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lSX=UTIV~ SW - ARY Many people spend large shunts of each day Indoors -in many cases, 80-908- in a bouse, an automobile, ~ waiting room, an office or other workplace, or ~ confined space accessible to the general public, sueb as ~ store or a'~estaurant. It has been abown that indoor exposure to en~rironmenta1 pollutants can be subetantial. Although there is little epidemiologic evidence on the health effects of indoor pollutants, indoor concentrations of Bore pollutants that already beve primary ambient-air quality standards exceed those standarde. Indoor exposure teas been largely overlooked in researob on the health effects of environmental pollutants, but it can constitute an isportant fraction of tbe total exposure to many pollutants. Indoor pollution in residences, public building, and offices is created for the most part by the occupante' activities and their use of appliances, power equipment, and chemicals, by wear and tear and outgassing of ewe structural or decorative materials, by thermal factors, and by the intrusion of outdoor pollutante. In some cases, the outdoor pollutants that penetrate to the indoors may represent the most important pollutant stress on human health and welfare, and such effects base been addressed at length in reports of previous National Researeb Council committees. Ibis report is focused primarily on the indoor air contaminants tbat are liberated indoors. When they attain high concentrations, they may cause nuisances, irritation of sensitive tissues, illness, and death fras acute as well as chronic ensures. She pollutant sources such as cigarette saoking--have been recognized for a long tis - , but their importance "e only recently been evaluated. Othere arise fro. new products or from old products in new uses, such as building materials, pesticides, and insulation. A number of sources are of concern only in the indoor environment, e.g., cooking, use of con suer products, space-heating devices, and floor and wall ooveringe. me expanded use of wood and coal for residentis1 speck beating, of home bobby and craft products, and of products that liberate organic subetances is a potential contributor to the contamination of indoor en~riror~ente. Infectious microbes and allergenic agents can grow indoor e or be transmitted into indoor environments. 1
2 Ventilation alone (whether natural or forced) may not be sufficient to dilute indoor pollution to an acceptable point. Natural ventilation may be inappropriate because it is variable and generally not controllable in a precise way for many indoor settings. Exclusive dependence on forced ventilation is inappropriate because it i" not universally available; moreover, introduction of untreated outdoor air may not always be desirable. Also, natural ventilation and forced ventilation may have substantial energy penalties, owing to heating and cooling losses. He adoption of energy-saving proposals to reduce ventilation rates could aggravate problems in indoor air quality, create new problems, and perhaps be generally detrimental to health and property, unless appropriate pollution-control measures are also taken. Public-health laws are broad enough to permit evaluation and, when required, control of indoor environments. The public expects a safe and healthful outdoor environment, and the same expectation applier to public indoor environments. The regulatory authority to control contaminant sources, to set or recommend building codes, and to support or conduct research on or monitoring of indoor contaminants rests with diverse federal, state, and local government units, but no specific government unit has been directly charged with the responsibility for protecting the quality of indoor environments. For all the reasons stated above, the present quality of the indoor environment and how this quality may change are matter. of immediate and great concern. SCOPE OF TEE REPORT This report was prepared, at the request of the Environmental Protection Agency (EPAl, by the Committee on Indoor Pollutants, which was appointed by the National Researct; Council in the Board on Toxicology and Environmental Bealth Hazards, Assembly of Life Sciences. It is intended to characterize the quality of the indoor environment--primarily with respect to airborne pollutants, although others are discussed--and to determine the potential adverse health effects of indoor pollutants. The charge was to review, compile, and appraise the available knowledge. The Committee has also identified the research needed for abatement of indoor pollution. .Indoor. refers to the environments in homes, schools, public buildings, and similar spaces to which the ~ blic has accese' industrial working environments, however, are excluded from consideration here. It is beyond the scope of this report to list all the pollutants found indoors that are hazardous to human health. The examples given make it plain that humans are exposed to a variety of potentially hazardous indoor pollutants from diverse sources. It ts hoped that this report will encourage researchers to broaden the list of hazardous indoor pollutants and to characterize the hazards, so that the general public and those responsible for pollution control and abatement can be informed.
3 Throughout this report, pollutants are mentioned without dissuasion of their health effects. Thin does not constitute an oversight on the part of the Committee, but rather reflects a decision that the discussion here be adequate to show that there are indoor pollutants that cause adverse health effects in humans. The reader's attention is directed to Chapter III, which offers gone recommendations for further health research with respect to these pollutants, for further exposure studies, and for public education about effective ways of reducing exposure to many contaminants encountered indoors. The Committee on Indoor Pollutants and its contributors prepared concise reviews of such physical aspects as sources and concentrations and of such biologic aspects as the physiologic and toxicologic effects of B variety of contaminants encountered indoor=. In addition , the of feats of those contaminants that bear on human well-being in a Ore general way, such as soiling and corrosion, and the available means of controlling the presence of the contaminants are discussed in some detail. The report attempts to focus personal, corporate, and government attention on present and potential problems related to indoor contaminants. The Committee notes that documentation of excessive indoor air pollution should not in itself be considered sufficient reason to relax standards for ambient air. m e barriers between indoor air and outdoor air are not absolute, and ambient air contributes to indoor air. Furthermore, outdoor and indoor air pollutants may interact chemically and physiologically. The Committee recognizes the complexity of human exposures that have multiple sources. The development of effective and efficient strategies for mitigating hazardous contamination requires improved understanding of responses to exposure and of pollutant interactions. The Committee has not attempted to set priorities for research on or regulation or control of indoor pollutants. Nor has it attempted to develop risk analyses for these pollutants. The order in which contaminants are presented in this report does not constitute a ranking of importance by the members of the Committee. To set priorities for differentiating among indoor contaminants and to establish objectives for research and control program=, there must be a system for comparison. The dimensions of this system include the numbers of people exposed, the severity of exposures, and the consequences of the exposures. To be comprehensive. the system must also deal with ecologic and material damage, loss of productivity, degradation of artifacts, and other kinds of impact not related to health. Priorities could be derived from a ranking of these variable" for pollutants of interest, but proper risk analysis would require measurement of exposures by population subgroups and weighting of exposure-response relationships by importance of outcome. The Committee unanimously agreed that e';tabli'3hing firm priorities for research on indoor pollutants that ranks one contaminant as save important than another is premature. In most instances, we do not appreciate the extent of population exposures. Available reports on indoor air pollutants contain almost no data on the incidence of disease or even annoyance related to changes in pollutant
ooncentratione. Nevertheless, the Committee has made judg~aents based on its interpretation of reported concentrations, of prevalence of sources, and of evidence of effects on health and welfare. The Committee offers guidance for research, development, and educational programs by specifying current gaps in information and scientific and engineering deficiencies. Priorities within these program will have to depend on the extent of federal and private funding the Committee believes that the determination of such priorities is urgent. OmANI ZATION OF ]= REPORT The introduction, sugary and conclusions, and recommendations of the Committee are in Chapters I, IT, and TII, respectively. This material is based OR both the body of the report and Committee deliberations. Some conclusions and recommendations were derived from consideration of the documented information in specific sections of the report and the substantiating discuselons therein. Opera, based on Committee consensus, were formulated from a Fore comprehensive perspective on the subject of indoor pollutants. After the introduction, awry and conclusions, and recommendations in Chaptcre I, II, and III, the treatment of indoor pollutants is presented in three primary chapters and three secondary chapters. The three primary chapters are Chapter IV, on the sources and characterization of indoor pollution' Chapter VII, on the health effectes and Chapter ~X, on the control of indoor pollutants. They are the most voluminous chapters and respond got directly to the Co~ittee's charge to review and appraise the available knowledge on indoor air pollution. me other chapter-Chapter V, on factor e that influence indoor pollutions Chapter VT, on the measurement of indoor pollution and exposures' and Chapter VITI, on other non-health-related effecter offer tepor ten t additional information. They elaborate on material presented in the primary chapters, and they introduce factus1 and conceptual material that the Committee feels essential for evaluating indoor pollution c:o~rehensively. Chapter TV, on the sources and characterization of indoor pollution, covers radon and its decay products, formaldehyde and other organic subetances, asbestos and fibrous glass, combustion produce, tobacco Ike, consumer products, odors, temperature and humidity, and other pollutants not specifically treated. The objective of "e chapter, as of Chapter WI {on health effects), is not a global treatment of every possible hazard encountered Indoors, but rather a selective treatment. me chief criterion for selection is direct or ct~cu~tantial evidence that ~ contaminant causes or is reasonably likely to cause human stress, iliness,.or material damage indoors. Chapter I, on factors that influence indoor pollution, expands on the physical characterization of indoor pollutions in Chapter nit. Aspects of geography, building design, and hit - n activity that lead to variations in ventilation rates and in the distribution of pollutant sources are presented.
s Chapter VI, on the aessurement and monitoring of indoor pollution and exposure. reviews the design and components of indoor and personal monitors, mathematical models for esti~ting indoor pollutant concentrations, and methods of estimating total personal exposure. Chanter VII, on the health effects of indoor Pollution, relates the current understanding of the toxicologic and physiologic effects of specific contaminants that are found at high enough concentration and in a broad enough range of indoor environments to constitute an actual or reasonably likely challenge to the occupants of those environments. In some cases, as in Chapter Tv, the diecuse$on is structured by source, such as involuntary Poking or indoor combustion productes the health effects may be attributable to specific components of a mixture of gases and particles, or tt soy be attributable to the general, mixed exposure. The chapter also considers indoor airborne contagion and allergens. Chapter VTII, on the effects of indoor pollution on human welfare, covers a number of items related to comfort, productivity, and mater ial protection in indoor environments . Chapter TX, on the control of indoor pollution, emphasizes the engineering aspects of air-conditioning and indoor sir-cleaning. Ventilation codes and standards are reviewed, and mechanical systems for conditioning and cleaning air are described. The chapter discusses strategies for controlling contaminants to Contain acceptable indoor air quality in general. Some pollutants, because of their sources or their physical and chemical properties, cannot be treated with conventional control systems, and strategies for controlling these pollutants are described specifically. Appendix A lists national primary ambient-air quality standards and occupational-health standards (for ache industrial environment) established for the United States . In addition, it lists indoor-air pollution standards and guidelines of several foreign countries. Ventilation standards for dwellings are also listed. This appendix ts not exhaustive with respect to relevant pollution or ventilation standards, but it does offer a point of reference for some of the more commonly used standards. Appendix B presents an example of the interactions among energy conservation, comfort, and indoor air pollution in a residence. This simulation exercise illustrates the tradeoffs among energy-cost savings, retrofit costs, and thermal comfort under the constraints of maintaining various hypothetical conditions of indoor air quality in particular kind of single-fa~ily residence. PRINCIPAL FINDINGS ON SPl3CIFIC POLL=~S - CLASSES OF POLLUTANTS RADON Radon and its alpha-emitting decay products contribute ~ major portion of the biologically significant dose associated which natural background radiation. Many natural substances contain radium, a
6 precursor of radon gas. Soil, construction materials, and groundwater are the major sources of indoor radon. Indoor radon concentrations are often an order of magnitude greater than outdoor concentrations. The dose-response relationships for alpha-emitting radionucliaes are not sufficiently well accepted to allow quantitation of tbe health risk associated with measured indoor concentrations, and surveys of radiation In homes are very limited. Expansion of the date base on the variation of indoor radon exposure with time and Ovation is a necessary prerequisite for assignment of a health risk to indoor radon. In theory, techniques for controlling radon exposure are available; but they need development and evaluation before they can be applied economically on a large scale. The effectiveness of several contaminant control strategies, other than ventilation, has not been demonstrated in practice. awes for new construction may be necessary to prevent the occurrence of high radon concentrations in modern or refurbisbed dwellings. In any event, prudent judgment concerning reduced ventilation in residences must be based on a better understanding of radiation exposures in present houses. FoRMALDEEryDE The major indoor sources of formaldehyde have been identified. Aldehydes and other organic substances emanate from outgassing of urea-formaldehyde foam insulation, particleboard, plywood, fabrics and, to a lesser extent, cigarettes and indoor combustion sources. The high surface-to~volume ratio of particleboard and plywood used as building materials in mobile bones, as well as lower air~exabange rates, causes the high measured formaldehyde concentrations. Formaldehyde can cause skin, eye, and throat irritation in occupants. Moreover, potential health problems associated with formaldehyde exposure. are readily identified in acute cases when concentrations a re high and tolerance is low. In addition to ire itation, respiratory disorders and allergies have been associated with high formaldehyde concentration". There i" evidence of a decreased threshold of sensitivity with prolonged exposure. Recent studies have indicated that exposure of rats and mice to formaldehyde produces nasal cancer. Owing to the ubiquitous and increasing use of resins and solvents in building materials and furnishings, indoor formaldehyde concentrations have increased. U"tes~ent technology is available, although at times expensive, new and less expensive techniques are being developed. Me Committee is especially concerned with long-term and essentially continuous indoor exposures to low concentrations of formaldehyde. ASBESTOS AND OTHER FIBERS The health hazard posed by indoor exposure to asbetos has been perceived as a problem by virtue of tbe presence of asbestos fibers in insulating and decorative materials. Abrasion, mechanical vibration,
7 or deliberate disruption of asbestos-containing surfaces can result in increased`.fiber Concentration in the indoor environment. There have been ~ small number of studies in which fiber counts bare been documented in association with normal building use. Extrapolation from what we currently understand about the expo~ure-response relationehips for asbestos fibers to the very low concentrations reported in indoor spaces, such as saboole, suggests ~ small health risk under conditions of normal use. However, deliberate Edification of surfaces to remove asbestos from buildings may create a risk of exposure of occupants and workers. Buildings in which asbestos exposure is likely to occur can be identified. m e risk of exposure from dislodged fibers can be reduced by containment. m e occurrence of me~othelioma (a specific form of cancer believed to result only from the inhalation of asbestos fibers) may provide a very sensitive indicator of the exposure of the qaneral population. Bbme exposure to asbestos due to aging, cracking, or physical disruption of insulated pipes or asbestos-containing ceiling tiles and speckling compounds may be greater than public exposures in schools, which beve received the most attention. Bomes built before 1950 in northern climates are more likely to beve pipes insulated with asbestos plaster. Given the very common use of asbestos in bones, sclmole,and other buildings, there i. a need for further aseesament to identify structures where actual asbestos exposure constitutes substantial risk to humane. The extent of exposure of the geners1 public to asbestos fibers teas not been assesseds however, the occurrence of me~othelioma should be carefully monitored in the general population. Man-made fibers have produced skin irritation, but have not otherwise been demonstrated convincingly as hazardous to health. Epidemiologic and toxicologic investigation of synthetic fibers abould continue. On the basis of present knowledge, synthetic fibers in the indoor environment should not cause undue concern. TOBACCO SMOKE Virtually every member of our society is exposed to tobacco smokes 331 of the population smokes, and the rest are exposed to the smoke released by others. Tbe constituents of tobacco smoke are well documented as hazardous, the prevalence of population exposures is very high, and there ts an increased incidence of respiratory tract symptoms and functional decrements in children residing in home. with Pokers, compared with those in bodes without smokers. Tbese considerations and recent evidence of increased lung~cancer rates among nonsmoking women living with smoking husbands have led us to conclude that indoor exposure to tobacco Ike has adverse effects. Coughing, beadacbe, nausea, and irritation of eyes, nose, and throat are among the reported symptoms. Although many studies have measured various components of tobacco smoke indoors, total exposure teas not been determined. Passive exposure to tobacco smoke may constitute an important exposure to respirable particles, such gaseous compounds as
8 acrolein and fo~ldebyde, bencolalpyrene, and various trace metals. Reduced ventilation increases concentrations of tobacco spoke. As an energy~conserving compromiser spoking could be restricted to zones that are well ventilated. public policy abould clearly articulate that involuntary exposure to tobacco smoke teas adverse health effects and ought to be minimized or avoided where possible. Under this framework, the prohibition or restriction of poking in public buildings, offices, etc., is a Control option to be considered with ventilation and air~cleaning. INDOOR COMBUSTION When fuel combustion occurs indoors-~e.g.r for heating' ~king, and power machinery, including suto~biles it gives rise to increased concentrations of gases and particles. Unvented gas cooking is probably responsible for a large portion of nitrogen dioxide exposures in our population. In many bones, chronic exposures to nitrogen dioxide indoors may exceed established national ~bient-air quality Standards. Sborter-tera 1-h average concentrations indoors often exceed the highest hourly concentrations Measured outdoors. Me concentrations of nitrogen dioxide and carbon monoxide in residences have not been fully documented. Bowever, ape studies have ~ rn an association between gas cooking and the impairment of lung function in children. Gas ~ King appliances are also sources of carbon monoxide, carbon dioxide, formaldebyde, hydrogen cyanide, sulfate particles, organic particulate matter, and organic vapors. m e problem of chronic or even peak exposures to combustion products indoor e will be accentuated with decreased ventilation and the increased use of portable space heaters, wood- and coal-burning stoves, and indoor venting of gas dryers. Carbon monoxide, nitrogen oxides, and particles from automobile exhaust can produce increased concentration in office buildings and public areas. Concentrations exceeding 1-h carbon monoxide national ambient-air quality standards (NAAQS) by a factor of 2-4 have been reported in several ice-akating rinks that use gasoline~powered ice resurfacing Machinery. Office buildings and apartment buildings with attached or underground garages can also have sustained high concentrations of carbon monoxide inform. Secau" both carbon Monoxide and nitrogen dioxide are odorless at iced concentrations, the presence of increased and possibly hazardous concentrations may go undetected. Although confirmation te necessary, the available evidence suggests that important population exposures to nitrogen dioxide and carbon Monoxide can occur indoors and may constitute a sufficient threat to the genera, public bealtb to Justify r_dis1 action. Reducing exposure to those gases is relatively straightforward. Source removal or direct venting of combustion sources abould be considered. Efforts to conserve energy present other potential problems indoors. Effective energy~coneervation measures can result in an overcapacity of existing heating equipment. Operation of such
9 equipment at low load factors any decrease its overall combustion efficiency and increase emission of the products of combustion. MICPOORG~NISMS AND A~R~S Microorganisms are present in the indoor environment and are associated with human activity and the presence of domestic article. The aicroorganie include bacteria, viruses, and fungi. Many Microorganism such as spores, Molds, and fungi-~ultiply in the presence of increased humidity. It is possible that reduced ventilation arid the increased use of untreated recirculating air could increase the concentrations of aicroorganisme. - ny of these microorganism can produce infection, disease, or allergic reactions. Respiratory viruses and bacteria can be trsnss~ltted fray person to person in buildings and confined spaces. Certainly, respiratory infections are an important cause of Morbidity that results in lost earnings and discomfort. It is reasonable to assume that Come of the incidence of respiratory disease results fro. airborne tran - lesion, but it is not at all clear what effect ventilation, air-~nditioning. Or air~cleaning will have on incidence. If the Win transmission is between persons in contact with or close to each other, the mechanism and efficiency of disease transfer will be relatively ineensitive to ventilation rates and other operating conditions of tbe air handling system. However, to the extent that infectious and allergenic microorganisme remain viable and airborne, Substantial reduction in Ventilation rates will tend to increase concentratior,~ and most likely the probability of infection and allergy. MOISTURE Water vapor in confined spaces is a product of metabolic and respiratory procesees, as well as of indoor combustion and evaporation from clothes and dish~washing and bathroom functions. Condensation of water indoors has been shown to increase corrosive effects of absorbed gases. Decreases in ventilation tend to increase the indoor relative humidity during the beating seasons. Access water vapor adsorbs or condenses on drier or colder surfaces, and tot gives ri" to increased deterioration or corrosion of building ~teriale, furnishings, decorations, artwork, and other artifacts. Tncres~d relative humidity may also promote the growth of molds, algae, and fungi. Thus, humidity control may become an important component of reduced-ventilation strategies. Some energy penalty easy result that abould be considered in relation to the energy savings tot may be obtained through reduced ventilation. RBSPONSI8TLITI~; The quality of the indoor environment ts not the responsibility exclusively of any individual or government body. Even ~ single hose
10 built in isolation (away fro. outdoor sources of cont~inante} teas the potential to be con taming ted by its occupants, soil, outgassing from piped~water use, building arteriole, cooking, space-heating, conquer products, pesticides. molds, and fungi. Responsibility for the indoor environment is on four levels: indi~ridualas arodilat aanufaetur~ra, building designers, contractors, and ownerat and government. st sources of contamination are associated with human activity. Individuals also exercise ace control over contamination sources and ventilation. Bience, the individual can directly affect bis or her own exposure, a. well as the exposure of those with wow the indoor space is shared. rnis is also true, to a lesser extent, in the nonindustrial workplace and in public buildings. Building comers and operators are responsible for maintaining the indoor environment and ensuring that at least minimal ventilation standards are being set. It should be noted that there is little or no enforcement of ventilation standards, once building plans are approved. Architects, engineers, and contractors should treat indoor environmental quality as a design objective. There are Many opportunities in building design to separate people from the Sources of contamination or to remove the sources entirely. Manufacturers have the responsibility to warn the Consumer adequately of the potential hazards of products. As evidence on specific contaminants such as formaldebyde and nitrogen dioxide from gas stoves--becomes available, less harmful substitutes can be considered, and results of research on the control of the sources can be made available. Government Cores the responsibility to ensure that the indoor environments to which the public has access are healthful. Clearly. in the assessment of indoor concentrations, in instrument de~relop'sent, and in the contrc>1 of health~directed research on indoor pollutants, government can nerve the public interest. Government can establiab ordinance. (regulations) to protect the general public from nuisances, contamination, or direct health damages such ordinances may include performance standards related to building materials and ventilatior~ codes for public and priorate buildings. In the same vein, go~rerns~ent can require product certification in the case of know or potential hazards. Furthermore, government can establiab concentration standards or source~oontrol specifications. Radon, a naturally occurring substance, is ~ clear example of con~minanto that would require government attention, as opposed to that of industry or the individual. , ~ ~ , CONCLUSIONS Definitive conclusions on the character of indoor sir are prevented by the lack of systematic studies. The alterable data base has been generated by a series of pilot studies and does not fully characterize the variety of pollutants, indoor environments, and occupancy cond$tione. Furthermore, the implementation of energy~con~ervation measures and the introduction of new building mater$ale have $ntene$f$ed the problem of indoor air contamination.
11 Studies explicitly addressing both long-term and episodic events have not been undertaken. Episodic release of contaminants in the indoor environment may be rare, but can lead to short-term high contaminant concentrations, which must be considered (in addition to long-term low concentratione} in assessing the overall health risk of indoor contaminants. Measurement of indoor contaminants necessitates a sampling protocol that considers the spatial and temporal profile of several pollutants, as well as air diffusion and ventilation characteristics. In addition, measurement techniques for assessing indoor concentrations have to meet more rigorous requirements, particularly with regard to sensitivity and interferences. Unfortunately, many of the instruments required to characterize long-term and short-term indoor pollutant concentrations do not exist. From a practical viewpoint, it would be desirable to determine the emission rate of an indoor pollutant by simple physical measurements and to infer the dose received by a human inhabiting the trapdoor space. But several intervening steps must be evaluated that involve degrees of uncertainty ranging from good estimates to total ignorance. The first process to be considered is the transport by diffusion and convection; transport is influenced initially by the fluid motion of the air near the source and throughout the indoor space. Cede modes of transport depend on a number of factors and are usually spatially and temporally variable. They lead to a concentration profile of the contaminant as a function of position and time. Measuring such profile" is virtually impossible, so the usual approach is to use mathematical models of dispersion. The human receptor is not stationary. Therefore, to obtain an exposure history, the spatial history of the receptor ebould be specified or estimated. Inexact knowledge of this function introduces a further degree of uncertainty. Dose to the receptor is related to exposure through deposition functions that express the fraction of the exposure that is available to reach specific receptor sites and produce effects. These deposition functions are themselves functions of several variables that are usually Eagerly specified or unknown. Thus, several layers of uncertainty are embedded between emission rate and receptor dose. Indoor air pollutants generated or released indoors typically occur in concentrations and mixtures that are often episodic and generally vary over a wide range of time and from one space to another. As a result, human exposures are difficult to assess for individually or groups. If, in addition, the adverse health effects are subtle, and especially if they are delayed, associations between indoor air pollutants and disease or premature mortality are unlikely to be discovered or demonstrated without a specific and substantial effort. Thus, efforts to improve indoor air quality most likely will have to be guided by information on the adverse health effects of pollutants demonstrated and studied in other settings, such a. the occupational environment. For a limited number of air contaminants that can be found in residential and public buildings, there is direct and circumstantial evidence that human exposures are large enough and come-on enough to
12 agent for subetantial morbidity and premature mortality. These include radon progeny. sidestrea. tobacco poker formaldehyde, carbon monoxide, nitrogen dioxide, aeropatbogene, and aeroallergene. Bowever, our knowledge of the extent of the exposures and of the exposure-reeponse relationships is inadequate to permit measurement or even estimation of the resulting mortality and morbidity. Furtber-~re, the kinds of health effects and the latent periods between exposures and effects are quite varied. For exe pie, they extend from acute intoxication from carbon monoxide and formaldehyde to cancer that appears long after exposure to radon decay products and as - ados. In evaluating health ricks, it is reasonable to compare indoor exposure with ambient air-quality standards for pollutants for which there are suab standerde (carbon monoxide, sulfur dioxide, nitrogen dioxide, ozone, lead, and total suspended particles). Depending on bow the standards were developed, however, tbey may or may not consider exposure of the aost sensitive population groups (the ill or infirm or the very young). In addition, the composition of particulate matter indoors, the potential synergistic interaction of gaseous and particulate Batter, and the tine characteristics of exposures can differ widely between the inshore and the ambient environment. Bence, for cone pollutants, the ambient air-guality standerde may actually underestimate the health risks. Current knowledge would permit the establishment of defensible indoor-air gusItty standards for only a few, if any, contaminants. In any case, the establishment of such standards would not necessarily lead to rational or enforceable con t role beyond ventilation codes for dilution.-~Bcononica1 and reliable technigues for sampling and anslyzing~tbe airborne oont~.inante of interest at very low . Hi. . ~ concentrat-ione beve not been developed, nor have methods been developed to relate spot samples fro. specific locations to integrated doses. He conclude tbst the best approach to the reduction of health damage from exposure to indoor contaminants is to reduce the population exposure to those oont~minante. Control strategies for come pollutants would target the bigh-exposure groups. For other pollutants, lowering the population~eighted wean exposure would, by best estimates, reduce the bealth hazards. 8ecauee of the diversity of indoor pollutants and their sources and because of the unpredictability of the distribution of such points over tic and in different buildings, efforts to improve indoor air quality s "uld ooncentrate on reducing the number and strength of the sources by substitution of other asteris18. Control strategies basal on the specifications of source Control are preferred, ubenever feasible, because they are generally the most dependable, with respect to tbeir extent and reliability of exposure reduction. That suggests that reducing exposure through source control or removal or through material substitution aunt be teared by the practical realities of existing sources, which might not be easy to eliminate, and by the unknown long-term toxicity of substitute materials. When those strategies cannot achieve the desired degree of
13 control at reasonable cost, they can be supplemented or replac" by other engineering oontrole, such as dilution ventilation or air~cleaning. however, it should be recognized that the cor~centration reduction achieved through dilution may be less than that achievable with source control or air~cleaning, whereas the effectiveness of sir~cleaning devices usually depends on frequent and effective application of maintenance procedures. The specific source controls appropriate to each kind of contaminant can be expected to crazy. For example, local exhaust control is seost appropriate for nitrogen dioxide and carbon monoxide from gas ranges, the sealing of walls and floors for radon control, prohibition for asbestos~n~ining products, and specifications for care of furniture, drapery, and carpeting materials prepared with formaldehyde~containing subetances. Air~conditioning systemize are generally designed to provide for all or most of the thermal environmental requirements (i.e., heating, cooling, and ventilating) of the occupied space. In the design of tbese systems, it is necessary to select components that will ~ t the particular requirements, such as heating coils or furnaces to beet winter design temperatures, evaporator coils and condensing units to meet summer design temperatures and humidities, and sir-cleanere or ventilation air-flow rates to meet the sir-quality requirements of the occupied space. The functional requirements of the space {i.e., residential, office, theater, etc.} also impose constraints on the type of system that might be selected. Because of the wide variety of functioned requirements of indoor environments and the other constraints on design, a vast variety of control systems are used. For instance, lighting and acoustic require'sents can influence the size and location of the air~conditioning system, tbe location of air supply and return devices, and air velocities in the air distribution system. Available information suggests that this trend will continue. Although the requirements may be described discretely and some performance specifications are available for components of the system, the effecti~renese of the system as ~ whole, including its impact on indoor air quality, must be evaluated. Unfortunately, very few data are available to indicate whether these systems, under actual loads, perform in accordance with their designs. R~ATIONS 1. A staged assessment of the exposures of the general population to indoor pollutants and of the effects of such exposures on health and welfare should be conducted by the federal government in both residential and office buildings. Federal agencies with subetantia1 interests in definition of the indoor exposures i.e., the Environsaental Protection Agency, the Department of Energy, the Consumer Product Safety Mission, the Matione1 Institute for Occupational Safety and Bealth, the Centers for Disease Control, the National Inetitute of - 'riron~nte1 Bealth Sciences, the Pi and Drug Administration, the National Center for Toxicological Re - arch, the
14 Department of - I a" Urban "velo~nt. atc.-~ld "rtict~te in the formulation of the study objectives and protocols and should provide technical asaistance and financial support, as appropriate and feasible. Congress should enunciate clearly its interest in healthful and safe indoor environments. 2. Monitoring protocols and properly designed ~acn$toring instruments must be developed to satisfy the special requirements involved in investigating the indoor environment. 3. The indoor pollutants that should receive the initis1 Major focus in investigation of sources, concentrations, dispersion, and referral are radon and its progeny, tobacco smoke, for~ldebyde, nitrogen dioxide, carbon monoxide, pesticides, water vapor, carbon dioxide, and airborne contagion, including allergens. 4. The health effects that abould receive the initial major focus in investigation are respiratory-infection rate. and respiratory mechanical function in relation to nitrogen dioxide, tobacco~emake, and airborne~contagion exposures s res~piratory-tract irritation and potential carcinogenic effects in relation to formaldehyde, tobacco smoke, asbestos, and alpha~emitting radon decay productat and Acute intoxication, blood carboxybe~lobin, and cardio~rascular~dise~ aggravation in relation to carbon monoxide and nitrogen dioxide exposures. 5. The low-le~rel acute and chronic complaints of malaise, headache, stuffiness, and eye and throat irritation that are reported with increasing frequency in large buildings deserve careful study. 6. me welfare and behavioral effects that should receive the initial major focus in investigatior~ are material damage from mold formation in relation to relative hum~ditys corrosion and surface deterioration in relation to nitrogen dioxide' sulfur dioxide, and water vapors fabric fading and deterioration in relation to solar radiation in combination with nitrogen dioxide, sulfur dioxide, house dust, and water vapor; soiling due to tobacco smokes and the lowering of work productivity due to indoor air pollution and associated discomfort. 7. Responsibility for conducting a well~coordinated investigation of the influence of building design and operational factors on the concentrations of pollutants in both residential and co_rcia1 facilities should rest with the federal government, assisted by the appropriate professional and scientific organizations. 8. The building factors that should receive the initial Moor focus in investigation are as followas a. The effects of reducing infiltration rates in existing buildings on combustion efficiency of space-beating equipment and on increases in relative humidity and concentration of indoor~generated air pollutants and airborne contagion.
J 15 b. The effects of materials of conetruction-and furnishings on indoor-pollutant content--apecifically, there should be systematic evaluations of outgassing and surface attrition of particleboard and plywood (for formaldehyde and other organic subetances~s of wall and floor coverings and fabrics {for organic substances); of masonry products (for radon and dust) S of wallboard, pleater, and speckling compounds (for dust and fibers) ~ and of the materials used for heat storage in dry solar systems (for radon, dust, surface molds, etc.~. c. The differences in air distribution, diffusion, mixing, etc., associated with the use of different climate-control systems, suab as forced-air, baseboard, and radiant floor or ceiling systems. d. The effectiveness of air-cleaning systems in capturing pollutants in recirculating air--epecifically, this will require in-place testing of systems, rather than test-stand evaluation of components, and the effectiveness of a variety of commonly used systems should be evaluated for radon and radon progeny, formaldehyde and solvent vapors, and cigarette smoke. 9. The potential for consumer products to contaminate the indoor environment needs to be evaluated. Hazardous components of these products must be identified and tested. Adequate labeling, warning users of bazards associated with product use and misuse in enclosed spaces, should be required. Testing in homes is needed to assess the extent of contamination, allergic reactions, and other health effects of pesticides, residues, and consumer products.
