Most water damage indoors is due to natural disaster (e.g., flooding) or human error (e.g., disrepair). Water can seep into a building as a result of melting snow, heavy rain, or sewer system overflow. Water vapor can be produced by human activities like cooking, laundering, or showering and then condense on cold surfaces like outer walls, windows, or furniture. Damp or water-damaged building materials are at high risk of fungal growth (mold growth), possibly resulting in health problems for the occupants and the deterioration of the buildings. The water activity (aw) (aw × 100 = % relative humidity at equilibrium) of a building material is the determining factor for fungal growth and varies with the temperature and the type of material (27). The longer a material’s aw is over 0.75, the greater the risk of fungal growth (49), though different fungi have different aw preferences (11). Some filamentous fungi can grow on a material when the aw is as low as 0.78 (26), while others can survive 3 weeks at an aw of 0.45 (30). The severity of indoor dampness varies with the climate, but WHO (52) estimates that in Australia, Europe, India, Japan, and North America, dampness is a problem in 10 to 50% of the buildings, and Sivasubramani et al. (41) estimate that fungal growth is a problem in 15 to 40% of North American and Northern European homes.
The negative health effects of damp building materials and fungal growth in homes, institutions, and workplaces have been reported in many publications, including the WHO guidelines Dampness and Mould (52), which concluded that there is sufficient epidemiological evidence to show that occupants of damp or moldy buildings are at increased risk of respiratory problems, respiratory infections, and the exacerbation of asthma. The causality between fungal exposure and development of type I allergy has been proven (18), but clinical evidence linking specific fungal spores, hyphal fragments, and/or metabolites to particular health complaints is lacking. The symptoms reported by occupants in moldy buildings are many and diverse (20, 23), as are the fungal species found on moldy building materials (14, 19). The fact that some people are hypersensitive to fungi while others do not react at all further complicates the issue.
Detection and species identification of all fungi present in a moldy building are the first step toward resolving the cause and effect of building-related illness (sick building syndrome), so the choice of sampling methods is essential. Air and dust samples have been taken in order to associate fungal exposure and health problems (e.g., 10, 17, 48), but no conclusive links have been found. This may be because spore liberation from a surface is sporadic (41) and spore distribution in the air is random (21). Toxic fungi (e.g., Stachybotrys spp. and Chaetomium spp.) growing on damp building materials do not readily become airborne and/or lose their culturability soon after liberation (21, 29, 45, 47) and may therefore not be detected during air or dust sampling. Correct species identification of the fungi is also important, since new research has indicated that species-specific metabolites, like atranone C produced by Stachybotrys chlorohalonata (37), are cytotoxic or immunotoxic or induce inflammatory responses when inhaled (24, 33, 34). The purpose of this study was therefore to estimate the qualitative and quantitative diversity of fungi growing on damp or water-damaged building materials. The study was based on more than 5,300 surface samples taken by means of V8 contact plates from building materials with visible fungal growth in Denmark and Greenland. The aim was to determine if there exists an association between the most common fungi found and particular types of water-damaged building materials.
Samples from building materials with visible fungal growth were taken by means of 65-mm contact plates (VWR International) containing V8 agar with antibiotics (200 ml Campbell’s original V8 100% vegetable juice, 3 g CaCO3 [Merck], 20 g agar [VWR International]) and 800 ml water. Penicillin (100,000 IU/liter [Sigma]) and streptomycin (1 g/liter [Sigma]) were added after autoclaving (12). The plates were subjected to fungal analysis at the Mycological Laboratory (ML) at the Danish Technological Institute (DTI). Samples were collected from June 2005 to February 2008 and originated from private residences (houses, apartments, and holiday cottages) and private businesses (shops and offices) as well as from public buildings (kindergartens, schools, and offices) from all parts of Denmark and Greenland. Samples were taken from buildings where either professional building inspectors had reported visible fungal growth or water damage or occupants had contacted DTI with self-reported fungal or health problems. Several samples may have been taken from the same building, but only one sample was taken from each damage site. Approximately 75% of all Charlotte fire water damage company samples were taken on site by the building inspectors by means of contact plates and mailed overnight to ML. The remaining 25% were moldy building materials sent to ML by the occupant after thorough instruction. The materials were then sampled by ML by means of contact plates.
Identification of fungi in a sample was done directly on the V8 contact plates after 7 days of incubation at 26°C in darkness. Whenever possible, fungi were identified to species using direct microscopy and identified according to the methods of Domsch et al. (7), de Hoog et al. (6), and Samson et al. (36). Fungi present in the sample were determined qualitatively (taxon present) and quantitatively (number of colonies).Since different Penicillium species can be difficult to identify on V8 medium, special attention was given to this genus in the spring of 2010. DTI randomly selected 80 V8 contact plates with Penicillium growth and delivered them to the Center for Microbial Biotechnology (CMB) at the Technical University of Denmark (DTU). At CMB, all different Penicillium colonies on each plate were isolated, resulting in 120 Penicillium cultures. After transfer to Czapek yeast extract agar (CYA) for purity control, the isolates were inoculated onto CYA, malt extract agar (MEA), yeast extract sucrose agar (YES), and creatine sucrose agar (CREA) and identified to species level after 7 days at 25°C in the dark by methods reported by Samson et al. (37).