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- Humidity -
7/26/05 re: Relative humidity in pre-schools (follow-up) As I indicated I am a mechanical engineer specializing in Heating, Ventilating and Air Conditioning (HVAC) systems. As a member of the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) I volunteered to write the new chapter for HVAC design of Educational Facilities. As part of my task in writing the chapter we have to recommend acceptable humidify range for thermal comfort and health related issues. The industry is well informed on thermal comfort models, high humidity risks for health, construction damage etc, for the older population but unfortunately the pre school population is not covered (to the best of my knowledge) at all.
Since the pre-school children are more sensitive to low humidity in cold climate I am looking for any research, papers, direction etc. that will educate us (engineers) on the medical implications of low humidity for pre school children. This is critical for us as an organization the recommends systems for these applications. For example in typical K-12 school or college / universities you will not find winter humidification equipment (since the older population is more forgiving to low humidity), on the other hand pre-school children are more sensitive. We can recommend installing humidifiers in pre-schools, but unfortunately without proper maintenance this equipment can create major health hazard, which we want to avoid.
I am familiar with activities under the Tools for Schools program of the EPA (see enclosed abstract) but have not seen any reports dealing specifically with guidelines for relative humidity in pre-schools. I suggest that you contact Dr. Petronella (E mail - spetrone@utmb.edu) the first author (in Galveston) listed in the abstract below to see if their activities (or those of other groups) dealt with air quality in pre-schools and whether guidelines for relative humidity in pre-schools have been promulgated.
You may also wish to consult a web site likely known to you, the National Clearinghouse for Educational Facilities, checking their resources list for information pertinent to your question (http://www.edfacilities.org/rl/iaq.cfm)
J Environ Health. 2005 Jun;67(10):35-42.
Clearing the air: a model for investigating indoor air quality in Texas schools.
Petronella SA, Thomas R, Stone JA, Goldblum RM, Brooks EG.
Department of Pediatrics, The University of Texas Medical Branch at Galveston, 77555-0366, USA .This pilot project focused on the assessment of indoor air quality at a local high school in Galveston, Texas, using methods based on guidelines for the U.S. Environmental Protection Agency's Indoor Air Quality Tools for Schools program. Tools for Schools, developed for evaluating and ensuring acceptable air quality for schools, takes a low-cost, minimal-involvement, primarily educational approach. The authors also compared the findings from this approach with the results of an air-sampling program. The overall goal was to determine if use of Tools for Schools was sufficient to identify conditions with the potential to cause adverse health effects. The primary objectives were to 1) establish an indoor air quality committee for the school to implement Tools for Schools assessments and management strategies, 2) collect air quality data in high-risk areas identified within the school by the indoor air quality committee, 3) collect outdoor air quality data at or in close proximity to the school, and 4) develop methods and instruments for assessing environmental risks associated with daily school attendance. Data were gathered on levels of formaldehyde and other volatile organic compounds (VOCs), ozone, particulate matter (PM10), mold, relative humidity, and temperature. Data values for each sampled pollutant were compared with federal standards, recommended values established by the American Conference of Governmental Industrial Hygienists for non-industrial populations, and effects screening levels developed by the Texas Commission on Environmental Quality. Levels of all VOCs except formaldehyde were found to be well within guidelines, as were ozone and particulate-matter levels. Mold, however, was widespread, including both common species and species associated with allergy and asthma, such as Aspergillus and Alternaria. In general, Tools for Schools provides an excellent foundation for a school indoor air quality program, although the authors did find it necessary to streamline data collection and did find that mold with the potential for adverse health effects was present, albeit not visible in some areas.
7/20/05 re: Recommended relative humidity in schools I am mechanical engineer specializing in design of Heating, Ventilation and Air Conditioning systems. I am wondering if there are any research papers, studies, information or recommendations regarding recommended indoor design conditions (Temperature and Humidity) for heated and air conditioned pre-schools. My major concern is the winter minimum humidity in cold climates. Typically indoor design conditions are driven by thermal comfort and issues such as mold and mildew prevention(in more humid environments), I am looking for information that will address the low humidity side of the acceptable humidity level and the medical implication of this humidity level for pre school children.
I suggest that you look at the section in the U.S. Environmental Protection Agency website dealing with this subject (www.epa.gov/iaq/schooldesign/moisturecontrol.html). In that section, they recommend a relative humidity of 30-50%. In my experience, it is very unusual to be able to maintain the relative humidity as high as 40-50% with a forced air system during the heating season in cold climate areas unless a potent humidifier is placed in the air handling system. The very low humidity is good in one respect in that the growth of dust mites and molds (major allergens) is inhibited more as the relative humidity decreases. Conversely, growth rates of dust mites increase considerably when the relative humidity exceeds 50%.
However, in my experience, when it gets too dry (usually 20% or below), there is increased irritation of the nasal passages and sometimes the eyes. This effect may be worse in individuals with pre-existent chronic rhinitis (nasal inflammation). You are likely familiar with adverse effects of excessively dry air on wooden furniture, etc. in rooms with chronic very low humidity.
7/10/01 re: Relationship of high humidity to asthma worsening I do not know anything about high humidity causing bronchospasm yet patient after patient (asthmatics and some COPD) tell me they get more SOB when the humidity is high. Is there a link, and, if yes, what is the mechanism? I have shared your experience. Many patients have told me that their asthma symptoms are worse in high humidity environments. This has been most apparent when there is a sudden exposure to a very high humidity environment such as a steam room in a gym or a basement area that is humid and musty. This area has been investigated (see enclosed abstracts for some examples). At least part of this adverse effect is a direct evidence of very high humidity on the airways, including a stimulus to cough. Recall that inhalation of high humidity air has been used for many years to induce coughing in order to obtain sputum specimens for analysis. Individuals with asthma appear to be particularly affected by such inhalation of high humidity air. Also, the high humidity environments tend to have very high airborne levels of molds/fungi to which the individual may be allergic. In addition, dust mite proliferation is enhanced considerably when the relative humidity exceeds 50%; mite-sensitive individuals will be likely affected.
However, in my experience, asthmatic symptoms (particularly the "asthmatic cough") may also be worse in excessively dry environments (relative humidity below 15%). Therefore, I have advised asthmatic patients to aim for a "happy medium" relative humidity in their homes, monitoring their home humidity regularly with a reliable gauge. Depending on the ambient relative humidity, dehumidifiers or humidifiers can be used judiciously to avoid extremes of relative humidity. I also advise asthmatics who appear to be very sensitive to high humidity to stay indoors in a humidity-controlled environment when the outdoor weather is very humid. If the individual is allergic to molds and/or dust mites, additional avoidance/control measures are indicated.
Int J Tuberc Lung Dis 2001 May;5(5):468-77
Asthma symptoms in relation to building dampness and odor in older multi-family houses in Stockholm.
Engvall K, Norrby C, Norback D.
Stockholm Office of Research and Statistics, Sweden.SETTING: Respiratory symptoms and hay fever in adults in relation to the indoor environment.
OBJECTIVES: To study relationships between reports on respiratory symptoms and hay fever and building dampness and odors in older multifamily dwellings.
DESIGN: A questionnaire study in a random sample of 231 multifamily buildings built before 1961, which included 4224 apartments. The response rate was 77% (n = 3241). Information on building characteristics was gathered from building owners and the central building register in Stockholm. Multiple logistic regression analysis was applied, adjusting for age, sex, current smoking, population density, type of ventilation and ownership.
RESULTS: In total, 22% reported at least one sign of dampness, and 32% reported odor in the dwelling. All types of odors were more common in damp buildings. Reports on dampness and odors were related to asthma symptoms and current cough, even when adjusting for potential confounders. A combination of odor and signs of high air humidity was related to an increase in asthma symptoms (OR = 2.82; 95%CI 2.70-2.95) and current cough (OR = 5.29; 95%CI 4.99-5.62). Similar findings were observed for a combination of odor and history of water leakage in the last 5 years, with an increase in asthma symptoms (OR = 3.59; 95%CI 3.37-3.82) and current cough (OR = 2.86; 95%CI 2.61-3.14). There was a dose-response relationship between respiratory symptoms and the number of signs of dampness. An association was also observed between dampness and a history of pollen allergy.
CONCLUSIONS: Signs of high indoor air humidity, water leakage and odors were common, and related to respiratory symptoms. Exposure to odorous compounds from building dampness may be significant with respect to respiratory symptoms and possibly atopic sensitisation.
J Asthma 2000 Apr;37(2):191-8
Sick building syndrome. III. Stachybotrys chartarum.
Mahmoudi M, Gershwin ME.
Division of Rheumatology/Allergy and Clinical Immunology, University of California at Davis, 95616, USA.Increasingly, physicians are being asked to evaluate patients with putative environmentally associated illnesses. These can include a variety of problems, including infectious illnesses (Legionnaire's disease), chemical exposure in the workplace, and sick building syndromes. The latter has been an issue particularly in asthma because of the association of mold and increased bronchial responsiveness. Recently, attention has been focused on the mold Stachybotrys in human disease. Stachybotrys was first identified more than 60 years ago following an epidemic of stomatitis, rhinitis, conjunctivitis, pancytopenia, neurologic disorders, and death in horses. Since then, Stachybotrys has been identified in several outbreaks of disease in animals. It has also attracted attention as a possible agent in idiopathic pulmonary hemorrhage in infants. Stachybotrys is a relatively uncommon fungus but has been isolated from a variety of sources, including contaminated grains, tobacco, indoor air, insulator foams, and water-damaged buildings with high humidity. This fungus is particularly important because it is one of a series of fungi that produces trichothecenes mycotoxins; these mycotoxins are biologically active and can produce a variety of physiological and pathologic changes in humans and animals, including modulation of inflammation and altered alveolar surfactant phospholipid concentrations. The presence of Stachybotrys in a building does not necessarily imply a cause-and-effect relationship with illness, but should alert physicians and healthcare professionals to do more vigorous environmental testing. Guidelines are presented herein for intervention measures in the maintenance of heating, ventilation, and air-conditioning systems.
J Allergy Clin Immunol 2000 Jan;105(1 Pt 1):75-82
Mechanical ventilation and high-efficiency vacuum cleaning: A combined strategy of mite and mite allergen reduction in the control of mite-sensitive asthma.
Warner JA, Frederick JM, Bryant TN, Weich C, Raw GJ, Hunter C, Stephen FR, McIntyre DA, Warner JO.
School of Medicine Allergy and Inflammation Sciences Division (Child Health), University of Southampton, Southampton, United Kingdom.BACKGROUND: The relationship between exposure to house dust mite (HDM) allergens and prevalence of sensitization to these allergens in patients with asthma has been confirmed in many studies. Mite population growth is regulated by humidity. Reducing humidity and removing allergen by efficient vacuuming should control mite allergen and reduce symptoms.
OBJECTIVE: We sought to investigate the effect of mechanical ventilation and high-efficiency vacuuming on HDM numbers and Der p 1 concentrations in the homes of mite-sensitive asthmatic subjects and to evaluate the effect of any reductions on symptoms.
METHODS: The homes of 40 HDM-sensitive asthmatic subjects were randomized to receive (1) mechanical ventilation and a high-efficiency vacuum cleaner (HEVC); (2) mechanical ventilation alone; (3) an HEVC alone; and (4) no intervention. Homes and patients were monitored for 12 months. Change in absolute humidity, mite numbers, Der p 1 concentrations, lung function, bronchial hyperresponsiveness, and symptom scores were analyzed.
RESULTS: Homes with mechanical ventilation achieved significantly lower humidity levels than those without (P <.001), with an associated reduction of mite numbers (P <.05) and Der p 1 concentrations (P<.001 ?in nanograms per gram, P =.006 ?in milligrams per square meter) in bedroom carpets and some other mite sources in the ventilated areas of the homes. The addition of a vacuum cleaner enhanced this effect. There was a trend for an improvement in histamine PC (20) (P =.085) in the patients whose homes were ventilated.
CONCLUSION: The use of a mechanical ventilation system in suitable homes resulted in some reduction in numbers of HDM and Der p 1concentrations. The addition of an HEVC slightly enhanced the effect but not sufficiently to see an improvement in symptoms.
