Chaetomium is a cellulolytic mould commonly found in soil, air, and decaying plant material. There are about 80 species of Chaetomium. The most common ones are Chaetomium atrobrunneum, C. funicola, C. globosum, and C. murorum.
In indoor environments the most common species of Chaetomium is Chaetomium globosum. C. globosum is frequently isolated in water-damaged buildings and produces two mycotoxins called chaetoglobosins A and C when cultured on building material. Presence of Chaetomium species in indoor environment is a sign of serious water problem.
Chaetomium may occur together with other water-loving moulds such as Fusarium, Stachybotrys and Ulocladium. Species of Chaetomium are known to produce mycotoxins but to what extent these toxins contribute to poor indoor air quality or affect human health is not documented. However, injection of chaetoglobosin A in rodents has been shown to be fatal at relatively low doses. In medical literature some species have been reported to cause disease in immuno-compromised individuals.
Species that have been reported to cause invasive human disease grow well at 35 to 37oC, and those with a predilection for the central nervous system often display growth at up to 42 to 45oC.
Spores of Chaetomium are produced within structures (asci) contained in a flask-shaped fruiting body known as perithecium. Once the spores are mature, the walls of the asci dissolve releasing mucilaginous spores within the perithecium. The spores ooze out of the perithecium (plural perithecia) and get trapped by coiled or dichotomously branched hairs that grow around the neck of the perithecium.
Since the spores of this commonly found mould are cemented together by mucilage and also trapped by hairs, few become airborne until the mould has completely dried out or disturbed, say during renovations or mould remediation. It is therefore not uncommon to find low Chaetomium spore counts in pre-remediation samples and relatively higher counts in post-remediation samples