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Indoor emissions and fate of flame retardants: A modelling approach
Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A significant number of consumer goods and building materials act as emission sources of flame retardants (FRs) in the indoor environment. As a result, FRs have become ubiquitous indoors raising concerns about human exposure and possible health implications. Once released indoors, FRs can escape to the outdoors where they can persist, be transported over long distances and present a threat to the environment. Despite the increasing number of studies reporting the occurrence of FRs in the indoor environment, the understanding of i) how and to what extent these chemicals are released from indoor sources, and ii) their subsequent fate indoors remains limited. The overarching objective of this thesis was to improve this understanding by assessing the indoor emissions and fate of FRs using a combination of multimedia modelling strategies and experimental/empirical approaches. Paper I identifies a number of knowledge gaps and limitations regarding indoor emissions and fate of FRs and the available modelling approaches. These include a limited understanding of the key emission mechanisms for low volatility FRs, uncertainties regarding indoor air/surface partitioning, poor characterization of dust and film dynamics and a significant lack of knowledge regarding indoor reaction/degradation processes. In Paper II we highlighted the serious scarcity in physicochemical property data for the alternative FRs and demonstrated the applicability of a simple QSPR technique for selecting reliable property estimates for chemical assessments. A modelling fate assessment indicated a strong partitioning to indoor surfaces and dust for most of the alternative FRs. Indications for POP (persistent organic pollutant)-like persistence and LRT (long-range transport) and bioaccumulative potential in the outdoor environment were also identified for many alternative FRs. Using an inverse modelling approach in Paper III we estimated 2 to 3 orders of magnitude higher emissions of organophosphate FRs (0.52 and 0.32 ng.h-1) than brominated FRs (0.083 μg.h-1 and 0.41 μg.h-1) in Norwegian households. An emission-to-dust signal was also identified for organophosphate FRs suggesting that direct migration to dust may be a key fate process indoors. No evidence of a direct source-to-dust transfer mechanism was seen in Paper IV where the chemical transfer between a product treated with an organophosphate FR and dust in direct contact was experimentally investigated. It was concluded though that direct contact between an FR source and dust can result in contamination hotspots indoors.

Place, publisher, year, edition, pages
Stockholm: Department of Environmental Science and Analytical Chemistry, Stockholm University , 2016.
Keyword [en]
flame retardants, BFRs, OPFRs, indoor environment, emissions, fate, modelling
National Category
Environmental Sciences
Research subject
Applied Environmental Science
Identifiers
URN: urn:nbn:se:su:diva-127258ISBN: 978-91-7649-341-0 (print)OAI: oai:DiVA.org:su-127258DiVA: diva2:907770
Public defence
2016-04-08, Nordenskiöldsalen, Geovetenskapens hus, Svante Arrhenius väg 12, Stockholm, 13:00 (English)
Opponent
Supervisors
Funder
EU, FP7, Seventh Framework Programme, 264600
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.

Available from: 2016-03-16 Created: 2016-02-29 Last updated: 2017-02-20Bibliographically approved
List of papers
1. Emissions and fate of brominated flame retardants in the indoor environment: A critical review of modelling approaches
Open this publication in new window or tab >>Emissions and fate of brominated flame retardants in the indoor environment: A critical review of modelling approaches
2014 (English)In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 491, 87-99 p.Article, review/survey (Refereed) Published
Abstract [en]

This review explores the existing understanding and the available approaches to estimating the emissions and fate of semi-volatile organic compounds (SVOCs) and in particular focuses on the brominated flame retardants (BFRs). Volatilisation, an important emission mechanism for the more volatile compounds can be well described using current emission models. More research is needed, however, to better characterise alternative release mechanisms such as direct material-particle partitioning and material abrasion. These two particle-mediated emissions are likely to result in an increased chemical release from the source than can be accounted for by volatilisation, especially for low volatile compounds, and emission models need to be updated in order to account for these. Air-surface partitioning is an important fate process for SVOCs such as BFRs however it is still not well characterised indoors. In addition, the assumption of an instantaneous air-particle equilibrium adopted by current indoor fate models might not be valid for high-molecular weight, strongly sorbing compounds. A better description of indoor particle dynamics is required to assess the effect of particle-associated transport as this will control the fate of low volatile BFRs. We suggest further research steps that will improve modelling Precision and increase our understanding of the factors that govern the indoor fate of a wide range of SVOCs. It is also considered that the appropriateness of the selected model for a given study relies on the individual characteristics of the study environment and scope of the study.

Keyword
BFRs, SVOCs, Emissions, Indoor fate, Multimedia models, Deposition
National Category
Earth and Related Environmental Sciences
Research subject
Applied Environmental Science
Identifiers
urn:nbn:se:su:diva-107096 (URN)10.1016/j.scitotenv.2014.02.005 (DOI)000339534700013 ()
Note

AuthorCount:3;

Available from: 2014-09-05 Created: 2014-09-03 Last updated: 2017-12-05Bibliographically approved
2. Physical-chemical properties and evaluative fate modelling of 'emerging' and 'novel' brominated and organophosphorus flame retardants in the indoor and outdoor environment
Open this publication in new window or tab >>Physical-chemical properties and evaluative fate modelling of 'emerging' and 'novel' brominated and organophosphorus flame retardants in the indoor and outdoor environment
2015 (English)In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 524, 416-426 p.Article in journal (Refereed) Published
Abstract [en]

Several groups of flame retardants (FRs) have entered the market in recent years as replacements for polybrominated diphenyl ethers (PBDEs), but little is known about their physical-chemical properties or their environmental transport and fate. Here we make best estimates of the physical-chemical properties and undertake evaluative modelling assessments (indoors and outdoors) for 35 so-called 'novel' and 'emerging' brominated flame retardants (BFRs) and 22 organophosphorus flame retardants (OPFRs). A QSPR (Quantitative Structure-Property Relationship) based technique is used to reduce uncertainty in physical-chemical properties and to aid property selection for modelling, but it is evident that more, high quality property data are required for improving future assessments. Evaluative modelling results show that many of the alternative FRs, mainly alternative BFRs and some of the halogenated OPFRs, behave similarly to the PBDEs both indoors and outdoors. These alternative FRs exhibit high overall persistence (Pov), long-range transport potential (LRTP) and POP-like behaviour and on that basis cannot be regarded as suitable replacements to PBDEs. A group of low molecular weight alternative BFRs and non-halogenated OPFRs show a potentially better environmental performance based on Pov and LRTP metrics. Results must be interpreted with caution though since there are significant uncertainties and limited data to allow for thorough model evaluation. Additional environmental parameters such as toxicity and bioaccumulative potential as well as functionality issues should be considered in an industrial substitution strategy.

Keyword
BFRs, OPFRs, Indoor fate, Persistence, Physical-chemical properties
National Category
Earth and Related Environmental Sciences
Research subject
Applied Environmental Science
Identifiers
urn:nbn:se:su:diva-118329 (URN)10.1016/j.scitotenv.2015.02.106 (DOI)000355010400042 ()
Available from: 2015-06-18 Created: 2015-06-15 Last updated: 2017-12-04Bibliographically approved
3. Relationships between estimated flame retardant emissions and levels in indoor air and house dust
Open this publication in new window or tab >>Relationships between estimated flame retardant emissions and levels in indoor air and house dust
Show others...
(English)Manuscript (preprint) (Other academic)
Abstract [en]

A significant number of consumer goods and building materials can act as emission sources of flame retardants (FRs) in the indoor environment. We investigate the relationship between the emission source strength and the levels of 19 brominated flame retardants (ΒFRs) and 7 organophosphate flame retardants (OPFRs) in air and dust collected in 38 indoor microenvironments in Norway. We use modelling methods to back-calculate emission rates from indoor air and dust measurements and identify possible indications of an emission-to-dust pathway. Experimentally-based emission estimates provide a satisfactory indication of the relative emission strength of indoor sources. Modelling results indicate an up to two orders of magnitude enhanced emission strength for OPFRs (median emission rates of 0.083 and 0.41 μg.h-1 for air-based and dust-based estimates) compared to BFRs (0.52 and 0.37 ng.h-1 median emission rates). An emission-to-dust signal was identified for 4 of the 7 OPFRs, but only for 1 out of the 19 BFRs. The influence of the sensitivity and uncertainty of KOA on model-estimated emission rates is explored and it is concluded that uncertainty in the model input KOA value could potentially lead to the false identification of an emission-to-dust signal given the high sensitivity of dust-based emission estimates to KOA.

Keyword
indoor emissions, modelling, BFRs, OPFRs, emission mechanism, emission-to-dust
National Category
Environmental Sciences
Research subject
Applied Environmental Science
Identifiers
urn:nbn:se:su:diva-127259 (URN)
Funder
EU, FP7, Seventh Framework Programme, 264600
Available from: 2016-02-29 Created: 2016-02-29 Last updated: 2016-03-02Bibliographically approved
4. Chemical mass transfer of an organophosphate flame retardant between product source and dust in direct contact
Open this publication in new window or tab >>Chemical mass transfer of an organophosphate flame retardant between product source and dust in direct contact
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Organophosphate flame retardants (OPFRs) are a group of semi-volatile organic compounds (SVOCs) which are ubiquitous and among the most abundant contaminants indoors. Despite the fact that their indoor presence has been shown to contribute significantly to human exposure and has been associated with potential health risks there is limited understanding as to how they are released from indoors sources. This study uses an emission micro-chamber to explore one of the currently understudied chemical migration pathways; direct transfer between a source material and settled dust in contact with the source. A tris(2-chloroisopropyl) phosphate (TCIPP)-treated insulation board is used as the source material. Rapid and substantial transfer was observed after only 8 h of source-dust contact, resulting in 80 times higher concentrations in dust compared to pre-experiment levels. Further time points at 24 h and 7 d showed similarly high average dust levels and the TCIPP in the dust and air in the chamber was calculated to be close to thermodynamic equilibrium during the experiment. It was concluded that TCIPP was effectively transferred from the insulation board to the dust on its surface and the surrounding air via gas-phase diffusion. As the TCIPP in the air and dust in the chamber appear close to equilibrium, there is no evidence from this experiment that TCIPP levels in dust in direct contact with product surfaces indoors would be enhanced compared to dust levels in the rest of the room. In a real room however where such well-mixed conditions as in the micro-chamber do not generally apply there might be a gradient of concentrations of TCIPP in air above the surface of a product. This could result in higher concentrations in dust sitting on the product than dust in the rest of the room.

National Category
Environmental Sciences
Research subject
Applied Environmental Science
Identifiers
urn:nbn:se:su:diva-127261 (URN)
Available from: 2016-02-29 Created: 2016-02-29 Last updated: 2016-03-02Bibliographically approved

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