The health effects of mould exposure can cause a range of health effects in adults and children.
Allergic reactions may include runny nose, sneezing, red eyes, skin rash, and asthma attacks.
Respiratory issues can manifest as coughing, wheezing, shortness of breath, and increased risk of airway infections. Mould exposure may also impair brain function, leading to problems with concentration, judgment, and overall cognition. In some cases, mould-related memory loss is reversible once the mold is eliminated from the home. Certain moulds, such as Stachybotrys and Aspergillus, can produce toxic substances called mycotoxins, which may result in more serious illnesses. However, severe infections from moulds are relatively uncommon and tend to occur primarily in individuals with severely compromised immune systems.
The health effects of mould exposure for individual species are listed below.
Acremonium strictum
Acremonium strictum is found naturally in soil and in dead plant material and can therefore occur naturally indoors in small quantities. However, if a large number of spores are detected in household dust, this is evidence of indoor growth.
The mould can grow for example on concrete, plaster, damp wallpaper or woodwork.
Alternaria
A common allergen and has been associated with hypersensitivity pneumonitis. Alternaria is capable of producing toxic metabolites which may be associated with disease in humans or animals. Occasionally an agent of onychomycosis, ulcerated cutaneous infection and chronic sinusitis, principally in the immunocompromised patient.
Alternaria alternata
This fungus occurs worldwide and sustains itself primarily by decomposing dead organic matter. Spores from Alternaria alternata are spread in the air during the summer months and will therefore occur naturally indoors in limited quantities.
In rare cases, the fungus can grow in buildings and produce large quantities of spores. This can be very problematic for people who are allergic to fungus.
Aspergillus fumigatus
Aspergillus fumigatus like most other Aspergillus species, thrives in relatively high temperatures, which makes damp and heated homes ideal locations for growth. Aspergillus fumigatus is one of the few moulds that is potentially pathogenic for people with weakened immune systems, e.g. people who have had organ transplants and AIDS patients, since it can invade lung tissue (aspergillosis). The mould can also produce several different mycotoxins such as gliotoxin and fumagillin, which may cause discomfort and allergic reactions. It should be noted that Aspergillus fumigatus also occurs naturally in outdoor air and only rarely causes serious problems.
Aspergillus glaucus grp.
This is a collection of various Aspergillus species which primarily occur naturally in warm regions. In homes they can be found on food, in carpets and on plasterboard walls. Aspergillus glaucus requires lower moisture levels than other mould species. If large numbers of Aspergillus glaucus spores are present in a sample without there being any spores from more moisture-dependent moulds, this can be a sign of damage from damp without there being high moisture levels.
Aspergillus niger
Aspergillus niger is a frequently occurring fungus both outdoors and in homes. It forms large colonies, which are often found on vegetables and fruit, but can also grow in soil from potted plants and on building materials. It thrives in high temperatures and at lower moisture levels compared to some other moulds, and can therefore grow where there is only minor moisture damage. Aspergillus niger can be pathogenic for people with weakened immune systems and produce the mycotoxin aflatoxin.
Aspergillus versicolor
Aspergillus versicolor is one of the least demanding fungi in terms of growth conditions and is therefore widespread throughout the world, from Arctic regions to the Dead Sea. It is among the most common fungus found in damp buildings, where it needs only slightly elevated levels of moisture in order to grow. Spores from Aspergillus versicolor are found naturally in small amounts in dry buildings. Very high levels can occur in buildings that are damaged by damp. This species can produce sterigmatocystin and aflatoxin.
Ascospores
Health affects are poorly studied, but many are likely to be allergenic.
Basidiospores
Common allergens and are also associated with hypersensitivity pneumonitis.
Chaetomium sp.
This fast-growing fungus requires high levels of moisture and is often found on concrete and on materials that contain cellulose such as wallpaper and wood. Chaetomium globosum can produce mycotoxins such as chaetoglobosin A, which are suspected of causing discomfort to people who occupy moisture-damaged buildings.
Cladosporium cladosporioides
Spores from Cladosporium cladosporioides occur in huge numbers in outdoor air, especially during the summer months and early in the autumn. Spores from this mould occur naturally in household dust, which means that it can be used to assess the age of the dust. However, Cladosporium cladosporioides can also grow indoors and can thrive at lower temperatures and places with varying moisture levels (such as in a loft with a leaky roof) or in a location that has alternating wet and dry weather, which provides the ideal growth conditions.
Cladosporium herbarum
Cladosporium herbarum spores are the most common fungal spores in outdoor air and can cause allergic reactions during the summer and autumn months when it is most active. Cladosporium herbarum is found in wallpaper, woodwork and elsewhere in damp buildings. See also Cladosporium cladosporides.
Cladosporium sphaerospermum
Cladosporium sphaerospermum occurs naturally in outdoor air, but it can also grow in homes, including on wallpaper, plasterboard walls, painted surfaces and wood. It requires less moisture than most moulds. See also Cladosporium cladosporides.
Mucor/rhizopus grp.
Mucor/rhizopus grp. is a large group of mould containing several thousand species. Despite this, only a few spores will ever be found in the dust from a building that does not have damp problems. Mould in this group generally requires high levels of moisture to grow indoors, where they can be found on concrete, wood, carpets and elsewhere.
Myceila sterilia
This is a group of fungi having no known spore stage and producing sclerotia, rhizomorphs, or simply mycelial masses. As they produce no spores the risk to humans is considered minimal.
Myxomyces
Some allergenic properties reported, but generally pose no health concerns to humans.
Penicillium/Aspergillus/Pae grp.
This large group contains all the fungi belonging to the genus Penicillium, Aspergillus and Paecilomyces. Spores from these fungi occur naturally in outdoor air and they accumulate in the dust in buildings that do not have moisture damage. However, when there is damage from moisture they will be some of the first mould species to grow and can rapidly begin releasing large quantities of spores into the indoor air. Several species in this group can grow in relatively low moisture levels.
This group contains common allergens and many can cause hypersensitivity pneumonitis. They may cause extrinsic asthma, and many are opportunistic pathogens. Many species produce mycotoxins which may be associated with disease in humans and other animals. Toxin production is dependent on the species and on the food source for the fungus. Some of these toxins have been found to be carcinogenic.
Penicillium chrysogenum
Penicillium chrysogenum is well known because it produces the antibiotic penicillin, which is toxic to bacteria but not to people. This makes it ideal for treating certain bacterial infections. However, Penicillium chrysogenum can also produce mycotoxins such as citrinin and cause allergic reactions, so this species of mould can be very problematic when it grows in homes. This mould is found in small quantities in outdoor air and in large quantities in dust in homes and therefore is a strong indication that the indoor air is being adversely affected by damage from damp and associated mould growth.
Penicillium chrysogenum can grow at lower temperatures and lower moisture levels than most moulds.
Penicillium expansum
Penicillium expansum often grows on fruit, where it can produce mycotoxins that spoil the food. In buildings it frequently grows on woodwork. Because of its ability to produce several different mycotoxins such as citrinin, ochratoxin and chaetoglobosin, it is suspected of causing discomfort to people who occupy buildings where it grows. Penicillium expansum requires relatively high levels of moisture to thrive.
Rhizopus stolonifer
Rhizopus stolonifer is a fast-growing mould that often grows on bread and fruit and thrives at high moisture and temperature levels. If large quantities of spores from this species are found in a dust sample this can indicate that there is moisture damage to insulation or there is a burst hot water pipe.
Stachybotrys
Allergenic properties are poorly studied and no cases of infection have been reported in humans. They do however produce potent tricothecene mycotoxins. The toxins produced by this fungus can suppress the immune system affecting the lymphoid tissue and the bone marrow. The mycotoxin is also reported to be a liver and kidney carcinogen.
Stachybotrys chartarum
Stachybotrys chartarum can produce mycotoxins, e.g. roridin E, verrucarin A and satratoxins, and it is thought to be responsible for some of the discomfort experienced by people who occupy damp buildings. The species grows on plasterboard in particular and requires a sustained and high level of moisture over a prolonged period of time. It is typically found in connection with older - and extensive - damp damage Stachybotrys chartarums spores are heavy and, unlike most other fungal spores, they do not spread very efficiently in the air. If these spores are found in a dust sample, therefore, the sample was probably taken very close to the location where the mould is growing. The spores are only present in very low levels in outdoor air, so finding even a small number of these spores will strongly indicate that the indoor air quality is being affected by moisture damage.
Streptomyces spp.
Streptomyces spp. is not a mould but a group of bacteria that are primarily found in soil, where they release substances that give soil its earthy odour. Streptomyces spp. frequently occurs in connection with damp in floor structures and in concrete elements on the ground, but it can also find its way into dust via contamination caused by dogs or cats bringing dirt into the home. Streptomyces spp. is able to produce a large number of organic compounds, some of which can adversely affect indoor air quality and can cause discomfort.
Trichoderma viride
In natural environments this mould lives on dead trees and in the soil, where it can attack other fungus. It can grow in buildings on materials that contain wood where there is moisture damage and it prefers high temperatures. It can grow very rapidly where there is moisture damage and the presence of even a few spores in a dust sample is an indicator of moisture damage.
Ulocladium chartarum
Ulocladium chartarum grows relatively rarely in buildings, even when there is damage from damp. However, at high levels of humidity and over a long period of time, it can grow on wood, wallpaper and plasterboard. The outdoor level is very low, so even a few spores in the dust indicates a problem with moisture.
Wallemia sebi
Wallemia sebi is very difficult to identify using traditional methods but the HouseTest DNA method has shown that it is one of the most frequently occurring mould species in damp buildings. Small amounts of Wallemia sebi can be found even in dry buildings, but if there is indoor growth the number of spores can increase dramatically and cause discomfort to allergy sufferers. The spores are also very small and are thought to be able to penetrate deeply into the respiratory passages. Wallemia sebi can grow at relatively low levels of moisture.