No 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.

No abstract

Materials that are stored or used in damp conditions may be subject to mould growth. However, all materials are not equally susceptible; for each specific material, there is a critical moisture level for mould growth. If this is exceeded, there is a risk that mould fungi will develop on the material. This level can be determined in accelerated laboratory tests, at constant temperatures and relative humidity (RH) favourable to mould growth. Within a building however, these parameters are expected to vary from one part of the construction to another, and are seldom constant; there is fluctuation in temperature and RH due to seasonal or shorter-term variations. In this study, test pieces of the same materials tested in a laboratory environment were placed in three outdoor ventilated crawl spaces and three outdoor ventilated attics, where the temperature and RH varied, and mould growth on the test pieces was studied over 2.5 years. Material-specific mould growth curves were produced based on critical moisture levels, as determined in laboratory experiments under constant temperature and RH. When the actual conditions of RH and temperature exceeded these curves, there was mould growth on the test pieces if the time was sufficiently long. The conclusion from the study is that although conditions in laboratory studies are simplified and accelerated, the results serve well to indicate mould growth within a building construction.

We have investigated the levels of cat (Fel d I), dog (Can f I), and cockroach (Per a I) allergens in dust from bedrooms, living rooms, kitchens, and bathrooms from 123 homes of asthmatic children in three zones of Sweden with varying climates. Absolute indoor humidity (AIH), relative humidity (RH), rate of ventilation in air changes per hour (ach), and number of airborne particles were also measured. Fel d I, Can f I, and Per a I allergen contents were determined by mab ELISA, and the levels were related to various environmental factors. The major cat allergen. Fel d I, was detected in all homes, and the concentrations varied between 16 ng and 28000 ng/g fine dust. The dog allergen, Can f I, was detected in 85% of the homes, and the levels varied from 60 ng to 866000 ng/g dust. Cockroach allergen was detected in only one home (40 ng/g). Fel d I and Can f I allergens were equally distributed geographically. Dust from living rooms contained significantly higher (P < 0.05) concentrations of both Fel d I and Can f I allergens than dust from bedrooms, kitchens, and bathrooms. The levels tended to be higher in homes with poor ventilation (<0.5 ach) and in homes with wall‐to‐wall carpets. Significantly higher (P < 0.01) numbers of airborne particles were found in homes with high humidity (i.e., AIH ≥ 7 g/kg or RH ≥ 45%). We conclude that pet allergens are ubiquitous in different climatic regions, being found in bedrooms, living rooms, kitchens, and bathrooms. Current or previous presence of a cat or dog, high indoor humidity, presence of wall‐to‐wall carpets, and poor ventilation all increase the risk for high allergen exposure. In contrast, cockroach allergens arc rarely found in a temperate climate.