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Thesis (M.A.)--West Virginia University, 2000. / Title from document title page. Document formatted into pages; contains viii, 123 p. Includes abstract. Includes bibliographical references (p. 63-68).

Mites are endemic and allergy to mite excreta and parts is one of the most common allergies. Health care practitioners have recommended the removal of carpets from homes of people with mite allergies. Little, if any, consideration is given to the fact that some persons may benefit directly from the presence of carpet in their homes. In the allergen and mite research literature, carpets are rarely described as having unique characteristics and are generally referred to as a generic entity. Carpets, however, do have unique characteristics that define their construction, appearance, wearability, and cleanability. Seventy-two pieces of commercially available, residential flooring materials were inoculated with identical numbers of mites, Dermatophagiodes farinae, and placed in the Textiles Conditioning Lab at Virginia Tech. The mites and carpet pieces were maintained in the lab, under identical, environmentally controlled conditions for 6 weeks, then the mites were extracted and counted. On the basis of the results of statistical tests run on the study data, the null hypothesis, that there is no difference between the numbers of mites grown on the different flooring conditions, was rejected. Statistically significant differences exist between the hard floor and the nylon carpet, between hard floor and olefin carpets, but no difference between hard floor and wool carpet. Nylon was the carpet fiber that was most supportive of the growth of house dust mites, olefin was the second most supportive, and wool carpet and hard floor were similar in being the least supportive. / Master of Science

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Understanding the transport of particulate and gaseous indoor air pollutants from source to exposure is paramount to improve our understanding of the complexities of the built environments in which we spend the majority of our time. This dissertation offers new insights on particle resuspension from indoor surfaces, infant exposure to organic contaminants released from crib mattresses, and the dynamics of pollutant transport and human exposure while sleeping. Particle resuspension is the physical process by which settled particles detach from a surface and become airborne through application of various aerodynamic and mechanical removal forces. Resuspension is an important indoor source of coarse mode particles (> 1 µm in diameter) and can be a source mechanism for biological matter and organic contaminants that accumulate in house dust. Settled dust deposits on indoor surfaces can vary considerably in their structure and mass loading, yet little is known as to how these parameters affect resuspension. Through wind tunnel experiments, this research demonstrates that the deposit structure (monolayer or multilayer) can have a significant impact on the number of particles that aerodynamically resuspend. Furthermore, this dissertation presents the first full-scale experimental chamber study to show that human body movements in bed can resuspend settled mattress dust particles. An indoor aerosol model was utilized to provide a mechanistic understanding of the impact of movement intensity, surface vibrations, bedroom ventilation rate, and dust loading on the resuspension flux and intake fraction of resuspended particles. Infants spend most of their time sleeping and are likely to be exposed to elevated concentrations of chemicals released from their crib mattresses. Through a combination of chamber experiments and solvent extractions, this research shows that infant crib mattresses can emit a variety of volatile organic compounds (VOCs) and contain numerous chemical additives, including phthalate and alternative plasticizers, flame retardants, and unreacted isocyanates. Additionally, this study discovered that infants are exposed to approximately twice the concentrations of VOCs in their breathing zones as compared to the bulk bedroom air, due to their close proximity to the source.

[Truncated abstract] The last few decades have witnessed an increase in the prevalence, morbidity and economic burden associated with asthma and allergic disease. This rising incidence cannot be completely explained by changes in genetic factors or by improvements in diagnostic procedures. Environmental factors, particularly those associated with a westernised lifestyle, are considered to be involved in this increase. In the late 1980’s Strachan was the first to link environmental factors with allergic disease, this theory became to be known as the ‘hygiene hypothesis’. This hypothesis links the “cleaner” more “healthy ” environment we now live in, with an increased risk of developing allergic disease. This effect is highlighted by studies linking farm and animal exposure (rich in microbial compounds) during early life with a decrease in allergic disease. Since then numerous studies have been undertaken to ascertain the factors present in the microbe rich environment, which elicit this protective effect. Many studies have revolved around endotoxin, however microbial components (mainly from Gram-positive bacteria) which signal through Toll-like receptor 2 (TLR2), have also shown that they can alter the allergic immune response. In mice models TLR2 has been shown to both exacerbate and inhibit allergic disease. The above research highlights the need for further studies into the effect of TLR2 ligands, and to define the mechanisms by which they exert their effects in human allergic disease. These mechanisms will be relevant to understanding the pathogenesis of allergy, but also might provide novel ways to treat allergy. The aims of the study outlined in this thesis were to determine whether in vitro exposure to TLR2 ligands could modify the established immune response to house dust mite allergen (HDM), and to examine the mechanisms by which this occurs. ... The addition of glucocorticoids to LTA enhanced the ability of this TLR2 ligand to inhibit IL-5 and IL-13 production by HDM-activated blood mononuclear cells. In conclusion, this study shows that TLR2 ligands have the ability to inhibit the Th2 response to mite allergen in previously sensitized individuals by an as yet unknown mechanism. However the findings described herein do provide an impetus for future studies designed to uncover novel mechanisms by which allergic responses can be ameliorated, and may open new treatment modalities.

House dust mites are a major source of allergens in house dust and, thus, the main trigger of perennial allergic respiratory diseases [1,2,3,4,5]. Scientific research on the life cycle, diet, and reproductive behavior of dust mites and on the biology of mite allergens has uncovered mechanisms leading to the development of respiratory allergies and suggests measures that can minimize exposure to dust mite allergens. Here, we discuss the evidence linking house dust mite exposure and respiratory allergies and present the efficacy of avoidance measures and their scientific evidence.

<p>The overall aims of our studies were to identify risk factors for respiratory symptoms and asthma in indoor environment but even to look at some personal risk factors such as body mass index and gastroesophageal reflux. The study population is based on participants of the European Community Respiratory Health Survey I and II. </p><p> In the first study, water damage and visible moulds were reported in 7.4% and 17% of the homes respectively. The combination of water damage and visible moulds was independently associated with attacks of breathlessness when resting and after activity and also to long term cough. In the second study, the prevalence of nocturnal GER increased with higher BMI and the same pattern could be seen for habitual snoring. Reported onset of asthma, wheeze and night-time symptoms increased in prevalence along with the BMI gradient. In the multivariable analysis, obesity and nocturnal GER were independent risk factors for onset of asthma, wheeze and night-time symptoms. Habitual snoring was an independent risk factor for onset of wheeze and night-time symptoms, but not for onset of asthma. In the third study, a total of 18% of the subjects reported indoor dampness in the last 12 months and 27% of the subjects reported indoor dampness since the previous survey. Respiratory symptoms and asthma were significantly more prevalent in individuals exposed to indoor dampness and indoor dampness was a risk factor for respiratory symptoms and asthma after adjusting for possible confounders. Indoor dampness was an independent risk factor for onset of respiratory symptoms but not for asthma onset. Remission of respiratory symptoms was less likely to occur if subjects reported indoor dampness. In the fourth study, the lowest prevalence of atopy and the lowest levels of all indoor allergens, bacteria and moulds were found in Iceland. A positive association was found, between cat allergen exposure and asthma symptoms and between bronchial hyperresponsiveness and the amount of viable mould in indoor air.</p>