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ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 69 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 settingsâsuch as public, industrial, nonindustrial occupational, and residential buildingsâand 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
ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 70 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: â¢ unique or nearly unique to the tobacco smoke so that other sources are minor in comparison, â¢ 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, â¢ similar in emission rates for a variety of tobacco products, and â¢ 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 2â4) 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
ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 71 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 5â1) 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 Âµm, 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 5â1). 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.
ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 72 TABLE 5â1 Particulate Levels Measured in Indoor Environments, Including Smoking and Nonsmoking Occupancy Study Type of Occupancy Volume, Ventilation Monitoring Concentrations Comments Premise m3 Type/Rate Type/Time Mean (range), Âµ g/m3 Brunekreef and 4 NS â N/â G/2 mo 55 (20â90) TSP, Boleij, 1982 residences repeat measures 0.2 mg 7 S=1 â N/â G/2 mo 125 (60â250) TSP residences sensitivity 14 S=2 â N/â G/2 mo 152 (60â340) TSP residences sensitivity 1 S=3 â N/â G/2 mo 335 (â) TSP residence sensitivity Outdoors â â â G/2 mo â(41â73) Cuddeback et 2 taverns S=5â40 â N,M/1â6 G/9 h 446 (233â986) TSP al., 1976 NS=5â260 ach ventilation T=10â300 estimated Elliot and 3 arenas NS â â G/24 h 55 (42â92) TSP Rowe, 1975 3 arenas S â M/â G/0.3 h 350 (148â620) TSP T=2,000â 14,277 First, 1984 1 school NS â M/â P/â 20 (â) TSP 8 public S â N,M/â P/â 260 (40â660) TSP buildings Hawthorne et 11 NS 150â674 M/0.18â QCMI/5â 9â40 (â) RSP, al., 1984 residences 0.96 15 min winter/ (over 6 h) summerâ no sources 8 NS 150â674 M/0.26â QCMI/5â 12â46 RSP, residences 1.98 15 min winter/ (over 6 h) summerâ sourcese 2 S 150â674 M/0.27â QCMI/5â 96â106 RSP, residences 1.47 15 min winter/ (over 6 h) summerâ sourcese +cig. Leaderer et al., 3 public NS 163â M/0.37â G/4â21 h 17.8 (9.1â32.2) TSP, personal buildings 1,326 5.6d repeat communication measures, all var. 7 public 1.7â4.57b 168â600 M/0.77â G/2â24 h 205.1 (58â452) Measured buildings T=2â6 7.53 d (160.0 peak)
ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 73 Moschandreas et Outdoors â â â G/24 h 17.0 (â) RSP, TSP al., 1981 also measured 2 offices â â â G/24 h 16.8â20.2 RSP, TSP (53 peak) also measured 5 residences NS â N/0.5â1.3 G/24 h 19.4â4.01 RSP, TSP T=2â6 ach (118.9 also peak) measured 5 residences S â N/0.5â1.3 G/24 h 36.9â99.9 RSP, TSP ach also measured Nitschke et al., Outdoors â â â G/168 h 11.3Â±6.0 RSP 1985 (1â28) 19 residences NS 315â N/â G/168 h 26.0Â±22.6 RSP, repeat 1,021 (6â88) measures, source mixe 11 residences S 290â800 N/â G/168 h 59.2Â±38.8 RSP, repeat (10â144) measures, source mixe Parker et al., 1984 1 residence NS â N/0.2â1.9 0/24 h <10 (â) TSP T=3 ach 2 residences S=1â2 â N/0.2â0.7 0/24 h 10â46 TSP T=3â4 ach (â) Repace and Outdoors â â â P/2 min 42.9 (22â RSP, average Lowrey, 1980, 63) of 2-min 1982 samples 27 Public 0.13â â M/â P/2 min 278 (86â RSP, average buildings 3.54 f 1,140) of 2-min samples Sexton et al., 1984 Outdoors â â â G/24 h 17.0Â±1.6 RSP, repeat 19 homes (6â23) samples 24 residences NSc â N/â G/24 h 25.0Â±1.0 Used (13â63) fireplaces Spengler et al., Outdoors â â â G/24 h 21.1Â±11.9 RSP, repeat 1981 (â) measures 35 residences NS â N/â G/24 h 24.1Â±11.6 RSP, repeat (â) measures 15 residences S=1 â N/â G/24 h 36.5Â±14.5 RSP, repeat (â) measures 5 residences S=2 â N/â G/24 h 70.4Â±42.9 RSP, repeat (â) measures Spengler et al., Outdoors â â N/â G/24 h 18Â±2.1 RSP, repeat 1985 (â) measures 73 residences NS â â G/24 h 28Â±1.1 RSP, repeat (â) measures 28 residences S â â G/24 h 74Â±6.6 RSP, repeat (â) measures Sterling and 1 office S restr. â â G (?)/â 25.5 (15â TSP Sterling, 1983 36) 22 offices S â â G (?)/â 31.7 (â) TSP
ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 74 Study Type of Occupancy Volume, Ventilation Monitoring Concentrations Comments Premise m3 Type/Rate Type/Time Mean (range), Âµg/m3 U.S. 8 S â M/â G/1â1/4, Not given (â) TSP Department of domestic T=27â110 2â1/2 h Transportation, planes 1971 20 S â M/â G/6â7 h <10â120 (â) TSP military T=165â planes 219 Weber and 44 S â N,M/â P/2 min (30 133Â±130 (962 RSP, minus Fischer, 1980 offices ea) peak) background level aActive smokers per 100 m3. b Grams of tobacco consumed. cSome smoking was reported during 9 of the 280 samples. d Measured 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 m 3 . 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
ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 75 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 2â5). 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 2â6 and 2â9), acrolein and acetone (Tables 2â7 and 2â8), 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
ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 76 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 Âµm) 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 5â1. Personal exposures to RSP were dominated by indoor levels of ETS. Those reporting passive smoke exposure had
ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 77 mean personal respirable participate levels 28 Âµg/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 Âµm and does not specify chemical composition. A direct comparison with the EPA standard requires a consideration of average time exposed as well as concentration. FIGURE 5â1 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). 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 Âµg/m3 higher than those who reported no exposure (50.1 Âµg/m3 versus 31.7 Âµg/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,
ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 78 from 1.76 Âµg/m3 in a laboratory to 83.13 Âµg/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 exposureâthat 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
ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 79 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 2â4 to 2â9). 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: â¢ the representativeness of the air contaminant measured to the total ETS in the space is unknown; â¢ the proxy air contaminant measured may have a variety of other potential sources that were not accounted or controlled for; â¢ data were not collected on smoking rates or numbers of smokers; and â¢ 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 Âµm) associated with ETS. This RSP comprises
ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 80 a major general category of ETS contaminants and is produced in concentrations that are easily measured in occupied spaces where smoking occurs. FIGURE 5â2 Monthly mean RSP concentrations in six U.S. cities. Reprinted with permission from Spengler (1981). In a survey of more than 80 homes in six U.S. cities (Spengler et al., 1981), 24-hour gravimetric samples of RSP were collected every sixth day for up to 2 years in stationary samplers in each home and outdoors. The resulting data (monthly RSP means) aggregated by the number of smokers are shown in Table 5â1 and Figure 5â2. Homes without smokers exhibited RSP levels roughly equal to outdoor levels and followed outdoor trends. The presence of just one smoker in a home had a pronounced impact on RSP levels. Using regression analysis, the authors estimated that the impact on overall average RSP levels in a residence of a pack-per-day smoker was approximately 20 Âµg/m3. The impact of smoking in a home with central air conditioning was effectively doubled, presumably due to reduced air exchange. Table 5â1 presents the range of RSP levels measured in a variety of indoor microenvironments for smoking and nonsmoking occupancies. It also indicates whether direct measures of the variables necessary for the model outlined in Equation 5â1 below, or necessary to explain the RSP levels measured, were recorded. These variables include, among others, ventilation, mixing, removal by surfaces, and smoking occupancy. Outdoor levels of
ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 81 RSP or total suspended participates are generally lower than or equal to indoor levels in homes without smoking. Smoking occupancy is strongly associated with elevated levels of RSP in a variety of indoor microenvironments at levels well above outdoor concentrations and indoor concentrations where there is nonsmoking occupancy. However, few studies have directly recorded the data on the parameters that are necessary to validate models for predicting RSP levels due to smoking occupancy (see section below). Even so, using a number of assumptions, data in Table 5â1 have been used for model validation by some studies (Repace and Lowrey, 1980, 1982). MODELING The process of assessing exposure and attributing it to various microenvironments requires knowledge of the time individuals spend in such microenvironments and the typical air-contaminant levels (average and peak) occurring in them. The nature of the health or comfort effect under study determines the time-average concentration of concern. A number of microenvironments have been identified (Moschandreas, 1981), and time- budget surveys have shown that most individuals spend more than 90% of their time indoors, that is, in residential, industrial, and nonindustrial occupational environments (Szalai, 1972). The indoor residential and nonindustrial occupational environments represent the major microenvironments in which exposure to ETS takes place. Tobacco combustion is a major source category that affects the quality of the air indoors. The air- contaminant concentrations in an enclosed space resulting from tobacco combustion, and hence human exposures, are the result of a complex interaction of several interrelated variables (Figure 4â1), including source air- contaminant emission characteristics and source use, building characteristics, infiltration or ventilation rates, air mixing, loss terms (removal by surfaces or chemical transformations), and the efficiency of air-cleaning equipment. The interaction of these variables in determining the resultant indoor concentrations of ETS has typically been evaluated in both controlled laboratory (chamber and test house) studies and field studies within the theoretical framework of the general mass-balance equation (Turk, 1963; Shair and Heitner, 1974; Esmen, 1978; Ishizu, 1980; Repace and Lowrey, 1980; Leaderer et al., 1984).
ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 82 The mass-balance equation may be applied to tobacco smoke as either an equilibrium model (time- independent) or a dynamic model (time-dependent). Equilibrium models rely on the assumption that many of the input parametersâsuch as source rates, removal or loss rates, and ventilation ratesâare constant, even though these parameters in actuality may vary considerably in time. These models are useful in developing air- contaminant emission factors for ETS in controlled laboratory studies and in assessing long-term average exposures in given indoor microenvironments. Dynamic models are usually more flexible than equilibrium models and can provide information on short-term concentrations. They may be used to compare the sensitivity of results to variations of input parameters. Equilibrium models, when applied to field studies of ETS, require average information on the impact variables, while dynamic models require a great amount of detailed information obtained as a function of time. Dynamic and equilibrium models are useful in laboratory studies; equilibrium models are best suited to evaluating and predicting ETS concentrations in field studies, particularly when average concentrations over a period of days or longer are of interest. Equilibrium Models for RSP Laboratory and field studies typically utilize some form of a single-compartment equilibrium model to evaluate the input parameters to the mass-balance equation, to evaluate field-study data, and to project RSP concentrations from ETS indoors. These studies have reduced the general single-compartment mass-balance equation to the following simplified form. (5â1) where Ceq is the equilibrium concentration of RSP in a space expressed as micrograms per cubic meter (Âµg/m3) due to ETS, G is the RSP generation rate from tobacco combustion into the space in micrograms per hour (Âµg/ hour), nv is the ventilation or filtration rate in air changes per hour (ach), ns is the loss rate of RSP due to surface removal in a space in air changes per hour, V is the volume of the space in cubic meters (m3), and m is the mixing rate expressed as a fraction. The above model assumes no air-cleaning devices, either in the space or recirculated air.
ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 83 Under laboratory conditions, the input parameters can be controlled and evaluated. In conducting field studies or in estimating past RSP levels indoors, the values on the right side of Equation 5â2 have to be determined from available data. It should be emphasized that this equation assumes equilibrium conditions, and, to the extent that any of the generation or removal terms are intermittent (e.g., smoking rate) or variable (e.g., ventilation rate), errors are introduced. Generation Rate The generation rate of RSP for ETS is a function of the number of cigarettes smoked and the emission rate of RSP per cigarette. Few studies have investigated the RSP emission rate for SS plus exhaled MS, i.e., contributions to ETS. One recent study (Rickert et al., 1984) examined sidestream and mainstream emissions of tar, nicotine, and carbon monoxide in 15 brands of Canadian cigarettes with a range of advertised mainstream tar deliveries (0.7 to 17.0 mg tar/cigarette). The experiments utilized a single-port smoking machine and collected mainstream emissions and sidestream emissions, from a small chamber, onto Cambridge filters. The subsequently measured sidestream emissions of tar were found to average 24.1 mg/cigarette with a range of 15.8 to 36.0 mg/cigarette. These emissions were independent of mainstream emissions, which averaged 11.4 mg of tar per cigarette with a range of 2.5 to 19.4 mg/cigarette. Sidestream emissions were higher for ventilated brands. RSP emission rates were developed for 10 brands of U.S. cigarettes with rated tar deliveries from 1.0 to 23.0 mg and for one standard cigarette (University of Kentucky #1R3F). The study (B.P.Leaderer, S.K.Hammond, and T.Tosun, personal communication) utilized a 34-m3 chamber in which the cigarettes were smoked by occupants at a prescribed rate in an effort to create realistic environmental conditions. RSP measurements were made over a 4- hour period during equilibrium conditions via collection of well-mixed room air on filters with subsequent gravimetric analysis. RSP emission levels were found to range from 18.0 to 35.4 mg/cigarette, with an average of 26.9Â±4.8 mg/cigarette. Three brands of British cigarettes (very low tar, 1.5 mg; low tar, 12 mg; and medium tar, 18 mg) were evaluated for both mainstream and sidestream emissions of tar (U.K. Government,
ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 84 1980). The average RSP sidestream emission rate measured was 24.5 mg/cigarette, with a range of 23.0 to 26.4 mg. This study utilized a small test chamber and a smoking machine. The emission by-products were collected onto Cambridge filters. Only one study (Hoegg, 1972) reports mainstream and sidestream RSP levels for cigarettes prior to 1970. This test chamber study reported a sidestream particle emission rate of 25.8 mg/cigarette and mainstream particle emission rate of 36.2 mg/cigarette for one brand of cigarette. Current data would suggest an overall RSP emission rate from ETS in the range of approximately 20 to 36 mg tar/cigarette. An accurate estimate of an average emission rate for modeling purposes requires the weighing of the above emission data by the sales-weighted average cigarette brand sold. Data are not available to estimate the historical trend, if any, in the RSP emissions for ETS. Equation 5â1 assumes a constant, or near constant, source emitting over a sufficiently long time period to reach and maintain equilibrium conditions. In controlled experiments a constant rate of tobacco combustion is easily obtained. In practice, however, tobacco combustion rates in terms of numbers of cigarettes consumed over some period of time in different indoor environments is variable. In the absence of detailed data on cigarette consumption in a space, such as number of cigarettes smoked, time smoked, total weight of tobacco consumed, etc., estimates are required. For example, one smoker in a household smoking at a national average rate of two cigarettes/hour and 10 minutes/cigarette constitutes an intermittent source [G(t)dt]. A continuous source would be the smoking of six cigarettes/hour. Using a 26-mg/cigarette emission rate, the estimated total RSP emissions from the intermittent source, i.e., 52 mg/hour, would be represented as being emitted uniformly over a 1-hour period for the full averaging time considered. In large occupied spaces where smoking is permitted, such as nonindustrial occupational environments, estimates (Bridge and Corn, 1972; Jaffe, 1978; Repace and Lowrey, 1980) would indicate that, at any given time, 11% of the population would be smoking (one-third of the U.S. population are smokers, who are smoking at the rate of two cigarettes/hour and 10 minutes/cigarette). This would constitute a continous source. In practice, the smoking rate is probably highly variable in time. The RSP emissions from this
ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 85 example would also be averaged over time to produce uniform average emission rates per hour. For the estimation of equilibrium conditions in Equation 5â1, G=NE, where N is equal to the number of cigarettes consumed per hour in a space and E is the number of milligrams of RSP emitted into the environment per cigarette. The assumption of a continuous source introduces errors in the estimated RSP concentration. It is also important to note that the equilibrium model assumes that the source will be emitting contaminants over a sufficiently long period of time to achieve balance with the removal mechanisms (ventilation, removal by surfaces, and air cleaning). If C t is the concentration at time t (in hours) then: (5â2) where C eq is the equilibrium concentration and N is the effective removal rate (N=nv+ns). If the total impact of the removal rate, i.e., ventilation plus loss to surfaces, is equivalent to one ach, 85% of the equilibrium concentration would be obtained in 2 hours. Thus, to the extent that the source emissions do not combine over long periods of time, the equilibrium concentration will not be reached and maintained, introducing errors into the estimated or modeled RSP. Ventilation/Infiltration The supply of fresh air to a space by ventilation (air supplied by mechanical systems) or by infiltration (uncontrolled movement of air through cracks and unintentional openings in the building envelope) serves to reduce the levels of air contaminants generated by an indoor source. Building codes adopted and enforced by local, state, and federal government agencies generally specify minimal acceptable ventilation criteria to be maintained in buildings. These codes are usually derived from standards that have been promulgated by authoritative bodies (American National Standards Institute, American Society of Heating, Refrigerating and Air-Conditioning Engineers, etc.). These standards are usually developed by consensus and are generally voluntary until adopted by municipal or state governments. The studies of Yaglou et al. (1936) formed the basis of minimum required ventilation rates that persisted until 1979. These studies reported ventilation rates (fresh odor-free
ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 86 air) in cubic feet per minute per person (cfm/person) necessary to provide an acceptable odor environment. They found that, as occupant density increased, so did the required cfm/person ventilation rate. Because of the odor level, smoking occupancy required significantly more ventilation air. A minimum ventilation rate of approximately 10 cfm/person for nonsmoking occupancy and an occupant density of 400 ft3/person was recommended. Prior to 1936, minimum recommended ventilation rates were as high as 30 cfm/person. In 1973, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) adopted and published Standard 62â73 (Standards for Natural and Mechanical Ventilation). This standard recommended ventilation rates for various residential and commercial spaces on an occupancy-density basis. In 1981, ASHRAE adopted Standard 62â81 (Ventilation for Acceptable Indoor Air Quality), which also recommended ventilation rates for various residential and commercial spaces on an occupancy-density basis but distinguished between smoking and nonsmoking occupancy. Modal ventilation rates in this standard equaled 35 cfm/occupant for smoking occupancy and 7 cfm/occupant for nonsmoking occupancy. As noted in Equation 5â1, ventilation rates are incorporated as ach. ASHRAE 62â73 recommended from 15 to 25 cfm/person for general office space with an estimated 10 persons/1,000 ft2 density, while ASHRAE 62â81 recommended 20 cfm/person when smoking is permitted and a 5-cfm/person minimum for nonsmoking occupancy with an estimated 7 persons/1,000 ft2 density occupancy. Assuming full occupancy and an 8-ft ceiling, ASHRAE 62â73 ventilation rate ranges are 1.13 and 1.9 ach, while ASHRAE 62â81 recommends a rate of 1.3 ach for smoking occupancy and 0.26 ach for nonsmoking occupancy. When considered on a space-by-space basis for commercial or residential environments as recommended by either ASHRAE 62â73 or ASHRAE 62â81, the ach rates vary considerably, depending on the use of the space and whether smoking is permitted. In estimating ach's for inputs into Equation 5â1, to assess either current or past RSP concentrations in occupied space due to ETS, the following points should be kept in mind:
ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 87 â¢ There are no data to indicate the current or past distribution of ach's currently are or have been in a variety of commercial spaces in which smoking is or has been permitted. â¢ Air-exchange rates are calculated from cfm/person rates specified in the standards for full occupancy. To the extent that occupancy is less than or greater than the designed figure, the cfm/person could be significantly different. â¢ Ventilation codes are equivalent to design standards. In actual practice, the heating, ventilation, and air- conditioning (HVAC) system may not operate as designed. Interior alterations, modifications in occupancy, maintenance, and repair of equipment, and operator practice can significantly affect the performance of the HVAC system. Air-infiltration values in housing are induced by differences in pressure across the structure envelope. Limited data exist to indicate what the current or past distribution of air-exchange rates in houses in the United States are or what the intra- or interseasonal variations are. One study of seasonal infiltration rates of 312 houses in North America (Grimrsud et al., 1982; Figure 5â3) found a median value of 0.5 ach. This study was based on new energy-efficient houses. Another study (Grot and Clark, 1979; Figure 5â3) of 266 low-income houses in North America found the median seasonal air-exchange rate to be 0.9 ach. Air-infiltration rates for both studies were taken without occupants in the houses. Normal activities of occupants would add an average 0.10 to 0.15 ach to the values reported in these two studies. Ventilation or infiltration rates in commercial and residential buildings can vary by an order of magnitude among and within buildings, season to season and within a season. Unfortunately, there are few data available that would allow for an accurate estimate of the distribution of air-exchange rates in commercial and residential spaces currently or over the past several years. A range of 0.4 to 1.5 ach would seem reasonable. Removal by Surfaces Next to ventilation, the major mechanism for removal of suspended particulate matter is surface deposition. Surface deposition of particles indoors is a function of several variables, including particle size and composition, temperature, humidity, type and quantity of surface material in a room, surface-to-volume rates,
ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 88 and turbulence. In laboratory studies under conditions of ideal mixing, surface-deposition rates (hâ1) for ETS were found to vary from an equivalent 0.1 hâ1 to 1.8 hâ1 (Leaderer et al., 1986). The greater the degree of turbulence introduced into the chamber and the higher the surface-to-volume ratio, the higher the surface deposition. FIGURE 5â3 Histograms of infiltration values in two different samples of North American housing, (a) Average seasonal infilitration of 312 recently constructed houses; the median value is 0.5 air changes per hour (ach). Reprinted with permission from Grimsrud et al. (1982). (b) Average seasonal infiltration of 266 older low-income houses; the median is 0.9 ach. Reprinted with permission of Grot and Clark (1979). One recent chamber study evaluated the importance of materials (rugs, wall paper, and painted wall board), surface area of
ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 89 materials, temperature, humidity, and turbulence on the deposition rate of RSP generated by tobacco combustion under conditions of ideal mixing (Leaderer et al., 1986). In these experiments, the deposition rate of RSP was determined by monitoring the decay of RSP and carbon dioxide (injected into the chamber) under the experimental conditions examined. The difference between the RSP and carbon dioxide (nonreactive tracer gas) represented the RSP deposition rate. This study found the most pronounced impact on deposition in this chamber to be the air-recirculation rate (fresh-air-ventilation rate held constant) or turbulence. The type and quantity of material, temperature, and humidity were also found to impact particle deposition in a significant way. The results of this study indicate that a particle deposition rate of 0.2 to 0.8 hâ1 for ideal mixing might typically be encountered in occupied spaces. Mixing Once released into an enclosed space, air contaminants move through it by dispersion. Dispersion determines where the high and low concentrations of the contaminant will occur. Dispersion is controlled by diffusion, which is the movement from areas of high to low concentrations, and by mixing, which is the movement of air in the space. When ideal mixing occurs in a space, i.e., m=1 in Equation 5â1, no spatial gradient of an air contaminant like RSP exists, and the full effectiveness of ventilation and sink rates in removing the contaminant is seen. In controlled laboratory studies, ideal mixing is easily obtained through the use of mixing fans or the rapid recirculation of the air. In occupied spaces, however, ideal mixing is hardly ever obtained unless a great deal of turbulence is introduced to the space and the supply- and exhaust-air system is carefully designed. Less than ideal mixing can result in a pronounced concentration gradient of a contaminant in the space. The ventilation rates and removal by surfaces under those conditions are not as effective in lowering air-contaminant levels. The mixing term is usually defined as the ratio of effective ventilation to theoretical ventilation. In an occupied space, the value of the mixing factor is affected by the source and its use, room geometry, air supply and exhaust design, air-flow rates, obstacles in a room, and activity of the occupants. In addition, the mixing factor is specific for a precise
ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 90 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 5â1, 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 5â4 and 5â5 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 5â5 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 5â4 is then entered into Figure 5â5 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: â¢ an average total RSP emission rate is 26 mg/cigarette, â¢ the emissions are nearly consistent and averaged over a 1-h period, â¢ near steady-state or equilibrium conditions are reached quickly, â¢ no air-cleaning devices are in use, â¢ background levels of RSP in a space are zero, and
ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 91 FIGURE 5â4 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 5â5 to determine the ETS respirable suspended particulate mass concentration in any space in Âµg/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 5â3) 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.
ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 92 FIGURE 5â5 Diagram to calculate the ETS RSP concentration in a space as a function of the total mass of ETS RSP emitted (determined from Figure 5â4) 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 5â4) for a range of typical volumes of U.S. residences and rooms in these residences. â¢ 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 5â1 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 5â4 and 5â5 highlight the large effect that small variations in the input parameters can have on the predicted RSP concentration.
ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 93 For example, for a range of conditions that can be expected to be encountered in private residences with one smoker (shaded areas in Figures 5â4 and 5â5), 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 Âµg/m 3. 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 5â4 and 5â5 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 (5â3) where C eq 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
ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 94 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 5â3, 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 5â3, 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 5â3, 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
ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 95 less than 2.5 Âµm 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 Âµg/m3 to more than 200 Âµg/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
ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 96 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 1. 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. 2. 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. 3. 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. 4. 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 1. 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. 2. 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. 3. Information on current or past distributions of the input parameters for the mass-balance models of RSP concentrations is
ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 97 not available for a range of microenvironments in which individuals spend the majority of their time. 4. 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. 5. 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. 6. 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 62â1973. Standards for Natural and Mechanical Ventilation. Atlanta: ASHRAE, 1973. ASHRAE Standards 69â1981. 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 fumÃ©e de tabac. Ann. Pharm. Fr. 36:443â452, 1978. Brief, R.S. Simple way to determine air contaminants. Air Eng. 2:39â44, 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. 5:192â209, 1972. Brunekreef, B., and J.S.M.Boleij. Long-term average suspended particulate concentrations in smokers' homes. Int. Arch. Occup. Environ. Health 50:299â302, 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. 345â350. 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):500â573, 1985. Cuddeback, J.E., J.R.Donovan, and W.R.Burg. Occupational aspects of passive smoking. Am. Ind. Hyg. Assoc. J. 37:263â267, 1976. Elliot, L.P., and D.R.Rowe. Air quality during public gatherings. J. Air Pollut. Control Assoc. 25:635â636, 1975. Esmen, N.A. Characterization of contaminant concentrations in enclosed spaces. Environ. Sci. Technol. 12:337â339, 1978.
ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 98 Eudy, L.W., F.A.Thorne, D.L.Heavner, C.R.Green, and B.J.Ingebrethsen. Studies on the vapor-particulate phase distribution of environmental nicotine by selected trapping and detection methods. Presented at the 39th Tobacco Chemists' Research Conference, Montreal, Canada, Oct. 2â5, 1985. First, M.W. Environmental tobacco smoke measurement: Restrospect and prospect. Eur. J. Respir. Dis. 5(Suppl.):9â16, 1984. Galuskinova, V. 3,4-Benzpyrene determination in the smoky atmosphere of social meeting rooms and restaurants. A contribution to the problem of the noxiousness of so-called passive smoking. Neoplasma 11:465â468, 1964. Grimsrud, D.T., M.H.Sherman, and R.C.Sonderegger. Calculating infiltration: Implications for a construction quality standard, pp. 422â452. Proceedings of the ASHRAE-DOE Conference on the Thermal Performance of the Exterior Envelope of Buildings II, held in Las Vegas, Nev., Dec. 1982. New York: ASHRAE. 442 pp. Grot, R.A., and R.E.Clark. Air leakage characteristics and weatherization techniques for low-income housing, pp. 178â194. Proceedings of the ASHRAE-DOE Conference on the Thermal Performance of the Exterior Envelope of Buildings, held in Orlando, Fla., Dec. New York: ASHRAE, 1979. Hammond, S.K., B.P.Leaderer, and A.Roche. Collection and analysis of nicotine as a marker for environmental tobacco smoke in personal samples. Atmos. Environ., in press. Hawthorne, A.R., D.Gammage, C.S.Dudney, B.E.Hingerty, D.D.Schuresko, D.C.Parzyek, D.R.Womack, S.A.Morris, R.R.Westeley, D.A.White, and J.M.Schrimscher. Air Indoor Quality Study of Forty East Tennessee Homes. ORNL 5965. Oak Ridge, Tennessee: Oak Ridge National Laboratory, 1984. 134 pp. Hoegg, U.R. Cigarette smoke in closed spaces. Environ. Health Perspect. 2:117â128, 1972. Ishizu, Y. General equation for the estimation of indoor pollution. Environ. Sci. Technol. 14:1254â1257, 1980. Jaffe, J.H. Behavioral pharmacology of tobacco use. Life Sci. Res. Rep. 8:175â198, 1978. Just, J., M.Borkowska, and S.Maziarka. Zanieczyszczenie dymen tytoniowym powietrza kawiarn Warszawskich. (Tobacco smoke in the air of Warsaw coffee house.) Rocz. Panstw. Zakl. Hig. 23:129â135, 1972. Kusada, T. Control of ventilation to conserve energy while maintaining acceptable indoor air quality. ASHRAE Trans. 82:1169, 1976. Leaderer, B.P., W.S.Cain, and R.Isseroff, and L.G.Berglund. Ventilation requirements in buildings. II. Particulate matter and carbon monoxide from cigarette smoking. Atmos. Environ. 18:99â106, 1984. Leaderer, B.P., S.Renes, P.Bluyssen, and H.Van De Loo. Chamber studies of NO2, SO 2 and RSP deposition rates indoors. Proceedings of the 79th Annual Meeting of Air Pollution Control Association, Minneapolis, Minn., June 23â27, 1986. APCA No. 86â38.3, 1986. Moschandreas, D.J., D.J.Pelton, and J.Zabransky. Comparison of indoor and outdoor air quality. EPRI EA-1733. Electric Power Research Institute, 1981.
ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 99 Moschandreas, D.J. Exposure to pollutants and daily time budgets of people. Bull. N.Y. Acad. Med. 57:845â859, 1981. Muramatsu, M., S.Umemura, T.Okada, and H.Tomita. Estimation of personal exposure to tobacco smoke with a newly developed nicotine personal monitor. Environ. Res. 35:218â227, 1984. Muramatsu, T., A.Weber, S.Muramatsu, and F.Ackermann. An experimental study on irritation and annoyance due to passive smoking. Int. Arch. Occup. Environ. Health. 51:305â317, 1983. Nitschke, I.A., W.A.Clarke, M.E.Clarkin, G.W.Traynor, and J.B.Wadach. Indoor air quality, infiltration and ventilation in residential buildings. NYSERDA #85â10. Albany: New York State Energy Research and Development Authority, 1985. Parker, G.B., G.L.Wilfert, and G.W.Dennis. Indoor Air Quality and Infiltration in Multifamily Naval Housing, pp. 1â14. Annual PNWIS/ APCA Meeting, held in Portland, Oreg., Nov. 12â14, 1984. Penkala, S.J. and G.De Oliveira. The simultaneous analysis of carbon monoxide and suspended particulate matter produced by cigarette smoking. Environ. Res. 9:99â114, 1975. Perry, J. Fasten your seatbelts: No smoking. B.C. Med. J. 15:304â305, 1973. Repace, J.L., and A.H.Lowrey. Indoor air pollution, tobacco smoke, and public health. Science 208:464â472, 1980. Repace, J.L., and A.H.Lowrey. Tobacco smoke, ventilation, and indoor air quality. ASHRAE Trans. 88:894â914, 1982. Rickert, W.S., J.C.Robinson, and N.Collishaw. Yields of tar, nicotine and carbon monoxide in the sidestream smoke from 15 brands of Candian cigarettes. Am. J. Public Health 74:228â231, 1984. Schenker, M.B., T.Smith, A.Munoz, S.Woskie, and F.E.Speizer. Diesel exposure and mortality among railway workers: Results of a pilot study. Br. J. Ind. Med. 41:320â327, 1984. Sexton, K., J.D.Spengler, and R.D.Treitman. Personal exposure to respirable particulates: A case-study in Waterbury, Vermont. Atmos. Environ. 18:1385â1398, 1984. Shair, F.H., and Heitner, K.L. Theoretical model for relating indoor pollutant concentrations to those outside. Environ. Sci. Tech. 8:444â451, 1974. Spengler, J.D., D.W.Dockery, W.A.Turner, J.M.Wolfson, and B.J.Ferris, Jr. Long-term measurements of respirable sulphates and particles inside and outside homes. Atmos. Environ. 15:23â30, 1981. Spengler, J.D., R.D.Treitman, T.D.Tosteson, D.T.Mage and M.L.Soczek. Personal exposures to respirable particulates and implications for air pollution epidemiology. Environ. Sci. Technol. 19:700â707, 1985. Sterling, T.D., and E.M.Sterling. Investigations on the effect of regulating smoking on levels of indoor pollution and on the perception of health on comfort of office workers. Eur. J. Respir. Dis. 65(Suppl. 133):17â32, 1983. Szalai, A, Ed. The Use of Time. Daily Activities of Urban and Suburban Populations. The Hague: Mouton, 1972. 868 pp. Turk, A. Measurements of odorous vapors in test chamber: Theoretical. ASHRAE 9(5):55â8, 1963.
ASSESSING EXPOSURES TO ENVIRONMENTAL TOBACCO SMOKE IN THE EXTERNAL ENVIRONMENT 100 U.S. Department of Transportation and U.S. Department of Health, Education, and Welfare. Health aspects of smoking in transport aircraft. Washington, D.C.: U.S. Department of Transportation, Federal Aviation Administration, and U.S. Department of Health, Education, and Welfare, National Institute of for Occupational Safety and Health, 1971. 85 pp. U.K. Government. Smoking and health, p. 83. In U.K. Government. London Laboratory of the Government Chemist Report 1979. Annual Report. London: U.K. Government, 1980. 197 pp. Wallace, L.A., and W.R.Ott. Personal monitors: A state-of-the-art survey. J. Air Pollut. Control Assoc. 32:601â610, 1982. Weber, A. Acute effects of environmental tobacco smoke. Eur. J. Respir. Dis. 68(Suppl. 133):98â108, 1984. Weber, A., and T.Fischer. Passive smoking at work. Int. Arch. Occup. Environ. Health 47:209â221, 1980. Weber, A., C.Jermini, and E.Grandjean. Irritating effects on man of air pollution due to cigarette smoke. Am. J. Public Health 66:672â676, 1976. Weber, A., T.Fischer, and E.Grandjean. Passive smoking in experimental and field conditions. Environ. Res. 20:205â216, 1979a. Weber, A., T.Fischer, and E.Grandjean. Passive smoking: Irritating effects of the total smoke and the gas phase. Int. Arch. Occup. Environ. Health 43:183â193, 1979b. Winneke, G., K.Plischke, A.Roscovanu, and H.-W.Schlipkoeter. Patterns and determinants of reaction to tobacco smoke in an experimental exposure setting, pp. 351â356. In B.Berglund, T.Lindvall, and J.Sundell, Eds. Indoor Air, Vol. 2. Radon, Passive Smoking, Particulates, and Housing Epidemiology. Stockholm, Sweden: Stockholm Swedish Council for Building Research, 1984. Yaglou, C.P., E.C.Riley, and D.I.Coggins. Ventilation requirements. ASHRAE Trans. 42:133â162, 1936.