions which were considered also during the following of this study. One of these assumptions is based on the fact that 100% of the analytes contained by dust are adsorbed at the gastro-intestinal tract; therefore they are assumed to be 100% bioavailable.

Table 9. Estimation of the BDE 209 human (adults) exposure (ng/day and ng/kg bw/day respectively) through dust ingestion

Table 10. Estimation of the BDE 209 human (toddlers) exposure (ng/day and ng/kg bw/day respectively) through dust ingestion

Additionally, the human exposure scenarios to dust ingestion are based on the existence of two accepted models of exposure for both adults and toddlers, namely:

– one scenario of average human exposure to dust which considers that an adult (70 kg) ingests 20 mg of dust, while a toddler (6-24 months old, 24 kg) ingests 50 mg of dust daily;

– a second scenario of high exposure to dust which is based on the following exposure figures: an adult (70 kg) ingests 50 mg of dust, while a toddler (6-24 months old, 24 kg) ingests 200 mg of dust daily.

Table 11. Estimation of the differences recorded for the human (adults) exposure scenarios to BDE 209 through dust ingestion due to instrumental protocol modification

Table 12. Estimation of the differences recorded for the human (toddlers) exposure scenarios to BDE 209 through dust ingestion due to instrumental protocol modification

Based on the above mentioned exposure scenarios and on measured levels of BDE 209 from collected dust samples the estimation of the human exposure to BDE 209 through dust ingestion data is presented in Tables 9 and 10 (adults and toddlers) and differences recorded for such exposure scenarios based on analytical protocol modification are presented in Tables 11 and 12 (adults and toddlers).

Published/Submitted research articles

1. Dan Maftei, Mihai Dumitras, Dragos L. Isac, Alin C. Dirtu. Density functional study of bond dissociation energies in highly brominated diphenyl ethers. Studia UBB Chemia, LXI, 4, 137-146, 2016. (http://chem.ubbcluj.ro/~studiachemia/chemia2016_4.html)

2. Mihai Dumitras, Dan Maftei, Dragos L. Isac, Anton Airinei, Alin C. Dirtu. Thermal degradation study of decabromodiphenyl ether. Translating thermo-analytical results into optimal chromatographic conditions. Acta Chemica Iasi, 24 (2), 76-87, 2016. (https://www.degruyter.com/view/j/achi.2016.24.issue-2/issue-files/achi.2016.24.issue-2.xml)

3. Mihai Dumitras, Dan Maftei, Anton Airinei, Nita Tudorachi, Alin C. Dirtu. NPK analysis of the thermal degradation of decabromodiphenyl ether. Revista de Chimie, 68 (11), 2017 – article in press. (http://www.revistadechimie.ro/)

4. Mihai Dumitras, Liviu Leontie, Dan Maftei, Alin C. Dirtu. Kinetic analysis of the thermal degradation of two brominated flame retardants. Journal of Thermal Analysis and Calorimetry, 2017 – article submitted. (https://link.springer.com/journal/10973)

5. Dan Maftei, Dragos L. Isac, Mihai Dumitras, Stefan Bucur, Alin C. Dirtu. Trends in Bond Dissociation Energies of Brominated Flame Retardants from Density Functional Theory. Structural Chemistry, 2017 – article submitted. (https://link.springer.com/journal/11224)

Conference participation

1. Alin C. Dirtu, Dan Maftei, Mihai Dumitras, Mirela Suchea, Adrian Covaci. Influence of the chromatographic analysis of flame retardants on the estimation of human exposure to organohalogenated compounds. Nanoscience in Chemistry, Physics, Biology and Mathematics – NanoMathChem, 12-14 November 2015, Cluj, Romania. (http://www.esmc.ro/#!nanomathchem2015/c6ve)

2. Alin C. Dirtu, Mihai Dumitras, Dan Maftei, Anton Airinei, Nita Tudorachi, Dragos L. Isac. Thermal degradation study of brominated flame retardants with emphasis on the estimation of human exposure through indoor dust ingestion. 12^th International Conference on Colloid and Surface Chemistry – ICCSC, 16-18 May 2016, Iasi, Romania. (https://iccsc2016.wordpress.com/)

3. Alin C. Dirtu, Dan Maftei, Mihai Dumitras, Adrian Covaci. Challenges in gas-chromatographic analysis of thermal unstable compounds. Case study for brominated flame retardants. 3^rd International Conference on Analytical Chemistry – RO-ICAC, 28-31 August 2016, Iasi, Romania. (http://roicac.acadiasi.ro/)

4. Dan Maftei, Mihai Dumitras, Dragos L. Isac, Alin C. Dirtu. Thermal degradation pathways of selected brominated flame retardants from first principles. International Conference of Physical Chemistry – ROMPHYSCHEM, 21-23 September 2016, Galati, Romania. (http://gw-chimie.math.unibuc.ro/romphyschem/)

5. Mihai Dumitras, Dan Maftei, Anton Airinei, Alin C. Dirtu. NPK analysis of the thermal degradation of selected brominated flame retardants. International Conference of Physical Chemistry – ROMPHYSCHEM, 21-23 September 2016, Galati, Romania. (http://gw-chimie.math.unibuc.ro/romphyschem/)

6. Mihai Dumitras, Dan Maftei, Dragos L. Isac, Alin C. Dirtu. Study on the kinetics and mechanism of decabromo-diphenyl ether thermal degradation. XXXIV-th Romanian Chemistry Conference, 04-07 October 2016, Calimanesti-Caciulata, Valcea, Romania. (http://conferinta.oltchim.ro/)

7. Dan Maftei, Mihai Dumitras, Dragos L. Isac, Alin C. Dirtu. Computational thermochemistry of brominated flame retardants. Case study of decabromo-diphenyl ether. XXXIV-th Romanian Chemistry Conference, 04-07 October 2016, Calimanesti-Caciulata, Valcea, Romania. (http://conferinta.oltchim.ro/)

8. Dragos L. Isac, Mihai Dumitras, Dan Maftei, Anton Airinei, Alin C. Dirtu. Study on the thermal degradation of brominated flame retardants: computational thermochemistry, kinetics and degradation mechanism. 'Alexandru Ioan Cuza' University Days, Faculty of Chemistry Conference, 27-28 October 2016, Iași, România. (http://www.chem.uaic.ro/ro/manifestari/program-zu-2016.html)

9. Alin C. Dirtu, Mihai Dumitras, Dan Maftei, Adrian Covaci. Challenges in brominated flame retardants analysis in dust samples from personal computers. Case study in a university campus from Eastern Romania. 19th International Conference – Materials, Methods & Technologies, 26-30 June 2017, Elenite, Bulgaria. (https://www.sciencebg.net/en/conferences/materials-methods-and-technologies/)

10. Dan Maftei, Dragos L. Isac, Stefan Bucur, Alin C. Dirtu. Bond dissociation enthalpies in selected brominated flame retardants from density functional theory. 19th International Conference – Materials, Methods & Technologies, 26-30 June 2017, Elenite, Bulgaria. (https://www.sciencebg.net/en/conferences/materials-methods-and-technologies/)

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11. Mihai Dumitras, Dan Maftei, Dragos L. Isac, Alin C. Dirtu. Comparative study of the thermal degradation of two brominated flame retardants. 19th International Conference – Materials, Methods & Technologies, 26-30 June 2017, Elenite, Bulgaria. (https://www.sciencebg.net/en/conferences/materials-methods-and-technologies/)

12. Stefan Bucur, Dragos L. Isac, Dan Maftei, Mihai Dumitras, Alin C. Dirtu. New insights into brominated flame retardants structure: computational assessment of σ-hole effect. Scientific Communications Session for Bachelor, Master of Science and PhD Students, 30 June 2017, Faculty of Chemistry, 'Alexandru Ioan Cuza' University of Iasi, Romania (http://www.chem.uaic.ro/ro/manifestari/program-scsmd-2017.html).

13. Dragos-Lucian Isac, Stefan Bucur, Dan Maftei, Mihai Dumitras, Alin C. Dirtu. Aspecte teoretice privind structurile chimice ale compusilor ignifugi bromurati. Metode noi de evidentiere a efectelor regiunii σ si π. Zilele Academice Ieșene (ZAI), 5 – 6 Octombrie 2017, Iași, România (http://www.icmpp.ro/zai/program.html).

14. Mihai Dumitras, Dan Maftei, Dragos L. Isac, Alin C. Dirtu. NPK analysis of the thermal degradation of two brominated flame retardants. Colloque Franco-Roumain de Chimie Médicinale (CoFr-RoCM) – 4^th Edition, 5-7 October 2017, Iasi, Romania (http://www.chem.uaic.ro/cofrrocm-2017/).

IRIS Toxicological Review of Pentabromodiphenyl Ether (Final Report)

Citation:

U.S. EPA. IRIS Toxicological Review of Pentabromodiphenyl Ether (Final Report). U.S. Environmental Protection Agency, Washington, DC, EPA/635/R-07/006F, 2008.

Impact/Purpose:

The draft assessments will present reference values for the noncancer effects (RfD and RfC) and a cancer assessment, where supported by available data, for the BDE-47, BDE-99, BDE-153, and BDE-209 congeners of polybrominated diphenyl ethers.

Description:

The purpose of this Toxicological Review is to provide scientific support and rationale for the hazard and dose-response assessment in IRIS pertaining to chronic exposure to 2,2',4,4',5-pentabromodiphenyl ether. It is not intended to be a comprehensive treatise on the chemical or toxicological nature of 2,2',4,4',5-pentabromodiphenyl ether (BDE-99).

The majority of the available toxicological information on the pentabromodiphenyl ether homolog group (CAS No. 32534-81-9) relates to the pentabromodiphenyl congener BDE-99 (CASRN 60348-60-9). Toxicological information related to other congeners in the pentabromodiphenyl ether homolog group is also discussed. However, this health assessment does not deal with commercial mixtures of brominated diphenyl ether homologs containing pentabromodiphenyl ether as one of the constituents of commercial formulations. In addition to BDE-99, IRIS health assessments have also been prepared for three other polybrominated diphenyl ether congeners: tetraBDE-47, hexaBDE-153, and decaBDE-209. These four congeners are those for which toxicological studies suitable for dose-response assessments were available and are the ones most commonly found in the environment and human biological media.

Master Of Typing 2 4 4 5 Pentabromodiphenyl Ethernet