Harmful effects of molds
The type and severity of health effects that result from molds exposure is widely variable among different locations, from person to person and over time.
Although difficult to predict, exposure to molds growing indoors is most often associated with the following allergy symptoms:
Indoor molds exposure leads mostly to upper respiratory tract symptoms
Long-term exposure to indoor molds is certainly unhealthy to anyone, but some groups will develop more severe symptoms sooner than others, including:
- Infants and children
- Elderly people
- Individuals with respiratory conditions, allergies and/or asthma
- Immunocompromised patients
Some indoor molds are capable of producing extremely potent toxins (mycotoxins) that are lipid-soluble and readily absorbed by the intestinal lining, airways, and skin. These agents, usually contained in the fungal spores, have toxic effects ranging from short-term irritation to immunosuppression and cancer. (Photo: Mold growing behind wallpaper)
More severe symptoms that could result from continuous human exposure to indoor mycotoxigenic molds include:
- Cancer (aflatoxin best characterized as potential human carcinogen)
- Hypersensitivity pneumonitis/pulmonary fibrosis
- Pulmonary injury/hemosiderosis (bleeding)
- Hematologic and immunologic disorders
- Hepatic, endocrine and/or renal toxicities
- Pregnancy, gastrointestinal and/or cardiac conditions
It is important to notice that the clinical relevance of mycotoxins under realistic airborne exposure levels is not fully established. Further, some or much of the supporting evidence for these other health effects is based on case studies rather than controlled studies, studies that have not yet been reproduced or involve symptoms that are subjective.
(Photo: Black mold spores micrography)
Among the indoor mycotoxin-producing species of molds are Fusarium, Trichoderma, and one that, although less commonly isolated, became notorious during the past decade, Stachybotrys atra (aka S. chartarum, black mold). Between 1993 and 1994, there was an unusual outbreak of pulmonary hemorrhage in infants in Cleveland, Ohio, where one kid died. Researchers found that the kids’ homes had previously sustained water damage that resulted in molds contamination, and the quantity of molds, including S. chartarum, was higher in the homes of infants with pulmonary hemorrhage than in those of controls. (Photo: Stachybotrys growing on Potato Dextrose Agar (PDA))
It was this Cleveland event that initiated the headline news of Stachybotrys. The American Academy of Pediatrics produced guidelines in the wake of the outbreak. Other incidents involving kids in Stachybotrys-contaminated water-damaged school buildings have captured headlines as well, with children becoming symptom-free after being removed from those environments.
Article from the Fargo Forum newspaper, North Dakota (5/1/1997)
The role of S. chartarum in pulmonary hemorrhage in the Cleveland incident and in human health in the indoor environment is not clear though. There is not enough evidence to prove a solid causal relationship between S. chartarum and these health problems. Actually, in 2000 the CDC released two reports critical of the study conducted in Cleveland and concluded that the association between S. chartarum and acute pulmonary hemorrhage was not proven.
While case studies certainly indicate the possibility or even the plausibility of an effect from molds exposure, such studies by their nature cannot address whether the effect is common or widespread among building occupants. Results from studies that have not been reproduced may be spurious or have yet to be confirmed by well-designed follow up studies. (Photo: Moldy humid walls in a closet space)
In large epidemiologic studies, general symptoms have been associated with moisture damaged and presumably moldy buildings. Many of the reported symptoms are subjective and difficult to quantify. Results are confounded by the fact that the association is general, and mold is not the only possible cause of the symptoms. Neither condition proves that mold is NOT a cause.
In any case, molds growth in the indoor environment should be considered unacceptable from the perspectives of potential adverse health effects and building performance.
There is almost a complete lack of information on specific human responses to well-defined exposures to molds contaminants. There is currently no proven method to measure the type or amount of mold that a person is exposed to, and common symptoms associated with molds exposure are non-specific, aggravated by the facts that molds are present everywhere in the environment and that responses to exposure vary greatly among individuals. (Photo: Heavy mold growth on the underside of spruce floorboards)
There are no accepted standards for molds sampling in indoor environments or for analyzing and interpreting the data in terms of human health. Most studies are then based primarily on baseline environmental data rather than on human dose-response data. Neither OSHA or NIOSH, nor the EPA has set a standard or PEL for molds exposure.
Mold growth on air diffuser in ceiling
Miller et al. (1988) stated that it is reasonable to assume there is a problem if a single species predominates with >50 CFU/m3, that <150 CFU/m3 is acceptable if there is a mix of benign species, and that there is no problem when up to 300 CFU/m3 of Cladosporium or other common fungi is isolated. There is no source material to support these assertions, as few inhalation studies have been conducted.
American Academy of Pediatrics Committee on Environmental Health. 1998. Toxic effects of indoor molds. Pediatrics. 101:712-714. 11/23/03
Centers for Disease Control and Prevention. 2002. State of the Science on Molds and Human Health. 11/15/03
US Environmental Protection Agency – Indoor Air Quality – Molds. 11/15/03
Kuhn, D. M., and M. A. Ghannoum. 2003. Indoor mold, toxigenic fungi, and Stachybotrys chartarum: infectious disease perspective. Clin Microbiol Rev. 16(1):144-172. 11/15/03
Miller, J. D., A. M. Laflamme, Y. Sobol, P. Lafontaine and R. Greenhalgh. 1988. Fungi and fungal products in some Canadian houses. Int. Biodeterior. 24:103-120.
Morbidity and Mortality Weekly Report – Centers for Disease Control and Prevention. 2000. Update: Pulmonary Hemorrhage/Hemosiderosis Among Infants --- Cleveland, Ohio, 1993-1996. 49(9):180-184. 11/17/03
Nelson, B. D. 2001. Stachybotrys chartarum: The Toxic Indoor Mold – APSnet. 11/23/03
What Types Of Mold Are Considered Toxic Mold
"Toxic mold" is a term that is used to describe types of mold that are considered deadly to humans. Most people believe that the name refers to one particular species of mold; however, it encompasses hundreds of species, a small fraction of which are not very harmful to the human body. Black mold is commonly used as a name for the most harmful mold species, which happen to be black in appearance. However, even molds of a different color can be toxic to the human body.
Any place that is dark and where there is an accumulation of moisture, is a potential breeding pool for mold. Mold can grown on almost any organic surface as long as moisture and oxygen are present. When large amounts of moisture build-up in buildings, or building materials mold growth will occur. It is virtually impossible to remove all indoor mold and mold spores, but it is possible to manage.
People are exposed to some amount of mold everyday. When mold is growing on a surface, spores can be released into the air where a person can then inhale them. A person who is subject to inhaling a large amount of these spores may be subject to some medical damage.
There are five categories of toxic mold. They are Cladosporium, Penicilium, Fusarium, Aspergillus, and Stachybotrys. Some of the species included in these categories may only cause hay fever-like allergic reactions, while others can cause potentially deadly illnesses. All five of these mold families can be found lurking indoors, in damp spaces. Each has its own particular characteristics that can greatly affect whatever organism or material it contacts. Indoor mold is not always obvious. Mold can manifest on hidden surfaces, such as wallpaper, paneling, the top of ceiling tiles, and underneath carpet.
The toxin produced by Stachybotrys chartarum is the most deadly. It has been tied to diseases as minor as hay fever, to those as serious as liver damage, pulmonary edema, and in the most severe cases, brain or nerve damage and even death. It has also been linked to severe illness in infants. Those with compromised immune systems, small children, and the elderly are highly susceptible to illness when they come in contact with this species of mold. Some symptoms associated with exposure to Stachbotrys include:
nasal and sinus congestion
central nervous system issues
aches and pains
Cladosporium, Fusarium, and Penicillium
These mold families have been connected to illnesses such as nail fungus, asthma, and also infections of the lungs, liver, and kidneys. Additionally, Fusarium may cause gastrointestinal illnesses, and even illness which affect the female reproductive system. Chronic cases of Cladosporium may produce pulmonary edema and emphysema.
The least serious of the toxic mold groups, the Aspergillus mold family consists of over 160 species. Only 16 of those cause illness in humans, none of which are fatal if treated.
Toxic molds produce chemicals during their natural growth that are classified as toxins or poisons. The types that have been found to have profound effects on human health, are given the label of "toxic mold."
Toxic molds are all very dangerous if allowed to grow inside the home. Proper precautions should be taken to prevent and eliminate their growth. These measures should include eliminating every material that nourishes the molds, such as old remodeling materials left in a basement. Also, never try to determine the type of mold in your home. Contact a professional to test any mold colony you may find, and consult with your family physician.