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Doctoral Degrees (Chemistry)

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Browsing Doctoral Degrees (Chemistry) by Author "Abafe, Ovokeroye Akpojevwe."

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    Organic flame retardants in the indoor environment.
    (2014) Abafe, Ovokeroye Akpojevwe.; Martincigh, Bice Susan.
    Flame retardants (FRs) have become ubiquitous contaminants found in humans, animals, various outdoor environments, e.g. air, soil, sediment, etc., and indoor environments particularly, homes, automobiles, classrooms and workplaces all over the world. These chemicals are global contaminants of concern as they are persistent, can bioaccumulate, biomagnify and have potential for long-range atmospheric transport. Most FRs are toxicants to human health since they affect thyroid hormones, endocrine systems and neurobehavioural development and are possibly carcinogenic. The overall hypothesis of this study is that the use of FRs in consumer goods and materials is leading to contamination of indoor environment at levels that may be detrimental to human health. In this study, analytical methods based on gas chromatography-electron impact/mass spectrometry and liquid chromatography electrospray ionization/mass spectrometry were developed and/or validated for the separation, identification and quantitation of various classes of FRs. The FRs investigated included polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), tetrabromobisphenol A (TBBPA) and organophosphate esters [tris(1,3-dichloro-2-propyl) phosphate (TDCPP), tris(2-chloroethyl) phosphate (TCEP), tris(1-chloro-2-propyl) phosphate (TCPP) and triphenyl phosphate (TPP)]. These were measured in indoor dust from a wide range of microenvironments, including homes, offices, classrooms, automobiles, three workplaces – an e-waste recycling site, a polyurethane factory and a textile industry – and an in vitro human gastro-intestinal tract (GIT). The measured concentrations of the FRs were used to estimate the exposure of toddlers, teenagers and adults to the FRs of interest via dust ingestion and in some cases dermal absorption of dust by using various exposure scenarios. The relative importance of each exposure route was assessed for the studied population groups. The potential sources of the FRs in the different microenvironments were established by using various advanced parametric and non-parametric statistical tests. Causes of variability in indoor dust concentrations of FRs were elucidated. Two types of in vitro GIT models mimicking the enzymatic and physiochemistry preponderant for a FED and a FASTED state were developed, validated and applied for the first time to study the oral bioaccessibility of organophosphate esters and also to study the bioaccessibility of PBDEs. Strong relationships were found for the bioaccessibility of OPEs and their water solubilities as well as the log Kow of PBDEs.