Mould Contamination of Indoor Air

Until recently there has been little special concern about fungi in the indoor air of buildings and dwellings (Gravesen, 2000; Trout et al., 2001). Recent interest has been due to dysfunctions such as mouldy smells, dampness and visible mould growth on internal surfaces of houses in the UK (Hunter & Bravery, 1989; Flannigan & Morey, 1996), European dwellings (Kilpeläinen et al., 2001) and schools (Rudblad et al., 2002), and Australian houses (Garret et al., 1998a, b). Epidemiological studies and reviews of the literature have found an emerging relationship between “home-dampness” and respiratory symptoms (Verhoeff et al., 1994a; Bornehag et al., 2001; Kilpeläinen et al., 2001; Rudblad et al., 2002) and particularly in children (Garret et al., 1998a; Kilpeläinen et al., 2001). However, little is known about the underlying mechanisms for these associations (Garret et al., 1998a; Bornehag et al., 2001; Kilpeläinen et al., 2001).

In the UK, the Building Research Establishment (BRE) in a study of 16.8 million houses estimated that 18% of houses (2.8 million) had mould growth or damage to decorations and furnishings caused by dampness (Hunter & Lea, 1994). Humid air-conditioned buildings with design, operation and maintenance problems (in central and south Florida) are also often contaminated with fungal growth (Morey, 1994).

Fungal problems associated with occupant complaints are also well known and documented (Yang, 1994) and are often cited as contributing to sick building syndrome (SBS) complaints (Stetzenbach, 1997; Szponar & Larsson, 2000). However, little is known about the health risks of fungi in indoor air in normally functioning, "non-complaint" or "non-problem" buildings without water damage (Yang, 1994; Levetin, 1995; Schillinger et al., 1999). From the few studies performed so far, fungal species in non-problem buildings are in low concentrations (Godish, 1995) but different to those in problem buildings (Roponen et al., 2001). However, this should not be construed to mean that fungal air quality issues do not exist (Godish, 1995). An example are the Schools studied by Rudblad et al., (2002) that required renovation due to water damage and fungal contamination, but the levels of fungi indoors were the same as found in similar schools in normal operating condition and without any reported damage.

Outdoor Air as a Source of Indoor Fungi

Much of our knowledge on airborne fungi indoors has resulted from case studies performed following occupant complaints or from attempts to diagnose illnesses believed to be caused by environmental exposures to fungi (Levetin, 1995). These studies have demonstrated that fungi with allergenic and pathogenic potential exist in the indoor air, which suggests that these fungi were able to survive, grow, and sometimes proliferate in indoor environments and even in normally functioning and well maintained interiors (Jaakkola & Miettinen, 1995; Morey & Ansari, 1996).

In some cases there is strong evidence that the source of all fungi is outdoors (Lowenstein et al., 1979) particularly in relatively clean interiors (Solomon & Burge, 1984). The influx of bioaerosols such as pollens from the outdoors is especially evident in naturally ventilated buildings and illustrates the potential for entrainment of other bio-aerosols including algae, insects, and fungi (Solomon & Burge, 1984).