Mite allergens in relation to home conditions and sensitization of asthmatic children from three climatic regions

Abstract

We investigated the levels of mite (Der p I and Der f I) allergen in dust from bedrooms, living rooms, kitchens, and bathrooms from 130 homes of asthmatic children in three climatic zones of Sweden. Bedroom dust samples included the child's mattress, carpets, floors, and other plain surfaces. Living-room dust samples were taken from sofas and other furniture, carpets, floors, and other plain surfaces. The allergen levels were related to home characteristics, including absolute indoor humidity (AIH), relative humidity (RH), and air changes per hour (ach). Mite allergen was detected in 62% of the homes. Levels of Der p I varied between < 16 ng and 50 micrograms/g dust, and Der f I between < 16 ng and 73 micrograms/g dust. Because we have designed a composite type of dust collection in our study, the allergen levels found tend to average down the results. Mite allergen levels were higher in homes with dampness problems, in homes with a smoker, and in homes without a basement. Homes with high absolute humidity (> or = 7 g/kg) or relative humidity (> or = 45%) and poor ventilation (< 0.5 ach) contained higher levels of mite allergens than homes with lower humidity and better ventilation. However, the number of ach measurements in homes was not high, and few homes had > 0.5 ach. Sensitization to house-dust mites was more common in southern than in northern and central Sweden. High levels of house-dust mite allergen in a temperate climate where mites are not ubiquitous are thus associated with dampness problems in homes and with tobacco smoking. Our data confirm and extend previous findings that high AIH and RH and poor ventilation increase the risk of mite infestation in homes. It seems to be important and necessary to control indoor humidity and ventilation levels, to avoid high mite allergen exposure in a temperate climate, because 34% of mite-sensitized asthmatic children were exposed to levels of mite allergen < 2 micrograms/g dust in their homes. The study also shows that mite allergen levels below the suggested threshold level (2 micrograms/g dust) are associated with mite sensitivity in children with perennial symptoms of asthma.

Domestic aeroallergen exposures among infants in an English town

“…The reason for this is unclear but may reflect systematic differences in domestic ventilation. Conversely, MUNIR et al [18], in a survey of 126 homes, reported higher levels of Der p 1 in the homes of smokers. The present results showed a trend towards increasing Der p 1 concentrations in the living room carpets and mattresses of homes with more inhabitants and, as a corollary, in the mattresses of children with more older siblings.…”

Climate, traffic-related air pollutants, and asthma prevalence in middle-school children in taiwan.

“…This is especially true during the colder seasons. Although in areas with lower humidity indoor dampness is probably more important than outdoor humidity in the domestic development of mites (20), the high outdoor humidity in Taiwan (monthly average 68-80%; Figure 2C) could have been an important determinant of the indoor humidity. The results of this survey suggest that exposure to dust mites or other humidity sensitive allergens was elevated in the children from warm and humid areas in Taiwan.…”

Update of the scientific evidence for specifying lower limit relative humidity levels for comfort, health, and indoor environmental quality in occupied spaces (RP-1630)

“…House dust mite literature consisted of laboratory tests (Arlian, 1992;Arlian et al, 1998), and environmental sampling of dust mite allergens (Munir et al, 1995;Sundell et al, 1995;Arlian et al, 2001;Howieson et al, 2003), with test conditions shown in Figure 2. Arlian (1992) With a brief (2 or 4 hour) exposure to 75% RH, dust mites were unable to complete the entire life cycle, but they laid eggs and many adult females survived.…”