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Environmental Tobacco Smoke: Measuring Exposures and Assessing Health Effects 5 Assessing Exposures to Environmental Tobacco Smoke in the External Environment Environmental tobacco smoke (ETS) is composed of more than 3,800 compounds. The emitted compounds are found in vapor or particulate phases, or in some cases both. Volatile material may evaporate from particles within seconds to minutes after emission (e.g., nicotine, see Chapter 2). ETS has not yet been adequately characterized such that its chemical and physical nature can be clearly defined. The concentration of any individual or group of ETS constituents in an enclosed space is a function of: (a) the generation rate of the contaminant(s) from the tobacco, (b) the source consumption rate, (c) the ventilation or infiltration rate, (d) the concentration of the contaminant(s) of interest in the ventilation or infiltration air, (e) the degree to which the air is mixed, (f) the removal of the contaminant(s) by surfaces or chemical transformations, and (g) the effectiveness of any air-cleaning devices that may be in use. Exposure to ETS takes place in many settings—such as public, industrial, nonindustrial occupational, and residential buildings—and is a function of the time an individual spends in a microenvironment and the concentration of the ETS constituents in that environment. ETS exposures can be determined either by extrapolation from fixed-location monitoring survey instruments that are portable or by direct personal monitoring, using lightweight pumps and filters worn by subjects. This chapter will consider the methodology and data available for assessing human exposures to ETS in the physical (external) environment, including the suitability of proposed tracers or proxy air contaminants that would be representative of ETS, available data on ETS exposure from personal monitoring and monitoring of
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Environmental Tobacco Smoke: Measuring Exposures and Assessing Health Effects indoor environments, and the application of modeling to assessing ETS exposures. TRACERS FOR ENVIRONMENTAL TOBACCO SMOKE It is difficult to assess the ETS contribution to exposures because it usually exists in a complex mix of air contaminants from other sources. It is not practical, or possible, to monitor the full range of air contaminants associated with ETS, even under laboratory conditions. Chamber and field studies of ETS have monitored proxy contaminants as indicators of ETS. Most studies to date have been less than ideal because the component that was measured did not meet all the following criteria for an ETS tracer. A marker or tracer for quantifying ETS concentrations should be: unique or nearly unique to the tobacco smoke so that other sources are minor in comparison, a constituent of the tobacco smoke present in sufficient quantity such that concentrations of it can be easily detected in air, even at low smoking rates, similar in emission rates for a variety of tobacco products, and in a fairly consistent ratio to the individual contaminant of interest or category of contaminants of interest (e.g., suspended particulates) under a range of environmental conditions encountered and for a variety of tobacco products. While a variety of measures have been used as proxies or tracers of ETS, no single measure has met all the criteria outlined above, nor has any measure been universally accepted or recognized as representing ETS exposure. Carbon monoxide (CO) has been measured extensively both in chamber studies (Bridge and Corn, 1972; Hoegg, 1972; Penkala and De Oliveira, 1975; Weber et al., 1976, 1979a,b; Weber and Fisher 1980; Weber, 1984; Muramatsu et al., 1983; Leaderer et al., 1984; Winneke et al., 1984; Clausen, et al., 1985) and in occupied public and nonindustrial occupational indoor spaces (see Table 2–4) to represent ETS levels. Under steady-state conditions in chamber studies, where outdoor CO levels are known and the tobacco brands and smoking protocols constant, CO can be a reasonably reproducible indicator of ETS exposure. The variability
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Environmental Tobacco Smoke: Measuring Exposures and Assessing Health Effects of CO production from tobacco combustion is not well known and may vary considerably as a function of a number of variables (puff volume, puff duration, temperature, etc.). The ratio of CO, a nonreactive contaminant, to the more reactive gas-phase contaminants in ETS and to reactive suspended particulate mass is not well established, particularly in the dynamic phase of smoking, that is, the non-steady-state phase. Chamber and field studies have indicated that, under realistic smoking conditions that would be encountered in residences or offices, the typical smoking and ventilation rates would produce CO levels well within the levels observed in the outdoor air or in the indoor air generated from the indoor sources, such as kerosene heater, gas stove, etc. Consequently, it is difficult to factor out the contribution of CO from ETS in any specific, uncontrolled situation. In areas where heavy smoking is experienced, and where other sources of CO do not exist, CO may provide a rough measure of ETS exposure because the CO produced by the tobacco combustion will dominate. Both chamber and field studies (Table 5–1) have demonstrated that tobacco combustion has a major impact on the mass of suspended particulate matter in occupied spaces in the size range <2.5 µm, defined in this report as respirable suspended particulates (RSP). Suspended particulate mass is a major component of environmentally emitted tobacco smoke. Even under conditions of low smoking rates, easily measurable increases in RSP have been recorded above background levels (Table 5–1). The term RSP, however, encompasses a broad range of particulates of varying chemical composition and size emanating from a number of sources (outdoors, cooking indoors, etc). Smoking is not the only source of particulate matter suspended in the indoor air. The apportionment of the measured RSP to tobacco combustion in an occupied space will not be accurate unless the RSP emission rates for a variety of brands of tobacco are similar under a variety of conditions and source use information is obtained. The variability of RSP emissions into the environment for a variety of brands of tobacco needs to be investigated, as does the relationship between the vapor and particulate phases of tobacco-combustion emissions under a variety of environmental conditions, such as different humidities, and under a variety of smoking conditions, such as subject smokers versus smoking machines.
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Environmental Tobacco Smoke: Measuring Exposures and Assessing Health Effects TABLE 5–1 Particulate Levels Measured in Indoor Environments, Including Smoking and Nonsmoking Occupancy Study Type of Premise Occupancy Volume, m3 Ventilation Type/Rate Monitoring Type/Time Concentrations Mean (range), µg/m3 Comments Brunekreef and Boleij, 1982 4 residences NS — N/— G/2 mo 55 (20–90) TSP, repeat measures 0.2 mg 7 residences S=1 — N/— G/2 mo 125 (60–250) TSP sensitivity 14 residences S=2 — N/— G/2 mo 152 (60–340) TSP sensitivity 1 residence S=3 — N/— G/2 mo 335 (—) TSP sensitivity Outdoors — — — G/2 mo —(41–73) Cuddeback et al., 1976 2 taverns S=5–40 NS=5–260 T=10–300 — N,M/1–6 ach G/9 h 446 (233–986) TSP ventilation estimated Elliot and Rowe, 1975 3 arenas NS — — G/24 h 55 (42–92) TSP 3 arenas S T=2,000–14,277 — M/— G/0.3 h 350 (148–620) TSP First, 1984 1 school NS — M/— P/— 20 (—) TSP 8 public buildings S — N,M/— P/— 260 (40–660) TSP Hawthorne et al., 1984 11 residences NS 150–674 M/0.18–0.96 QCMI/5–15 min (over 6 h) 9–40 (—) RSP, winter/summer—no sources 8 residences NS 150–674 M/0.26–1.98 QCMI/5–15 min (over 6 h) 12–46 RSP, winter/summer—sourcese 2 residences S 150–674 M/0.27–1.47 QCMI/5–15 min (over 6 h) 96–106 RSP, winter/summer—sourcese+cig. Leaderer et al., personal communication 3 public buildings NS 163–1,326 M/0.37–5.6d G/4–21 h 17.8 (9.1–32.2) TSP, repeat measures, all var. 7 public buildings 1.7–4.57b T=2–6 168–600 M/0.77–7.53d G/2–24 h 205.1 (58–452) Measured (160.0 peak)
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Environmental Tobacco Smoke: Measuring Exposures and Assessing Health Effects Moschandreas et al., 1981 Outdoors — — — G/24 h 17.0 (—) RSP, TSP also measured 2 offices — — — G/24 h 16.8–20.2 (53 peak) RSP, TSP also measured 5 residences NS T=2–6 — N/0.5–1.3 ach G/24 h 19.4–4.01 (118.9 peak) RSP, TSP also measured 5 residences S — N/0.5–1.3 ach G/24 h 36.9–99.9 RSP, TSP also measured Nitschke et al., 1985 Outdoors — — — G/168 h 11.3±6.0 (1–28) RSP 19 residences NS 315–1,021 N/— G/168 h 26.0±22.6 (6–88) RSP, repeat measures, source mixe 11 residences S 290–800 N/— G/168 h 59.2±38.8 (10–144) RSP, repeat measures, source mixe Parker et al., 1984 1 residence NS T=3 — N/0.2–1.9 ach 0/24 h <10 (—) TSP 2 residences S=1–2 T=3–4 — N/0.2–0.7 ach 0/24 h 10–46 (—) TSP Repace and Lowrey, 1980, 1982 Outdoors — — — P/2 min 42.9 (22–63) RSP, average of 2-min samples 27 Public buildings 0.13–3.54f — M/— P/2 min 278 (86–1,140) RSP, average of 2-min samples Sexton et al., 1984 Outdoors 19 homes — — — G/24 h 17.0±1.6 (6–23) RSP, repeat samples 24 residences NSc — N/— G/24 h 25.0±1.0 (13–63) Used fireplaces Spengler et al., 1981 Outdoors — — — G/24 h 21.1±11.9 (—) RSP, repeat measures 35 residences NS — N/— G/24 h 24.1±11.6 (—) RSP, repeat measures 15 residences S=1 — N/— G/24 h 36.5±14.5 (—) RSP, repeat measures 5 residences S=2 — N/— G/24 h 70.4±42.9 (—) RSP, repeat measures Spengler et al., 1985 Outdoors — — N/— G/24 h 18±2.1 (—) RSP, repeat measures 73 residences NS — — G/24 h 28±1.1 (—) RSP, repeat measures 28 residences S — — G/24 h 74±6.6 (—) RSP, repeat measures Sterling and Sterling, 1983 1 office S restr. — — G (?)/— 25.5 (15–36) TSP 22 offices S — — G (?)/— 31.7 (—) TSP
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Environmental Tobacco Smoke: Measuring Exposures and Assessing Health Effects Study Type of Premise Occupancy Volume, m3 Ventilation Type/Rate Monitoring Type/Time Concentrations Mean (range), µg/m3 Comments U.S. Department of Transportation, 1971 8 domestic planes S T=27–110 — M/— G/1–1/4, 2–1/2 h Not given (—) TSP 20 military planes S T=165–219 — M/— G/6–7 h <10–120 (—) TSP Weber and Fischer, 1980 44 offices S — N,M/— P/2 min (30 ea) 133±130 (962 peak) RSP, minus background level aActive smokers per 100 m3. bGrams of tobacco consumed. cSome smoking was reported during 9 of the 280 samples. dMeasured during 24-h periods by the perfluorocarbon tracer technique. eSome residences had combinations of sources (kerosene heaters, wood stoves, etc.) and no cigarettes. fActive smokers density per 100 m3. ABBREVIATIONS: ach=Air changes per hour G=Gravimetric M=Mechanical ventilation N=Natural ventilation NS=No smokers O=Optical monitor P=Piezoelectric balance QCMI=Quality Crystal Microbalance Cosade Impactor RSP=Respirable suspended particles S=Smokers T=Total occupants TSP=Total suspended particles restr.=building with smoking restrictions
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Environmental Tobacco Smoke: Measuring Exposures and Assessing Health Effects Nicotine exhibits many of the properties necessary to serve as a potential marker for ETS. It is unique to tobacco smoke, is a major constituent of the smoke, and occurs in environmental concentrations that are easily measurable. It has been used as a marker for ETS in several studies (Table 2–5). The major problems with using nicotine are: (a) the ratio of nicotine [recently found to be in vapor phase in ETS (Eudy et al, 1985)] to other ETS constituents (RSP, in particular) for a variety of brands of tobacco is not known, (b) the reactivity rate (removal rate) of nicotine relative to other ETS constituents is not known, (c) particulate-or vapor-phase nicotine once deposited on surfaces may be re-emitted, and (d) until recently sampling methods for nicotine have not been efficient in collecting total nicotine (both vapor and particulate phase). Two new air-sampling methods for nicotine (Muramatsu et al., 1984; Hammond et al., in press) hold promise for obtaining total nicotine concentrations with the sensitivity and accuracy required for environmental air monitoring. A number of aromatic hydrocarbons (benzene, toluene, benzo[a]pyrene, pyrene, etc.) have been measured in field studies (Galuskinova, 1964; Just et al., 1972; Perry, 1973; Elliot and Rowe, 1975; Badre et al., 1978) investigating the impact of smoking on indoor air quality. Many of these air contaminants have other important sources, indoors and outdoors, that make measured levels difficult to interpret. Therefore, the aromatic hydrocarbons generally are poor indicators of ETS alone. Controlled chamber studies that elevate the variability of emission of the compounds from a variety of brands of tobacco have not been carried out, and the ratios of these compounds to categories of ETS contaminants (for instance, RSP) have not been established. Tobacco-specific nitrosamines and nitrogen oxides (Tables 2–6 and 2–9), acrolein and acetone (Tables 2–7 and 2–8), and polonium-210 have been measured as indicators of ETS. The low environmental concentrations, existence of other sources, reactivity of the tracer contaminants, and lack of data on the ratios of these contaminants to ETS contaminants for a variety of brands of tobacco limit their usefulness as indicators of ETS in indoor spaces. Research efforts need to be directed toward identifying a tracer or proxy air contaminant for ETS that meets the four criteria outlined above. At present, RSP is widely used as a general measure of ETS exposure indoors, particularly if the measurements are limited to locations where the levels of RSP from other sources
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Environmental Tobacco Smoke: Measuring Exposures and Assessing Health Effects are known and present at a low background concentration. The variability of RSP emissions for a number of brands of cigarettes, however, has yet to be evaluated. PERSONAL MONITORING Measurements of concentrations of air contaminants in the immediate breathing zone of an individual provide information on personal exposure. Personal monitoring can be accomplished with active samplers that integrate concentrations across a variety of locations or conditions using filters or vapor traps with subsequent laboratory analysis. Continuous portable monitoring instruments are available but have not been widely used. Particles are measured by light-scattering principles or frequency change as mass is deposited on a vibrating quartz crystal. For the most part, gases are measured using IR absorption or electrochemical reactions. Continuous-recording instruments have been utilized more for characterizing microenvironments than for direct measurements of personal exposures. Passive personal monitoring utilizes diffusion and permeation to concentrate gases on a collection medium for subsequent laboratory analysis. Both active and passive monitors have been employed in assessing an individual’s total exposure to individual or general categories of air contaminants. A discussion of the type, application, and usefulness of passive monitors to assess air contaminant exposures can be found in Elliott and Rowe (1975) and Wallace and Ott (1982). A relatively small number of studies have utilized personal monitors to determine total exposures to ETS (Muramatsu et al., 1984; Schenker et al., 1984; Sexton et al., 1984; Spengler et al., 1985; Hammond et al., in press). In one study (Spengler et al., 1985) indoor (residential), outdoor, and personal 24-hour concentrations of RSP (measured in this study as particles with a 50% cut point of 3.5 µm) were obtained for a sample of 101 nonsmoking individuals living in Roane County, Tennessee. In the sample, 28 of those monitored reported some exposure to ETS in either the home or workplace (nonindustrial), while 73 reported no such exposure. Each participant was sampled on 3 nonconsecutive days. Personal exposures to respirable particles for the subgroup exposed to ETS and the subgroup not exposed to ETS are shown in Figure 5–1. Personal exposures to RSP were dominated by indoor levels of ETS. Those reporting passive smoke exposure had
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Environmental Tobacco Smoke: Measuring Exposures and Assessing Health Effects FIGURE 5–1 Cumulative frequency distributions of RSP concentrations from central site ambient and personal monitoring of smoke-exposed and nonsmoke-exposed individuals. Reprinted with permission from Spengler et al. (1985). mean personal respirable participate levels 28 µg/m3 higher than those without passive smoke exposure. Particulate levels for those exposed to ETS showed a large variation, with approximately 25% of the personal samples having RSP levels in excess of the EPA ambient standard for outdoor total suspended particles. The EPA standard, however, includes particles up to approximately 50 µm and does not specify chemical composition. A direct comparison with the EPA standard requires a consideration of average time exposed as well as concentration. Sexton et al. (1984) conducted 24-hour personal monitoring for RSP for 48 nonsmoking individuals for 24 different residences. Samples were collected every other day, for a 2-week period, during a heating season in Vermont. Those individuals reporting exposure to ETS for more than 2 hours per day had RSP levels 18.4 µg/m3 higher than those who reported no exposure (50.1 µg/m3 versus 31.7 µg/m3). In demonstrating a new method for the collection and analysis of nicotine in air, one study (Muramatsu et al., 1984) obtained personal-monitoring samples of nicotine for one nonsmoker in 53 nonindustrial indoor microenvironments, including offices, houses, restaurants, cars, buses, etc. The samples were collected over a 1-hour to 8-hour time period in each space and were specific for nicotine. A wide range of nicotine concentrations were reported,
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Environmental Tobacco Smoke: Measuring Exposures and Assessing Health Effects from 1.76 µg/m3 in a laboratory to 83.13 µg/m3 in a car. It is difficult to interpret these results in terms of an integrated exposure for a large segment of the population, since the sampling scheme did not explicitly provide population estimates of exposure—that is, personal samples were obtained on a microenvironment basis for only one individual. Lacking good data for the ratio of total nicotine to RSP in ETS, it is difficult to estimate the RSP exposure levels. The data, however, do demonstrate that the variability of nicotine concentrations and the occurrence of high concentrations of other ETS components can be found in various microenvironments. In an epidemiologic study of the health effects of diesel exhaust on railroad workers (Schenker et al., 1984), which included a control group of railroad office workers who were not exposed to diesel exhaust but were exposed to ETS, ETS was recognized as an important component of the respirable particulate exposures. Hammond et al. (in press) used a newly developed air-sampling and analytical method for measuring total nicotine in collected RSP personal samples to determine the contribution of ETS to the RSP levels measured. Their results indicated that the major portion of the office workers’ RSP exposure is due to ETS. Ratios of nicotine to RSP for a variety of brands of tobacco need to be established before absolute ETS exposures can be assessed. Personal monitoring can provide a useful measure of an individual’s exposure to an air contaminant or class of contaminants over a period of several hours to several days. The usefulness of personal monitors for assessing ETS exposure would be greatly enhanced if the personal monitor were passive in nature and inexpensive. Personal and portable monitors, however, need to be evaluated to determine their usefulness in establishing ETS exposures associated with long-term adverse health outcomes, such as cancer. They may be useful in establishing ETS exposures, in a background of confounding air contaminants, associated with short-term effects. A variety of sample collection and analysis methods has been used to monitor individual constituents and categories of contaminants found in ETS for both personal monitoring and air monitoring of spaces. While this report does not offer a review and evaluation of the monitoring methods that have been employed and are available, it should be clearly noted that the specificity and sensitivity of the measurement method must be evaluated to
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Environmental Tobacco Smoke: Measuring Exposures and Assessing Health Effects assess the uncertainties in the measured concentrations. The constituents of ETS will exhibit a pronounced spatial and temporal distribution in an indoor space and among indoor environments, due to variations in smoking rates and building characteristics. In interpreting measured concentrations of ETS constituents, one must recognize the potential for pronounced spatial and temporal variations. CONCENTRATIONS OF ENVIRONMENTAL TOBACCO SMOKE IN INDOOR ENVIRONMENTS Various Environmental Tobacco Smoke Constituents There is a sizable body of literature reporting on measurements of various constituents (acrolein, aromatic hydrocarbons, carbon monoxide, nicotine, etc.) of ETS in a variety of microenvironments. These studies have reported a wide range of concentrations of ETS-related air contaminants under conditions of normal space use (Tables 2–4 to 2–9). However, the majority of the measurements are of very limited use in assessing actual human exposures to ETS for a large segment of the population for the following reasons: the representativeness of the air contaminant measured to the total ETS in the space is unknown; the proxy air contaminant measured may have a variety of other potential sources that were not accounted or controlled for; data were not collected on smoking rates or numbers of smokers; and important building characteristics such as infiltration or volume were not recorded. While these studies have indicated the range of concentrations of several ETS-related air contaminants that can be found indoors, they do not provide a sufficient basis on which ETS indoor exposure estimates can be made. Particulate Levels and Smoking Occupancy The most extensive and suitable data base for modeling ETS is the RSP (<2.5 µm) associated with ETS. This RSP comprises
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Environmental Tobacco Smoke: Measuring Exposures and Assessing Health Effects location. No data exist that would indicate the distribution of the values for the mixing factor in occupied spaces. A limited number of studies show a range of mixing factors from 0.1 to near 1.0 (Brief, 1960; Kasuda, 1976). Volume The volume of the space in which smoking occurs is highly variable. It can range from a few cubic meters in a car to several thousand cubic meters in large auditoriums or sports arenas. The highest RSP levels from ETS will tend to occur in smaller spaces with high smoking rates. Predicting Environmental Tobacco Smoke Exposures from Tobacco Combustion Utilizing Equation 5–1, expected RSP concentrations indoors from ETS can be estimated for a range of the input parameters that realistically can be expected under normal smoking occupancy. Figures 5–4 and 5–5 allow for the easy calculation of RSP levels due to ETS as a function of Smoking rate, ventilation, sink rate, mixing, and volume of the space (see the example outlined in the legends of these figures). The calculations treat the spaces of concern (e.g., multiroom home or a single room in a house) as a single compartment with no air-cleaning devices. The total amount of RSP (in milligrams) from ETS can be determined in Figure 5–5 as a function of the smoking rate and effective removal rate (N). The removal rate is equal to the sum of ventilation plus removal by surfaces times the mixing factor. The total amount of RSP calculated from Figure 5–4 is then entered into Figure 5–5 to determine the RSP concentrations (in micrograms per cubic meter) expected for a given volume of space. The calculations used to generate these figures assume that: an average total RSP emission rate is 26 mg/cigarette, the emissions are nearly consistent and averaged over a 1-h period, near steady-state or equilibrium conditions are reached quickly, no air-cleaning devices are in use, background levels of RSP in a space are zero, and
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Environmental Tobacco Smoke: Measuring Exposures and Assessing Health Effects FIGURE 5–4 Diagram for calculating the RPS mass from ETS emitted into any occupied space as a function of the smoking rate and removal rate (N). The removal rate is equal to the sum of the ventilation or infiltration rate (nv) and removal rate by surfaces (ns) times the mixing factor m. The calculated ETS RSP mass determined from this figure serves as an input to Figure 5–5 to determine the ETS respirable suspended particulate mass concentration in any space in µg/m3. Smoking rates (diagonal lines) are given as cigarettes smoked per hour. Mixing is determined as a fraction and nv and ns are in air changes per hour (ach). All three parameters have to be estimated or measured. Calculations were made using the equilibrium form of the mass-balance equation (Equation 5–3) and assume a fixed emission rate of 26 mg/cigarette of RSP. Shaded area shows the range of RSP emissions that could be expected for a residence with one smoker smoking at a rate of either 1 or 2 cigarettes per hour for the range of mixing, ventilation, and removal rates occurring in residences under steady-state conditions.
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Environmental Tobacco Smoke: Measuring Exposures and Assessing Health Effects FIGURE 5–5 Diagram to calculate the ETS RSP concentration in a space as a function of the total mass of ETS RSP emitted (determined from Figure 5–4) and the volume of a space (diagonal lines). The concentrations shown assume a background level in the space of zero. The particulate concentrations shown are estimates during smoking occupancy. The dashed horizontal lines (A, B, C, and D) refer to National Ambient Air Quality Standards (health-related) for total suspended particulates established by the U.S. Environmental Protection Agency. A is the annual geometric mean. B is the 24-hour value not to be exceeded more than once a year. C is the 24-hour air pollution emergency level. D is the 24-hour significant harm level. Shaded area shows the range of concentrations expected (from Figure 5–4) for a range of typical volumes of U.S. residences and rooms in these residences. a one-chamber model is appropriate. In these figures, the RSP-emission rate is assumed constant. If, in fact, this rate is variable, then the predicted RSP level will also vary. As already discussed, the input parameters to Equation 5–1 are known to vary greatly under realistic occupancy conditions, with few or no data available on the distribution of the values of those input parameters. Figures 5–4 and 5–5 highlight the large effect that small variations in the input parameters can have on the predicted RSP concentration.
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Environmental Tobacco Smoke: Measuring Exposures and Assessing Health Effects For example, for a range of conditions that can be expected to be encountered in private residences with one smoker (shaded areas in Figures 5–4 and 5–5), RSP levels in residences or public places during smoking occupancy can vary by more than two orders of magnitude from approximately 17 to 5,000 µg/m3. This example assumes one smoking resident smoking at a rate of either one or two cigarettes/hour. Relatively easy-to-obtain information on some of the input parameters, such as building volume or typical smoking densities, obtained through questionnaires or observation, can serve to significantly reduce the range of estimated exposures. It is also clear from Figures 5–4 and 5–5 that, for the vast majority of conditions, RSP levels due solely to ETS can be expected to equal or exceed levels specified in National Ambient Air Quality Standards for the total suspended particulates (Code of Federal Regulations, 1985). These standards are health-based and reflect different averaging times as well as levels of exposure. Direct comparison of exposures with the standards requires consideration of particle size, concentration, and time. The physical and chemical nature of the particulate matter resulting from tobacco smoke is different from particulate matter observed outdoors in ambient air. These different particulate matters no doubt have different biological effects. Therefore, direct comparisons of exposures to outdoor standards should be made with caution. Application of Respirable Suspended Particulates Model The most extensive use of the mass-balance equation for assessing RSP levels due to ETS in occupied spaces has been by Repace and Lowrey (1980). Drawing upon the best available data from several sources, including both measured and estimated parameters, they proposed and applied in field observations a condensed version of the mass-balance equation for estimating RSP exposures due to ETS in a variety of indoor microenvironments. Their model is (5–3) where Ceq is the equilibrium of concentration of RSP due to ETS expressed in micrograms per cubic meter, Ds is the density of active smokers expressed as units of burning cigarettes observed in a space per 100 m3 over the sampling time frames, and nv is the
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Environmental Tobacco Smoke: Measuring Exposures and Assessing Health Effects ventilation or infiltration rate in ach. The constant term (650) is calculated from a standard set of assumed conditions for smoking rates, RSP emission rates, mixing factors, ventilation rates, and sink rates. These standard sets of conditions are derived largely from experimental data and building standards. Although many of the input parameters were estimated from the literature, which is based on limited experimental data, Repace and Lowrey (1980, 1982) applied Equation 5–3, or similar equations, to a variety of situations and found that they produced reasonably accurate estimates in a limited number of occupied spaces with smoking occupancy. Apparently, easy-to-obtain data on building volumes, design occupancy, smoking occupancy, type of ventilation systems, and building standards can improve the prediction of RSP concentrations. In using Equation 5–3, the major assumptions deal with mixing, ventilation rates, and sink rates. Additional field testing of the Repace and Lowrey model, as well as a better understanding of the variability of the input parameters, either estimated or measured for use in Equation 5–3, is needed. SUMMARY AND RECOMMENDATIONS In investigating the adverse health and comfort impact of air contaminants, it is important to specify the exposure to a specific air contaminant or a class of air contaminants on the time scale corresponding to the health or comfort effect being evaluated. Accurate data on exposure is essential to minimize misclassification of exposure in epidemiologic studies of air contaminants. In the absence of an indicator of the dose of the contaminant, target tissue exposures may be estimated by use of biological markers, by personal monitors, or by the air monitoring of microenvironments in which people spend time combined with time activity patterns. ETS is comprised of several thousand chemicals in both the gas and particulate phases. While several individual constituents of ETS have been measured in a number of microenvironments as a proxy for ETS (nicotine, CO, acrolein, etc.), none have met all of the criteria necessary for a suitable proxy, nor has an individual contaminant been uniformly accepted or recognized as representing ETS exposure. New methods of measuring nicotine in air hold promise for using nicotine as a suitable proxy for ETS, but considerable development and testing need to be done. The single largest component of ETS by weight is the RSP, which refers to particles
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Environmental Tobacco Smoke: Measuring Exposures and Assessing Health Effects less than 2.5 µm and is highly variable in chemical composition. The RSP fraction of ETS is currently the best and most-utilized general category of air contaminants to represent ETS exposure. A limited number of studies that employed personal monitors to measure total RSP found that individuals who reported being exposed to ETS were exposed to RSP concentrations consistently greater than those who reported no exposure. Furthermore, the distribution of RSP concentrations varied widely (from 10 µg/m3 to more than 200 µg/m3). The limited number of samples, lack of data on the environments where the exposure took place, and lack of a specific proxy for ETS do not permit accurate estimation of the ETS exposure or extension of the data to a larger population. They do indicate, however, that individuals who report exposure to ETS will have greater RSP exposures than those who do not. Measurements of RSP levels in various indoor environments (residences, offices, restaurants, bars, bowling alleys, airplanes, arenas, etc.) have clearly shown that RSP levels will be considerably above background levels (outdoor levels or nonsmoking levels) when smoking is reported in the space. Modeling of RSP concentrations due to ETS in any indoor environment usually utilizes a simplified form of the mass-balance equation. These models are typically single-chamber models that assume steady-state or equilibrium conditions to estimate RSP levels and require as input parameters an RSP-emission rate for tobacco combustion, number of cigarettes consumed, ventilation or infiltration rates, removal rates by surfaces, air mixing in the space, and volume of the space. Information on the current or past distribution of these input parameters in the range of microenvironments in which individuals spend the majority of their time (residences, offices, etc.) is not available. The variability of one or more of the input parameters can make a difference of as much as an order of magnitude in the estimated RSP concentration. Additional variability in the estimated RSP levels is introduced to the extent that the equilibrium assumptions do not hold (i.e., an intermittent rather than continuous source). Gathering data on easily measured input parameters such as smoking rates or volume can substantially reduce the variability of the estimated RSP levels. Limited field tests of the general equilibrium model, in which some of the input parameters were measured and others were estimated either from chamber studies or building codes, have predicted RSP levels reasonably well over a
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Environmental Tobacco Smoke: Measuring Exposures and Assessing Health Effects wide range of values of input parameters. While the predicted level of RSP exposure due to ETS may be highly variable using models, it is clear from the models that, even using the most conservative estimates for the input parameters, RSP levels when smoking is allowed will result in substantial increases over nonsmoking occupancy RSP levels. This is consistent with the concentrations measured through personal monitoring or area monitors in various microenvironments. What Is Known Various individual chemical constituents of ETS have been measured in indoor spaces as proxies for ETS, but their suitability as proxies for ETS exposures has not been well established. The total RSP, measured by personal monitors, has been found to be elevated for individuals who reported being exposed to ETS as compared with those who reported no exposure. The distributions of RSP measured by personal monitors and by portable monitors vary widely. However, levels of RSP measured in various indoor environments have clearly shown that RSP levels will be considerably above background levels when smoking is reported in the space. Limited field tests of the mass-balance, general-equilibrium model in which some of the input parameters are measured and others are estimated have predicted RSP levels reasonably well over a wide range of values of input parameters. What Scientific Information Is Missing There is a lack of data on the environments where measurements have been taken. Consequently, an accurate estimate of the ETS exposure or extension of the data to a large population based upon present data may not be possible. A suitable proxy or tracer air contaminant is not available for total ETS exposure. Nicotine may be a good indicator for exposure to the vapor phase. However, the relative proportions of various constituents of ETS in the particulate and vapor phases need further study to determine the extent to which a tracer for one phase can be used to infer exposure to the other phase. Information on current or past distributions of the input parameters for the mass-balance models of RSP concentrations is
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Environmental Tobacco Smoke: Measuring Exposures and Assessing Health Effects not available for a range of microenvironments in which individuals spend the majority of their time. When levels of various constituents of ETS are measured in field situations, data should be gathered on input parameters such as smoking rates or volume so that a detailed field evaluation of the equilibrium model can be made. ETS exposure in epidemiologic studies needs to be improved. Questionnaires must be validated. Personal and microenvironmental monitoring studies should be conducted to determine the predictive value of various exposure assessment methodologies. This might be achieved as part of a nested design in a larger epidemiologic study. The variability of RSP emissions into the environment and the relationship between vapor and particulate phases need to be investigated for a variety of brands of tobacco. REFERENCES ASHRAE Standards 62–1973. Standards for Natural and Mechanical Ventilation. Atlanta: ASHRAE, 1973. ASHRAE Standards 69–1981. Ventilation for Acceptable Indoor Air Quality. Atlanta: ASHRAE, 1981. 19 pp. Badre, R., R.Guillerme, N.Abram, M.Bourdin, and C.Dumas. Pollution atmospherique par la fumée de tabac. Ann. Pharm. Fr. 36:443–452, 1978. Brief, R.S. Simple way to determine air contaminants. Air Eng. 2:39–44, 1960. Bridge, D.P., and M.Corn. Contribution to the assessment of nonsmokers to air pollution from cigarette and cigar smoke in occupied spaces. Environ. Res. 5:192–209, 1972. Brunekreef, B., and J.S.M.Boleij. Long-term average suspended particulate concentrations in smokers’ homes. Int. Arch. Occup. Environ. Health 50:299–302, 1982. Clausen, G., W.S.Cain, P.O.Fanger, and B.P.Leaderer. The influence of aging, particle filtration and humidity on tobacco smoke odor, pp. 345–350. In P.O.Fanger, Ed. CLIMA 2000, Vol. 4. Indoor Climate. Copenhagen: VVS Kongress-VVS Messe, 1985. Code of Federal Regulations (CFR). National primary and secondary ambient air quality standards. Code Fed. Regul. 40(PT50):500–573, 1985. Cuddeback, J.E., J.R.Donovan, and W.R.Burg. Occupational aspects of passive smoking. Am. Ind. Hyg. Assoc. J. 37:263–267, 1976. Elliot, L.P., and D.R.Rowe. Air quality during public gatherings. J. Air Pollut. Control Assoc. 25:635–636, 1975. Esmen, N.A. Characterization of contaminant concentrations in enclosed spaces. Environ. Sci. Technol. 12:337–339, 1978.
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Representative terms from entire chapter: