| Summary: | Polybrominated diphenyl ethers (PBDEs) are a class of brominated flame retardant, which has been widely used around the world to meet fire safety regulations for fabrics, furnishings, electronics and vehicles since the 1970s. During the life-cycle of the product, PBDEs leach out into indoor air and dust. From there they are transported into the wider environment, and bioaccumulate through food chains. The human body burden of PBDEs increased dramatically from the 1970s until the 1990s as a result of this wide use and their lipophilic and persistent character. In 2009, the Stockholm Convention to protect human health and the environment from persistent organic pollutants, added PBDEs to its list of chemicals for which production, import, export and use should be eliminated. However, the effects of such measures are slow to impact levels in human tissue. Furthermore, recovery and recycling of electronics is an additional newer source of exposure. Potential adverse human health effects of PBDE body burden include reproductive toxicity, neurotoxicity, endocrine activity, DNA damage and immune effects. Aim The aim of this study was to investigate human body burden of polybrominated diphenyl ether (PBDE) flame retardants, PBDE sources and exposure pathways. This was divided into three more specific objectives: (a) To measure current UK human body burdens of PBDE and their contributors, (b) To investigate concentrations of PBDEs in UK diets and influencing factors, and (c) To investigate concentrations of PBDEs in UK indoor dusts and influencing factors. Thesis Summary This doctoral thesis by published works presents four articles that addressed those objectives, investigating current dietary and indoor environment exposure sources and pathways that lead to human PBDE body burden. The study centred on a crosssectional cohort in the North East of England. A short pre-screening questionnaire identified volunteers who could be expected to provide a divergent range of exposures. The study recruited individuals to potentially reflect low, medium and high levels of exposure to PBDEs, such as oily fish eaters and vegetarians, and those iv with possible occupational exposure. 20 study participants were selected: 10 cohabiting couples (10 males and 10 females) aged 26-43 years, living in the North East of England. Samples of matched serum, human milk, 24 hour duplicate diet and indoor dust from living areas, bedrooms, vehicles and workplaces were collected and anthropometric measurements taken. Seven day food and activity diaries, food frequency and lifestyle exposure questionnaires and room surveys were also completed. The first article presents the findings of a systematic review into the relationships between diet and indoor environment exposure and human body burden to PBDEs. The second article presents concentrations of PBDE and polybrominated biphenyl in participants' serum and milk. It also compares the current findings with global concentrations and previous UK measurements taken prior to EU use restrictions. A risk assessment for infant intake of PBDE via milk is included. Relationships between anthropometric information and body burden are explored. The next article presents concentrations of PBDEs (and a range of other persistent organic pollutants (POPs) of interest) measured in 24 hour duplicate diet samples. These measurements are compared with estimations of adult dietary exposure derived from the Food Standards Agency's Total Diet Study 2011/12. Strengths and weaknesses of both methods were explored. Both sets of findings were then compared with previous UK dietary exposure estimates as well as estimates from around the globe. Temporal changes in dietary exposure to the POPs were explored. The final article presents the concentrations of PBDEs in the indoor dusts for the cohort and findings from the room surveys, diaries and questionnaires. Together with the body burden and duplicate diet exposure findings previously presented, the influence of diet, indoor environments, behaviour and anthropometrics on the PBDE body burdens of the cohort are explored. Based on these findings, recommendations for reducing PBDE body burden are made. For each article I discuss its contribution to the literature and a critique of the method. To close I reflect on my individual contribution to each article.
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