MITE ANTIGEN IN-HOUSE DUST - RELATIONSHIP WITH DIFFERENT HOUSING CHARACTERISTICS IN THE NETHERLANDS

As part of a case-controlled study on the relationship between home da mpness and respiratory symptoms of children, the concentration of the major allergen of Dermatophagoides pteronyssinus (Der p I) in floor du st and mattress dust in 516 dwellings in the Netherlands was measured. A checklist, completed by the investigators, was used to obtain infor mation on home and occupant characteristics, which may have an impact on the Der p I concentration in house dust. The geometric mean mite an tigen concentrations were 2370 ng Derp I/g floor dust for the living r oom, 2201 ng Der p I/g floor dust for the bedroom and 5075 ng Der p I/ g mattress dust. In 86% of the houses the maximum concentration was hi gher than 2000 ng Der p I/g dust, that is regarded as representing a r isk for genetically predisposed individuals for the development of spe cific IgE to house dust mite allergen. In 55% of the houses the maximu m concentration exceeded 10 000 ng Der p I/g dust, regarded as a risk factor for acute attacks of asthma for mite allergic patients. The Der p I concentrations in dust from carpeted floors were six to 14 times h igher than in dust from floors with a smooth floor covering. Higher De r p I concentrations in floor dust were also significantly associated with increasing age of the dwelling and of the floor covering, with an increasing number of occupants, and with the absence of floor insulat ion. For mattress dust, the age of the mattress, the presence of an ou ter cavity wall and mechanical ventilation were important factors. Old er mattresses had higher levels, and mattress dust from bedrooms with solid brick outer walls had higher levels than that from bedrooms with outer cavity walls. Mattresses in homes with continuous mechanical Ve ntilation had almost twice lower levels than mattresses in homes with natural ventilation. There was a tendency towards higher Der p I conce ntrations in dust in homes with reported or observed signs of dampness . The Del p I concentrations in dust from carpeted bedroom floors and mattresses were positively associated with the average relative humidi ty in the bedroom over a period of 3-6 weeks in a subset of the homes where relative humidity was measured. Similar results were obtained us ing the concentrations of Der p I in ng/m(2) instead of ng/g dust. The results obtained in this study are of importance for planning and eva luating allergen avoidance measures advised to mite allergic patients.