published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

University of Macau / Faculty of Science and Technology. / Department of Civil and Environmental Engineering

Thesis (M.Sc.)--University of Hong Kong, 2008. / Includes bibliographical references (p. 59-68).

Phthalate esters are extensively used as plasticizers in building materials and consumer products, but are associated with serious health concerns. They are ubiquitous indoors, redistributing from their original source to all interior surfaces, including airborne particles, dust, and skin. The main objective of the research is to investigate the influence of temperature on the fate and transport of phthalates in indoor environments. In this study, the concentrations of benzyl butyl phthalate (BBzP) and di-2-ethylhexyl phthalate (DEHP) in indoor air, settled dust, and on different interior surfaces including mirror, glass, plate, cloth and wood were measured periodically in a test house. The measurements were conducted at temperatures of 21°C and 30°C, respectively. In addition, sorption kinetics was also monitored at the temperature of 21°C. The air concentrations of BBzP and DEHP at 21°C range from 141 ng/m₃ to 210 ng/m₃ and 66 ng/ m₃ to 100 ng/ m₃, respectively. For impervious surfaces such as dish plates, the surface concentrations reached steady-state concentrations in less than 24 hours, to the level between 2 and 8 [mu]g/m₂ for both BBzP and DEHP. In contrast, the time to reach steady state was much longer for porous surfaces such as hardwood (>1 week) and dust (> months). With the temperature increase to 30°C, the gas phase concentrations of BBzP and DEHP increased by about five times, and the surface concentrations on various surfaces also increased correspondingly. This investigation suggests that temperature has an important influence on the fate and transport of phthalates in indoor environments. / text

Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

Thesis (M. Phil.)--University of Hong Kong, 2005. / Title proper from title frame. Also available in printed format.

There is general concern whether human exposure to selected Canadian bottled waters and the chemicals which may leach from them, could potentially cause deleterious effects. This research was designed to determine whether exposures to bottled water and plastic leachates caused toxicity to the freshwater Cnidarian Hydra viridissima (green hydra). Three chemicals used in the production of polycarbonate and polyethylene plastics, bisphenol A (BPA) and two phthalate esters: dibutyl phthalate (DBP) and bis (2- ethylhexyl) phthalate (DEHP) along with one type of commercial bottled water were investigated. One brand of bottled water was analyzed over four months (stored in light and dark conditions) along with lab water similarly stored in glass, polycarbonate and polyethylene bottles. Following 2, 4, 8 and 16 weeks in each of the two treatments, hydra bioassays were conducted. Chronic toxicity tests were also conducted on the two phthalates and BPA. The chronic toxicity tests showed that BPA caused effects on hydra morphology and population at low doses and DBP and DEHP both showed signs of hormesis.

Phthalate esters (phthalates) such as dibutylphthalate (DBP) are commonly used as plasticisers and pesticides in a variety of products such as children‟s plastic toys, food packaging, cosmetics, medical equipment (including surgical equipment), and acaricides. Because of their widespread use phthalates are ubiquitous environmental contaminants that humans are commonly exposed to. Phthalates are known endocrine-disrupting chemicals (EDCs) that are well known to cause male reproductive defects such as cryptorchidism (failed descent of the testes) and hypospadias (malformations in the urethra) in a range of different species if they are exposed in utero. They do this by reducing testosterone production in Leydig cells, which are the primary site of testosterone biosynthesis in the male. Because phthalates are dose-additive they are considered to share the same mechanism of toxicity. However, the details of phthalates mechanism of toxicity are not fully understood. The aim of this research was to investigate the effects of DBP on the steroidogenesis pathway using the cultured rat Leydig cell cancer line R2C as a Leydig cell model. R2C cells were exposed to a range of DBP concentrations (10 μg/mL, 5 μg/mL, 1 μg/mL, and 0.1 μg/mL) and their steroid hormone production was analysed using reverse phase HPLC. R2C cells did not synthesise testosterone at detectable levels. However, DBP exposure stimulated cortisol biosynthesis at all concentrations but caused no change in progesterone biosynthesis. This cortisol stimulation in Leydig cells has not been observed before. Because cortisol and testosterone compete for precursors an increase in cortisol synthesis could starve testosterone synthesis of precursors. On top of this it has been shown that glucocorticoids including cortisol have an adverse effect on Leydig cell development reducing steroid production and even causing apoptosis. This could explain how DBP and other phthalates can cause male developmental defects such as cryptorchidism and hypospadias.

Thesis (Ph. D.)--Rutgers University, 2008. / "Graduate Program in Microbiology and Molecular Genetics." Includes bibliographical references (p. 164-179).

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.