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6 Prevention and Remediation of Damp Indoor Environments Among the concerns that people face when dealing with indoor mois- ture problems are how to prevent microbial growth from starting and how to get rid of established growth safely and effectively. This chapter discusses prevention strategies, published guidelines for the removal of fungal growth (remediation), remediation protocols, and research on the effectiveness of various cleaning strategies. It also identifies weaknesses in the literature on remediation and offers suggestions for further research. The chapter does not offer guidance on which interventions are appropriate in which circum- stances--this is beyond the scope of the report. The chapter focuses on mold because most of the pertinent literature deals with mold. The observations offered here are also likely to be relevant to other indoor microbial exposures, but, because they have not been well studied, it is not possible to make definitive statements about them. PREVENTION The most effective way to manage mold in a building is to eliminate or limit the conditions that foster its establishment and growth. Every organ- ism has strategies for locating a hospitable environment, obtaining water and nutrients, and reproducing. Intervention in one or more of those strat- egies can improve the resistance of the environment against microbial contamination. The key to prevention in the design and operation of buildings is to limit water and nutrients. The two basic methods for accomplishing that 270

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PREVENTION AND REMEDIATION 271 are keeping moisture-sensitive materials dry and, when wetting is likely or unavoidable, using materials that offer a poor substrate for growth. Specifi- cally, design and maintenance strategies must be implemented to manage Rainwater and groundwater, preventing liquid-water entry and acci- dental humidification of buildings. The distribution, use, and disposal of drinking, process, and wash water, making equipment and associated utilities easily accessible for main- tenance and repair. Water vapor and surface temperatures to avoid accidental condensation. The wetting and drying of materials in the building and of soil in crawl spaces during construction. Existing buildings have more limited options for water and moisture control than new construction because the systems that manage drinking, process, and wash water and that control rainwater, groundwater, water vapor, and heat flow have already been selected and installed. Flawed constituents of existing systems must be repaired, replaced, or addressed through routine operations and maintenance. Operations and maintenance procedures that reduce the likelihood of mold growth include cleaning mold-resistant materials that routinely get wet in the course of ordinary operations (floors in entryways, showers, and condensate systems or cool- ing coils) and quickly drying mold-prone materials that accidentally get wet through plumbing leaks, rainwater intrusion and the like. Little scientific information on the efficacy and impact of prevention strategies is available, perhaps in part because it is easier to study problems than their absence. Moreover, little of the practical knowledge acquired and applied by design, construction, and maintenance professionals has been committed to print or subject to thorough validation; this complicates the study and dissemination of best practices. Chapters 2 and 7 address that topic and offer recommendations for research and for education of building professionals and others. PUBLISHED GUIDANCE FOR MOLD REMEDIATION Efforts to remediate microbial contamination involve direct interven- tion with building occupants, the source of the contaminant (the mold or other microbial agent), or the transport mechanism, (that is, the means by which a contaminant moves within a building environment). For example, moving people during intense remediation activities is an intervention that involves occupants, removing fungal growth and remediating the moisture problem are interventions that involve the source, depressurizing a moldy crawl space with fan-powered exhaust intervenes in the transport mecha-

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272 DAMP INDOOR SPACES AND HEALTH nism, and filtration and increased dilution ventilation intervene in contami- nant transport by lowering airborne concentrations in general. This section addresses similarities and differences in various published contamination-remediation guidelines, and the section that follows it is an extended discussion of the steps to be taken in remediation. Indoor mold has historically been treated as a nuisance contaminant. Two decades ago, there was little guidance for responding to fungal con- tamination in buildings beyond the general instruction to clean it up. That began to change as more became known about the potential hazards of mold exposures and the practice of remediation. In 1980, allergists sug- gested removing mold-contaminated materials and cleaning affected areas (Kozak et al., 1980). In the same year, the U.S. Department of Agriculture published a bulletin advising people to control dampness and to treat con- taminated materials with bleach (USDA, 1980). Four years later, Morey et al. (1984) recommended moisture control, improved filtration, and ventila- tion with outdoor air to prevent mold problems. Intervening in the mois- ture dynamic, cleaning contamination from hard-surface materials, and carefully discarding contaminated porous materials were suggested for deal- ing with existing problems. For the first time, respirators were proposed for workers performing remediation. No recommendations for containment were included. In 1989, the Bioaerosols Committee of the American Conference of Governmental Industrial Hygienists (ACGIH) released Guidelines for the Assessment of Bioaerosols in the Indoor Environment (ACGIH, 1989). Those guidelines included recommendations for the design and operation of buildings and equipment and remediation of contaminated materials. Cleaning with detergent and high-efficiency particulate air (HEPA) vacu- uming were suggested for removing biologic contamination, and cautious use of biocides was suggested for disinfection. For containment, the guide- lines recommended that air-handling equipment be turned off during reme- diation. The 1992 booklet Repairing Your Flooded Home published by the American Red Cross and the Federal Emergency Management Agency pro- vided guidance for drying, cleaning, and rebuilding a flood-damaged home but did not specifically address mold growth or exposure to dampness- related contaminants (ARC and FEMA, 1992). And in 1993, the Canadian Mortgage and Housing Corporation published a mold-cleanup guide for homeowners (CMHC, 1993). It recommended water and bleach cleanup, discarding some materials and using a hypochlorite-based sanitizer. Respi- rators and gloves were recommended during cleanup. Containment was not discussed. While the issue was receiving more attention in both the federal and private sectors, the late 1980s also saw an increase in attention from re- searchers. A 1989 study discussed containment during the remediation of

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PREVENTION AND REMEDIATION 273 fungal contamination in buildings (Light et al., 1989). Containment con- sisted of turning off heating, ventilating, and air-conditioning (HVAC) equipment, excluding occupants from the work area, and identifying criti- cal leakage sites and sealing them with plastic film. Contaminated materials were either to be cleaned with HEPA vacuuming, washed with a detergent disinfectant solution, or discarded. Worker protection was not mentioned. Criteria for assessing whether the remediation effort was successful--called "clearance" criteria in many guidance documents--were also discussed. In 1992, an American Society of Heating, Refrigerating and Air-Condi- tioning Engineers (ASHRAE) conference paper used a series of case studies to outline guidelines for occupant and worker protection during fungal remediation (Morey, 1992). These greatly increased the attention and detail devoted to this aspect of remediation. For a case with a high potential for dispersing spores, isolating work areas by using barriers over air leaks and HVAC openings was recommended, as was paying attention to possible bypass of leaks through ceiling and floor plenums (enclosed spaces in which air pressure is higher than outside). Airlocks and clean rooms were recom- mended at entries to prevent contaminant transport from the work area during entry and exit. HEPA-filtered exhaust was advised as a means to maintain the work area at a pressure 0.02 in. of water column (WC) lower than surrounding spaces. The ASHRAE paper recommended that refuse be double-bagged before removal from the work area and that HEPA vacuum- ing be used for cleaning. The adequacy of containment was to be docu- mented by monitoring air-pressure relationships and collecting bioaerosol samples from occupied spaces. Air samples were to be used to document clearance after remediation activities but before containment barriers were removed. In 1993, the New York City Department of Health (NYCDOH) con- vened a panel of experts to develop guidance for the assessment and reme- diation of Stachybotrys atra (chartarum) (NYCDOH, 1993). The resulting document included a systematic set of steps to be undertaken for investiga- tion, including evaluation of medical issues, visual inspection, sampling, and interpretation. The second half of the document provided guidance for containment, worker protection, and training requirements for abatement personnel. Four levels of contamination were described, and identifying and eliminating the moisture source supporting mold growth was required for all four levels. Level I was for areas with less than 2 ft2 of contaminated material, Level II for areas with 230 ft2, Level III for areas with over 30 ft2, and Level IV for the remediation of contaminated HVAC equipment. Lev- els I and II required respiratory protection for building-maintenance per- sonnel with very little containment or clearance testing. Levels III and IV required full containment, including air-pressure management, isolation of HVAC equipment, and dermal and respiratory protection for workers. Air

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274 DAMP INDOOR SPACES AND HEALTH sampling was required to document containment and to provide a basis for reoccupancy. Since the 1993 NYCDOH document 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 Qual- ity (Flannigan and Morey, 1996). Bioaerosols: Assessment and Control (ACGIH, 1999). Guidelines on Assessment and Remediation of Fungi in Indoor Envi- ronments (NYCDOH, 2000). Mold Remediation in Schools and Commercial Buildings (U.S. EPA, 2001). Report of the Microbial Growth Task Force (AIHA, 2001). Table 6-1 compares those guidelines with regard to how they were developed, events that would trigger a fungal assessment or remediation, assessment methods, remediation activities, and prevention actions.1 The seven documents were each developed by a group of people with identified expertise in building and engineering issues, mycology, and occu- pant health assessment. Topics are not uniformly covered by the docu- ments--for example, the ACGIH document provides extensive coverage of health effects, health assessment, and sampling, but some of the other documents do not provide information on these subjects. 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. Only the International Society of Indoor Air Quality and Climate (ISIAQ) and ACGIH guidelines discuss moisture dy- namics, identifying problematic moisture or remediating moisture prob- lems. The Environmental Protection Agency (EPA) guidelines contain spe- cific recommendations for a variety of water-damaged materials. The best way to remediate problematic mold growth is to remove it 1After this report was completed, the Institute of Inspection, Cleaning, and Restoration Certification published IICRC S520: Standard and Reference Guide for Professional Reme- diation (IICRC, 2003). This document, which was not reviewed by the committee, also ad- dresses fungal assessment and remediation, and clearance criteria.

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PREVENTION AND REMEDIATION 275 from materials that can be effectively cleaned and to discard materials that cannot be cleaned or are physically damaged beyond use. Managing mold growth in place is not considered by any of the documents. 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 pro- tection. 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. HVAC systems are special cases. But the documents disagree on how to respond to contamination in HVAC systems. The documents are divided on the use of disinfectants. Four recom- mend that disinfectants be used sparingly, in appropriate locations, for specific purposes, and with caution. The original NYCDOH guidance re- quires the use of biocides, whereas ISIAQ suggests it for hard surfaces. Only two of the documents--those of ISIAQ and ACGIH--discuss the preven- tion of mold growth in buildings to any substantial degree. The American Industrial Hygiene Association (AIHA) document differs from the others in several respects. It identifies itself as supplementary to other guidance, and it is the only document that specifically reviews other guidelines, identifying common ground, disagreements, strengths and weak- nesses in the evidence, and gaps in knowledge. It also offers recommenda- tions for best practices. The AIHA document focuses on 11 questions: 1. When should microbial growth found in occupied buildings be remediated? 2. What amounts of mold should indicate what degrees of remediation? 3. What remediation methods should be used? 4. Should biocides be used in remediation? 5. Under what circumstances should buildings be evacuated and work areas isolated? 6. How should remediation work areas be isolated? 7. How should water-damaged items be treated? 8. What quality-assurance principles should be followed to ensure that mold remediation is successful? 9. What personal protective equipment is recommended during remediation? 10. Is personal air sampling appropriate to determine worker expo- sure during mold remediation? 11. What medical evaluation is recommended for remediators?

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276 DAMP INDOOR SPACES AND HEALTH TABLE 6-1 Comparison of Seven Mold-Remediation Guidance Documents Flannigan and NYCDOH, Health Canada, Morey, 1996 1993 1995 (ISIAQ) General Guidance specific Fairly In addition to to Stachybotrys comprehensive remediation atra; earliest best- discussions with guidance, problem practice cohesive logic tree moisture sources remediation for assessment and and indoor fungal document to give remediation of ecology receive guidance on indoor microbial substantial selecting contamination treatment containment and worker protection Process Summary of Sections written by Written by recommendations members of members of Task from expert panel federal-provincial Group 1, working group after International literature review Society of Indoor Air Quality and Climate ASSESSMENT Triggering events Visible mold, Not specifically Not specifically water damage, identified but by identified, but by symptoms implication visible implication consistent with mold growth, observation of exposure accumulations of sampling that bird droppings, or confirms evidence of fungal colonization by growth from mold, mites, or sampling bacteria Health assessment Conditional; brief Conditional/ No specific discussion extensive coverage discussion of assessment included Visual inspection Required; identify Required; extensive and building extent of mold coverage history growth and water damage Intrusive Not discussed Conditional; inspection cautions on disturbance Fungal Bulk sampling to Conditional; sampling document S. atra; coverage for many air, not routinely methods unless HVAC contaminated

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PREVENTION AND REMEDIATION 277 ACGIH, 1999 NYCDOH, 2000 U.S. EPA, 2001 AIHA, 2001 Most extensive Expands original Primarily schools and Reviews existing discussions of scope from single commercial buildings; guidance, basis for health effects, species to molds in has specific section on recommendations, sampling strategies, general; provides planning remediation information gaps, and data analysis detailed guidance and specific remediation and recommenda- on assessments, methods for different tions for 11 key containment, and materials issues worker protection Written by Based on literature Prepared by Indoor Review of existing members of review and Environments Division guidance by Bioaerosols comments from of EPA; internal and Microbial Growth Committee of expert review panel external review process Task Force of ACGIH AIHA; minority report included Visible fungal Presence of mold, Not specifically Consensus of growth identified water damage, or identified, but by published guidance: in remediation musty odors implication visible visible mold growth section; other identified in mold growth and moisture sections give assessment section damage; hidden insight into medical growth may be and environmental important but may sampling not be immediately obvious Conditional; Conditional; brief Conditional; brief Not covered extensive coverage discussion reference Required; extensive Required; brief Assumed; brief Not specifically coverage discussion reference covered but implicit in many sections Brief discussion; Brief reference Discussion of hidden Includes appendix cautions on mold; caution on on making holes; disturbance disturbance cautions on spore release Conditional; Conditional; part of Conditional; part of Discusses dust extensive coverage medical evaluation, medical evaluation, sampling and cavity for many methods suspect HVAC suspect hidden mold, sampling; other contamination, litigation methods extensively suspect hidden mold discussed in AIHA, 1996 (continued on next page)

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278 DAMP INDOOR SPACES AND HEALTH TABLE 6-1 continued Flannigan and NYCDOH, Health Canada, Morey, 1996 1993 1995 (ISIAQ) Interpretation Bulk for presence Coverage for many of S. atra; air, methods differential Analysis Screen Not covered laboratories for experience with indoor environmental mycology REMEDIATION Moisture problem identify; intervene identify; intervene identify; intervene Area 1 <2 ft 2 <3.23 ft2 (0.3 m 2) <2.15 ft2 (0.2 m 2) Containment Special Clean material Carefully remove containment not before removal materials needed; bag refuse Worker Full respiratory Mask and gloves No specific protection protection; guidance 29 CFR 1910.134 Training Building Trained personnel No specific maintenance with guidance some mold- cleanup training Area 2 230 ft2 3.2332 ft2 2.132.3 ft 2 (0.33.0 m 2) (0.23.0 m 2) Containment Bag refuse; cover Clean before Bag refuse; local adjoining surfaces removal containment; with poly HEPA-filtered exhaust air Worker Full respiratory Half-face Proper respiratory protection protection; respirators and protection 29 CFR 191O.134 gloves Training Building Trained personnel Building- maintenance with maintenance some mold- personnel cleanup training

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PREVENTION AND REMEDIATION 279 ACGIH, 1999 NYCDOH, 2000 U.S. EPA, 2001 AIHA, 2001 Extensive coverage Species ID for Use trained Dust sampling and for many methods medical; differential professionals; cautions cavity sampling for hidden mold on uncertainty EMLAP accredited laboratories, interpretation by experienced professional identify; intervene identify; intervene identify; intervene identify; intervene Minimal 10 ft2 <10 ft2 Recommends: Source Vacate work area; None required, use containment based dust suppression, no professional judgment on combining special containment, innovative bag refuse, damp professional wipe area judgment with N95 mask and N95 mask, gloves, N95 mask, gloves, and areas defined by gloves and eye; eye; use professional NYCDOH (2000); 29 CFR 1910.134 judgment worker protection Building Not covered based on ACGIH maintenance with recommendations; some mold-cleanup health evaluation of training workers advised by NYCDOH (2000) recommended Moderate 1030 ft2 10100 ft 2 Local; HEPA- Vacate and cover Poly sheeting around filtered exhaust work area with poly; area; HEPA-filtered air dust suppression; exhaust air; block bag refuse; HEPA- HVAC vacuum and damp- wipe area N95 mask, full- N95 mask, gloves, N95 mask or half-face body covering and eye; HEPA coverall, eye and eye 29 CFR 1910.134 Building Not covered maintenance with some mold-cleanup training (continued on next page)

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280 DAMP INDOOR SPACES AND HEALTH TABLE 6-1 continued Flannigan and NYCDOH, Health Canada, Morey, 1996 1993 1995 (ISIAQ) Area 3 >30 ft2 >108 ft 2; area >32 ft2 between 32 and 108 ft2 does not seem to be directly addressed Containment Full; HEPA- Full; HEPA-filtered Full; HEPA- filtered exhaust exhaust air; critical filtered exhaust air; critical barriers; airlocks; air; critical barriers, airlocks; HVAC barriers; air locks; HVAC HVAC Worker Full-face HEPA, Full-face HEPA, Full-face HEPA, protection coverall, and eye coverall, and eye coverall, and eye implied but not specified Training Hazardous waste Trained personnel Hazardous waste Area 4 NA NA NA Containment Worker protection Training HVAC Containment Full; HEPA- Unclear Depends on area filtered exhaust as above air; critical barriers; airlocks; HVAC

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300 DAMP INDOOR SPACES AND HEALTH should be fixed and materials in the building should be dry, no methods for establishing whether materials are dry are offered. Remediation failures due to regrowth of mold frequently occur, and this is of particular concern and needs to be addressed in future research. Regrowth often occurs because a faulty moisture dynamic was not mended or because a damaged area was reassembled before materials were completely dry; for example, the surface of porous materials, such as wood and concrete, may be dry while the interior remains damp. "Clean" in the context of a clearance inspection means that the remed- iated area is free of residual microbial contamination. However, it is pos- sible to ascertain that only if all potentially contaminated visible and hidden spaces have been inspected. All spaces would have to be subjected to close inspection for dust, debris, fungal contamination, and dampness. Only in this unusual case could thorough examinations and measurements be easily made. The greater the chance of hidden dampness or contamination, the more difficult it is to determine whether a remediation can be defined as successful by this criterion. Even when visible contamination has been removed, air or surface measurements might detect mold or bacteria because fungal and other mi- crobial material is ubiquitous. Their presence alone thus does not indicate a contamination problem, so it is difficult to set quantitative standards for evaluating when and whether a space is clean. There is no agreement on requirements for, methods of, or interpreta- tion of microbiologic sampling for clearance purposes. One could under- take a sampling campaign after the completion of remediation identical with that before the remediation and document whether there was a decrease in microbial contamination as a result of the remediation. Such a decrease in concentrations and microbial diversity to those of a reference building has been reported in some studies (Meklin et al., 2002). How- ever, as discussed in Chapter 3, sampling may present an incomplete picture. A small number of studies report decreases in symptoms experienced by occupants after remediation of moisture damage. The Savilahti et al. (2000) and Meklin et al. (2002) studies took place in Finnish schools, and both used questionnaires before and after renovation in combination with fungal sampling. In the Meklin et al. study, a comparison was made with a control building. A third study (Jarvis and Morey, 2001) looked at a new building in a hot, humid climate. Biologic sampling and questionnaires were used before and after remediation. The study found that the occur- rence of illness was reduced after remediation was completed.

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PREVENTION AND REMEDIATION 301 Reassemble the Space to Prevent or Limit the Possibility of Recurrence by Controlling Sources of Moisture and Nutrients When portions of the building are reassembled after remediation, they must be modified so that the chance of recurring moisture damage and fungal growth is reduced. That may require Adding rainwater drainage elements. Back-venting for cladding. Elimination of intentional or unintentional water-vapor retarders. Air sealing and changes in air-handling equipment or operation to manage air-pressure relationships. Improvements in the dehumidification unit of the air-conditioning equipment. Removal of humidification equipment or controls of humidification or process-water systems. Replacement of materials that offer superior nutrient and substrate for fungal growth with materials that are resistant to microbial growth (ceramics, concrete products, stainless steel, and the like). Encapsulation of surfaces that have been dried and substantially decontaminated but cannot be completely decontaminated (for example, between floor joists and subfloors). There is very little guidance for planning, installing, and determining acceptability of the renovation in the guidance documents. The ISIAQ and ACGIH documents provide the best discussion of these issues, but they are limited in scope. EFFECTS OF AIR AND SURFACE CLEANING AND VENTILATION Ventilation, air cleaning, and surface cleaning can influence exposure. Airborne spores can be removed from a building with the out-going venti- lation airflow or trapped in a particle filter and thus removed from the air. Spores can also be removed from surfaces by washing or vacuuming. Model predictions indicate that normal variations in house ventila- tion rates when windows are closed will have only a moderate influence on indoor airborne concentrations of fungal spores 210 m in aerody- namic diameter (IOM, 2000; Chapter 10). For example, an increase of a factor of 8 in the ventilation rate from 0.25 to 2 air changes per hour would be expected to reduce airborne concentrations of 5-m-diameter spores by 60%. The decrease in concentration of 2-m spores would be larger (~70%); the decrease in 10 m spores smaller (40%). In most buildings, the practical increase in ventilation rates would be considerably

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302 DAMP INDOOR SPACES AND HEALTH smaller than a factor of eight, with correspondingly smaller decreases in airborne spore concentrations. When air enters a building through small cracks and holes, only a fraction (characterized by the penetration factor) of the particles will pen- etrate to the indoor air, and the remainder will deposit on the surfaces of the leaks. Considerable data indicate that the penetration factor for PM 2.5 (particle matter less than 2.5 m) is close to 1.0 (Thatcher et al., 2001). However, the penetration factor for particles of 210 m in air leaking into buildings is not well understood and varies with the size of holes through which the air leaks. In studies of particle penetration through simulated 0.5-mm-wide cracks, the penetration factor was less than 0.1 (Mosley et al., 2001). Particle penetration factors for the cracks in commercial windows were 0.61.0 for 5-m particles and 0.60.8 for 8-m particles (Liu and Nazaroff, 2002). Thus, the natural particle losses that occur during air infiltration provide a substantial but still uncertain amount of protection from outdoor fungal spores. Opening windows can cause large increases in ventilation rates, de- pending on the weather and how often and how long the windows remain open. That ventilation will reduce exposures to indoor-generated spores. However, large increases in indoor concentrations of spores from the out- doors may occur. The rate of flow of spore-laden outdoor air into a house will increase dramatically with open windows, and few spores will be lost by deposition on surfaces (such as window sills) as the air passes through a window. Predicted reductions in indoor airborne concentrations of spore-size particles by filtering were discussed in the 2000 Institute of Medicine report Clearing the Air. Reductions in spore concentrations by recirculation of air through filters in household furnace and air-conditioning systems--includ- ing filters with a much better efficiency than the common see-through furnace filter--will normally be less than 50% for 5-m-diameter spores. Portable fan filter units can reduce spore concentrations more, but only with high rates of airflow through the filtration unit (10 room volumes per hour). Few measurement data are available for evaluating those model predictions. It seems likely, however, that normal variations in ventilation rates and filtration in buildings with closed windows will have a moderate effect on inhalation exposure to mold spores. Surface cleaning, such as vacuuming, can remove spores, potentially preventing their resuspension and inhalation and reducing the probability of exposure dermal contact and incidental ingestion. A number of studies have been performed on surface cleaning to evaluate the reduction in total dust or lead on surfaces, fewer on the removal of dust-mite allergens, and fewer still on the removal of fungal matter. However, some data imply, but do not clearly demonstrate, that improved surface cleaning could reduce exposure to

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PREVENTION AND REMEDIATION 303 fungi. Cole et al. (1996) found that concentrations of fungi and bacteria in air correlate with concentrations of fungi and bacteria on indoor nonfloor sur- faces (r = 0.6 for fungi) and correlate with concentrations on floor surfaces (no statistic provided). Intervention studies have demonstrated that improved surface cleaning can reduce the loading of uncharacterized dust, lead, and mite allergen on surfaces. Reductions of 8090% in dust, lead, and mite allergen on surfaces were achieved by Roberts et al. (1999) after vacuuming carpets for 645 min/m2 of carpet surface. Kildes et al. (1998) compared nine cleaning practices and found that the quantity of dust remaining on floor surfaces where people walked varied by a factor of 2. In a cross-sectional study of schools that improved cleaning practices for floors, classrooms cleaned primarily with wet mopping had more airborne viable bacteria but less settled dust than classrooms cleaned primarily with dry methods (Smedje and Norbck, 2001). Franke et al. (1994) reported a substantial reduction in fungal spores on surfaces after a period of deep cleaning; however, the reduc- tion was temporary, and the benefits of the cleaning were not easily distin- guishable from natural variation. A few studies have also found that surface cleaning practices or fre- quency can influence airborne concentrations of particles or microorgan- isms. In a conference paper, Skyberg et al. (1999) described a study com- paring 49 offices that received improved cleaning with 55 control offices that received superficial cleaning. The concentration of inhalable dust de- creased by about one-third in the intervention offices and increased slightly in control offices (significance level not reported). In another conference paper, White and Dingle (2002) found that airborne PM 2.5 and PM 10 concentrations were decreased by about 50% (p < 0.01) after 14 weeks of intensive5 vacuum cleaning of 19 houses, but airborne particle concentra- tions were not significantly changed in 17 control houses. Kemp et al. (1998) reported an 85% reduction (p < 0.04) in respirable suspended par- ticles on two floors of an office building after improved surface cleaning (9% reduction on control floors) but initial particle concentrations were unusually high. In a cross-sectional study of classrooms, Smedje and Norbck (2001) found that cleaning practices were associated with concen- trations of airborne viable bacteria (p = 0.013 in a multivariate regression); however, no association of cleaning practices with airborne fungal concen- trations was reported. Finally, a few studies (Kemp et al., 1998; Skyberg et al., 1999; Wlinder et al., 1999) have reported significant improvements in subjective or objec- tive health measures with improved surface cleaning or lower concentra- 5Carpets were cleaned every 2 weeks for 4 min/m2 in the first cleaning, 2 min/m2 in the second cleaning, and 1 min/m2 in five additional cleanings. Upholstered sofas and beds were cleaned every 2 weeks for 1 min/m2.

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304 DAMP INDOOR SPACES AND HEALTH tions of dust on surfaces, which is indirect evidence of reductions in expo- sure to unidentified agents. In summary, the normal variations in ventilation rates, air-filtration rates, and surface-cleaning practices of homes may under some circum- stances substantially affect exposure to fungal spores and other dampness- related microbial bioaerosols. Improved surface cleaning appears to have the largest and most practical potential for bringing about large reduc- tions in exposure; however, further research is needed to characterize its effectiveness. FINDINGS, RECOMMENDATIONS, AND RESEARCH NEEDS On the basis of its review of the papers, reports, and other information presented in this chapter, the committee has reached the following findings and recommendations and has identified the following research needs re- garding the prevention of moisture problems and the remediation of build- ings that have water damage or microbial contamination. Findings The most effective way to manage a biological agent, such as mold, in a building is to eliminate or limit the conditions that foster its establish- ment and growth. There are several sources of guidance on how to respond to various indoor microbial contamination situations. However, determining when a remediation effort is warranted or when it is successful is necessarily subjec- tive because there are no generally accepted health-based standards for acceptable concentrations of fungal spores, hyphae, or metabolites in the air or on surfaces. Remediation must identify and eliminate the underlying cause of dampness or water accumulation. If the underlying causes are not ad- dressed, contamination may recur. Valuable information can be acquired from architects, builders, oc- cupants, and maintenance staffs regarding health complaints, the use his- tory of the building, moisture events, and locations of problems. Both expert assessment of the building's condition and knowledge of its history and current problems are needed to make a thorough evaluation of poten- tial dampness-related exposures and an effective plan for remediation. Fungal and other microbial material is present on nearly all indoor surfaces. There is a great deal of uncertainty and variability in samples taken from indoor air and surfaces, and it may be difficult to discern which organisms are part of the natural background and which are the result of problematic contamination. However, the information gained from a care-

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PREVENTION AND REMEDIATION 305 ful and complete survey may aid in the evaluation of contamination sources and remediation needs. The potential for exposure to microbial contaminants in spaces such as attics, crawl spaces, exterior sheathing, and garages is poorly under- stood. Disturbance of contaminated material during remediation activities can release microbial particles and result in contamination of clean areas and exposure of occupants and remediation workers. Containment has been shown to prevent the spread of molds, bacte- ria, and related microbial particles to noncontaminated parts of a contami- nated building. The amount of containment and worker personal protec- tion and the determination of whether occupant evacuation is appropriate depend on the magnitude of contamination. Very few controlled studies have been conducted on the effectiveness of remediation actions in eliminating problematic microbial contamination in the short and long term and on the effect of remediation actions on the health of building occupants. Available literature addresses the management of microbial con- tamination when remediation is technically and economically feasible. There is no literature addressing situations where intervening in the moisture dynamic or cleaning or removing contaminated materials is not practicable. Recommendations Homes and other buildings should be designed, operated, and main- tained to prevent water intrusion and excessive moisture accumulation when possible. When water intrusion or moisture accumulation is discov- ered, the sources should be identified and eliminated as soon as practicable to reduce the possibility of problematic microbial growth and building- material degradation. When microbial contamination is found, it should be eliminated by means that limit the possibility of recurrence and limit exposure of occu- pants and persons conducting the remediation. Research Needs Research is needed to characterize -- The effectiveness of remediation assessment and remediation meth- ods in different contamination circumstances. -- The dynamics of movements of contaminants from colonies of mold and other microorganisms in spaces such as attics, crawl spaces, exterior sheathing, and garages.

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306 DAMP INDOOR SPACES AND HEALTH -- The effectiveness of various means of protection of workers and occupants during remediation activities Research should be performed to develop -- Methods for finding microbial contamination in HVAC systems, and in crawl spaces, attics, wall cavities, and other hidden or seldom- accessed areas. -- Building materials that, when moist, are less prone to microbial contamination. -- Standard methods of assessing the potential of new materials, designs, and construction practices for dampness problems. -- Standardized, effective protocols for cleaning up after flood- ing and other catastrophic water events that will minimize microbial growth. -- Methods that can distinguish between naturally-deposited spores and active microbial growth in wall cavities. Research should be performed to determine -- How free of microbial contamination a surface or building mate- rial must be to eliminate problematic exposure of occupants (in particular, how concentrations of microbial contamination left after remediation are related to those found on ordinary surfaces and materials in buildings where no problematic contamination is present). -- Whether and when microbial contamination that is not visible to the naked eye but is detectable through screening methods should be remediated. -- The risk of microbial contamination in the building but outside the general air circulation of the building--in crawl spaces, attics, wall cavities, building sheathing, and the like. -- The effectiveness of managing contamination in place by using negative air pressure, encapsulation, and other means of isolation. -- The best ways to address microbial contamination in situations where remediation is not technically or economically feasible. -- The best ways to open a wall or other building cavity to seek hidden contamination while controlling the release of spores, microbial fragments, and the like. -- How to measure the effectiveness and health effects of a remedia- tion effort. REFERENCES ACGIH (American Conference of Governmental Industrial Hygienists). 1989. Guidelines for the Assessment of Bioaerosols in the Indoor Environment. Cincinnati, OH. ACGIH. 1999. Bioaerosols--Assessment and Control. Cincinnati, OH.

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