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IT SUMMARY AND CONCLUSIONS CHARACTERIZATION OF I~R AIR PORTION The air quality of the indoor environment has been characterized in a limited number of pilot studies. Because of the large variety of distinct indoor environments- - ingle and multifamily residence-, of f ices, hospitals, restaurants, schools, recreational facilities, transportation facilities, etc.--there is a major difficulty in characterizing The indoor air environment.. Moreover, even within one indoor environment differences in structure, in the operation and strength of emission sources, and in hogan acti~rittes add to the complexity of characterizing air quality. The available data, mostly from the residential environment, amply demonstrate the diversity of characteristics of indoor air and help in identifying subjects that warrant further research. RADIOACTIVITY (pp ~ 58-82 ) The data base on sources and source strengths of indoor radon is just beginning to be es~cablished. Initial attention focused on building materials and groundwa~cer. Recent evidence from regional studies in the United States points to ground soils {under buildings) as perhaps the major source of radon. Only a small number of buildings in the United States have been measured for radon and radon progeny. Indoor concentrations are affected by various factors, including ventilation rate, deposition of radon progeny on indoor surfaces, and interactions of radon progeny with fine particles from various sources (e.g., tobacco smoke and house dust). Data from severed studies indicate that indoor radon-222 concentrations vary by at least two orders of magnitude, with average values of about 1 nCi/~3. Such a large range is not surprising, inasmuch as the studies included -various types of buildings, building materials, underlying materials, and ventilation rates and used many different measurement techniques. Radon progeny concentrations are often given as potential alpha-energy concentration. (PA]3C), expressed 30

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31 in working levels (WL). Limited measurements indicate that typical average radon progeny concentrations in residential buildings range from 0.004 to 0.02 WL in some houses. Concentrations are muab higher indoors than outdoors. ALDEHYDES (pp. 82-100) AIdebyde concentrations are almost always higher indoors than outdoors. Formaldehyde is the most important aldebyde. Sources of aldebydes include building materials (particleboard and plywood}, urea-formaldehyde (UF) insulation, and, to a lesser extent, combustion appliances, tobacco smoke, and other consumer products. Variation" in indoor aldehyde concentrations are not well understood, and emanation rater from the various sources are not well quantified. Owing to the time spent inside residences (including mobile bones}, offices, and other indoor environments, human exposures to indoor formaldehyde are markedly higher than exposures to outdoor formaldehyde. Typical indoor formaldehyde concentrations in buildings with products containing urea-formaldehyde resins range between O.OS and 0.3 ppm, although in some unusual instances concentrations of a few parts per million have been measured in bosses with OF foam insulation. In residences with sources of high rates of emission of formaldehyde- containing products, the concentration typically range from 0.01 to 1 PP~ CONSUMER PRODUCTS - (pp. 100-111) Many consumer products may emit gaseous and particulate contaminants into tbe indoor environment during their use or even during storage. Moat of the chemicals in these gases and particles may be known or can be identified, but the chemical products resulting from mixtures and interactions of them are not known. Likely exposures and durations are poorly understood, even for cases in which the products are used as directed. Willful abuse of aerosols or careless use of solvents in enclosed spaces have resulted in acute and delayed disorders and in death. The carcinogenicity of some compounds. such as benzene and vinyl chloride, teas led to voluntary removal from consumer products, but many chemicals with potentially toxic effects are still in wide use. The use of insecticides, pesticides, and herbicides is widespread. Even when applied outdoors, some compound. have been measured indoors and have persisted over a considerable time. . ASBESTOS AND OTHER FIBERS (pp. 111-128) Asbestos is a widespread component of the structural environment in schools, homes, and private and other public buildings. Its release in the indoor environment depends on the cohesiveness of the a~bestos~containing material and the intensity of the disturbing

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32 force. - at contamination is episodic, activity-related, and local. Fiber counts and ~~s concentrations of fibers have been aessured and shown to exceed those outdoors, and on occasion they may approximate the occupational limit of 2 fibers per cubic centimeter. Fortunately, during normal use, buildings containing asbestos have not shown indoor fiber counts higher than outdoor counts. Current data are very limited and apply mostly to schools and ~ few office buildings, but it appears that the general public exposure to asbestos fibers is exceedingly low in public buildings. A systematic and comprehensive survey of indoor asbestos fiber contamination is needed and wil3. require reliable, portable, and continuous monitors. Asbestos control technologies have been applied in various indoor environments. Asbestos removed requires a complex protocol to be carefully applied. because the very activity of removal may cause severe asbestos contamination. INDOOR COMBUSTION (pp. 134-149 ) Unvented combustion appliance., especially gas stoves, are major sources of indoor sir pollution. Although emission rates from a appall number of gas alcoves have been determined for several pollutants, the data base is very limited. Indoor concentrations of carbon monoxide and nitrogen dioxide associated with incomplete combustion have been observed to exceed current ambient-air quality standards. Carbon dioxide emission from Invented combustion appliances may build up to concentrations in the range of occupational air quality standards. Local exhaust ventilation appears to be the most effective control strategy for reducing pollutants from combustion. Improved combustion efficiency and source elimination (lee., adsorbers or ~ change to the use of electric ranges} are two additional Control approaches. Residential wood and coal stoves are also potential sources of indoor contamination. Attached and underground garages can contribute to indoor carbon monoxide, nitrogen dioxide, and particle concentrations. . Carbon Monoxide Indoor carbon monoxide concentrations are often higher than corresponding outdoor concentrations. High indoor concentrations may be attributed to emission from such sources as gas cooking facilities, attached garages, faulty furnaces, and cigarette-~aoking. Typical average indoor carbon monoxide concentrations in residences very between 0.S and 5 ppm; observed E - ak values reach 25 ppe. In public buildinqs, the indoor concentrations are usually lower than observed residential concentrations, except under conditions of exceptionally heavy smoking, as in bars, or in office buildings with underground garages and improperly designed or malfunctioning ILIAC Myers.

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33 Carbon Dioxide The indoor-to~outdoor ratio is greater than 1 for at least 90S of the total monitored hours. Hourly indoor carbon dioxide concentrations often exceed 2,000 ppm. Observed typical outdoor carbon dioxide concentrations are approximately 400 ppm. The principal sources of indoor carbon dioxide are the metabolic activity of occupants and Invented combustion appliances. Nitrogen Oxides Emission from cooking appliances and emission from unrented heaters are the principal contributors of oxides of nitrogen in the indoor environment. The range of observed hourly indoor (residential} nitric oxide concentrations is 30-300 ppb, with a maximum of about 500 ppb. Indoor hourly concentrations of nitrogen dioxide '.rary between 50 and 500 ppbs indoor peaks of 700 ppb have been measured. Typical weekly indoor concentrations of nitrogen dioxide range from 20 to 100 ppb. The upper values in all the ranges just noted are associated with Invented Gas appliances. SHORING (ppe 149 - 168 ) Passive exposure of many nonsmoker" to the contaminants in tobacco smoke occurs repeatedly. The indoor concentrations of tobacco~smoke compounds that have other sources exceed the concentration. found outdoors. For many people, the main or sole exposure to numerous gaseous and particulate compounds results from passive exposure to tobacco Ike. Children of Inking parents are among the largest identifiable groups in this category. For the most part, however, the specific contribution of tobacco combustion products to personal exposures has not been documented. Most nonchamber measurements have been of the survey type; many have measured ~ single component of amok e without reference to outdoor concentrations, ventilation, or air dispersion. Smoking is the major source of indoor particles, but other human activities (e.g., cooking and vacuum cleaning} also contribute indoor particles. Particulate matter has variable composition, and the data base indicates that there are no constant ratios of indoor to outdoor concentrations. The ratio of observed daily indoor concentrations of total suspended particles (TSP) to corresponding outdoor TSP concentrations varies from 0.3 to 4. Residences occupied by families with pre-achool-age children and smokers often have higher indoor than outdoor concentrations. The TSP 24-h ambient-air quality standard, which must not be exceeded more than once a year, is 260 ~g/m3. The typical range of obeer~red indoor residential 24-h TSP concentrations is 30-100 ug/m3, with an obeer~red maximum of 600 ~/m3.

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34 Concentrations of fine particles (diameter, less than 2.5 - } range from 10 to more than 260 W/~3 for a 24-h sample. The higher concentrations are a~st always associated with smoking. Concentrations in bars, offices, and cars with smoking can be higher than 500 ),g/m3. ODORS (pp. 168-202) Odor. arising from occupant. and their activities figure in indoor-air quality issues predominantly on the basis of comfort, rather than health. Such routine indoor activities as cooking, Smoking, bathroom use, and maintenance give rise to odors that are often disagreeable and in some cases offensive. To a varying degree, almost all building materials and furnishings are sources of odor. We determination of odor attributes--such as intensity, character (pleasantness/unpleasantness), duration, and perceptual threshold--is complex, but can be effectively accomplished with ~ combination of instrumentation and the use of panels of human.obeervere. Odor controls increase in complexity from good housekeeping to ventilation to masking and, finally, to air-cleaning. OTHER CHEMICAL POLLUTANTS (pp. 82-111, 134-149) Nonmethane BYdrocar bon The ratio of indoor to outdoor total nonaethane hydrocarbon (NMHC) concentrations is greater than 1 for about 90% of the total monitored hours; that is, the SAC concentrations observed in the residential environment are ale - at always higher than the outdoor concentrations. Fluctuations in the indoor concentrations may be associated with cooking, cleaning, and other activities. Typical concentrations in residential buildings vary between 0 and 8.0 ppe, whereas typical outdoor concentrations are between 0 and 3.5 pp~. Measured ~HC concentrations in new office buildings often exceed 10 ppm and reach as high as 50 ppm; this may be attributed to the extenel~re use of synthetic organic building materials and furnishings in new office buildings, as well as cleaning solvents and maintenance materials. Ozone Indoor ozone concentrations are generally lower than outdoor. Unless there is an indoor generation source of ozone from electric arcing or ultraviolet radiation {such as an electrostatic precipitator or a document copier), the ratio of corresponding hourly indoor to outdoor concentrations is almost always less than 1. ozone is primarily a product of outdoor photochemical reactions. Precursor pollutants leading to the formation of ozone are primarily of automotive origin, but other sources include the combustion of fuels

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35 for heat and electricity, the burning of refuse, the evaporation of petroleum products, and the handling and use of organic solvents. Ozone is highly reactive and decays rapidly by absorption on indoor surfaces. Indoor ozone has been measured at up to 120 ppb; typical concentrations are between O and 20 ppb. Sulf ur Dioxide Indoor sulfur dioxide concentrations are usually lower than corresponding outdoor concentrations. Sulfur dioxide emission indoors is usually small, and, because it is a relatively reactive contaminant. it is absorbed by indoor surfaces. Indoor hourly sulfur dioxide concentrations are typically below 20 ppb. Particulate Chemical Composition There is very limited information on the chemical composition of indoor particles. Measured lead concentrations in residences are commonly iow--often below 0.5 ug/m3. Lead concentrations as high as 2 vg/m have been measured in residences with wall paints that contain lead compounds or in residences that are near major roads. Indoor residential concentrations of nitrates are quite low and are driven mainly by the outdoor concentrations. Observed daily indoor concentration" of nitrates do not vary widely--between 1.0 and 5 ug/m3, with typical values at the lower end of the range. The data base on sulfates shows that the indoor 24-h sulfate concentration is usually lower than the corresponding outdoor concentration. The type of fuel used for cooking and heating is important in determining the indoor~outdoor relationship; houses with gas appliances have a slightly higher indoor/outdoor ratio than houses without gas appliances. Sulfor-containing compounds are added to residential gas for detecting leaks of the otherwise odorless fuel. Indoor daily sulfate Concentrations range between 2.0 and 15.0 ~g/~3, with typical values at the lower end of the range. AIDE MIC~R~ISMS AD DEGAS (pp . 394-417 1 For indoor biogenic pollutants' the sparseness of satisfactory measurement methods and the resulting lack of an adequate quantitative data bare constitute serious problems. In contrast with other indoor pollutants, biogenic pollutants bear complex and varied organic structures that defy automatic chemical assay. Biogenic agents exhibit limited direct toxicity, more often provoking infection or allergic responses. Bacterial and viral agents can produce infections in humans; however, the indoor transmission of these agents i. not fully understood. A broad array of fungi, algae, actinomycetes, arthropod fragments, and dusts have been confirmed as airborne antigen sources that evoke human allergic responses. Indoor biologic pollutants--most `-~e

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36 notably bacteria and fungi--also play important roles in the deterioration of surfaces and spoilage of stored materials. MONI=d~NG AND MOD4=I~ OF I~R PQ==TON . Indoor air quality Monitoring, in addition to pollutant sampling, must involve ventilation-rate measurements and daily activity logs of occupants. in addition, meteorologic data and outdoor pollution measurements may also be needed for the monitoring and assessment of indoor pollution. Most indoor monitoring studies have relied on instrumentation developed for monitoring workplace or ambient air. The use of conventional monitoring instrumentation is frequently awkward, expensive, and suitable only for a limited number of comprehensive indoor air quality studies. Owing to the special requirements, instruments and sampling strategies are being developed specifically for indoor residential and office environments. The advent of personal monitors ha. permitted, in a few cases, the startup of monitoring and exposure studies for specific pollutan~--nitrogen dioxide and radon. Personal and portable monitors are being developed for carbon monoxide, formaldehyde, and particulate matter. Monitoring the indoor environment, either with fixed-location sampling devices or with personal monitors, requires special protocols addressing pollutant sampling, instrument calibration, source operations, and occupant activity. When indoor monitoring takes place under normal occupancy conditions, the protocol must ensure that the act of monitoring itself avoids influencing those occupancy conditions. Indoor-air pollution simulation model. provide a theoretical framework for relating outdoor pollutant concentrations, meteorologic factors, building factors, ventilation rates, and indoor source and sink dimensions with indoor pollutant concentrations. Most importantly, a validated simulation model must accurately predict a desired concentration for conditions other than those tested experimentally. Depending on ventilation conditions and the geometry ~ ~ . . of the structure, a single room, a Floor, or a whole outsang may De adequately approximated as a single air-quality compartment (entity). However, if sources and sinks are not uniformly distributed and if the indoor environment is large, pollutant stratification occurs within a building and a multicompartment numerical model is required to simulate the indoor-air pollution concentrations. Almost all numerical models are mass-balance equations that simulate the dynamic relationships among indoor pollutant concentrations, outdoor concentrations, indoor sources, and sinks ~ including ventilation) . FACTORS MAT AFFECT EXPOSURE TO INDOOR POLLUTION Exposure is ~ dynamic concept that is defined as Me joint occurrence of two perhaps independent events: the presence of ~ person in ~ specific environment and the presence of a pollutant at a specific

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37 concentration in the same environment. Because both human activities and air pollutant concentrations vary spatially and temporally, pollutant concentrations obtained from outdoor monitoring networks arc inadequate for determining haven exposure. Bumen activities are among the factors that must be addressed in assessing exposure to air pollutant". They have been studied by many researchers, mostly sociologists, to determine population mobility patterns and time budgets. The results indicate that, on the average, employed Americana spend 90% of the day indoors, whereas homemakers and retired people spend up to 95S of their time indoors. General sociologic studies may be used in air-pollution research, but do not address specific topics of interest for the assessment of human exposure to air pollutants. The exact indoor location (or environmental Cadet its of paramount importance in exposure studies. Of all environmental types, the in-transit mode has been studied more extensively than any other microenvironment. Indoor air quality, and therefore exposure to pollutants, varies geographically as a function of outdoor regional air quality and as a function of the rural, urban, or suburban character of the location of the indoor environment in question. In rainy residences, the indoor sir quality does not vary substantially. In larger buildings with many ventilation zones, indoor sir quality pay very in accordance with the f unction {utility) of each zone. Building factors that influence exposure include the site condition., such as microclimate and proximity to major outdoor pollution sources, building design (age, size, ventilation systems), occupancy, and building operations. she exact nature of the cause-and-effect relationships between these factors and indoor air quality has not been established. Hl3AI.TE EATS OF I~R FO"=ION Several classes of pollutants with major indoor sources were identified as having important known or reasonably likely effects on human health: sidestream cigarette smoke, radon and radon progeny, mineral and vitreous fibers, formaldehyde, indoor combustion products, agents of indoor contagion and allergens, and, to a lesser extent. temperature and humidity extremes, noise, and odors. Other classes of indoor pollutants may have impacts on human health, such as consumer-product aerosols and pollutants from hobby, interior~decorating, and maintenance activities (e.g., solvent and pigments). Because the evidence of their effects on health is meager, the Committee could not determine whether specific effects were attributable to them and concluded that effective review at an appropriate depth was not feasible. Many airborne solvents, pigments, mineral dusts, and other products used in hobbies and interior decoration are present in the indoor air. The best data base on the effect. of exposure to those substances is that drawn from studies of the industrial workplace, and the reader is therefore referred to the occupational-health l iterature .

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38 INVOLUNTARY SHORING - (pp. 364-382 ) Tobacco smoke is a major source of both gaseous and particulate pollution in the indoor environment, and the nonsmoker absorbs measurable amounts of carbon monoxide and nicotine, as well as s~11 Bunts of other smoke constituents, owing to involuntary smoking. The carbon monoxide absorbed varies from negligible in well-ventilated office buildings to Bunts that raise the carboxyhemoglobin (COlIb) concentration by 2-31 in an exposure of 1-2 h. The Comb produced by tone most severe Involun~ry-s~king ensure likely to occur in everyday living is capable of reducing the maxi - 1 exercise capacity of normal healthy adults, but does not measurably affect submaximal exercise capacity. Carbon monoxide has been shown in one study to reduce the amount of exercise that pa~cients with hypoxia chronic obstructive lung disease can perform before the onset of dyspnea . Patients with angina pectori" have a reduced exercise tolerance After involuntary smoking that may be a combination of paychologic stress and a carbon monoxide induced decrease in oxygen delivery to the yocardz~. Carbon monoxide clearly reduces the Bunt of exercise possible before the onset of angina in patients with angina pectoris. Sell changes in visual and auditory vigilance have been demonstrated at COMb concentrations that can be produced by involuntary smoking, but no change in tests of complex function has been demonstrated. Involuntary smoking has not been shown to produce acute change. in lung volumes or in a number of small-airway resistance measurements in normal healthy aduL - . Long-term exposure to cigarette Bake has been related to small-airway dysfunction in healthy nonsmok ing adults . Children whose parents smoke have been shown in some studies to be more likely to have respiratory symptoms, bronchitis, and pneumonia as infants. This relationship has been found in some studies to be independent of parental symptoms, socioeconomic class, and the smoking habits of other children in the household. It abows, in those studies, a dose-response relationabip with the number of cigarettes smoked per day by the parents. To the extent that these associations may be due to cigarette smoke, it is reasonable to assume that the particle mass or a specific compound contained therein, rather than nitrogen dioxide or carbon monoxide, is responsible. A twofold risk of cancer mortality in nonsmoking women has been associated (in a Japanese study} with having husbands who Bake. Apparently, the risk is proportional to the amount of passive smoking. RADON AND RADON PRO - (pp. 307-322) The radon gas that diffuses out of radium-bearing building materisIs, subsurface soil beneath buildings, and well water into the indoor air undergoes radioactive decay. As a result, the indoor sir contains both radon gas and alpha~emitting decay nuclides in particulate form, herein referred to as credos progeny..

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39 The health effects of radon and radon progeny are well established from studies of workers. Exposure to radon and its progeny at high concentrations has resulted in several hundred excess cases of lung cancer among uranium miners in tbe western United States. The health effects of much smaller amounts of radon progeny from indoor exposures can be estimated on the basis of a linear, no-threshold dose model, which yields upper-limit estimates of excess cancer in populations exposed to various indoor concentrations of radon and radon progeny. Lifetime cumulative exposures to radon progeny that result from current indoor exposures are lower by approximately a factor of 100-10,000 than those received by the U.S. uranium miners who have been studied. The reliability with which the uranium-miner lung-cancer experience can be extrapolated to the effects of indoor exposure. to radon progeny among the general population i. limited by several important difference. between the populations and by uncertainty about the extent of the effect of cigarette-~moking on the incidence and latent period for lung cancer related to radon progeny. The population differences include: (1) an adult, male, healthy working population versus a general population that includes the very old, the very young, and the chronically ill; {2) coexposures to relatively high concentrations of silica duct and diesel exhaust among the miners versus coexposure" to relatively low concentrations of household pollutants and conewmer products among the general populations and {3) differences in the ethnic and social backgrounds and smoking histories Wang the different populations. ASBESTOS AND OTEI13R FIBERS tPP. 339-350 ) The inhalation of asbestos fibers can lead, many years later, to pulmonary fibrosis, lung cancer, and mesothelioma of the pleura and peritoneum. All these diseases have been seen in humans who had chronic occupational exposures to airborne asbestos fibers, and they have all been reproduced in animals. Lung cancer and mesotbelio~a have also been seen in humans who bad no occupational exposures, but who lived either in the same households as asbestos~worker. or in neighborboods where the ambient air had increased asbesto--fiber concentrations resulting from proximity to an asbestos-related industry or a geologic anomaly that acted as a source of airborne fiber. Asbestos and asbestos~containing products such as ceiling tiles, floor tiles, pipe insulation, and speckling compounds were widely used in bonnet and public buildings because of their excellent thermal and acoustic insulation and structural properties. When these materials and products are displaced or disturbed by abrasion of deteriorating surfaces during housekeeping and maintenance operations, renovations, redecorating, or, especially in public building-, malicious mischief, asbestos fibers can be released into the sir. Concern about the inhalation of fibers that can result "e led to extensive and expensive programs to remove asbestos, under controlled conditions, from accessible regions of public buildings, such as saboole and libraries.

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do Fibrous ~teriale used as substitutes for asbestos include glass fiber, rock ~ol, and slag wool. They have been abase, in aniaa1 injection and implantation studies, to be capable of producing lung fibrosis and aesotbelio~a. Bowever, they are wah lees important in this regard than asbestos, and there is no corresponding buman-healtb evidence associated with the forms in which they are used in industrial and consumer products. Thus' their substitution for asbestos appears to be beneficial, inasmuch as sueb substitution reduces the risk associated with asbestos exposure. ~ RMALDERYDE (pp. 322-338) Formaldehyde teas been the subject of numerous complaints regarding irritation of the eyes and respiratory tract, nausea, beadach*, rash, tiredness, and thirst. These sy~pta" bare been reported Mainly by residents of mobile and conventional ~es in which formaldebyde~yielding products have been identified. Documented cases of bronabial asthma due specifically to formaldehyde are few, More commonly, asthma is aggravated by the irritating properties of form Idebyde. Aqueous solutions of formaldehyde damage the eye and irritate the skin on direct Contact. Repeated exposure to dilute solutions any lead to allergic contact dermatitis. Poisoning from ingestion is uncommon, because the irritancy of formaldehyde makes ingestion unlikely. A preliminary report from the Chemical Industry Institute of Toxicology teas about that formaldehyde induces nasal cancer in laboratory rats and in some of the laboratory mice similarly e^pveed at the high dose. Nass1 cancer tree developed in the group of rats exposed at 15 ppm and 6 ppm, and dose-related histologic changes of the nasal mucosa in rats exposed at 2 and 6 ppm. Although the human mutagenic and teratogenic potential of formaldehyde is not known, it has exhibited mutagenic activity in a wide variety of organism. Data on the health effects of otber environmental factors and their interactione--such as cigarette-emoking history, variability of health status, age, and genetic predisposition Which may modify responses to formaldebyde} --have not been adequately evaluated. That saskes it difficult to assess accurately the bealth risks attributable to exposure to formaldehyde. However, the complaints of residents of homes with formaldebyde-containing products are similar to complaints made by persons studied in the [aboratory.~t similes formaldehyde concentrations' hence, these health complaints may be related to foraaidebyde exposure in the home. Accordingly, ~ subetantial proportion of the U.S. population may be likely to develop sy~ptona as a result of exposure to formaldehyde at low Concentration It has been estimated, on the basis of laboratory tests a" various kinds of population surveys, that perhaps 10-208 of the general population may be susceptible to the irritant properties of formaldehyde at extremely low concentrations. For exe - le. cove persons report mild eye, nose, and throat irritation and other sy~ptosas at concentrations lese than 0.5 ppse, and come note sy.}?toas at concentrations as low as 0.25 ppe.

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~1 These concentrations could also cause bronchooonstriction and asthmatic symptom in some susceptible persons, and chronic exposure to low concentrations can result in sensitization. mere appears to be ~ wide range of individual susceptibility to formaldehyde exposure. We cannot determine Me exact numbers of susceptible people residing in indoor environments where exposure to formaldehyde could produce adverse responses. On the basis of estimates of the number of susceptible persons among the geners1 population and the estimate that about 11 million persons in the United States now reside in mobile homes of varied age, construction, and quality, it Day be concluded that ~ substantial number of persons are at risk of developing adverse health effects associated with formaldehyde. I NDOOR COMBUSTION (pp. 3S0-364) The combustion of fossil fuels in air results in the generation of effluent stream. containing carbon monoxide, nitric oxide, nitrogen dioxide, formaldehyde, carbonaceous particle-, and other products of incomplete combustion, as well as the products of complete combu~tion--carbon dioxide, water, and sulfur dioxide. When the effluents are not vented to the outside, as in the cane of most gas ranges and some space-heaters, the effluents are mixed into the indoor air . The percentage increase in the indoor concentration of the combustion effluents resulting from such indoor sources is generally greatest for nitric oxide and nitrogen dioxide. For homes with gas ranges, indoor nitrogen dioxide concentrations are frequently twice a. h igh as outdoor concentrations . The long-term integrated concentrations can exceed thy national annual ambient-air quality standard (MAAQS) of 100 ~/m (0.05 ppm) in some houses. Although chronic animal inhalation studies and community air-pollution epidemiology studier using central ~sonitorinq-station data have not established that exposures at or near the NhAQS for nitrogen dioxide produce measurable health effects, several recent studies of the health statue of children living in homes with gas ranges have shown that they had more respiratory illness and poorer respiratory function than children living in comparable homes with electric ranges. Increases in carbon monoxide sufficient to cause measurable health effects are usually associated with improperly operated flames or especially prolonged use of unrented space-heatere. Both carbon monoxide and nitric oxide bind with hemoglobin and reduce tissue oxygenation. Carbon monoxide from indoor combu8tio~ sources and sidestream cigarette smoke can be shown to cause measurable increases in Comb of exposed persons, but the health implications of such i ncreases remain speculative. The Importance of increased carbon monoxide and formaldehyde concentrations in indoor air was discussed above.

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42 INDOOR AGENTS OF CONTAGION AND Air (pp. 382-417 ) There is considerable evidence that a number of contagious~disease organisms--including those associated with influenza, Legionnaires' disease, tuberculosis, measles, mumps, and chicken pox--are capable of airborne transmission in the indoor cnviron~nt. Other respiratory diseases, such as the con cold and pulmonary infections, involve airborne transmission. Because of the important role of respiratory diseases in overall acute morbidity, airborne transmission of contagious agents is important in the indoor environment. The droplet-nucleu. theory--whereby liquid particles emitted from the human respiratory tract evaporate to ~ particle size that can remain airborne for a period sufficient to be carried by natural air currents or convective ventilation flows and later deposited in the human airways--is generally accepted and used as a basis for transmission models. The effect of reduced ventilation in residences and off ices on the incidence of infections is unknown. Only a few airborne allergens are found in enclosed spaces. Their health effects are difficult to estimate, although their impact is sometimes appreciable. EFFECTS OF I~R POLLUTION ON B~ ~F~ - Effects on human welfare are taken to include loss of productivity, human discomfort, and effects on Materials, primarily soiling and corrosion of exposed surfaces. SOCIOECONOMIC STATUS (pp. 419-421) Members of low income classes are more likely to live in pearly insulated housing with higher air-exchange rates. Several reports have indicated that gas Stoves or unrented gas or kerosene heaters are used for supplemental space-heating in northern cities. The percentage of homes with smokers appears to be inversely related to parental educational level. Lead intoxication in children occurs disproportionately in lower-inco~e urban populations; higher ambient airborne-lead concentrations may contribute. Bowever, sooe potential sources of indoor pollution may occur More frequently in the middle and upper income brackets. Many consumer products, as well as oral and wood stoves, exemplify such sources. Although the distributions of these and other factors nary be functions of socioeconomic status that cause some segments of society to be more or less disadvantaged winch respect to a hazardous indoor environment, We available data allow little more than speculation.

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43 PRODUCTIVITY (pp. 431-437 ) There is a growing recognition of the difficulties in clearly demonstrating the linkage between environmental quality and productivity. Perhaps as a result of these difficulties, there appears to be a slackening of research in this subject. Anecdotal or observational evidence can be found to support the conclusion thee improving air quality should improve productivity, but objective documentation does not appear to exist or to be readily available. The most promising avenues for research appear to be tbose which demonstrate direct health effects of the various pollutants. Nevertheless, under the modern, broad definition of ~productivity,. a reduction in productivity is an almost certain consequence of pollution itself . SOILING ~ corset (pp. 437-445) Reduced indoor environmental quality can result in degradation and deterioration of indoor materials, furnishings, and artifacts. As efforts required for maintenance and housekeeping increase, the costs of owning or operating a building increase. To protect property or reduce costs of operation, more stringent control of indoor environmental quality may be required than may be indicated for protection of the health of occupants. DISCOMFORT ,- (pp e 4 214 31 ) Control of indoor environments in nonindustrial facilities is designed to provide a degree of comfort acceptable to the occupants. When a stimulus (whether odor, temperature, humidity, noise, or air pollution) is changed beyond an acceptance threshold, there can be adverse effects. This kind of environmental control may be difficult to provide. However, the comfort-discomfort relationship may be one of the more important aspects to consider in evaluating the performance of indoor environmental control systems. CONTROL OF INDOOR POLLUTION CONTROI, STRATEGIES (pp e 488498 ) Three basic strategies have been identified: source removal. dilution, and air-cleaning. In each of these classifications, methods can be selected that will reduce exposure. The appropriate strategic. to be used, either separately or in combination, must be selected with respect to other and interacting factors--thermal, acoustic, energy-conservation, and economic.

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44 CODES AND STANDARDS _ (pp. 451-465 S Ap - - ix A) Minimal requirements of acceptability are often stated in building codes and standards in terms of air-exchange rules, temperature limits, and so forth. These documents tend to cause minimal requirements to be established for such direct effects as temperature, humidity, and odors, but may not be sufficient to provide for other effects, such as sir pollution or noise. Nor do these codes consider the interactions that can occur awns these factors and other system features such as lighting, thermal load O and spatial requirements . . . . ~ AIR DIFFUSION COrr=L . . . (pp. 465-471) Indoor air quality is most Only Controlled by fore - -air systems. Bowever, if diffusion control is designed without considering possible stratification of air within a room or a building, there may be local violations of thermal, humidity, or air~quality criteria for acceptability, and occupants may be exposed to conditions other than expected from the design. . . INDOOR ENVIRON CONTROL SYSTEM .~7 (pp. 465-471 ) Control methods::.for indoor environments require specification of environmental criteria and definition of the control variables. The environmental criteria that are identified in this document are health, comfort, welfare, energy consumption, and costs. The control variables identified are spatial requirements, lighting factors, thermal factors, air quality, and acoustic factors. Although environmental criteria and control variables can be identified and described, the capability of sensing the appropriate variables and controlling the system to meet the specified criteria is severely limited. Moreover, most indoor environmental control systems must attempt to respond activity or passively to all five of the Control variables simultaneously. Residentis1 air-oonditioning systems are conventionally designed to respond to spatial, thermal, and air-quality variables And, to a limited extent, acoustic variables. For larger facilities, such as offices and schools, air-conditioning systems must also respond to variations in occupancy and lighting loads, in addition to spatial, thermal, air-quality, and acoustic factors. For other functional spaces (e.g., concert auditoriums, art galleries, museums, and hospitele}, some or all of the verishles must be controlled with additional precision. For many years, air-conditioning systems were designed to meet the required environmental criteria (primarily thermal) at ainDeal first cost. Operating costs were not considered important as first costs, because energy was relatively inexpensive, compared with labor and material. However, as the costs of energy increased rapidly during the last decade, operating costs became a major factor in environmental control. Energy-conservation measures were implemented in many

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~5 buildings to reduce operating costs. Soac of these measure {e.~., improved system efficiency through better esintenance) had no is pact on environmental control, but others {e.g., reduced ventilation, heat, and lighting) had potentially adverse effects. One reason for the occurrence of adverse effects was lack of understanding' by building operators and owners, of the interrelationships axons ventilation rates, lighting, and health responses. . ~ ~ ~ ~ ~ ~ . . ~ ~ . As an example, changes in Gong can arrect tnerma~ comas, which affect ventilation rates. Conversely, results of come energy~oonservation measures have indicated that indoor environmenta1 quality not not be degraded and, in fact, may be enhanced by these changes {e.g., reduced stratification within occupied spaces). Thus, two general conclusions can be drawn: control methods may not be capable of adequately responding to environmental changes as energy-conser~ra~cion measures and cost contraints are applied; and the quality of the indoor environment need not be degraded, but can be enhanced if care is exercised in the selection and implementation of the energy and cost oonatrainta. AIR~CLEANING EQUIPMENT (pp. 471-488 ) Air~cleaning equipment for residential. and commercial applications is generally limited to particle filtration. Some gas and vapor removal equipment is available, primarily for commercial applications. Methods of rating or evaluating the performance of the gas and vapor removal systems are not yet available. Methods are available for rating and evaluating particle removal equipment, but they are simplistic and outdated. Moreover, in-place methods of system evaluation are available only for special cases, such ss hospitals and laboratories. COST m.F~:TIVENESS .. (Appendix B) Several economic models are available that can be used to evaluate the costs associated with various control strategies. Cost-effectiveness models that incorporate life~cycle costing are needed for decision-ouking. An approach to estimating the tact of residential energy~conser~ration Measures on air quality is discussed in Appendix B. The approach has not been validated or put into practical use, but is presented for illustration and discussion.