The escalation of allergies and asthma among children is a national crisis. In fact, a recent Executive Order from President Clinton, "Protection of Children from Environmental Health Risks and Safety Risks," addressed this concern and the need to reduce environmental risks. The U.S. Environmental Protection Agency responded by issuing new air quality standards to provide additional protection for children and asthmatics. In January 1999, Hillary Rodham Clinton announced that monies were budgeted for the "Presidential Fiscal Year 2000 Asthma Initiative." Additional efforts will be directed toward understanding the link between the indoor environment and asthma, particularly in schools, homes, and daycare centers.

Health effects of exposure to environmental pollutants, including those that trigger asthmatic and allergic reactions, are of particular concern in schools. Common pollutants include molds and fungi, allergens from pets and insects, particles and fibers, ozone, and volatile organic chemicals (VOCs). Allergens of concern originate from cats, dust mites, cockroaches, and molds, commonly known as biocontaminants.

For all air pollutants, children are more vulnerable to exposure and face greater environmental health risks than adults. Their immune and neurological systems are still developing, and because of their lower body weight, they breathe a relatively larger volume of air than adults. This results in a higher body burden of air pollutants than experienced by adults for the same amount of exposure.

We know that outdoor air pollution can exacerbate asthma. Curiously, however, outdoor pollution levels have generally improved over the last 20 years. At the same time, many schools, offices, and homes have become much tighter buildings with minimal fresh air flow. As a result, pollutants are being retained in buildings at greater levels.

The Culprits
This has led public and environmental health professionals and indoor air quality (IAQ) investigators to consider the indoor environment as a potential source for the asthma increase. Adding to this concern is the frequent inability of schools to control humidity and temperature levels effectively. Structural defects, roof leaks, HVAC systems with insufficient capacities, and poor maintenance and operation have led to excessive dirt and moisture in many schools. Unfortunately, poor maintenance and excessive moisture encourage the growth of molds and dust mites, which put students at greater risk of developing allergies.

Different types of asthma are caused or aggravated by numerous factors. For example, studies have shown that in many asthma cases among children and young adults, allergic reactions are often an important part of their attack. A landmark study published in The New England Journal of Medicine reported that exposure to cockroach allergen causes asthma-related conditions in inner-city school children.

The Journal of Allergy and Clinical Immunology recently published a study that found children are exposed to significant cat allergen in schools. The National Heart, Lung, and Blood Institute's 1997 revised guidelines for asthma management recommended asthma sufferers be tested for sensitivity to dust mites, cats, cockroaches, and various fungi or molds. There is growing belief that more aggressive measures should be taken to address asthma and allergies from both an environmental and medical point of view.

Analyzing a Building's Dust
Increasingly, IAQ investigators are monitoring for biocontaminants including allergens and molds. Analyzing a building's dust can indicate what allergens are present and at what levels. Results can be compared to risk factor ranges (thresholds associated with an increased risk of becoming sensitized to the allergen) to indicate if and protective remedial actions and/or avoidance measures are warranted.

Testing for indoor allergens involves collecting settled dust from surfaces such as flooring, upholstered furniture (chairs), and other furnishings (cabinet tops, shelving). Settled dust samples can provide an excellent "fingerprint" of biocontaminants in a building, identifying allergens and molds.

The sampling procedure is simple, using a filter cassette and vacuum pump. It is important to collect a sufficient quantity of dust; i.e., a teaspoon's worth is recommended as a minimum. Allergen samples are analyzed by a qualified laboratory using a technique called enzyme-linked immunosorbent assay (ELISA).

Molds should be analyzed by a qualified laboratory with expertise in identifying environmental fungi. The laboratory should be able to speciate the molds present so that allergens and toxic molds can be distinguished from those more common in the environment.

Cat Allergens? In School?
Exposure to pet allergens have been shown to be a risk factor that may trigger asthmatic symptoms and allergic reactions. Building evaluations conducted by Air Quality Sciences, Inc., have frequently shown the presence of cat allergens in schools. In fact, a number of school districts are establishing policies regarding pets in the classroom, recognizing that children are more susceptible to pollutants and/or pathogens (disease causing organisms) that are adults, and should be protected accordingly.

For example, sensitization to cat dander and other domestic animals is not uncommon and research indicates that in some areas of the world, as many as 50-70 percent of children with asthma are sensitized to furry pets. Recent research has shown that even non-pet owners can become sensitized to pet allergens from environmental or "second hand" exposure. For example, studies have shown that allergens are transferred in classroom through clothing of cat owners to that of non-cat owners.

Dust Mites
Dust mites are everywhere in indoor environments and share with molds and fungi an affinity of moisture. Dust mites are able to extract moisture from the air and can obtain enough moisture in this manner as long as the relative humidity remains above 60 percent for at least a few hours per day. Their food source is human-shed skin scales, a major component of indoor dust.

Dust mites accumulate primarily in upholstered furniture, floor dust, or other fleecy or porous materials; in homes, mattresses are the major reservoir for mite allergens. Control measures such as regular dusting and vacuuming of both flooring and upholstered surfaces have been shown to be beneficial in reducing the severity of asthmatic symptoms.

Molds and Fungi
Attention to molds and fungi is certainly warranted when addressing environmental biocontaminants. Many molds can trigger allergic responses in sensitive individuals, and some molds can be pathogenic or toxic. Mold spores are abundant outdoors, and normally outdoor air should be the source of indoor molds. The mixture of airborne spores indoors should reflect those found in outdoor air, although in mechanically ventilated buildings, their numbers should be lower indoors.

No building surfaces are sterile. Scattered spores will often be present on surfaces and in dust indoors. Difficulties arise when a building has moisture problems from leaks or other sources of water intrusion, or from consistently high indoor relative humidity.

Moisture control is the key to preventing mold problems; such preventive and corrective maintenance issues are constantly being addressed by schools. The growth of molds and fungi indoors is not normal or desirable, and when found, should receive prompt attention. In air samples, a mold problem may be detected when the comparison of the indoor and outdoor air shows the mixtures to be disproportionate. In dust samples, an abundance of one or two species of molds rather than a more widely dispersed mixture may indicate colonization or growth of molds in the building.

What to Do
There are many proactive measures for existing school buildings, including:
- providing an adequate amount of clean, controlled outdoor air throughout the building;
- ensuring that HVAC design and operation complies with ASHRAE 62-1989;
- controlling relative humidity to less than 60-65 percent;
- ensuring good and effective cleaning and maintenance procedures;
- repairing all water leaks immediately; and
- controlling the presence of pets and animals in schools.
 

The ultimate goal is to provide healthful indoor environments for all students and staff, so that the focus can be on learning.

(Barb Epstien, MPH, CIH, is senior industrial hygienist with Air Quality Sciences, Inc., Atlanta, Georgia. This article has been reprinted with permission from School Planning and Management magazine.)

Copyright © Modular Building Institute, January, 2000.