Prevention and Remediation Strategies for the Control and Removal of Fungal Growth

• Highlights
• Prevention
• Tasks Involved in Remediation
• Emergency Actions

This overview of prevention strategies, published guidelines for the removal of fungal growth (remediation), remediation protocols, and the effectiveness of various cleaning strategies for mold is based on Chapter 6 ("Prevention and Remediation of Damp Indoor Environments," pages 270-310) of the 2004 Institute of Medicine (IOM) report Damp Indoor Spaces and Health. The full report is accessible from http://www.nap.edu/books/0309091934/html/.

Important Highlights

• The most effective way to manage mold in a building is to eliminate or limit the conditions that foster its establishment and growth.
• Mold should not be allowed to colonize materials and furnishings in buildings.
• The underlying moisture condition supporting mold growth should be identified and eliminated.
• To remediate problematic mold growth, mold should be removed from materials that can be effectively cleaned and materials that cannot be cleaned or are physically damaged beyond use should be discarded.
• Occupants and workers must be protected from contaminants during remediation.
• After emergency situations (such as flooding due to hurricanes), to avoid fungal growth on susceptible materials, it is important to dry them quickly.
  • Take emergency actions to stop water intrusion if needed.
  • Identify vulnerable populations, extent of contamination and water source.
  • Plan and implement remediation activities.
• Quick and effective response to water intrusion can prevent or greatly reduce fungal growth and occupant exposure to bioaerosols, further disruption to building operations, and future needs for fungal remediation.

Prevention

The key to prevention in the design and operation of buildings is to limit water and nutrients. The two basic methods for accomplishing that are keeping moisture-sensitive materials dry and, when wetting is likely or unavoidable, using materials that offer a poor substrate for growth. Specifically, design and maintenance strategies must be implemented to manage:

• Rainwater and groundwater, preventing liquid-water entry and accidental humidification of buildings.
• The distribution, use, and disposal of drinking, process, and wash water, making equipment and associated utilities easily accessible for maintenance and repair.
• Water vapor and surface temperatures to avoid accidental condensation.
• The wetting and drying of materials in the building and of soil in crawlspaces during construction.

Little scientific information on the efficacy and impact of prevention strategies is available. Moreover, little of the practical knowledge acquired and applied by design, construction, and maintenance professionals has been subject to thorough validation. Since the 1993 New York City Department of Health (NYCDOH) document (Assessment and remediation of Stachybotrys Atra in Indoor Environments) was produced, a number of other guidance documents have been written, including:

• Fungal Contamination in Buildings: A Guide to Recognition and Management (Health Canada, 1995).
• Control of Moisture Problems Affecting Biological Indoor Air Quality (Flannigan and Morey, 1996).
• Bioaerosols: Assessment and Control (American Conference of Government Industrial Hygienists [ACGIH], 1999).
• Guidelines on Assessment and Remediation of Fungi in Indoor Environments (NYCDOH, 2000).
• Mold Remediation in Schools and Commercial Buildings (U.S. EPA, 2001).
• Report of the Microbial Growth Task Force (The American Industrial Hygiene Association, 2001).

The seven documents were each developed by a group of people with identified expertise in building and engineering issues, mycology, and occupant health assessment. Topics are not uniformly covered by the documents. The documents agree that:

• Mold should not be allowed to colonize materials and furnishings in buildings.
• The underlying moisture condition supporting mold growth should be identified and eliminated.
  • The International Society of Indoor Air Quality and Climate (ISIAQ) and ACGIH guidelines discuss moisture dynamics, identifying problematic moisture or remediating moisture problems.
  • U.S. EPA guidelines contain specific recommendations for a variety of water-damaged materials.
• The best way to remediate problematic mold growth is to remove it from materials that can be effectively cleaned and to discard materials that cannot be cleaned or are physically damaged beyond use.
• Occupants and workers must be protected from dampness-related contaminants during remediation.
  • All the guidelines agree that some mold situations present a small enough exposure potential that cleanup does not require specific containment or worker protection but that other situations warrant full containment, air-pressure management, and full worker protection. Situations between those extremes need intermediate levels of care. Guidance for selecting appropriate containment and worker protection for different situations lacks clarity within and between documents.
• Heating, Ventilation, and Air Condition (HVAC) systems are special cases. The documents disagree on how to respond to contamination in HVAC systems.
• The documents are divided on the use of disinfectants.

Tasks Involved In Remediation

Responding to mold problems requires a series of actions. The order in which actions take place is sometimes important. Typically, the following actions are implemented to some extent regardless of whether a problem is small and simple or large and complex:

• Take emergency actions to stop water intrusion if needed.
• Identify vulnerable populations, extent of contamination, and moisture dynamic.
• Plan and implement remediation activities.
  • Establish appropriate containment and worker and occupant protection.
  • Eliminate or limit moisture sources and dry the materials.
  • Decontaminate or remove damaged materials as appropriate.
  • Evaluate whether space has been successfully remediated.
  • Reassemble the space to prevent or limit possibility of recurrence by controlling sources of moisture and nutrients.

For small, simple problems, the entire list may be implemented by one person. For larger, more complex problems, the actions in the list may be accomplished by a series of people in different professions and trades. For circumstances that fall between those extremes, some combination of occupant action and professional intervention will be appropriate. In general, no single discipline brings together all the required knowledge for successful assessment and remediation.

Emergency Actions To Stop Water Intrusion

At times, water intrudes into a building so quickly that it must be responded to as an emergency. Broken water lines, gaping holes in the roof or walls during rainstorms (or hurricanes), or rising water tables may cause severe wetting or structural damage. To avoid fungal growth on susceptible materials, it is important to dry them quickly. Porous materials can absorb and retain a great deal of water. If nutrients are readily available in the material itself or in collected dust, visible fungal growth can occur within a few days of wetting. Recent research indicates that common construction materials may contain mold spores when they arrive from distributors and that some of the spores will germinate if exposed to relative humidity (RH) of 95% for extended periods (22–60 days); if they are wetted with water, germination can occur in less than 5 days.

Interventions to prevent continuing wetting and to dry out a building out should be chosen appropriately for the nature of the water source and the wet materials. Emergency actions may include turning off the water main, repairing pipes, temporarily closing holes in roofs or walls, pumping water out of buildings, unclogging drains, vacuuming water from materials in buildings, and actively dehumidifying buildings, rooms, or cavities. Appropriate worker protection may be necessary, depending on the source of the water, for example, flood water must be considered septic.