This study assessed the relationship between indoor allergens and allergic diseases such as asthma and hay fever. It found the indoor environment to have many allergens that cause allergic disease. African Americans and children were found to be at greatest risk of adverse effects. By recommending relatively simple control strategies, the study provided practical guidance to patients and professionals, many of whom have little or no information about the adverse health effects of indoor allergens. It also proposed an agenda for further research.
An expert committee of the Institute of Medicine (IOM) at the National Academy of Sciences was charged with providing an independent, comprehensive, state-of-the-science evaluation of the impact of nonindustrial indoor allergens on the development of adverse health effects in humans (e.g., asthma and other allergic conditions). Its report was designed to assess the extent of the problem in the United States, to define the populations commonly affected, and to identify specific indoor airborne agents responsible for inducing asthma and/or other allergic reactions.
More than 50 million Americans--about 20 percent of the population--will develop an allergy-related disease at some point in their lives. Asthma alone afflicts an estimated 10 to 20 million Americans. Asthma is a major reason for trips to the emergency room and for work and school absenteeism. The economic burden of asthma in 1990 was estimated at $6.2 billion, a 39 percent increase since 1985. This information, combined with steady increases in the occurrence and severity of asthma and other allergic diseases, raises concerns about the potential adverse health effects of indoor air and the extent to which the indoor environment can be controlled.
Indoor allergens may be responsible for a large proportion of allergic diseases, including asthma, hay fever, chronic bronchitis, "sick building" syndrome, and allergic skin reactions. The increased incidence, prevalence, and severity of these conditions may be the result of Americans' spending more than 90 percent of the day inside buildings that are increasingly airtight and that frequently contain numerous sources of allergens, including dust mites, fungi, house pets, rodents, cockroaches, and certain chemicals.
On the basis of these concerns, several Federal agencies requested that IOM evaluate the public health significance of indoor allergens. The Committee on the Health Effects of Indoor Allergens was created by the IOM Board on Health Promotion and Disease Prevention, in collaboration with the U.S. Environmental Protection Agency, the National Institutes of Health, and the Agency for Toxic Substances and Disease Registry. This multidisciplinary committee included nationally renowned allergists, immunologists, biomedical engineers, epidemiologists, psychologists, physicians, and other health professionals.
The 16-member committee conducted an extensive review of published information, including population studies, medical case reports, basic research studies, and engineering and architectural documents, as they related to the design and operation of heating, ventilation, and air-conditioning systems. The committee also evaluated the methods used to (1) diagnose asthma and other allergic diseases, (2) measure levels of indoor allergens, and (3) reduce the concentrations of these allergens. Where possible, committee members used quantitative risk assessment methods to identify relationships between specific indoor allergens and allergic reactions.
The committee's review of research revealed African Americans and children (particularly those under age 5) to be at greatest risk for developing complications associated with exposure to indoor allergens. Children under 18 years old account for nearly 50 percent of all emergency room visits for asthma. Asthma mortality rates for African Americans are two to three times greater than rates for whites.
The committee found that allergens produced by these organisms cause allergic disease: house dust mites, fungi and other microorganisms, cats, dogs, cockroaches, and rodents. Dust mites--microscopic organisms that live primarily in carpeting and upholstery--appear to be critical for the development of allergic asthma in children. Allergens shed by house pets cause hay fever and asthma and can persist for a long time after a pet has left the premises.
The diagnosis of allergic disease is based primarily on a medical history linking exposure to symptoms. Laboratory studies, including skin tests or in vitro tests for allergic antibodies (immunoglobulin E [IgE]) or other classes of antibodies, are important for confirming a diagnosis of allergy. Pulmonary function tests are helpful for following the course of disease. Peak flow meters, because they are portable and can be used by patients, are particularly useful for the diagnosis and management of asthma.
Research suggests steps to markedly reduce exposure to indoor allergens, thus lowering the health risks and medical needs and costs of asthma/allergy patients. Relatively simple measures, such as washing bedding regularly at high temperatures, keeping carpeting to a minimum, and using special air filters, can significantly improve indoor environmental conditions. Well-designed and maintained heating, vacuuming, and air-conditioning equipment will eliminate most indoor allergens.
Panel members found that physician and other health care providers had little or no information about the adverse health effects of indoor allergens. Awareness was similarly low among patients, the general public, and those involved in the design and maintenance of residential and commercial buildings.
Use of Results
The committee's report contained numerous recommendations for patient education and treatment, research, and environmental controls.
One of the recommendations for those diagnosed with asthma is to determine whether they are among the 50 percent of cases whose asthma can be attributed to allergic factors. The committee recommends allergy testing of asthmatics who require more than occasional treatment. If these patients are found to be allergic to one or more indoor allergens, the committee recommends that they be given specific, practical information about how to reduce their exposure to indoor allergens.
Control of indoor allergens also requires engineering control strategies to improve the use of heating, vacuuming, and air-conditioning equipment; to consider the serious problem of carpeting as a reservoir of indoor allergens; and to define moisture control in naturally and mechanically ventilated buildings.
The research agenda developed by the committee represents a variety of approaches to understand and control indoor allergens. Research recommendations range from improvement of testing methods and identification of new allergens to developing more allergen-free products and determining the effects of long-term allergen avoidance on the quality of life.
The report has stimulated the development of a research program announcement, "Environmental Agents and Asthma," prepared by NIEHS in collaboration with NIAID and NHLBI. An announcement of this kind is one vehicle NIH uses to channel research on specific topics of public health importance. Within the Healthy People 2000 Environmental Health Subcommittee, the report has served as a springboard for extensive discussions on effective ways to alter indoor environmental conditions and on additional research needs.
Pope, A.M., R. Patterson, and E. Burge, eds. Indoor Allergens: Assessing and Controlling Adverse Health Effects. Washington, DC: National Academy Press, 1993.
National Institutes of Health
Marshall Plaut, M.D.
Asthma and Allergy Branch
Division of Immunology, Allergy, and Transplantation
National Institute of Allergy and Infectious Diseases
National Institutes of Health
Solar Building, Room 4A23
6003 Executive Boulevard
Rockville, MD 20892
(301) 496-8973 Fax: (301) 402-2571
Andrew Pope, Ph.D.
National Academy of Sciences, Washington, DC