the forest through the trees

Summary

This article describes two strategies for reducing occupational mold exposure: a high-risk and population-level approach. An argument is made that rather than waiting for a moisture intrusion event to occur and promptly responding, it may be a more cost-effective use of resources to address this risk factor during the building design phase and through ongoing operations and maintenance.

Background

Occupational exposure to indoor molds is now a topic of great interest in both the scientific literature and building industry. Research has drawn a link between exposure to mold and the onset of illness including fungal infections, allergic rhinitis, and hypersensitivity pneumonitis among others.¹ Mold exposure has also been found to contribute towards the development of occupational asthma.² Several organizations have published guidelines on the prevention, assessment and remediation of microbial contamination in buildings.^3,4

In terms of a prevention strategy, any individual working in a building would be considered within the “at risk” population. Mold growth requires moisture and a nutrient capable of supporting growth, such as organic building materials.³ Therefore, the presence of moist building materials is an important risk factor for occupational mold exposure and many preventative strategies involve limiting these conditions.

High-risk Strategy

A high-risk population for mold exposure could be defined in two ways:

1. Exposure to environments with a high-risk factor for mold contamination, i.e. current or historical moisture intrusion issues.
2. Perceived mold exposure: either through complaints of mold odors or symptoms that suggest an exposure.¹

The strategy for preventing mold related illness in this high-risk population is through the prompt removal of moisture-affected building materials before mold growth can occur. This is often performed by a drying contractor with industrial size fans and dehumidifiers. The goal of a drying operation is to remove moisture within the 48 to 72 hour window required for mold colonization to occur.³

Population-level Strategy

A second, potentially more effective approach would be to apply a population-level strategy to preventing mold exposure is based on the principle of preventing the “cause of the cause”, preventing moisture intrusion before it occurs. Many facilities management professionals are taking this proactive approach by working with environmental consultants to develop building-specific mold operations and maintenance programs. This includes routine checks of areas prone to moisture intrusion, maintaining equipment to prevent condensation and looking for early signs of moisture issues.⁵ Preventative measures can also be implemented further upstream by considering moisture intrusion early in the building design process. Barriers isolating areas of potential moisture intrusion and sensors to detect pipe leaks are installed. All of these measures are aimed at preventing moisture damage to building materials and mold growth.

High-risk vs. Population-level Approaches

The high-risk strategy of responding to a moisture leak has the benefit of focusing efforts on the most obvious problem. However, only a qualified drying contractor will be capable of making the difficult decisions of removing materials that will not be able to dry in time. Assessing moisture intrusion in a building can be a difficult process involving inspection of inaccessible areas including test probes, borescopes and moisture meters. In many situations, by the time an environmental consultant is involved, there is already substantial mold growth. As a result the careful removal of contaminated materials must be undertaken by specialized remediation contractors. If building staff were better prepared to respond, many resources can be saved by effective drying in-house. Removing moist materials could then be performed by less costly general contractors before mold contamination has occurred.

The high-risk strategy of moisture response illustrates the prevention paradox. Focusing efforts on the most grossly contaminated areas benefits only the small number of individuals within these environments. Due to the potential for chronic exposure to slightly elevated mold and for those who are genetically pre-disposed to allergic reactions, a large number of mold related illnesses will develop amongst individuals with a lower building moisture risk factor. Therefore a greater benefit may occur from a population strategy of lowering every person’s risk factor by preventing moisture in the first place.

Conclusion

Promoting education and preventative maintenance among building management is a population strategy that will impact anyone working in a building. Added awareness and practice to reduce moisture intrusion will effectively shift the entire distribution of mold exposure. However, in the absence of regulations and building codes, much is left to the judgment of individual building managers and environmental consultants. The limitations of this strategy often arise from the inconsistent interpretation of available guidelines and a lack of knowledge among decision makers. The adoption of a federal regulations or building codes aimed at moisture prevention would help overcome this limitation. Looking upstream and redefining mold prevention in terms of moisture can create effective strategies that are clearly understood and implemented.

Acknowledgment

Supported by the Education and Research Center for Occupational Safety and Health CDC/NIOSH grant award T42/OH008416 at the Harvard School of Public Health (grantee: Kevin Banahan, 2007-2009).

References

1. Storey, E et al. Guidance for Clinicians on the Recognition and Management of Health Effects related to Mold Exposure and Moisture Indoors. University of Connecticut Health Center, Division of Occupational and Environmental Health, Center for Indoor Environments and Health. September 30, 2004.

2. Centers for Disease Control and Prevention. You can control your Asthma: A guide to understanding Asthma and its triggers. September 6, 2005. Online at www.cdc.gov/asthma/pdfs/asthma_brochure.pdf  September 21, 2007.

3. U.S. Environmental Protection Agency. Mold Remediation in Schools and Commercial Buildings. June 25, 2001. Online at http://www.epa.gov/mold/pdfs/moldremediation.pdf  September 17, 2007.

4. New York City Department of Health and Mental Hygiene. Guidelines on Assessment and Remediation of Fungi in Indoor Environments. January 2002. Online at www.ci.ny.us/html/epi/moldrpt.html September 17, 2007.

5. U.S. Environmental Protection Agency. Building Air Quality: A Guide for Building Owners and Managers. U.S. Government Printing Office. December 1991.