Growth response of stachybotrys chartarum to moisture variation on common building materials
The mould Stachybotrys chartarum has been found to be associated with idiopathic pulmonary haemorrhage in infants and indoor exposure has also been linked to other pulmonary diseases, including allergies and asthma. S. chartarum has been studied both for toxin production and its occurrence in water-damaged buildings. Growth of S. chartarum on building materials such as gypsum wallboard has been frequently documented. Given that there may be a high frequency of occurrence and so the risk of exposure, environmental factors leading to the growth of S. chartarum have been studied. Samples of commonly used building materials were sterilised, inoculated with S. chartarum and exposed to controlled levels of relative humidity and wetting. A quantitative analysis of viable S. chartarum was performed on the building materials during a 7-month period. The results indicate that for environments with a relative humidity below total saturation, wetting was necessary for visible growth to occur. Conversely, high levels of relative humidity without wetting did not initiate growth. Porous materials, after becoming sufficiently wet and measuring saturation on a moisture meter, exhibited mould growth in every experiment conducted.