PORTABLE DEHUMIDIFIERS IN THE CONTROL OF HOUSE-DUST MITES AND MITE ALLERGENS

Humidity is a decisive limiting factor for house dust mite (HDM) popul ation growth and decreasing humidity may be the control method of choi ce. This study investigates the effects of portable dehumidifiers on t he mite counts and concentration of the HDM allergen Der p I in the ho mes in northwest England. Mite counts and Derp I were measured in the paired dust samples collected by vacuuming a 1 m(2) area of bedroom ca rpet, living room carpet, mattress and sofa for 2 min in six houses su pplied with the dehumidifier and six control houses, before and 1, 2 a nd 3 months after the instalment of dehumidifier. Temperature and rela tive humidity were recorded daily. There was no difference in mite cou nts in either of the groups throughout the study. Derp I decreased sig nificantly in both groups and in all sampling sites, but no significan t differences in the levels of reduction between the groups were found . Condensation was decreased in the dehumidifier group, but the level of indoor humidity capable of retarding mite population growth was not achieved. A single portable dehumidifier placed centrally in the hous e is unable to decrease indoor humidity to the level capable of retard ing mite population growth and decreasing HDM allergens in the type of houses predominantly found in the northwest of England.