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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- stancesâthis 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
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 â¢ Rainwater and groundwater, preventing liquid-water entry and acci- dental humidification of buildings. â¢ The distribution, use, and disposal of drinking, process, and wash water, making equipment and associated utilities easily accessible for main- tenance and repair. â¢ Water vapor and surface temperatures to avoid accidental condensation. â¢ 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-
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
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 detergentâ disinfectant solution, or discarded. Worker protection was not mentioned. Criteria for assessing whether the remediation effort was successfulâcalled âclearanceâ criteria in many guidance documentsâwere 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 2â30 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
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 â¢ Fungal Contamination in Buildings: A Guide to Recognition and Management (Health Canada, 1995). â¢ Control of Moisture Problems Affecting Biological Indoor Air Qual- ity (Flannigan and Morey, 1996). â¢ Bioaerosols: Assessment and Control (ACGIH, 1999). â¢ Guidelines on Assessment and Remediation of Fungi in Indoor Envi- ronments (NYCDOH, 2000). â¢ Mold Remediation in Schools and Commercial Buildings (U.S. EPA, 2001). â¢ 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- mentsâfor 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 â¢ Mold should not be allowed to colonize materials and furnishings in buildings. â¢ 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. â¢ 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.
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. â¢ 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. â¢ 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 documentsâthose of ISIAQ and ACGIHâdiscuss 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?
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
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)
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 2â30 ft2 3.23â32 ft2 2.1â32.3 ft 2 (0.3â3.0 m 2) (0.2â3.0 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
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 â¤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 10â30 ft2 10â100 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)
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
PREVENTION AND REMEDIATION 281 ACGIH, 1999 NYCDOH, 2000 U.S. EPA, 2001 AIHA, 2001 Extensive; 30â100 ft 2 >100 ft2 references NYCDOH, 1993 and Flannigan and Morey, 1996; does not define areas Full; HEPA- Vacate work and Full; HEPA-filtered filtered exhaust adjacent areas; cover exhaust air; critical air; critical work area and barriers; air locks; barriers; HVAC directly adjacent HVAC areas with poly; seal HVAC openings; bag refuse; dust suppression; HEPA- vacuum and damp- wipe area; upgrade to next level of protection if dust will be raised N95 mask, N95 mask, gloves, Full-face HEPA, coverall, and eye; coverall, and eye and eye 29 CFR 1910.134 Hazardous waste Hazardous waste NA >100 ft2 NA Oversight by health and safety professional; vacate work area; full containment; HEPA- filtered exhaust air; critical barriers; airlocks; HVAC Full-face HEPA, coverall, and eye Hazardous waste Depends on area <10 ft same as Area Refers to EPA as above; specific 2; >10 ft2 same as document Should You guidance for Area 4 Have the Air Ducts in cooling towers Your Home Cleaned? included (continued on next page)
282 DAMP INDOOR SPACES AND HEALTH TABLE 6-1 continued Flannigan and NYCDOH, Health Canada, Morey, 1996 1993 1995 (ISIAQ) Worker Full-face HEPA, Unclear Depends on area protection coverall, and eye as above Training Hazardous waste Unclear Depends on area as above Remediating Not directly HEPA-vacuum; HEPA-vacuum; hard surfaces discussed damp-wipe damp-wipe; and semiporous disinfect Remediating Discard Discard Discard porous contaminated materials absorbent materials Biocide use Required use of Discouraged or Suggested for bleach to clean conditional; use hard surfaces areas adjacent to charcoal filters in contaminated respirators areas; cautions on use of chlorine dioxide or ozone in HVAC systems Clearance Air monitoring Not specifically Surfaces cleaned for >30 ft2 and covered; everything until only HVAC must be cleaned background fungi and bacteria remain; materials dry
PREVENTION AND REMEDIATION 283 ACGIH, 1999 NYCDOH, 2000 U.S. EPA, 2001 AIHA, 2001 Depends on area <10 ft2 same as Area as above 2; >10 ft2 same as Area 4 Depends on area <10 ft2 same as Area as above; refers 2; >10 ft2 same as to NADCA and Area 4 EPA;cautions against biocide use Clean; discard if Damp-wipe with Specific guidance for HEPA-vacuum, physically detergent solution different materials: damp-wipe, or damaged wet-vacuuming, scrub as needed; damp-wiping, discard damaged HEPA-vacuuming materials or discarding Discard Discard with See above Discard contaminated exceptions material; wash or HEPA-vacuum materials that may harbor spores Comprehensive Refers to ACGIH, Discussion; discouraged Discouraged or use discussion; 1999; recommends or use with caution with caution discouraged or detergent solutions; use with caution prohibits gaseous ozone and chlorine dioxide Visual; possible All areas left dry Judgment call; water Recommends sampling and visibly free of source fixed; dry and documenting contamination and free of visible mold; successful debris; air monitor- reoccupying produces intervention in ing for areas no complaints; if air moisture source, >100 ft2 samples have been containment, taken, differential cleaning, removal, interpretation completeness, final surface dusting, and use of HEPA vacuum (continued on next page)
284 DAMP INDOOR SPACES AND HEALTH TABLE 6-1 continued Flannigan and NYCDOH, Health Canada, Morey, 1996 1993 1995 (ISIAQ) PREVENTION Moisture Not covered Brief discussion Substantial control discussion by moisture source, climate type, envelope, and HVAC Materials in Not covered Not covered Limit nutrients; wet spaces avoid porous materials; some consideration of biostats Operation Not covered Brief discussion Incorporated in and moisture control maintenance (O&M) NOTES: â¢ ID: identify. â¢ 29 CFR 1910.134 denotes the Occupational Health and Safety Administration (OSHA) respiratory protection standard. A minority report in the AIHA document raises concerns about treating all molds as hazardous substances and the consequent recommendations for decontamination, worker protection, containment, and disposal. An extensive review of the literature regarding investigation, building ecology, and, to some extent, remediation is contained in a 2002 doctoral dissertation titled Characterizing Moisture Damaged BuildingsâEnviron- mental and Biological Monitoring (HyvÃ¤rinen, 2002). 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:
PREVENTION AND REMEDIATION 285 ACGIH, 1999 NYCDOH, 2000 U.S. EPA, 2001 AIHA, 2001 General discussion Not covered Checklist of moisture- Not covered of moisture control items dynamics; humidity control Brief discussion Not covered Not covered Not covered of nutrient and material issues Discusses Not covered Checklist of operation Not covered ventilation, and maintenance items filtration, monitoring moisture events, and cleaning â¢ N95 class masks meet the National Institute for Occupational Safety and Health (NIOSH) standards for respiratory protective devices specified in 42 CFR Part 84. â¢ Take emergency actions to stop water intrusion if needed. â¢ Identify vulnerable populations, extent of contamination, and mois- ture dynamic. â¢ Plan and implement remediation activities. â Establish appropriate containment and worker and occupant protection. â Eliminate or limit moisture sources and dry the materials. â Decontaminate or remove damaged materials as appropriate. â Evaluate whether space has been successfully remediated. â 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.
286 DAMP INDOOR SPACES AND HEALTH Maintenance workers may find a broken pipe flooding the building and turn off the water main. A firm that specializes in water-damage emer- gency response may pump the basement and dehumidify the building with specialized drying equipment. A remediation-assessment consultant may determine whether fungal growth has occurred and what actions are re- quired. Remediation contractors may set up the appropriate containment, remove some contaminated materials, and clean up materials that can be salvaged. A remodeling contractor may reconstruct damaged areas, and yet another contractor may repair the broken pipe that started the prob- lem. The remediation-assessment consultant may provide quality assur- ance while work is being carried out and determine whether clearance criteria have been satisfied. 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. Take Emergency Actions to Stop Water Intrusion If Needed 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 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 (Doll, 2002; Horner et al., 2001). Dollâs work indicates that com- mon 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 (22â60 days); if they are wetted with liquid water, germination can occur in less than 5 days. Interventions in continuing wetting and in drying a building out must be informed by the nature of the water source and the nature of the wet materials (IICRC, 1999). 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) (IICRC, 1999). Quick and effective response to water intrusion can prevent or greatly reduce fungal growth and occupant exposures to bioaerosols, further dis- ruption to building operations, and future needs for fungal remediation.
PREVENTION AND REMEDIATION 287 Identify the Vulnerable Populations, Extent of Contamination, and Moisture Dynamic The purpose of an assessment is to collect the information needed to respond appropriately to a contamination problem. People who are par- ticularly vulnerable to dampness-related exposures should be identified, and the location and extent of contamination must be inventoried. Sources of moisture and nutrient supporting the growth must be identified. Collect Histories of Building and Occupants As noted in Chapter 2, the people who design, construct, maintain, and occupy a building are a valuable source of information concerning occu- pant health, building history, microclimates that might support fungal growth, exposure mechanisms, and other essential information that helps to form an overview of the situation of the building and the occupants. Collecting histories can provide a wealth of information that may be in- valuable when planning a building remediation. The process can also help identify whether some occupants are particularly sensitive to fungal expo- suresâpeople with known mold allergies, asthma, and the likeâand thus require extra protection during investigations and remediations. Interviews, questionnaires, and contact with personal physicians (when authorized by the subjects) are some approaches to collecting such information. Some standardized questionnaires have been developed, including the MM-040- EA Indoor Climate Work Environment questionnaire (Andersson, 1998) and the Stockholm Indoor Environment Questionnaire (Engvall et al., 2004). Some of the guidance documents recommend removing people who are more sensitive to fungal contaminants from buildings during remediation activities. Building occupants who are exhibiting symptoms, have identified illness associated with fungal exposures, or have compromised immune systems may be at greater risk than the general population. The AIHA Task Force (2001) identified NYCDOH (2000) as providing a basis for making decisions regarding evacuation and containment. Occupants may also provide clues regarding the location of mold growth. Musty odors are sometimes reported, and their timing may be predictable or erratic. Odors, for example, might occur only in an entryway during periods of heavy rain, or respiratory problems may be more frequent in an area served by a particular air handler. Someone may recall that the lower floor floods during heavy rainstorms. A member of the buildings and grounds staff may know that there is an undocumented crawl space be- neath the basement, that roof drains run inside wall cavities, or that the enthalpy-control system has been disabled for 5 years. Photographs of a
288 DAMP INDOOR SPACES AND HEALTH house under construction may show details of foundation drainage or de- fects in rainwater control. Failing to take advantage of the information available from architects, builders, occupants, and maintenance staffs may lead to an incomplete and ineffective remediation plan. Ascertain Extent and Location of Fungal Contamination Microbial contamination may consist of active growth, relic colonies that have run out of moisture or nutrients, or remnants of growth that have accumulated with other dust particles beneath furniture or in corners, cush- ions, or carpets. Spores and hyphal fragments deposited on hard surfaces or contained in porous materialsâsuch as textiles, cushions, and fibrous insu- lationâmay have originated indoors or been transported from outside. Spores are known to spread from one portion of a building to another (Morey, 1993), to be transported inside on peopleâs clothing (Pasanen et al., 1989), and to enter with accidental or intentional ventilating air. A thorough inspection of the building is required. Because mold problems are also moisture problems, understanding how water behaves in buildings is a valuable component of the inspection. Some remediation-guidance documents base worker protection and containment recommendations on the area of visible mold growth (Flannigan and Morey, 1996; Health Canada, 1995; NYCDOH, 1993, 2000). The ACGIH guidance divides remediation into three levels of effort distinguished by worker protection and containment but does not relate them to specific areas of contamination. Instead, it urges the use of profes- sional judgment to determine which situations require what precautions. For remediation activities to comply with the guidance in the other docu- ments, the area of visible mold must be identified. However, it must be remembered that although some contamination is readily apparent, other contamination may be hidden behind furnishings or wallpaper, in acces- sible cavities, or in spaces with no ready access. To find fungal growth in a building, one must look for places that have both water and nutrients. Often, these are places that are likely to get wet and to take a long time to dry. Chapter 2 addresses the most common moisture dynamics. Several signs of water problems must be evaluatedâ not just mold, but also peeling paint, efflorescence, wet spots, wrinkled wallpaper, cracks in plaster, and warped wood. Rooms that are unavoid- ably wetâsuch as bathrooms, kitchens, spas, and pool roomsâare the most common places to find visible mold growth. Rainwater penetration, plumbing leaks, and condensation are common moisture sources for hidden locations. Exterior walls and walls below roof penetrations are generally the most vulnerable to such sources. Oriented
PREVENTION AND REMEDIATION 289 strand board (OSB), the backside of paper-covered gypsum board, and the topside of cellulose ceiling tile are also at risk (Doll, 2002). Often, growth is in spaces such as attics, crawl spaces, basements, and garages. Those largely unoccupied rooms are frequent sites of condensation and rainwater or plumbing leaks. The relative importance of microbial contamination in such spaces to overall exposures has not been extensively studied; available case studies (Miller et al, 2000; Pessi et al., 2002) yield inconsistent results. As a rule of thumb, microbial contamination is most likely to be found by â¢ Examining attics, foundations, penetrations through walls and roofs, and exterior drainage detailing. â¢ Tracing water lines. â¢ Examining surfaces chilled by mechanical equipment or by contact with the earth (air-conditioning ducts and coils, chilled water lines, outdoor air ducts, and basements and crawl spaces). Thorough examination can uncover mold hidden in closets, in cabinets, beneath wallpaper, under furniture, and beneath carpets. Cavities above suspended ceilings can be inspected by removing ceiling tile (unless the tile is fastened with clips as part of the fire-protection detailing). Often, access openings permit inspection of plumbing for bathtubs, utility trenches, crawl spaces, basements, and attics. However, a great deal of fungal growth in a building may be in cavities that are not open to inspection. Some organisms may cover an exposed surface with a light, nonpigmented growth (Horner et al., 2001; Miller et al., 2000). A number of methods can be used to augment the ability to find hidden mold, for example, moisture meters, bulk or surface samples to identify organisms that are contaminating materials, and air samples of rooms, cavities, and outdoor air to identify fungal spores. Moisture meters are useful in finding hidden damp spots and tracing leak pathways. They provide instant results that can guide an ongoing inspection. However, if a water source is intermittentâlike a rainwater leakâa hidden growth site may be dry at the time of inspection. Moisture meters may also report a saturated condition where no moisture is present, if metal is part of the assembly. They must thus be used with care. Meters that use pins or electromagnetic fields (EMFs) to penetrate materials are available. Models with pins need holes in the test material to make mea- surements, but EMF-based meters are nonintrusive. Insulated pins allow assessment to specific depths. EMF models reflect moisture content in a depth range that varies from a half-inch to a few inches. Hand lenses and microscopes can be used in buildings, and samples can
290 DAMP INDOOR SPACES AND HEALTH be sent to a mycologist for analysis to determine the presence of mold on a surface (Horner et al., 2001; Miller et al., 2000). Microscopic examination of surfaces, dust samples, and tape lifts can identify hyphae, sporangia (spore cases), and spores. In the field, a stand microscope with magnifica- tions of 20â200 can be used to examine surfaces in situ. Clear plastic tape can be used to collect samples from suspect surfaces (Swenson et al., 2003). The tape can be mounted on a slide and examined either in the field or in a laboratory to determine whether the surface is supporting or is contami- nated with fungal growth. Other means of estimating the amount of fungal material on a surface in the field include chemiluminescence analysis to detect microbial enzymes (Bjurman, 1999), and measurement of mold bio- mass parameters such as ergosterol content or Î²-N-acetylhexosaminidase activity (Reeslev et al., 2003). Fungal growth hidden in wall or ceiling cavities can be observed di- rectly by making inspection openings or inferred from bioaerosol measure- ments (ACGIH, 1999; AIHA, 1996; Miller et al., 2000). It is desirable to inspect the inside of cavities directly (Miller et al., 2000) and to use tape-lift or chemiluminescence methods to assess the surface. But there are also drawbacks to making inspection openings. To be certain of detecting fungal growth in ceiling and wall cavities, one has to make several holes in the large surfaces that enclose these spaces. Making openings in walls or ceil- ings requires repair of materials or installation of permanent inspection ports and may release dust or fungal material into the indoor air or make a more intimate connection between the indoor air and a large fungal mass. Although larger openings allow for more extensive inspection of a cavity, making them may release more fungal spores and construction dust than making smaller ones. Methods that reduce or confine the release of particles and facilitate immediate repair if extensive fungal contamination is revealed are preferable in opening cavities. For example, hole saws with dust-collecting shrouds can contain the dust released while a hole is being made and do not produce potentially aerosolizing vibrations as great as those made by reciprocating saws. Glove bags and temporary containments can provide more protection. To reduce the necessity for large openings and to limit the release of fungal spores, inspectors have developed several methods to detect fungal growth and to predict where it is most likely to occur. As already noted, wall or ceiling cavities that have visible signs of moisture damage, produce increased moisture-meter readings, or yield positive moisture-assessment test results are areas where inspectors will concentrate their efforts. Likely spots for cavity troubles include finished basement walls, plumbing walls behind and floor cavities beneath bathtubs and showers, and exterior walls that have a combination of masonry cladding, interior vapor retarders, and air-conditioning.
PREVENTION AND REMEDIATION 291 Boroscopes2 are sometimes used to reduce the number of particles released in the making of an opening and to decrease the damage to sur- faces around wall or ceiling cavities. The opening, measuring only a frac- tion of an inch, releases only a small number of particles and is easily repaired. However, a boroscope does not offer a full view of the cavity and makes it difficult to conduct a thorough inspection (Miller et al., 2000). Air samples can be drawn from wall or ceiling cavities through small openings and particles can be collected in spore traps or on culture media. For accurate analysis of spore traps or cultures, the investigator must use a microscope at the site or send samples to a laboratory. It is possible to draw air samples from wall cavities by accessing a cover plate for electric outlets, thereby obviating additional openings. The committee did not identify any research that established guidelines for interpreting bioaerosol samples drawn from cavities. Spore-trap or culturable samples taken from indoor and outdoor air can be used to infer the presence of hidden mold. Interpretation of the data is simple in principle: examine the indoor relative to outdoor results. Rela- tively high indoor concentrations are evidenceâbut not proofâthat micro- bial growth is occurring indoors. Organisms that appear indoors and are not likely to have entered with outdoor air are also evidence of an indoor source (ACGIH, 1999). In practice, spatial and temporal variability in spore concentrations (ACGIH, 1999), spores from settled dust disturbed by investigators (AEC, 2002), and inherent limitations of sampling methods introduce important uncertainties. Spore traps have the advantage of iden- tifying organisms that do not compete well in culture or are not viable, but they do not allow speciation of such important genera as Penicillium and Aspergillus. Speciation is essential in determining whether spores in out- door air are a likely source of spores found in indoor air. Culturable samples can be used to identify to the species level, but species that compete poorly may be missed. A number of studies have compared indoor spore concentrations in buildings or rooms that have visible mold growth with those in buildings or rooms that do not have visible growth. The studies are far from conclusive. Several reported that buildings or rooms with visible fungal growth had higher spore concentrations than control buildings or rooms (Dharmage et al., 1999; Hunter et al., 1988; HyvÃ¤rinen et al., 1993, 2001a,b; Johanning et al., 1999; KlÃ¡novÃ¡, 2000; Lawton et al., 1998). However, other investi- 2The boroscope is an instrument specifically designed to be inserted in wall cavities, duct- ing, and other otherwise inaccessible areas. It typically comprises a long thin rod with a light source at the tip and optics to direct and magnify the image.
292 DAMP INDOOR SPACES AND HEALTH gators found no differences between airborne spore concentrations (Dill and Niggeman, 1996; Garrett et al., 1998; Nevalainen et al., 1991; Pasanen et al., 1992; Strachen et al., 1990). A few studies have sought to identify a relationship between fungal growth hidden in cavities and indoor bioaerosol samples. Miller et al. (2000) conducted a series of experiments to assess the extent of fungal colonization of wall cavities in 58 apartments that had suffered some water damage but had little visible mold on interior surfaces (some apartments were reported to have light mold growth in bathrooms and behind refrig- erators). Air samples were taken in the center of living areas and bedrooms (four, six, or eight times depending on size of apartment). The bottom 30 cm of gypsum board was removed from the walls, the exposed wall cavities were examined, and the location and extent of observable, previously hid- den mold were mapped. Samples of gypsum board were collected from areas that had visible mold and from contiguous areas (within 50 cm) that did not. A relationship was found between the area of fungal growth un- covered and the percentage of indoor air samples that yielded measure- ments significantly different from outdoor-air measurements. That led the authors to conclude that indoor-air sampling was potentially useful for identifying spaces where more intrusive testing (such as opening walls) to find mold infestations might be appropriate. Morey et al. (2002) studied two buildings that had extensive fungal growth in the envelope. Air sam- pling found many spores from the organism that was contaminating the shell in one of the buildings; in the other, air samples yielded no evidence of hidden fungi in the building. Pessi et al. (2002) compared indoor air-con- centrations of actinomycetes, other bacteria, and fungi with concentrations of these contaminants in the insulation layer of an adjoining wall. The study was conducted in 50 apartment buildings in a subarctic climate. Actinomycete-contaminated insulation was associated with increased in- door-air concentrations of actinomycetes, and the moisture content of the indoor air significantly affected all measurable airborne concentrations. The authors noted that the relationship for fungi might be an artifact of the climate. Disturbed spores may be released into the air in large numbers during inspection activities, exposing inspectors and others present to microbial materials. Little research was found on spore concentrations resulting from inspection activities. One study did report increased spore concentrations resulting from walking or vacuuming a carpet contaminated with Penicil- lium chrysogenum spores (Buttner and Stetzenbach, 1993). Activity raised spore concentrations by an order of magnitude.
PREVENTION AND REMEDIATION 293 Identify Moisture Dynamic To ensure that a fungal problem will not recur after remediation, the moisture source supporting the growth must be identified, and an interven- tion in the moisture dynamic must be made. Floods are the easiest moisture dynamic to identify but may be the most difficult to prevent. For example, if a basement floods because storm drains are too small and cause recurring backups throughout the year, the system must be redesigned and modi- fiedâa potentially costly intervention. The basement would need to be waterproofed, and back-flow valves would have to be installed in the drain- age system. The foundation might need to be structurally reinforced to withstand hydrostatic pressure caused by flood waters. Even then, a suffi- ciently high water level could still float the foundation. In comparison, large plumbing leaks are usually easy to identify and mend. Many moisture problems are chronic, such as a slow leak in a plumbing line. Materials moistened by plumbing leaks remain wet until the leaks are repaired. Windows with leaks at the bottom corners wet the materials beneath them whenever they are hit by a driving rain; this wetting is more erratic because it depends on the occurrence of rain and on the direction and force of the wind. Materials wetted by intermittent sources might not always be wet. Condensation on chilled surfaces is often seasonal; surfaces are chilled by cooling equipment during the warm season and by outdoor air during the cold season. Absorptive claddings are wetted by rain only when the temperature is above freezing. As noted elsewhere in this report, the moisture sources most difficult to identify are combinations of erratic wetting in hidden locations and mul- tiple transport mechanisms. For example, water leaking through flashing at a roof curb may seep through the roof deck, run along the bottom side of a steel truss until it reaches the end of the bottom chord, drip onto a sus- pended ceiling tile, eventually run off the tileâs edge, and only then become a noticeable drip. The combination of condensation, absorptive materials, capillary suc- tion, and temperature-driven vapor flow creates problems that are difficult to diagnose. Among the more complex of these dynamics is wind-driven rain against a brick veneer. This may create an interior pocket of moisture that heating by the sun turns to vapor. The vapor may then condense on the backside of (interior) vinyl wallpaper under the influence of air-condition- ing. This dynamic can result in extensive fungal contamination without revealing a drop of moisture on the interior or exterior finish of the wall. Identifying and solving moisture problems parallel identifying the ex- tent and location of fungal problems. Building occupants are interviewed about problems with water, and then the building and site are thoroughly inspected. Tests and measurements with moisture meters and other instru-
294 DAMP INDOOR SPACES AND HEALTH ments may also be used. Humidity and temperature measurements are useful in a number of ways. They can be used to identify microclimates that support fungal growth. For example, if the temperature and RH are 75ÂºF (24ÂºC) and 60% indoors, 10ÂºF (â12ÂºC) and 50% outdoors, and 65ÂºF (18ÂºC) and 99% RH in a closet on an exterior wall, the closet will be a hospitable niche for fungal growth. Temperature and RH can be used to calculate the amount of water vapor in each pound of air, and inferences can be drawn about moisture sources. In the example just mentioned, there is 0.0127 lb (5.8 g) of water per pound of dry air indoors, 0.0007 lb (0.3 g) of water per pound of dry air outdoors, and 0.011 lb (5.0 g) of water per pound of dry air in the closet. From that information, it is clear that moisture in the indoor air explains the moisture in the closet air. Although 60% RH is within general comfort conditions, it is too high for this building under these conditions. The next challenge would be to find the sources of water vapor. Common sources of water vapor in buildings include respiration, washing and drying (floors, dishes, and clothing), bathing, cooking, water- ing plants, damp foundations, and planned and unplanned ventilating air. Often, finding the source of water vapor requires a little more investi- gative work. In the example, the planned and unplanned ventilating air would typically be drying the building; therefore, the source of the un- wanted cold-weather humidity must be strong and sought elsewhere. Mois- ture-meter readings may find the basement walls saturated, indicating the basement as the source. Indeed, a damp basement may surpass the total of all other sources in a residential building. Infrared thermometers and scanners can be used to find cold surfaces that may result in condensation. In the example, the dew point of the indoor air is 64.4ÂºF (18.0ÂºC). Any surface in the building at or below that temperature will have water condensing on it. Challenge tests can be used to evaluate building components and plumb- ing fixtures for leaks. For example, a suspected rainwater leak at a window, door, flashing detail, or parapet wall can be tested with a water-spray rack, with simple gentle sprays, or by observing ponding (Endean, 1995). Two American Society for Testing and Materials (ASTM) methods specify flow rates and air-pressure differences for conducting spray tests in the field: ASTM E1105 and ASTM E514 (ASTM, 2000, 2002a). In practice, many investigators simply use a gentle spray and apply a film of water to the test surface with little inertia. The significance of air-pressure differences on the film can be assessed with using fan depressurization methods developed to test the air tightness of enclosures. Plumbing and fixtures can be tested by operating them. Sinks often leak where the basket drain seals to the sink or at the water trap in the drain line. Such leaks can be found by closing the drain, filling the sink with water, observing the drain from beneath the sink, releasing the water, and observing the trap. The same process can be used
PREVENTION AND REMEDIATION 295 to test shower pans. Pan leaks that would otherwise go unnoticed can be detected by running the shower for an extended time and making continual moisture-content readings of the floor around the shower. A simple and useful test can be made by masking suspected leaks. For example, if it is suspected that a skylight or a parapet wall is the source of a rainwater leak, plastic film can be temporarily installed over the suspect area. If the temporary protection prevents the leak during the next storm or during a spray test, it is taken as evidence that the leak has been found. Used in combination with the spray test, masking can distinguish between a poorly detailed flashing and a window that leaks. Vapor-emission testsâthe calcium chloride test (ASTM, 1998) and the equilibrium relative-humidity (ERH) test (ASTM, 2002b)âcan be per- formed on concrete slabs and walls to estimate the amount of water vapor being exhaled from the surface. Historically, these tests have been used to determine whether flooring materials can be applied to a concrete floor. Too high a vapor transmission rate may cause problems for flooring mate- rials applied to the concrete. Flooring manufacturers provide guidance on maximal emission rates. However, the committee did not find any refer- ences relating the results of either method to microbial contamination in buildings. Plan Remediation Activities Information collected during the assessment is used as the basis of remedial efforts. A remediation plan must protect those conducting the remediation, other building occupants, and people in the general vicinity. The guidance documents listed in Table 6-1 all specify means for interven- ing in the moisture dynamic and removing problem fungal material. As was noted above, implementation of a remediation involves five essential steps â¢ Establish appropriate containment and worker and occupant protection. â¢ Eliminate or limit moisture sources and dry the materials. â¢ Decontaminate or remove damaged materials as appropriate. â¢ Evaluate whether the space has been successfully remediated. â¢ Reassemble the space to prevent or limit the possibility of recurrence by controlling sources of moisture and nutrients. Establish Appropriate Containment and Worker and Occupant Protection The intention of containment and protection activities is to protect workers, building occupants, and people in the surrounding area from excessive exposure to microbial contaminants. The use of containment and
296 DAMP INDOOR SPACES AND HEALTH negative air pressure to control the spread of contaminants has been dis- cussed in the literature since 1989 (Light et al., 1989; Morey, 1992), many practical questions regarding when and how to use containment remain. It is known that spores may be released when contaminated materials are disturbed. Rautiala et al. (1996) report an increase of two orders of magni- tude in spore concentrations during a demolition. After the demolition, concentrations returned to baseline. A later study on containment com- pared three methods used in two contaminated buildings (Rautiala et al., 1998). The tests used plastic film as a barrier and exhaust fans for removing air from the work area. In all cases, spore concentrations in the work zone were one to two orders of magnitude higher in the contained area than in adjacent areas. In addition to negative pressure in the work area, there are a number of possible options for containment and managing indoor-air quality during renovation. Turner (1999) describes a fungal remediation in an occupied building where negative pressure was not possible in some work areas. Two alternative methodsâcreating a depressurized wall cavity between the work area and the occupied space and pressurizing the occu- pied spaceâare discussed. The AIHA task force recommends the use of professional judgment and encourages innovation in isolating work areas (AIHA, 2001). Many guidance documents link containment requirements to the area of contiguous visible mold,3 the presence of fungal contamination in HVAC equipment, and the health status of occupants. The logic behind linking the area of contiguous visible mold to requirements for containment and worker protection is straightforward: the more mold, the greater the risk of expo- sure. It is easy to envision the polar extremes. Spots of mold growth on a refrigerator gasket do not require extensive containment or worker protec- tion, but 1,000 ft2 of mold growth on the ceiling of a ground floor because of a flood on the second floor will require containment of the work area and respiratory, eye, and skin protection for workers. However, guidance documents are unclear on the subject of mold hidden in wall or ceiling cavities and growth that is not visible to the naked eye. The AIHA task force (2001) identifies several complicating issues (hid- den mold, density of contamination, reservoirs of settled spores, and risk assessment) in deciding what levels of contamination require remediation and what levels of containment and worker protection are required. It also identifies a need for clearer guidance on these issues. HVAC equipment is treated separately in all the guidance documents. The North American Air Duct Cleaners Association has published guidance 3The ACGIH guidance separates remediation options by level of concern but does not link them to the square footage of contamination. The ACGIH Bioaerosols Committee withdrew the numerical guidelines in 1999.
PREVENTION AND REMEDIATION 297 for cleaning hard-surfaced air-conveyance equipment that includes explicit containment and cleaning protocols (NADCA, 2002). Air-handling equip- ment is unique in that it is a contained area used to transport air throughout buildings. It also often contains processes that condense water from or intentionally add water to the air, and it may contain materials that are difficult to clean. Contaminant released inside an air-handling system is likely to be transported to other portions of the system and to other por- tions of the building. In hard-ducted systems, containment is relatively simple and straightforward. Hard-ducted systems convey air through ducts and fittings dedicated to the purpose rather than through building cavities formed by structural and architectural materials used as walls, ceilings, or floors. Containment and cleanup become much more complex when ple- num air-return or air-supply systemsâsuch as the plenum above a sus- pended ceilingâare involved: the surface areas are larger, materials with favorable nutrient content are more likely to be involved, and air leaks into building cavities and rooms outside the work area are almost certain. Those areas are enclosed by structural and architectural materials and finishes (for example, paper-covered gypsum board, roof sheathings, concrete masonry units, and ceiling tile), rather than by materials used in ductwork (such as galvanized or PVC-coated steel). A number of papers discuss fungal contamination in HVAC systems. Batterman and Burge (1995) surveyed the literature regarding effects of HVAC characteristics on indoor-air quality, addressing microbial growth in the presence of water sources (air washers and condensate on coils and humidification systems) and poor control of indoor humidity. Dust accu- mulation and internal fibrous insulation were found to be contributing factors. The survey reported that few of the HVAC studies evaluating contaminant emissions have been well controlled for confounding factors. Foarde et al. (1995) found that P. chrysogenum could colonize samples of fiberglass duct liner, fiberglass duct board, and fiberglass insulation. Al- though one sample amplified the mold when exposed to high humidity alone, most of the samples required wetting or soiling. Morey (1994) pre- sented recommendations for improving the ASHRAE 62 ventilation stan- dard with regard to HVAC contribution to production and distribution of fungal contaminants; they included suggestions to improve moisture con- trol in building enclosures, air handlers, and distribution systems and to ensure that materials do not provide good substrates for microbial growth. Eliminate or Limit Moisture Sources and Dry the Materials The relevant moisture dynamic must be identified and stopped, at least in the short term, for remediation to proceed. In some cases, such as a leak in an exposed pipe, the identification of the moisture source may be rela-
298 DAMP INDOOR SPACES AND HEALTH tively easy and the intervention relatively inexpensive. At other times, how- ever, finding the water and stopping it are more problematic. If water is condensing on the underside of a roof deck, on chilled water lines, or on the backside of gypsum board, permanent solutions may require extensive reno- vations. Foundations soaked by poorly managed rainwater may also re- quire extensive modifications to the building or site. In those cases, it is best to provide short-term solutions to the wetting, using some combination of ventilation, heat, dehumidification, airflow management, and interim drain- age to stop the water. It must also be remembered that drying may trigger spore release by some organisms. Decontaminate or Remove Damaged Materials as Appropriate Remediation should result in as much fungal contamination removal as possible. Materials that can be cleaned and are not excessively damaged can be salvaged and reused in some cases. Materials that are severely damaged by the fungi or the cleaning process are best replaced. The guidance docu- ments all agree that smooth, hard-surface materials like ceramic tile, met- als, glass, and porcelain are resistant to moisture damage and can be cleaned and salvaged. They also agree that some porous materials that are moisture- insensitiveâsuch as concrete, masonry, stone, and fiber-cement productsâ may be cleaned and saved. Most agree that solid lumber, unless contami- nated by wood-decaying microbes, can be cleaned and saved. Unless the contamination is minor or the value of the material great, the guidance documents recommend removing and disposing of soft porous materials that are difficult to clean or damaged by moisture.4 Paper, books, paper- covered gypsum board, cellulose ceiling tile, and textiles are examples of these materials. Recommended cleaning methods include dry vacuuming with a HEPA vacuum cleaner, wet vacuuming, damp wiping with water or detergent mixtures, and bagging and removing. Another factor that may be considered in selecting a containment strat- egy is the specific action required for removing the contamination. Gentle damp wipes or vacuuming of a hard surface with a HEPA-filtered vacuum may release only a small fraction of the contaminant being cleaned but the vibrations and effects of demolition can easily release large amounts. No studies of the comparative benefits of different cleaning and removal activi- ties are reported in the literature. The AIHA task force (2001) identified a number of control strategies for further research. They include blowing spores from surfaces into the air 4Conservation techniques have been developed to deal with materialsâsuch as those with historical significanceâthat cannot be replaced.
PREVENTION AND REMEDIATION 299 where they can be removed by high-volume, HEPA-filtered fans. The need for options other than removal to manage contaminated porous materials was also identified. The guidance documents do not specifically consider responding to mold growth in spaces such as attics, crawl spaces, and garages. It is pos- sible that intervening in the moisture dynamic and managing the direction of airflow with fan-induced pressure differentials can be used to prevent occupant exposure at a tiny fraction of the cost of removing all the fungi from the spaces. Caution must be exercised in applying this approach. Evaluate Whether the Space Has Been Successfully Remediated Whenever a remediation activity is undertakenâespecially when it re- quires containment that results in evacuation of portions or all of a build- ingâa determination must be made that the job has been completed and that the space is suitable for reoccupation. Such determinations are neces- sarily subjective because there are no generally accepted health-based stan- dards for acceptable concentrations of fungal spores, hyphae, or metabo- lites in the air or on surfaces (ACGIH, 1999; AIHA, 2001; Rao et al., 1996). There is substantial variation in recommended clearance criteria be- tween the guidance documents. The NYCDOH 2000, U.S. EPA, and AIHA guidance documents discussed above agree that the work site should be dry, clean, and free of visible mold growth. However, the NYCDOH guideline also requires air monitoring for areas that had more than 100 ft2 of con- tamination. The U.S. EPA document specifically says that air samples are not required but may be useful in some circumstances. Finally, the AIHA task force guideline suggests two principal quality-assurance indicators for successful remediation: documentation that the moisture problems have been solved and physical inspection of contaminated areas to ensure that the contaminants have been removed. Air sampling and surface sampling are left as options, but the task force suggests that surface sampling for cleanliness may be more useful than biologic surface sampling. The ISIAQ guideline states that materials should be dry and surfaces cleaned until only background concentrations of mold and bacteria remain, but it does not specify how that is to be determined. The Health Canada guideline does not specifically discuss clearance but does mention that things should be left clean. And the ACGIH guideline recommends that remediated areas be clean and leaves sampling of biologics as an option. There is no specific interpretation for biologic sampling in the remediation section, but there are extensive discussions on making and interpreting biologic samples in general. Although all the guidance documents agree that moisture problems
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. âCleanâ 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.
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 â¢ Adding rainwater drainage elements. â¢ Back-venting for cladding. â¢ Elimination of intentional or unintentional water-vapor retarders. â¢ Air sealing and changes in air-handling equipment or operation to manage air-pressure relationships. â¢ Improvements in the dehumidification unit of the air-conditioning equipment. â¢ Removal of humidification equipment or controls of humidification or process-water systems. â¢ 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). â¢ 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 2â10 Âµm 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-Âµm-diameter spores by 60%. The decrease in concentration of 2-Âµm spores would be larger (~70%); the decrease in 10 Âµm spores smaller (40%). In most buildings, the practical increase in ventilation rates would be considerably
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 Âµm) is close to 1.0 (Thatcher et al., 2001). However, the penetration factor for particles of 2â10 Âµm 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 0.6â1.0 for 5-Âµm particles and 0.6â0.8 for 8-Âµm 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 systemsâinclud- ing filters with a much better efficiency than the common see-through furnace filterâwill normally be less than 50% for 5-Âµm-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
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 80â90% in dust, lead, and mite allergen on surfaces were achieved by Roberts et al. (1999) after vacuuming carpets for 6â45 min/m2 of carpet surface. KildesÃ¸ 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 NorbÃ¤ck, 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 NorbÃ¤ck (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; WÃ¥linder 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.
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 â¢ 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. â¢ 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. â¢ Remediation must identify and eliminate the underlying cause of dampness or water accumulation. If the underlying causes are not ad- dressed, contamination may recur. â¢ 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 buildingâs 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. â¢ 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-
PREVENTION AND REMEDIATION 305 ful and complete survey may aid in the evaluation of contamination sources and remediation needs. â¢ The potential for exposure to microbial contaminants in spaces such as attics, crawl spaces, exterior sheathing, and garages is poorly under- stood. â¢ 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. â¢ 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. â¢ 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. â¢ 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 â¢ 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. â¢ 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 â¢ Research is needed to characterize â The effectiveness of remediation assessment and remediation meth- ods in different contamination circumstances. â The dynamics of movements of contaminants from colonies of mold and other microorganisms in spaces such as attics, crawl spaces, exterior sheathing, and garages.
306 DAMP INDOOR SPACES AND HEALTH â The effectiveness of various means of protection of workers and occupants during remediation activities â¢ Research should be performed to develop â Methods for finding microbial contamination in HVAC systems, and in crawl spaces, attics, wall cavities, and other hidden or seldom- accessed areas. â Building materials that, when moist, are less prone to microbial contamination. â Standard methods of assessing the potential of new materials, designs, and construction practices for dampness problems. â Standardized, effective protocols for cleaning up after flood- ing and other catastrophic water events that will minimize microbial growth. â Methods that can distinguish between naturally-deposited spores and active microbial growth in wall cavities. â¢ Research should be performed to determine â 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). â Whether and when microbial contamination that is not visible to the naked eye but is detectable through screening methods should be remediated. â The risk of microbial contamination in the building but outside the general air circulation of the buildingâin crawl spaces, attics, wall cavities, building sheathing, and the like. â The effectiveness of managing contamination in place by using negative air pressure, encapsulation, and other means of isolation. â The best ways to address microbial contamination in situations where remediation is not technically or economically feasible. â 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. â 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. BioaerosolsâAssessment and Control. Cincinnati, OH.
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