Clearing the Air Asthma and Indoor Air Exposures (2000) / Chapter Skim
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8 Indoor Dampness and Asthma
8 Indoor Dampness and Asthma
Pages 298-315
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From page 298... ...
There is a large and detailed literature addressing the engineering and physics underlying moisture control in buildings (e.g., Trechsel, 1994~. In addition, professional organizations such as the American Society for Testing and Materials and the American Society of Heating, Refrigerating, and Air Conditioning Engineers publish reference materials and promulgate consensus standards intended, in part, to limit indoor moisture problems.
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From page 299... ...
The equilibrium moisture content of a building material surrounded by air is primarily a function of the relative humidity of the air; however, the equilibrium relationship varies considerably among building materials (Kumaran et al., 1994~. Sources of water vapor in indoor air include the water vapor in incoming outdoor air, which is often a dominant source during hot humid weather.
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From page 300... ...
surfaces. In winter, the temperature of portions of the building envelope that exchange heat with outdoor air or soil may fall below the dew-point temperature of indoor air, leading to water vapor condensation.
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From page 301... ...
These pressure differences modify the rates of moist air transport through the building envelope in a manner that may inhibit or increase indoor moisture problems. In cold climates, the design intent is often to maintain buildings Repressurized relative to outdoors and to prevent humid indoor air from flowing outward through the building envelope.
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From page 302... ...
Pin-type moisture meters measure material moisture content, although calibration difficulties may limit their effectiveness. Smoke pencils can help identify envelope leakage sites and also the effectiveness of combustion product discharge.
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Questions are typically formulated to seek information on whether conditions such as leaks, floods, wet basements, window condensation, visible fungal growth, or moldy odors are currently present or have been present in the past. It should be noted, however, that reporting bias is an important source of error in such studies.
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From page 304... ...
304 In Q to In In Q Cal C]
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From page 305... ...
Similarly, landlords who do not reside in the affected building may not be motivated to repair water leaks rapidly. Despite the technical knowledge about prevention of moisture problems that is available in current scientific and engineering literature, the errors in building design and construction reported in case studies indicate that many architects, engineers, builders, and roofers have an inadequate knowledge of the means of preventing moisture problems.
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From page 306... ...
increase the risk of fungal growth on some surfaces (Foarde et al., 1996~. It should be noted that indoor middle-of-the-room humidity is not a consistent predictor of the presence of fungal growth, and fungal control cannot be achieved just with ambient indoor air humidity control.
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From page 307... ...
Chapter 5 contains a discussion of the influence of humidity levels on dust mites. INDOOR DAMPNESS AND RESPIRATORY DISEASE Overview Table 8-2 summarizes studies that report odds ratios (ORB)
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From page 308... ...
2.17-2.62a Slezak et al., Head Start Signs of dampness, 4.5 (1.25-16.3Jb 1998 (U.S.) children visible mold 1.94 (1.23-3.04Jb (1 ,085)
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studied respiratory symptoms, measured pulmonary function, and evaluated the home environment for reported dampness or mold. Wheezing in the past year was most closely associated with visible mold (adjusted OR = 3.0; CI 1.72-5.25~.
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From page 310... ...
DAMPNESS CONTROL Implementation of measures that are effective in reducing dampness problems should be a logical approach to lessening the indoor asthma problem. Several recommendations for prevention and remediation of moisture problems, including periodic inspections to prevent water leakage, are provided in a review article based on a workshop held by the American Thoracic Society (ATS, 1997~.
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From page 311... ...
RES"RCH NEEDS With respect to the association of dampness problems with asthma development and symptoms, research is needed to clearly identify the causative agents (e.g., molds, dust mite allergens) and to document more accurately the relationship between dampness and allergen exposure.
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From page 312... ...
Indoor air quality and health: validity and determinants of reported home dampness and moulds. International Journal of Epidemiology 26~1~:120-125.
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1998. Separate and combined effects of the outdoor and indoor air quality on chronic respiratory symptoms adjusted for allergy among preadolescent children.
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1998. Asthma prevalence and risk factors in selected Head Start sites in Chicago.
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1998b. Indoor environmental risk factors and childhood asthma: a case-control study in a subtropical area.
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