Prevalence and residential determinants of fungi within homes in Melbourne, Australia

Background Recent epidemiological studies suggest that the adverse respirat ory health effects caused by the inhalation of fungal propagules are substa ntial. Knowledge of the prevalence and environmental determinants of indoor fungal levels is essential in designing effective avoidance measures. Aim To investigate the prevalence of fungi and the influence of residential characteristics on levels of fungi within homes in Melbourne, Australia. Methods Floor dust and air samples were collected from bedrooms in 485 hous es over 1 year. The dust was analysed for ergosterol, a marker of cumulativ e fungal biomass exposure. Total and genera-specific fungal propagules were identified in air samples. Details of the relevant residential characteris tics were documented using a questionnaire. Independent predictors (P < 0.0 5) of ergosterol and total fungal propagules were identified by multiple li near regression. Results Fifty-five percent of the houses had viable fungal propagules excee ding 500 CFU/m(3). Cladosporium and Penicillium were identified as the most prevalent and abundant fungal genera in indoor air. The median ergosterol level in bedroom floor was 3.8 mu g/g of dust. Multivariate analysis showed that total fungal propagules in indoor air were lower in bedrooms with a c eiling fan, without visible mould, and those that were more frequently vacu umed, had a solid fuel fire, had windows closed at the time of the sampling or lacked pets. The presence of more than one cat had the greatest effect on total fungal propagules. Ergosterol levels were significantly lower in h omes without old fitted carpets, visible mould or pets and those with frequ ent airing and regular use of an extractor fan in the kitchen. Old wall-to- wall carpets had the greatest effect on ergosterol. Conclusions High indoor fungal exposures were associated with infrequent ve ntilation or vacuuming, presence of pets, visible mould and old carpets.