We recently undertook a survey and critical review of the published literature on indoor air quality (IAQ), ventilation, and IAQ- and building-related health problems in schools, particularly those in the state of California. The survey's objectives included identifying the most commonly reported building-related health symptoms involving schools, and assembling and evaluating existing measurement data on key indoor air pollutants most likely to be related to these symptoms. The review also summarizes existing measurements of ventilation rates in schools and information on the causes of IAQ and health problems in schools.
Most of the literature we reviewed (more than 450 articles and reports) dealt with complaint or problem schools. Among the papers were peer-reviewed scientific literature, conference proceedings, 77 Health Hazard Evaluation Reports (HHERs) from the National Institute of Occupational Health and Safety, and 70 reports of investigations of problem schools in California. The HHERs provided a national perspective; they are from a sampling of schools in 31 states not including California.
The types of health symptoms reported in schools were very similar to those defined as "sick building syndrome" symptoms, although this may be due at least in part to the type of questionnaires used in these studies. Some of the symptoms, such as wheezing, are indicative of asthma.
Formaldehyde, total volatile organic compounds (VOCs), CO, CO2, and microbiological pollutants were the most commonly measured air pollutants in schools. CO2 is often used as a surrogate for occupant-generated pollutants and an indicator of the adequacy of ventilation rates. It was the most commonly measured species in the papers reviewed, appearing in 46 of the HHERs. In one-third of these HHERs schools, 40% or more of the CO2 measurements were greater than 1,000 ppm, a level generally regarded as indicative of inadequate ventilation for pollutant removal.
The majority of the formaldehyde measurements in the U.S. were taken in complaint schools but were generally below 0.05 ppm. Measurements of other pollutants were too limited to draw any conclusions about the prevalence of indoor concentrations above levels of concern, even in problem schools. However, there is some evidence that microbiological pollutants, also called bioaerosols, may be a particular concern. These include bacteria, allergens, and fungal spores. Although sampling and analysis methods do not make it possible to characterize exposures to these agents accurately, some recent measurements taken in California problem schools suggest that airborne bacterial levels are high enough to indicate inadequate ventilation. A significant fraction of these schools may not have ventilation rates high enough to dilute the concentration of bioaerosols that cause infectious diseases such as influenza, colds, and tuberculosis.
The few scientific studies on causes of symptoms in complaint schools indicate that exposures to molds and allergens in schools contribute to asthma, sick building syndrome, and other respiratory symptoms. Other indoor air pollutants such as VOCs and aldehydes have not been investigated closely, but we suspect they may also contribute to health symptom prevalences in schools.
The major building-related problem identified in this literature was "inadequate ventilation with outside air" (see Figure). Several lines of evidence indicate that inadequate ventilation with outside air is a fairly common problem in schools in general, including those in California. However, inadequate ventilation can only be considered an indicator, not the causal agent for health symptoms reported in problem schools. Water damage to the building shells of schools, leading to mold contamination and growth, was the second most frequently reported building-related problem.
The cause of many of the ventilation and water-damage problems in schools was inadequate or deferred maintenance, or both, in these buildings and their HVAC systems. However, in most studies, neither the building and ventilation-system problems nor the specific pollutants have been clearly and unambiguously demonstrated to be related causally to the symptoms.
Although there is considerable qualitative information on health complaints and ventilation and IAQ problems in schools, we do not know what fraction of schools is experiencing these problems and their related health symptoms. We also do not know whether mitigation measures intended to solve these IAQ problems have worked, or how effectively they have worked.
—Joan Daisey and William Angell
Indoor Environment Department
(510) 486-7491; (510) 486-6658 fax
Indoor Air Quality Project
Minnesota Extension Service
University of Minnesota.
The full text of this report, LBNL-41517, is available from the Indoor Environment Department Office, (510) 486-6591.
This research is supported by the California Environmental Protection Agency, Office of Environmental Health Hazard Assessment, and the U.S. Department of Energy.
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