House dust mite allergen levels in public places in New Zealand

Abstract

Background: House dust mite allergens are a risk factor for asthma in New Zealand, and levels in domestic dwellings have been found to be high compared with levels in most other countries. Studies in other countries have demonstrated lower levels of Dermatophagoides pteronyssinus allergens in public places compared with levels in domestic dwellings. Objectives: The purpose of this study was to measure reservoir Der p 1 levels in public places in New Zealand and to examine determinants of these levels. Methods: Reservoir dust was obtained in the two centers (Christchurch and Wellington) from hotels, hospitals, rest homes, churches, primary schools, childcare centers, cinemas, bank head offices, and airplanes; samples were also obtained from ski lodges. Single measurements of temperature and relative humidity were taken with thermohygrometers and an average humidity over 2 weeks was estimated with use of waxed wooden sticks. Information was collected on building construction, type of heating, and frequency of cleaning. Der p 1 levels (micrograms per gram of fine dust) for floor ( n = 202), bed ( n = 65), and seat ( n = 24) samples in public places were expressed as geometric means (95% confidence intervals). Results: Der p 1 levels in public places were significantly lower than domestic levels in both Wellington and Christchurch. Both floor and bed levels were higher in hotels than in other public places. After controlling for potential confounders, floor Der p 1 levels were higher with carpeted floors ( p < 0.0001) and lower with recent cleaning ( p = 0.02) and bed Der p 1 levels were higher with timber wall construction ( p = 0.03). Other building, heating, or cleaning characteristics did not show significant associations with allergen levels. Conclusion: Der p 1 levels were much lower in public places than in domestic dwellings with floor levels primarily affected by floor covering. (J Allergy Clin Immunol 1997;99:587-93.)