Aspergillus - Toxic Black Mould

aspergillus toxic black mould

Aspergillus is a well know group of soil fungi consisting of hundred mold species found in various climates worldwide.  It is a cosmopolitan species occurring almost everywhere. It produces large number of small spores which become readily airborne. Aspergillus is a type of mould called Ascomycota or sac fungi. Sac fungi have sexual spores that are produced in an ascus or saclike structure. Their asexual spores, are produced in long chains. 

Aspergillus mould are frequently isolated form carpet and mattress dust,  tarred wooden flooring, polyurethane foam,  particle board frames of filters, humidifiers and HVAC fans, bakeries, shoes, leather, cotton yarn, hay, cereals, flour, bread. It can grow on  building materials such as  damp walls, wallpaper, and glues or plastic cements. Aspergillus is often seen in dust infiltrating from outdoor air, particularly when cleaning standards are low.

Aspergillus spores are carried in the wind and through ventilation airstreams in homes. The asexual spores freely detach from the mould surface and, with the slightest disturbance float in the air like dust. When conditions within buildings cause the build up of moisture on surfaces and temperatures are right, Aspergillus grows well and is evidenced by a black deposit. When the spores land on a  wet surfaces, the spores grow hyphae. The hyphae grow, form a mass, and are soon visible to the naked eye. At this time the mould appears as a black fuzzy mass.

Members of the Aspergillus genus are known as biodeteriogens (organisms that cause deterioration of materials). Aspergillus  niger causes damage, discoloration, and softening of the surfaces of woods, even in the presence of wood preservatives. Aspergillus  niger also causes damage to cellulose materials, hides, and cotton fibres.  Aspergillus niger can also attack plastics and polymers (i.e., cellulose nitrate, polyvinyl acetate, polyester type polyurethanes). In cases of extensive growth, colonies will grow into wood, plaster, and/or drywall, causing a soft bulging area. This area lacks structural integrity and is subject to early deterioration.

Aspergillusis black or brown-black. The black colour of the mould surface is due to accumulation of debris and dust and production of black stain or tarlike liquid residue.

Aspergilus and Health

aspergillus spores

Breathing aspergillus spores  does not normally cause illness. However an individual with a weakened immune status may be susceptible to aspergillus infection. When individuals get exposed to large number of aspergillus mould spores it can cause asthma like symptoms or other lung irritation.  

The incubation period varies with different individuals. People with other weakening medical problems or general ill health are most susceptible. Aspergillus niger produces mycotoxins that can induce asthma-like symptoms. In situations when Aspergillus niger was found growing massive inhalation of spores has been documented as causing an acute, diffuse, self-limiting pneumonitis (lung irritation). Healthy individuals can exhibit otitis externa (inflammation of the outer ear canal) as a result of Aspergillus growth.

The most common pathogenic species are A. fumigatus and Aspergillus. flavus, which produces aflatoxin which is both a toxin and a carcinogen, and which can contaminate foods such as nuts. The most common species causing allergic disease are A. fumigatus and Aspergillus clavatus. Other species are important as agricultural pathogens. Aspergillus spp. cause disease on many grain crops. A common name of aspergillus caused disiease is Aspergillosis, which major form in humans are 

The great majority of Aspergillus infections are attributable to four species: Aspergillus fumigatus, Aspergillus  flavus, Aspergillus terreus and Aspergillus nidulans.