Effectiveness of vacuum cleaning and wet cleaning in reducing house-dust mites, fungi and mite allergen in a cotton carpet: a case study.

In order to evaluate the effect of continuous, thorough vacuuming on house dust organisms and mite allergen, a cotton carpet was vacuumed every other day, six times in total. Seven weeks later, the carpet was cleaned by means of spray extraction. Samples were taken before and after this wet cleaning. In total 1150 g of dust was collected, containing approximately 174,000 arthropods (dead and alive) and 9000 X 10(6) fungal spores. In the course of the experiment, the amount of dust collected at each vacuuming decreased. The number of extracted house dust mites did not decrease significantly, but that of the predator mite Cheyletus did. The number of extracted fungal spores showed a significant decrease (from 142 to 16 X 10(6) spores/m2 per minute vacuuming), as did the extracted mite allergen per m2. After 7 weeks the number of mite eggs and complete house dust mites had increased enormously. After cleaning by spray extraction another increase in the number of complete mites and mite eggs was found, while the amount of mite allergen was diminished. The population growth of the house dust mite between the 6th and the 7th vacuuming is probably due to the decrease of their most important predator, Cheyletus. After the wet cleaning a number of extra eggs hatched, probably due to the high humidity in the carpet. The procedures used in this study to combat house dust mites may have an adverse effect in the long run.