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Mold and Indoor Air Quality Resources

Common Types of Mold

There are thousands of mold types, but only a few dozen are commonly found indoor and even less are potentially harmful

Below is a list of the most common types of mold found in the United States. This is not a complete list of mold species, nor all of the types that are present in the US. They are the most dominant types found in nature and in contaminated properties.



Alternaria

Alternaria belongs to a Division of the fungi called the Deuteromycota. The word means "neuter fungi" and they are called this because they have no sexual spore stage (meiospores). It grows rapidly and the colony size reaches a diameter of 3 to 9 cm following incubation at 25°C for 7 days on potato glucose agar*. The colony is flat, downy to woolly and is covered by grayish, short, aerial hyphae in time. The surface is grayish white at the beginning which later darkens and becomes greenish black or olive brown with a light border. The reverse side is typically brown to black due to pigment production.

Natural Habitat
  • Soil
  • Plants and Wood
  • Food
Methods of Spore Dispersion
  • Wind/air
  • Direct contact
Potential Allergenic
  • Yes
Potential Health Effects
  • Asthma/hay fever/allergies
  • Hypersensitivity pneumonitis
  • Common pathogen for those in an immunocompromised/immunosuppressed state
  • Phaeohyphomycosis
  • Onychomycosis
  • Sinusitis
  • Visceral infections
Potential Mycotoxins Produced
  • Alternariol (AOH)
  • Alternariol monomethylether (AME)
  • Tenauazonic acid (TeA)
  • Altenuene (ALT)
  • Altertoxins (ATX)
Identifiable Through Testing
  • Yes; air and surface sampling



Arthrinium

Arthrinium is a mold that lacks a known sexual state. It grows rapidly, reaching a colony size of 3 to 9 cm in diameter following incubation at 25°C for 7 days on potato glucose agar*. The colonies are woolly to cottony and white with brown spots on the surface.

Natural Habitat
  • Soil
  • Plants
Methods of Spore Dispersion
  • Wind/air
  • Direct contact
Potential Allergenic
  • Yes
Potential Health Effects
  • Asthma/hay fever/allergies
  • Others unknown
Potential Mycotoxins Produced
  • Terpestacin
  • 3-nitropropionic acid (NPA)
Identifiable Through Testing
  • Yes; air and surface sampling



Ascospore

Ascospores are produced in a sac-like structure called an ascus. Ascus is spore-bearing cell of the fungi classification Ascomycota, which covers a huge number of fungi genera around the world.

Natural Habitat
  • Everywhere in nature
Methods of Spore Dispersion
  • Wind/air
  • Insects
  • Direct contact
Potential Allergenic
  • Varies; depends on specific species
Potential Health Effects
  • Asthma/hay fever/allergies
  • Others unknown
Potential Mycotoxins Produced
  • Varies; depends on specific species
Identifiable Through Testing
  • Yes; air and surface sampling



Aspergillus

Aspergillus fumigatus is the most common species of Aspergillus. Aspergillus fumigatus colonies grow rapidly. On potato dextrose agar* at 25°C are smoky gray-green with a slight yellow reverse. Some isolates may display a lavender diffusible pigment. Very mature colonies turn slate gray. Texture is woolly to cottony to somewhat granular. Atypical isolates may remain white with little conidiation. It likes high temperatures and its optimum temperature for growth is about 37°C (blood temperature). It is not surprising, therefore, that it is also known as a parasite of humans, other mammals and birds.

Natural Habitat
  • Soil
  • Plants
Methods of Spore Dispersion
  • Wind/air
  • Direct contact
Potential Allergenic
  • Yes
Potential Health Effects
  • Asthma/hay fever/allergies/flu and cold-like symptoms
  • Excessive fatigue and lethargy
  • Dermatitis
  • Impaired or altered immune function
  • Common pathogen for those in an immunocompromised/immunosuppressed state
  • Allergic bronchopulmonary aspergillosis (ABPA) and chronic pulmonary aspergillosis is common in asthmatic persons or those with lung disease
  • Aspergillus sinusitis
  • Toxicoses
  • Several others
Potential Mycotoxins Produced
  • Several
Identifiable Through Testing
  • Yes; air and surface sampling


Aureobasidium

Aureobasidium pullulans is the only well-known species of Aureobasidium. It grows moderately rapidly and matures within 7 days of incubation. The colony diameter is 1 to 3 cm following incubation at 25°C for 7 days on potato glucose agar*. The colonies are flat, smooth, moist, yeast-like, mucoid to pasty, shiny and leathery in appearance. The surface is white, pale pink or yellow at the beginning and becomes brown to black and velvety with a grayish fringe by aging. Reverse is pale or black.

Natural Habitat
  • Soil
  • Plants and wood
  • Water
Methods of Spore Dispersion
  • Wind/air
  • Rain/water
  • Direct contact
Potential Allergenic
  • Yes
Potential Health Effects
  • Asthma/hay fever/allergies
  • Hypersensitivity
  • Keratomycosis
  • Phaehyphomycosis
  • Pulmonary mycosis with sepsis
  • Dermatitis
Potential Mycotoxins Produced
  • Unknown
Identifiable Through Testing
  • Yes; air and surface sampling



Basidiospore

Basidiospores are sexually produced fungal spore that is born on basidium. A basidium typically bears four basidiospores.

Natural Habitat
  • Plants
  • Lawns
  • Forest ground
Methods of Spore Dispersion
  • Wind/air
  • Direct contact
Potential Allergenic
  • Yes
Potential Health Effects
  • Asthma/hay fever/allergies
  • Hypersensitivity pneumonitis
Potential Mycotoxins Produced
  • Amanitins
  • monomethyl-hydrazine
  • muscarine
  • ibotenic acid
  • psilocybin
Identifiable Through Testing
  • Yes; air and surface sampling



Bipolaris / Drechslera Group

Bipolaris colonies grow rapidly, reaching a diameter of 3 to 9 cm following incubation at 25°C for 7 days on potato dextrose agar*. The colony becomes mature within 5 days. The texture is velvety to woolly. The surface of the colony is initially white to grayish brown and becomes olive green to black with a raised grayish periphery as it matures. The reverse is also darkly pigmented and olive to black in color.

Natural Habitat
  • Plants
  • Soil
Methods of Spore Dispersion
  • Wind/air
  • Direct contact
Potential Allergenic
  • Yes
Potential Health Effects
  • Asthma/hay fever/allergies
  • Cerebral infections/brain abscess
  • Peritonitis in patients on continuous ambulatory peritoneal dialysis (CAPD)
  • Mycotic keratitis
  • Subcutaneous phaehyphomycosis (in both normal and immunocompromised people)
  • Allergic and chronic invasive sinusitis
Potential Mycotoxins Produced
  • Sterigmatocystin
Identifiable Through Testing
  • Yes; air and surface sampling



Botrytis

Botrytis cinerea is the most common species of Botrytis. It is a very common plant parasitic found on weakened plant tissues. It grows rapidly, reaching a colony size of 3 to 9 cm in diameter, following incubation at 25°C for 7 days on potato glucose agar*. The texture is woolly. The surface color is white at the beginning and becomes gray to brown in time. Dark spots may be observed on the surface of the colony. Reverse is dark.

Natural Habitat
  • Plants; houseplants, fruits, and vegetables are the most common
Methods of Spore Dispersion
  • Wind/air
  • Rain/water
  • Direct contact
Potential Allergenic
  • Yes
Potential Health Effects
  • Asthma/hay fever/allergies
  • Hypersensitivity pneumonitis
Potential Mycotoxins Produced
  • Unknown
Identifiable Through Testing
  • Yes; air and surface sampling



Chaetomium

Chaetomium contains several species. The most common are Chaetomium atrobrunneum, Chaetomium funicola, Chaetomium globosum, and Chaetomium strumarium. Its colonies are rapidly growing, cottony and white in color initially. Mature colonies become gray to olive in color. From the reverse, the color is tan to red or brown to black.

Natural Habitat
  • Soil
  • Plant debris
  • Dung
  • Seeds
Methods of Spore Dispersion
  • Wind/air
  • Insects
  • Rain/water
  • Direct contact
Potential Allergenic
  • Yes
Potential Health Effects
  • Asthma
    Onychomycosis
  • Cerebral phaeohyphomycosis/brain abscess
  • Peritonitis
  • Cutaneous lesions
Potential Mycotoxins Produced
  • Chaetomin
  • Chaetoglobosins A,B,D and F are produced by Chaetomium globosum
  • Sterigmatocystin is produced by rare species
Identifiable Through Testing
  • Yes; air and surface sampling



Cladosporium

The most common species of Cladosporium include Cladosporium elatum, Cladosporium herbarum, Cladosporium sphaerospermum, and Cladosporium cladosporioides. The growth rate of Cladosporium colonies is moderate on potato dextrose agar* at 25°C and the texture is velvety to powdery. Similar to the other dematiaceous fungi, the color is olivaceous green to black from the front and black from the reverse. Most of the Cladosporium spp. do not grow at temperatures above 35°C.

Natural Habitat
  • Dead plant matter
  • Soil
Methods of Spore Dispersion
  • Wind/air
  • Direct contact
Potential Allergenic
  • Yes
Potential Health Effects
  • Asthma/hay fever/allergies
  • Edema
  • Keratitis
  • Onychomycosis
  • Pulmonary infections
  • Sinusitis
Potential Mycotoxins Produced
  • Cladosporin
  • Emodin
Identifiable Through Testing
  • Yes; air and surface sampling



Curvularia

Curvularia contains several species. Curvularia lunata is the most prevalent cause of disease in humans and animals. Curvularia produces rapidly growing, woolly colonies on potato dextrose agar* at 25°C. From the front, the color of the colony is white to pinkish gray initially and turns to olive brown or black as the colony matures. From the reverse, it is dark brown to black.

Natural Habitat
  • Plants
  • Soil
Methods of Spore Dispersion
  • Wind/air
  • Direct contact
Potential Allergenic
  • Yes
Potential Health Effects
  • Immunocompromised/immunosuppressed persons are at a greater risk of adverse health issues
  • Asthma/hay fever/allergies
  • Phaeohyphomycosis
  • Endocarditis
  • Mycetoma
  • Ocular keratitis
  • Onychomycosis
  • Pneumonia
  • Dialysis-associated peritonitis
  • Allergic bronchopulmonary disease
Potential Mycotoxins Produced
  • Cytochalasin B
Identifiable Through Testing
  • Yes; air and surface sampling



Epicoccum

Epicoccum contains a single species, Epicoccum purpurascens. Epicoccum grows rapidly and produces woolly to cottony or felty colonies on potato dextrose agar* at 25°C. From the front, the colonies are yellow to orange, orange to red or pink initially and become greenish brown to black by aging. From the reverse, the same color is observed but is usually more intense than in the front view. Epicoccum may produce a diffusible pigment which turns the color of the inoculated medium to yellow, orange, red or brown. Black dots may be observed macroscopically on the colony surface. These are the tufts of hyphae which have conidiophores on their surface. These tufts of hyphae are cushion-shaped and non convoluted and are called sporodochia.

Natural Habitat
  • Plant debris
  • Soil
Methods of Spore Dispersion
  • Wind/air
  • Direct contact
Potential Allergenic
  • Yes
Potential Health Effects
  • Asthma/hay fever/allergies
Potential Mycotoxins Produced
  • Epicorazine A&B
  • Flavipin
  • Indole-3-acetonitrile
Identifiable Through Testing
  • Yes; air and surface sampling



Fusarium

Fusarium contains several species. The most common of these are Fusarium solani, Fusarium oxysporum, and Fusarium chlamydosporum. Fusarium spp. grow rapidly on Sabouraud dextrose agar* at 25°C and produce woolly to cottony, flat, spreading colonies. The only slow-growing species is Fusarium dimerum. From the front, the color of the colony may be white, cream, tan, salmon, cinnamon, yellow, red, violet, pink, or purple. From the reverse, it may be colorless, tan, red, dark purple, or brown.

Natural Habitat
  • Soil
  • Plants
Methods of Spore Dispersion
  • Wind/air
  • Insects
  • Rain/water
  • Direct contact
Potential Allergenic
  • Yes
Potential Health Effects
  • Immunocompromised/immunosuppressed persons are at a greater risk of adverse health issues
  • Asthma/hay fever/allergies
  • Keratitis
  • Endophthalmitis
  • Onychomycosis
  • Cutaneous infections
  • Mycetoma
  • Sinusitis
  • Pulmonary infections
  • Endocarditis
  • Peritonitis
  • Septic arthritis
  • Central venous catheter infections
  • Esophageal cancer
  • Cutaneous infections in burn victims
  • Esophageal cancer
Potential Mycotoxins Produced
  • Trichothecenes
  • Zearalenone
  • Fumonisins
Identifiable Through Testing
  • Yes; air and surface sampling



Memnoniella

Myrothecium echinata is considered a powerful cellulolytic cellulose decomposer. It is very similar to Stachybotrys, except it produces its spores in chains.

Natural Habitat
  • Plants
  • Soil
Methods of Spore Dispersion
  • Wind
  • Direct contact
Potential Allergenic
  • Yes
Potential Health Effects
  • Asthma/hay fever/allergies/flu and cold-like symptoms
  • Dermatitis
  • Impaired or altered immune function
  • Considered to be a possible cause respiratory diseases
Potential Mycotoxins Produced
  • Dechlorogriseofulvin
  • Epidechlorogriseofulvin
  • Griseofulvins
  • Memnopeptide A
  • Trichodermol
  • Trichodermin
Identifiable Through Testing
  • Yes; air and surface sampling



Myrothecium

Myrothecium verrucaria is the most common species in the Myrothecium genus. It is considered a powerful cellulose decomposer.

Natural Habitat
  • Dead agaric mushrooms
  • Grass/weeds
  • Soil
Methods of Spore Dispersion
  • Insects
  • Water
  • Direct contact
Potential Allergenic
  • Unknown
Potential Health Effects
  • Unknown
Potential Mycotoxins Produced
  • Trichothecene mycotoxins
Identifiable Through Testing
  • Yes; air and surface sampling



Nigrospora

Nigrospora sphaerica is the most well-known species of the genus Nigrospora. Nigrospora grows rapidly and produces woolly colonies on potato dextrose agar* at 25°C. The colonies mature within 4 days. Color of the colony is white initially and then becomes gray with black areas and turns to black eventually from both front and reverse. Sporulation may take more than 3 weeks for some isolates.

Natural Habitat
  • Grass/weeds
  • Soil
  • Seeds
Methods of Spore Dispersion
  • Direct contact
Potential Allergenic
  • Yes
Potential Health Effects
  • Asthma/hay fever/allergies
  • Keratitis
  • Skin lesions
Potential Mycotoxins Produced
  • Unknown
Identifiable Through Testing
  • Yes; air and surface sampling



Penicillium

Penicillium is one of the most commonly occurring fungi. The colonies of Penicillium other than Penicillium marneffei are rapid growing, flat, filamentous, and velvety, woolly, or cottony in texture. The colonies are initially white and become blue green, gray green, olive gray, yellow or pinkish in time. The plate reverse is usually pale to yellowish.

Natural Habitat
  • Soil
  • Seeds
  • Cereal crops
Methods of Spore Dispersion
  • Wind/air
  • Insects
Potential Allergenic
  • Yes
Potential Health Effects
  • Rarely; typically encountered in immunosuppressed hosts
  • Asthma/hay fever/allergies
  • Hypersensitivity
  • Penicilliosis
Potential Mycotoxins Produced
  • Several
Identifiable Through Testing
  • Yes; air and surface sampling



Pithomyces

Pithomyces is generally classified as a dematiaceous (dark-walled) fungus. The surface of these spores ranges from smooth, to slightly rough with small pointed projections, to warty with large, wide projections.

Natural Habitat
  • Soil
  • Plants
  • Tree bark
Methods of Spore Dispersion
  • Wind/air
  • Direct contact
Potential Allergenic
  • Unknown
Potential Health Effects
  • Etiologic agent in immunocompromised patients
Potential Mycotoxins Produced
  • Cyclodepsipeptides
  • Sporidesmin
  • Sporidesmolides
Identifiable Through Testing
  • Yes; air and surface sampling



Rusts

There are 5000 known species of rusts belonging to at least 150 different genera. Rusts are considered a parasite to many types of plants and the cause of great economic loss for cultivated crops.

Natural Habitat
  • Living plants
Methods of Spore Dispersion
  • Wind
  • Direct contact
Potential Allergenic
  • Yes
Potential Health Effects
  • Unknown
Potential Mycotoxins Produced
  • Unknown
Identifiable Through Testing
  • Yes; air and surface sampling


Smuts, Periconia, Myxomycetes

Considered plant parasites. Often found with dust. These three types of fungi are linked when testing because of their similarities and the difficulty in distinguishing them from each other.

Natural Habitat
  • Grass/weeds
  • Soil
  • Cereal crops
  • Dung
  • Decaying plant or wood
Methods of Spore Dispersion
  • Wind
  • Rain/water
  • Direct contact
Potential Allergenic
  • Yes
Potential Health Effects
  • Asthma/hay fever/allergies
Potential Mycotoxins Produced
  • Periconia circinata produces Periconin A and Periconin B (both are biologically inactive)
  • Others unknown
Identifiable Through Testing
  • Yes; air and surface sampling



Stachybotrys

There is only one species of Stachybotrys, Stachybotrys chartarum. It has been nicknamed the "black mold" or "toxic mold" by the media. Stachybotrys produces cottony, rapidly growing colonies which mature in about 4 days. From both front and reverse, the color of the colony is white initially and turns to black by aging.

Natural Habitat
  • Decaying plants
  • Soil
  • Seeds
Methods of Spore Dispersion
  • Wind/air
  • Water/rain
  • Insects
  • Direct contact
Potential Allergenic
  • Yes
Potential Health Effects
  • Asthma/hay fever/allergies/flu and cold-like symptoms
  • Excessive fatigue and lethargy
  • Dermatitis
  • Impaired or altered immune function
  • Considered to be a possible cause of acute idiopathic pulmonary hemosiderosis, lung cancer and other respiratory diseases
  • Toxicoses
  • Several others
Potential Mycotoxins Produced
  • Cyclosporins
  • Macrocyclic trichothecenes: roridin E, satratoxin F, G & H, sporidesmin G, trichoverrol, verrucarin J
  • Stachybotryolactone
Identifiable Through Testing
  • Yes; air and surface sampling



Stemphylium

The most common species of Stemphylium is Stemphylium macrosporoideum. Colonies of Stemphylium grow rapidly and mature in 5 days. At 25°C and on potato dextrose agar*, they are velvety to cottony in texture. From the front, the color is gray, brown, or brownish-black. Reverse is black.

Natural Habitat
  • Dead plants
  • Wood
  • Spinach leaf
Methods of Spore Dispersion
  • Wind/air
  • Direct contact
Potential Allergenic
  • Yes
Potential Health Effects
  • Asthma/hay fever/allergies
  • Possible links to phaeohyphomycosis
Potential Mycotoxins Produced
  • Stemphol
Identifiable Through Testing
  • Yes; air and surface sampling



Torula

Torula is a genus of wild yeasts that are imperfect and never form sexual spores. It is generally classified as a dematiaceous (dark-walled) fungus.

Natural Habitat
  • Leaves
  • Soil
  • Wood
  • Plant roots
Methods of Spore Dispersion
  • Wind/air
  • Direct contact
Potential Allergenic
  • Yes
Potential Health Effects
  • Asthma/hay fever/allergies
  • Possible links to phaeohyphomycosis
Potential Mycotoxins Produced
  • Unknown
Identifiable Through Testing
  • Yes; air and surface sampling



Ulocladium

Ulocladium has two species under it, Ulocladium chartarum and Ulocladium botrytis. Colonies of Ulocladium grow moderately rapidly. At 25°C and on potato dextrose agar*, the colonies are wooly to cottony. From the front and the reverse, the color is olive brown to black.

Natural Habitat
  • Soil
  • Decaying plants
  • Wood
  • Dung
Methods of Spore Dispersion
  • Wind/air
  • Direct contact
Potential Allergenic
  • Yes
Potential Health Effects
  • Asthma/hay fever/allergies
  • Phaeohyphomycosis
  • Subcutaneous infections
Potential Mycotoxins Produced
  • Unknown
Identifiable Through Testing
  • Yes; air and surface sampling



Zygomycetes

Zygomycetes is a class of fungus, not a particular genre. The classes include three orders, Mucorales, Mortierellales, and Entomophthorales. This class of fungi are extremely fast growing and can inhibit other fungi when competing for food or space.

Natural Habitat
  • Decaying plants and animals
Methods of Spore Dispersion
  • Wind/air
  • Water
  • Direct contact
Potential Allergenic
  • Yes
Potential Health Effects
  • Asthma/hay fever/allergies
  • Hypersensitivity
  • Zygomycosis in immunocompromised persons
Potential Mycotoxins Produced
  • Varies by genus
Identifiable Through Testing
  • Yes; air and surface sampling

 

* Using potato glucose/dextrose agar and Sabouraud dextrose agar are common laboratory method for studying mold growth and other behaviors.

Note: This library lists the common types of mold found during testing, their most common natural habitat, the means of their dispersion/dissemination, if they're considered a potential allergenic, their potential health effects, and other information. Side effects of mold exposure will vary from person to person. The information presented here is based upon medical and scientific findings from a variety of sources. The effects of mold as it relates to human health has been studied and studies are continuing.


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