Exposures to Toxic Fungus in Water-Damaged Areas*

April 2002


Building materials which have been damaged due to flooding or continuous moisture exposure are susceptible environments for the growth of mold or fungus. Several types of these molds can cause health effects in humans and animals when released into the air, either through sporing or disturbance during remediation activities. This may be of specific importance for building occupants, construction workers and in particular Fungal abatement crews. There are currently no published exposure limits for these fungal organisms. However, appropriate respiratory protection will reduce exposure to these agents.


The term "fungi" includes organisms such as yeasts, molds, mildews, and mushrooms. Fungi can exist as single cells or as threadlike strands which may branch extensively. Fungi normally reproduce as spores. Spores can contain one or many cells and are normally between 2 µm (micrometers) and 100 µm in size. They are adapted for airborne dispersal. Conditions which promote growth include high relative humidity, moisture, standing water, and a food source for the organism such as wood or paper. Fungi can produce secondary metabolites such as toxins, and volatile organic compounds (VOC) that are thought to be the source of odors associated with mold and mildew. The toxins are typically contained in the spores but a few have been shown to be volatilized (exist as a vapor).

Three types of fungi, which are commonly found in water-damaged buildings are Aspergillus, Penicillium, and Stachybotrys. These molds are known to produce toxin-containing spores and cause a variety of health effects via ingestion, inhalation, and skin contact. These may include allergenic affects, nausea, asthma, runny nose, coughing, sore throat and surface infection. Inhalation of the VOCs may also cause symptoms such as headaches, dizziness, and eye and mucous membrane irritation, which are typically not life-threatening.

  • Most of the information for this handout comes from the 3M Company Technical Bulletin #136. Tamarack has updated the bulletin with current information.

Mode of Transmission

Fungal spores may be released into the air naturally or can be aerosolized if the growth area is disturbed, as in remediation activities. Health effects occur when people are directly exposed to the fungi - no person to person transmission has been documented. For assistance in determining if fungal contamination has occurred please contact your local health department. Information which may be relevant is the color, appearance (i.e. slimy, dusty), odor, and size of the growth, and the materials and conditions (temperature, moisture) at which the growth is occurring.

Remediation of Fungal-Contaminated Areas

The best currently available approach for preventing fungal contamination is to prevent conditions which foster fungal growth. Immediate clean-up of water damage to building materials, fixing of leaks, maintenance of a moderate level of relative humidity (50%), and preventing dirt build-up in HVAC systems are important steps. If clean-up is necessary, household bleach has been recommended for cleaning areas contaminated with the fungi mentioned above. Household bleach should be diluted 5 to 1 with water. The area of concern should be misted with the bleach solution to saturate the area. Excessive water run off should be avoided. A second misting within one hour is recommended. The surface should be wet with the bleach solution for a minimum of two hours and then air dried.

Personal Protective Equipment (PPE)

Currently, there are no recommendations from the Centers for Disease Control and Prevention or the Occupational Safety and Health Administration on the personal protective equipment necessary when remediating fungal-contaminated buildings. In a 1996 publication, the National Institute for Occupational Safety and Health (NIOSH) made the following conclusion regarding remediation of fungal-contaminated building

"Remediation of microbiologically-contaminated building materials should be conducted when affected areas are unoccupied. All renovation and construction activities involving the removal or disturbance or microbiologically-contaminated building materials should be prohibited until the dissemination of spores to other parts of the building can be prevented. As seen from the results of this study, the potential exists for exposures (both from inhalation and skin contact) to toxigenic fungi. Remediation workers should wear NIOSH-approved full-face respirators with HEPA cartridges or powered air purifying respirators, disposable coveralls, and gloves."

The New York City Department of Health (NYCDH) has recommended guidelines for remediation of fungal contamination in indoor environments. Five levels of remediation activity are listed in the NYCDH, with recommended PPE. Training for remediation workers by qualified individuals is recommended before performing any remediation activity. Persons with asthma, allergy and immune suppressive disorders should not perform these activities.

New York City Department of Health (NYCDH) levels for remediation in indoor environments and recommended PPE.

Level Description NYCDH Recommended PPE
1 Small isolated areas of less than 10 ft2. Gloves and a half facepiece respirator (N95 air purifying element specified).
2 Larger isolated areas between 10 and 30 ft2 in size. (Same as level 1.)
3 Large isolated areas 30-100 ft2. (Same as level 1.)
4 Extensive greater than 100 ft2 in each area.
Full facepiece respirators with N100 cartridges or powered air purifying respirators, disposable protective clothing, head gear, foot covering and gloves.
5 HVAC systems. (Same as level 4.)

The VOCs or volatile toxins produced by the mold may include alcohols, aldehydes, ketones, aromatics, amines, terpenes, chlorinated hydrocarbons, and sulfur-containing compounds. These are thought to be at orders of magnitude lower than what is typical in industry. A particulate filter designed for nuisance level organic vapors may be appropriate for exposures to these chemicals at levels that are well below the exposure limits. Gases and vapors associated with disinfectants (i.e. chlorine) may also warrant the use of a cartridge with an acid gas approval in conjunction with the particulate filter.

Because of changes in government certification, dust/mist and HEPA respirators/filters for non-powered respirators can no longer be distributed by manufacturers for sale after July 10, 1998. NIOSH has created 9 new categories of particulate filters under regulation 42 CFR 84. There are filters for non-oil aerosols ("N" filters) and for oil-containing aerosols ("R" and "P" filters). The filters are also labeled with a rating of 95, 99, or 100 corresponding to 95%, 99% and 99.97% efficiency. A 95 level filter may be used in place of a dust/mist filter. OSHA has accepted the use of 100 level filters in place of HEPA filters. However, a less efficient filter may be acceptable for certain remediation work.

The use of NIOSH-certified respirators should be accompanied by a full respiratory protection program as specified in OSHA 29 CFR 1910.134. The American National Standard for Respiratory Protection, ANSI Z88.2-1992 also provides information on establishing and administering a respiratory protection program. Important components of a respiratory protection program include written standard operating procedures, user training, respirator maintenance procedures and properly fitting the respirator to the user. In addition, respirators with tight-fitting facepieces (including positive-pressure types) are not considered protective if facial hair interferes with the face seal, since proper fit cannot be assured.

Precautions for other occupational groups who may have exposures to toxigenic molds.

Insufficient information is available at this time to allow general recommendations for persons in other occupations which may be exposed to materials contaminated with toxigenic molds. Examples of such occupations include building maintenance personnel, construction workers, agricultural and livestock workers, workers in the food processing industry and those who inspect buildings for damage such as insurance representatives and health and safety professionals.

Precautions for homeowners who may have exposures to toxigenic molds.

The recommendations reviewed here have been prepared for professional industrial remediators and are not applicable for homeowners. Homeowners who suspect that they have mold contamination in their home are urged to contact their local health department and seek professional advice on how to perform clean-up.

Precautions for individuals with health problems who may have exposures to toxigenic molds.

It is recommended that all persons with asthma, hypersensitivity pneumonitis, severe allergies, immune suppression, or other chronic inflammatory lung diseases be removed from the contaminated area until remediation is complete.


Two documents offer recommendations on remediation of mold contaminated building materials: the NIOSH Health Hazard Evaluation (Martin County Courthouse and Constitutional Office Building, Stuart Florida.) and the New York City Guidelines on Assessment and Remediation of Fungi in Indoor Environments. For complete copies of these documents please contact either NIOSH publications (800-356-4674), the New York City Department of Health (212-442-3372), or 3M OH&ESD Technical Service Hotline (in US 800-243-4630). This Technical Data bulletin does not contain the recommendations in their entirety. For example, the NYC Guidelines also make recommendations regarding evaluation, monitoring and disinfection procedures which have not been listed here.

In addition, the reader is advised to contact their local health department and be alert to supplements, modifications, or additional recommendations in the future.

Indoor Air Quality Web Sites for schools: www.dehs.umn.edu/iaq/school/questions.html
for residences: www.dehs.umn.edu/homeiaq/homeiaq.html
California Indoor Air Quality Site - www.cal-iaq.org

Dearborn D.G. Ph.D., M.D. "Pulmonary Hemorrhage in Infants: The Cleveland Outbreak" Rainbow Babies & Childrens Hospital, Case Western Reserve University, Cleveland, Ohio 44106. gcrc.meds.cwru.edu/stachy/default.htm Also see CDC response to the Cleveland Outbreak at www.cdc.gov/mmwr/preview/mmwrhtml/rr5302a1.htm. Published at the conference "Microbiological Contamination of Indoor Environments", February 4-6, 1998, New Orleans, Louisiana.

Miller J.D. (1998): "Inhalation Exposure to Fungi" Institute of Biochemistry, Carleton University, Ottawa, Ontario. K1S 5B6. jdmiller@ccs.carleton.ca Published at the conference “Microbiological Contamination of Indoor Environments, February 4-6, 1998, New Orleans, Louisiana.

"Field Guide for the Determination of Biological Contaminants in Environmental Samples" An American Industrial Hygiene Association Biosafety Guide. For further information see their web page at www.aiha.org

"Bioaerosols Assessment and Control" Published by the American Conference of Governmental Industrial Hygienist. For further information see their web page at www.acgih.org

For further information regarding mold abatement contact the New York City Department of Health at (212) 788-4290. www.ci.nyc.ny.us/html/doh/html/epi/moldrpt1.shtml and the U.S. EPA at www.epa.gov/iaq/molds 1-800-438-2472 x2086

Minnesota Department of Health - Recommended Best Practices for Mold Investigations in Minnesota Schools - For further information call (651) 215-0909 or see their web page at www.health.state.mn.us