House dust-mite allergen and cat allergen variability within carpeted living room floors in domestic dwellings

Exposure to allergens from house dust-mites (Der p 1) and domestic cats (Fel d 1) is associated with symptom severity in atopic subjects with asthma and rhinitis. Assessment of allergen exposure in the domestic environment is normally determined by measurement from a single floor site. We determined the variability of these allergens and protein throughout the whole living room floor area. Dust samples were collected from 1 m2 areas from 16 carpeted living room floors in Wellington, New Zealand, and analyzed for concentrations of Der p 1 and Fel d 1. Mean coefficients of variation for Der p 1 and Fel d 1 were 53.1% (range: 28.5-136.8) and 65.6% (range: 28.5-131), respectively. This study has demonstrated a large variation of house dust-mite and cat allergens within living room floors and thus a single sampling site may not be representative for assessment of an individual's exposure risk. House dust-mite and cat allergen levels from the center of the room, in front of a couch or chair, or from a corner of the room are similar to mean levels from the whole room, these sites may thus be representative of the whole living room floor in large-scale epidemiological studies.