What Are Molds?

 

Not all molds are dangerous.  You do not always need to see mold to know you have a problem.  Moldy or earthy smells and any allergic reactions you are experiencing is a clue that you have a mold problem.

Molds are simple, microscopic organisms whose purpose in the ecosystem is to break down dead materials.  They can be found both inside and outside your home and are most prevalent in moist conditions.  Mold can be found on plants, dry leaves, foods and just about every other organic material.

Most mold found indoors come from outdoors.  Molds thrive where they can find sources of water, food and physical space.  Molds reproduce by very tiny particles called spores.  The spores float on air currents and find a suitable spot to grow.  Mold can be found throughout the home and is found in most bathrooms.  Mold also thrives in other moist areas such as areas that are moist from flooding, refrigerator water trays, plumbing leak areas, improperly vented clothes dyers, attics, basements and crawl spaces.

 

Types of Mold and Fungi

(information courtesy Restoration Consultants, Sacramento, CA)

Acremonium

This mold is commonly found in soil and on dead plant material. Indoors it grows on wet building materials like drywall ceiling tiles and building paper. Acremonium should be considered allergenic and may be a pathogen for immunocompromised individuals.

Alternaria

Commonly found in outdoor air, on many kinds of plants and foodstuffs and prefers rotting farmland manure. It may be resistant to fungicides. Alternaria is considered an occasional contaminant of water damaged building materials which contain cellulose. Although Alternaria is a notable source of fungal allergy, pathogenic infections are also reported infrequently.

Aspergillus

There are a wide variety of species of Aspergillus. Some are considered opportunistic pathogens and may cause pulmonary infections. Some members also produce mycotoxins and have been implicated in causing allergic reactions and hypersensitivity pneumonitis. Aspergillus type organisms are some of the first fungi to grow on water-damaged materials and are frequently found in water-damaged structures. Although they are commonly found in the outdoor environment, the outdoor frequency is generally considered low.

Aureobasidium

This yeast-like fungus is commonly found on caulk or damp window frames in bathrooms. Aureobasidium may be pink or black in color. Although it seldom causes infections, it can be allergenic. This is one type of mold that is a type of mildew. It will grow in cooler climates and along with Cladosporium is commonly found growing on siding.

Bacillus

Survives in soil. A gram positive rod which is part of a large family of organisms which are for the most part non-pathogenic for man.

Basidiospores

Frequently associated with dry rot, Basidiomycetes are primarily mushrooms, toadstools, puffballs, rusts and smuts. High levels of these spores can contribute to allergies in indoor environments. Poria incrassata is a particularly destructive fungal organism that falls into this classification. Poria has resulted in the collapse of severely infested buildings.

Botrytis

Most commonly associated with plants, Botrytis can cause allergic asthma after indoor exposure. High levels are likely to be found in greenhouses or other indoor areas with high humidity and large numbers of plants.

Ceratocystis/Ophiostoma

This is a very common plant pathogen that is frequently found on lumber in lumber yards and is built into most homes. It has not been well studied and has not been reported to be pathogenic or a producer of mycotoxins or allergens.

Chaetomium

Commonly found on deteriorating wood products, Chaetomium frequently emits a musty odor and is frequently found on water-damaged drywall. Its health effects have not been well studied, however some rare compounds have on occasion been identified as mutagenic.

Cladosporium

Cladosporium is the genera most frequently encountered in both outdoor and indoor air. It is frequently found in elevated levels in water-damaged environments. Some species may be resistant to certain types of treated lumber.

Epicoccum

A secondary invader of plant materials, Epicoccum can grow at higher temperatures than many fungi, allowing it to be a human skin pathogen. Colonies produce a wide variety of colors depending on the food source. Although it may be isolated from water damaged building materials, it is generally thought of as a typical outdoor organism. 

Fusarium

Found in soils and on plants worldwide, Fusarium can invade corn and barley and produce toxins at lower temperatures than many fungi. Fusarium has affected water-damaged carpets and a variety of other building materials, and can cause infection in immunocompromised individuals. Its spores are typically slimy and may be difficult to isolated from air samples. It has also been implicated in exacerbation of allergies and asthma and may produce mycotoxins.

Gram Negative Rods

Group of bacteria commonly found in standing water or water saturated structures. Most are opportunistic pathogens. Many species release endotoxins that can cause headaches and allergic type reactions.

Mucor

This mold is found worldwide and is frequently present in air samples. Mucor commonly grows on dung and moist hay. It is fast growing opportunistic and may cause rare infection in immunocompromised individuals. It is considered a mild allergen.

Penicillium

Penicillium species are common contaminants on various substances. This organism causes food spoilage, colonizes leather objects and is an indicator organism for dampness indoors. Some species are known to produce mycotoxins. The health of occupants may be adversely affected in an environment that has an amplification of Penicillium. Penicillium is one of the first fungi to grow on water-damaged materials and has been implicated in causing allergic reactions and hypersensitivity pneumonitis. It commonly produces a strong musty odor.

Pithomyces

Found in decaying wood, soil, and plant material, Pithomyces is not known to cause infections or major health problems in humans. It has been found growing on paper but is not commonly found growing indoors.

Rhizopus

Frequently found in house dust, soil, fruits, nuts, and seeds, Rhizopus often grows in fruit and vegetable garbage, or in forgotten leftover food. Exposure to large numbers of Rhizopus spores has reportedly caused respiratory complications. Rhizopus can be an allergen and opportunistic pathogen for immunocompromised individuals, especially those with diabetic ketoacidosis, malnutrition, or severe burns.

Scopulariopsis

A common contaminant that can cause toenail infections.

Sepedomium

A common soil contaminant. Non-pathogenic to humans.

Stachybotrys chartarum

Stachybotrys grows well on extremely wet building materials containing cellulose that have remained wet for more than a week. It produces mycotoxins that can irritate skin and mucous membranes. One potent mycotoxin produced by Stachybotrys is called satratoxin; it is also toxic when inhaled. Extreme care should be taken when this organism is amplified indoors.

Staphylococci

Opportunistic pathogen. It can survive and grow in nasal secretions and on skin. Produces many toxins which contribute to pathogenicity. Coagulase positive are considered potentially pathogenic.

Sterile Mycellium

Fungi that are not mature enough for speciation.

Streptomyces

Generally non-pathogenic. Some species can cause infections in humans. Also produces potentially harmful mycotoxins. Odor characteristic of freshly tilled soil. Important in the pharmaceutical industry.

Trichoderma

One of the most widespread soil fungi, Trichoderma grows in carpet, on unglazed ceramics, and on paper in damp homes. Some species produce metabolites related to trichothecenes, which can be toxic and may cause symptoms like those associated with Stachybotrys chartarum. It is also an allergen and may infect immunocompromised individuals.

Ulocladium

Isolated from soil, wood, and decaying plant material, Ulocladium grows on very wet walls and particleboard. Because of its high water requirements it is considered an excellent indicator of water damage. This genera is allergenic, contributing to the allergy load especially in those with Alternaria allergy.

Wallemia

Found worldwide in house dust, air samples, dry foodstuffs and soil. Wallemia attacks materials with low water activity, is an allergen and may produce mycotoxins. It is known to grow on materials with high salt content.

Yeast

Common in moist habitats and often able to grow at reduced oxygen levels. This organism can cause allergies and can be an opportunistic pathogen.