How dangerous is Penicillium mold? -Jodi, Texas 

            The genus Penicillium includes a number of species of what are described as imperfect fungi or Deuteromycetes.  They are characterized by their distinctive asexual reproductive structures and spores.  When the sexual stage is found, they may be classified in different genera which may not be as closely related as their asexual spores (which are the dominant features) would indicate. 

            As such, the genus Penicillium is a relatively heterogeneous grouping of fungal organisms.  Members of the genus Penicillium are found in both indoor and outdoor environments.  It is the blue-green mold(on the right in the photo below) that you may find growing on decaying citrus fruits and the mold from which the antibiotic penicillin is produced. 

            When conducting airborne mold sampling, Penicillium is one of the common mold types observed.  Concentrations are typically higher indoors than they are outdoors.  It is not uncommon to find Penicillium growing on paper and wood surfaces in high-humidity basements and living spaces.  It grows well on wetted ceiling tiles. 

            Penicillium species are prolific producers of asexual spores. A colony about 6 inches across has the potential for producing millions of spores that can become airborne.  Penicillium spores are relatively small so that they remain airborne longer than other mold spores.  Because of the larger number of spores produced by an infested surface and their relatively small size, the potential for human exposure is relatively high. 

            Exposure to elevated levels of Penicillium spores carries a risk of developing chronic allergic rhinitis, asthma, fungal sinusitis, and hypersensitivity pneumonitis.  Allergy and asthma can only occur in individuals who can be genetically sensitized to Penicillium on exposure.  Fungal sinusitis is an infection.  Hypersensitivity pneumonitis is an inflammation of lung tissue with characteristic flu-like symptoms (fever, ache-all-over, cough).  Hypersensitivity pneumonitis requires exposures to very high spore concentrations.  It is likely the small size of Penicillium spores that is responsible for its causal relationship with hypersensitivity pneumonitis. 

            A variety of Penicillium species are reported to produce mycotoxins.  There is no evidence that inhalation exposures pose any unique health risks.  

            Several Penicillium species are pathogenic, that is, they pose significant health risks to immune-compromised individuals, such as those with AIDS or on chemotherapy.