United States Government Accountability Office
INDOOR MOLD: Better Coordination of Research on Health Effects and More Consistent Guidance Would Improve Federal Efforts

September 2008

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Results in Brief:

In general, the Institute of Medicine’s 2004 comprehensive report, as well as reviews of the scientific literature published from 2005 to 2007 that we examined, concluded that certain adverse health effects are more clearly associated with exposure to indoor mold than others. For example, the Institute of Medicine’s report said that certain respiratory effects, such as nasal congestion and the exacerbation of pre-existing asthma, are associated with exposure to indoor mold but that the available evidence was not sufficient to determine whether associations exist between mold and a variety of other health effects, such as the development of asthma, rheumatologic and other immune diseases, cancer, acute pulmonary hemorrhage in infants, and reproductive effects. While the more recent scientific reviews we examined generally concurred with these conclusions, a few of the reviews judged the available evidence for some of these health effects to be somewhat stronger. For example, the American Academy of Pediatrics concluded in 2006 that a plausible link exists between acute pulmonary hemorrhage in infants and exposure to certain toxins that some molds produce. Conclusively associating exposure to mold with certain health effects is challenging, according to the Institute of Medicine’s 2004 report, because available studies have been of insufficient quality, consistency, or rigor. Two key research issues contribute to this difficulty: (1) the lack of standardized, quantitative methods of measuring exposure to mold and (2) the difficulty in determining which of several disease-causing agents in damp indoor environments may be responsible for the adverse health effects. In this regard, the 2000 and 2004 Institute of Medicine reports and the more recent reviews we examined identified the need for additional research to address these and other uncertainties related to the connection between exposure to indoor mold and adverse health effects. For example, the 2004 Institute of Medicine report concluded that there is a need for research to determine the health effects of long-term exposure to the toxins that some molds can produce.

The 65 ongoing federal research activities on the health effects of exposure to indoor mold conducted or sponsored by EPA, HHS, and HUD address to varying extents 15 gaps in scientific data reported by the Institute of Medicine. These gaps relate to the need to better define any association between a wide range of specific potential adverse health effects and exposure to indoor mold. Of the 65 research activities, nearly 60 percent address asthma, and more than half address measurement methods—that is, sampling and exposure assessment methods for indoor mold. Some other important data gaps are being minimally addressed. For example, 5 of the 65 research activities examine the effects of human exposure to molds that produce toxins that may cause a number of adverse health effects, and only 1 relates to acute pulmonary hemorrhage in infants—a rare but life-threatening condition that may be caused by exposure to mold. Further, identifying and coordinating research priorities, and efforts to achieve them, are particularly important given the wide range of research needs identified by the Institute of Medicine reports, the number of federal entities involved in conducting research on mold, and limited federal resources. However, federal officials reported that fewer than half of their ongoing research activities have involved coordination either with other units in their agencies or other federal agencies. For example, of the 36 ongoing research activities related to sampling and measurement methods, only 14 are being coordinated to some extent. Further, in many cases, research activities were only coordinated within the agency conducting or sponsoring the research. Moreover, although the Federal Interagency Committee on Indoor Air Quality could provide a structured mechanism for coordinating research activities, it does not serve this function. That is, instead of selecting specific topics and tasks to advance scientific knowledge in the area of indoor air quality—such as reviewing and prioritizing agencies’ ongoing and planned research in particular areas—the agendas for the committee meetings are largely driven by the interests of the agencies’ individual committee representatives.

Despite the limitations of current scientific evidence in establishing clear associations and causal linkages between a number of adverse health effects and exposure to indoor mold, enough is known that federal agencies have issued guidance to the general public about health risks associated with exposure to indoor mold, how to minimize mold growth, and how to mitigate exposure. For example, a majority of the 32 guidance documents we reviewed issued by the Consumer Product Safety Commission, EPA, FEMA, HHS, and HUD describe some common adverse health effects, such as asthma attacks and upper respiratory tract symptoms. However, the guidance documents inconsistently identify some other health effects that may be less common. For example, only 6 of the 32 documents warn that exposure to mold can lead to hypersensitivity pneumonitis, a relatively rare but potentially serious allergic reaction. In addition, most of the guidance documents offer consistent strategies for minimizing the growth of indoor mold—for example, keeping areas dry and promptly addressing moisture sources, such as leaks or spills. Finally, a majority of the documents also address mitigating exposure to indoor mold, including directions for cleaning up mold and protective clothing and equipment to wear while doing so. However, the guidance is somewhat inconsistent about which cleaning agents to use—for example, some documents recommend using bleach, a biocide that is toxic to humans, if the mold growth is due to floodwater; some recommend bleach regardless of the cause of the mold; and others recommend using detergent. Finally, most of the documents warn that certain populations may be more sensitive to mold than others, but only two provide specific recommendations about the varying levels of protective clothing and equipment (such as gloves, respirators, and eye and skin protection) that such populations should use under various circumstances. As a result of some of these omissions and inconsistencies, the public may be at risk of unnecessary exposure to indoor mold.

To better ensure that federal research on the health effects of exposure to indoor mold is effectively addressing research needs and efficiently using scarce federal resources, we are recommending that EPA use the Federal Interagency Committee on Indoor Air Quality to both (1) help guide federal research priorities on the health effects of indoor mold and coordinate information sharing on this topic and (2) help agencies better ensure that their guidance to the public provides sufficient information on health effects of exposure to indoor mold, and how to minimize it, and does not conflict among agencies. We provided a draft of this report to the Consumer Product Safety Commission, EPA, FEMA, HHS, and HUD for the agencies’ review and comment. EPA generally agreed with our recommendations regarding its use of the Federal Interagency Committee on Indoor Air Quality. With the exception of FEMA, the agencies also provided technical comments that we incorporated into the report, as appropriate.

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All Survey Results of Research on the Health Effects of Exposure to Indoor Mold - Recently Completed Research

Recently Completed Research on the Health Effects of Exposure to Indoor Mold by Government Agencies