Mycotoxins are produced by a few strains of moulds at some point during their growth under suboptimal growth conditions or limited nutrients. Production occurs preferentially on materials that both allow toxigenic moulds to grow and provide the conditions for mycotoxin production. From the many studies of the production of mycotoxins by mould isolates derived from agricultural environments, a great deal is known about the mould species that are capable of producing known mycotoxins and about the growth media and conditions that induce production. Conditions that favour production of one type of mycotoxins may not be favourable for production of another type. For example, aflatoxin production by Aspergillus is dependent on concentrations of O2, CO2, zinc, and copper, as well as physical location, while production of ochratoxin relates to air exhaustion. Understanding the conditions under which mycotoxins are produced is important since presence of toxigenic moulds in any environment does not prove the presence of a mycotoxin.
Frequently, toxigenic moulds have been isolated from building materials and air samples in buildings where residents have suffered from non-specific symptoms possibly related to mycotoxin production, such as cough; irritation of eyes, skin, and respiratory tract; joint ache; headache; and fatigue. It is only recently that the presence of some mycotoxins has been confirmed in crude building materials. Most mycotoxins have yet to be extracted from either air samples or bulk material derived from indoor environments. Also, very few studies have been conducted to show correlation between mycotoxin exposure and building-related illnesses.
