Mass occurrence of Penicillium corylophilum in crawl spaces, south Sweden

Buildings with crawl space foundations are looked upon as high-risk constructions with respect to mould growth, especially on the blind floor. This mould growth can be extensive and cover several square meters of the blind floor with potential health risks as a consequence. Mould occurrence and mould species diversity were investigated in a large small-house area in the south of Sweden, comprising 212 buildings. The crawl spaces were inspected and samples from the blind floor were taken. The relative humidity was measured and reached 80–100% for several consecutive months. Subsets of the samples were cultured and the fungi isolated were further analyzed by sequencing of the Internal Transcribed Spacer (ITS) region of nuclear ribosomal Deoxyribo Nucleic Acid (DNA). The results were compared with results from other, relevant studies and confirm that Penicillium corylophilum is the completely dominating mould species in crawl spaces. The occurrences could not be explained as accidental since the extensive occurrence in many dwellings had developed over several years.