Indoor factors associated with concentrations of house dust mite allergen, Der p 1, in a random sample of houses in Norwich, UK

BACKGROUND: Studies of house dust mite allergen concentrations suggest large variations both within and between homes. It is likely that different household characteristics influence allergen levels in different locations within the house. OBJECTIVES: To investigate household characteristics associated with higher concentrations of house dust mite allergen in a random sample of houses. METHODS: Information on indoor environment was obtained from 158 adults aged 20-44. Dust samples were collected from their living room floor, bedroom floor and mattress. Concentrations of Der p 1, the major allergen from the house dust mite Dermatophagoides pteronyssinus, were measured by monoclonal antibody immunoassay. Associations between mite allergen concentrations and household characteristics were examined using censored-normal regression models. Factors that were related to Der p 1 (P </= 0.2) in univariate analyses were included in multivariable regression models. RESULTS: Der p 1 was not detected in any location in 10 (6.3%) houses. Geometric mean concentrations of Der p 1 were 1.9 microg/g in living room floor dust, 1.7 microg/g in bedroom floor dust and 2.0 microg/g in mattress dust. Approximately 25% of living room floor and mattress, and over 30% of bedroom floor samples had Der p 1 concentrations greater than 10 microg/g. Household characteristics associated with Der p 1 concentrations in both living room and bedroom were floor level, extractor fan in the kitchen, and age of carpet. Living room Der p 1 concentrations were also associated with gas oven/hob, window condensation, open fires, vacuum cleaner type, smokers in the house and age of house. Bedroom Der p 1 concentrations were also associated with use of blankets and wash temperature of bedding. Mattress Der p 1 concentrations were associated with window condensation, concrete bedroom floor and age of mattress. CONCLUSION: Different household characteristics were associated with high Der p 1 concentrations in different parts of the house. These findings are relevant to design of allergen avoidance regimes or formulation of policy recommendations for reduction of disease associated with allergen exposure.