Many are carcinogens, and others can impare the immune system. There has been a great deal of interest in the past few years on mycotoxins in indoor air. Occurs indoors in wet environments on a variety of substrates. Considered allergenic but not well studied. It is a common saprophyte, leaf surface organism, and plant pathogens.
Alternaria spores are highly allergenic.
This is seldom found at high levels indoors. Usually from outdoor sources with the exception being Chaetomium which readily occurs on indoor substrates. Suspect allergens but not well studied. In nature this typically occurs in the soil. Various species of Aspergillus have been implicated in aspergillosis, a serious and persistent lung infection.