House-dust-mite allergen concentrations (Der f 1) and mold spores in apartment bedrooms before and after installation of insulated windows and central heating systems

Background: It has been hypothesized that changes in heating systems and in sulation of homes in developed countries have generated an indoor climate f avorable to organisms that excrete allergens inducing sensitization and all ergic disease. The purpose of this study was to determine the influence of the installation of highly insulated windows and central heating systems on indoor climate, and mite-allergen (Der f 1) and mold spore concentrations. Methods: The bedrooms of 98 apartments were examined before and 7 months (m ean) after installation of insulated windows and central heating systems. T he air-exchange rate, temperature, and humidity were measured. In settled d ust on carpets and mattresses, the number of colony-forming mold spores and the Der f 1 concentration were determined. The inhabitants completed a que stionnaire about their lifestyles and housing conditions. Results: The air-exchange rate decreased from geometric mean 0.73 to 0.52 p er hour (P = 0.029). Temperature (mean 13.4 vs 17.5 degrees C, P < 0.001), and absolute humidity (mean 4.6 g vs 6.2 g H2O/kg air, P < 0.001) increased . Relative humidity remained nearly unchanged (mean 47.6 vs 49.1%). Der f 1 concentrations on carpets (geometric mean 0.65 vs 1.28 mu g/g dust, P < 0. 001) and mattresses (geometric mean 1.56 vs 2.40 mu g/g, P = 0.002) increas ed. Among the fungi that were analyzed, only the thermotolerant species Asp ergillus fumigatus increased (geometric mean 20 vs 60 colony-forming units/ g carpet dust, P = 0.02). Conclusions: The findings of this study suggest that the installation of in sulated windows and central heating systems is associated with an increase of Der f 1 concentrations in carpet and mattress dust and of A. fumigatus i n carpet dust in apartment bedrooms.