A combined transient hygrothermal and population model of House Dust Mites in beds

This paper describes a current multi-disciplinary UK funded research project aimed at developing a hygrothermal model of house dust mite response to environmental conditions. The project involves the development of a transient hygrothermal bed model, which has been tested and validated by comparing its predictions with the environmental conditions measured in a bed in a test laboratory and in beds in dwellings. A dust mite population model is currently being developed and is being tested by carrying out mite population growth studies in the laboratory, where environmental conditions can be controlled and measured accurately, and in dwellings. The aim of the project is to integrate the hygrothermal model with the population model so that assessments of the risks associated with dust mite populations in dwellings can be made. The combined model can also be used as a practical tool for examining how the dust mite microenvironments can most effectively be improved by changing the design and use of a dwelling. INTRODUCTION Allergens derived from house dust mite (HDM) faeces play a major role in allergic disease, especially in childhood asthma. The number of people affected is rising throughout the world, now impairing the quality of life of a substantial proportion of children (ISAAC 1998) and placing a significant and growing burden on health services. The role that HDM allergen plays in allergic disease has been extensively researched and reported (Platts-Mills and Chapman 1987; Lau et al. 1989; Mahmic 1998). The project described in this paper focuses on the process whereby HDM allergen comes to be in the home in the first place. In particular, it investigates the potential for controlling mite populations by environmental means, that is to say, by preventing the hygrothermal conditions they require to survive from occurring. The development of a combined HDM population model plus a hygrothermal microenvironment model allows the investigation of past and future environmental changes, such as higher internal temperatures or reduced ventilation, to be investigated.