Environ. Sci. Technol. 1991, 25,770-777 (38) Connolly, J. P.; Pedersen, C. J. Environ. Sci. Technol. 1987, 22, 99. (39) Geyer, H.; Viswanathan, R.; Freitag, D.; Korte, F. Chemosphere 1981, IO, 1307. (40) Wang, K.; Rott, B.; Korte, F. Chemosphere 1982,11,525. (41) Lederman, T. C.; Rhee, G. Y. Can. J . Fish. Aquat. Sci. 1982, 39, 380.
(42) Mailhot, H. Environ. Sci. Technol. 1987, 21, 1009. Received for review July 20, 1990. Revised manuscript received November 9,1990. Accepted December 10,1990. This work was carried out at HydroQual, Inc. under subcontract to Battelle Ocean Sciences as part of the U.S. E P A New Bedford Harbor RIIFS Modeling Program.
Evaluation of Vapor-Phase Nicotine and Respirable Suspended Particle Mass as Markers for Environmental Tobacco Smoke Brian P. Leaderer" John B. Pierce Laboratory, Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, Connecticut 065 19
S. Katharlne Hammond Department of Family and Community Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 0 1655
Vapor-phase nicotine and respirable suspended particle mass (RSP) emissions from tobacco combustion were evaluated as markers for environmental tobacco smoke (ETS) in an environmental chamber and a field study. The chamber results indicated that emissions of vaporphase nicotine and RSP were similar among brands of cigarettes and both contaminants were emitted in quantities that are easily measured in enclosed environments. The field study collected 1-week measurements of vapor-phase nicotine and RSP as well as extensive source use information in 96 residences. Vapor-phase nicotine measurements were closely related to the number of cigarettes smoked and were highly predictive of respirable suspended particle mass generated by tobacco combustion. The observed field association between vapor-phase nicotine and RSP was consistent with chamber studies. The chamber and field studies reported here indicate that vapor-phase nicotine is a suitable qualitative and quantitative marker for environmental tobacco smoke in the residential indoor environment. Due to background levels of RSP from other sources, RSP measurements indoors should be supplemented by a measure of the quantity of tobacco consumed or a measure of the vapor-phase nicotine concentration before the portion attributable to ETS can be determined.
Introduction The health hazards associated with smoking have received extensive study and are well-known. Thus, it is not surprising that there is now a growing concern that exposure to environmental tobacco smoke (ETS) may be associated with adverse health and comfort effects in nonsmokers. The health and comfort effects associated with involuntary smoking have been extensively reviewed in two recent reports ( I , 2). While both reports found an association between exposure to ETS and a wide range of acute and chronic health effects, they noted that epidemiologic studies of ETS have been handicapped due to limitations in assessing exposures to ETS. Accurate methods of assessing ETS exposures are needed for conducting epidemiologic studies, for calculating risks, and in developing effective control measures to reduce or eliminate risks. ETS is a complex mix of over 4000 chemicals found in both the particle and vapor phase; it is primarily composed of exhaled mainstream smoke and contaminants emitted 770
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from the burning end of a cigarette between puffs. ETS is a major source of both particle- and vapor-phase indoor air contaminants (1-3). Some of the ETS contaminants are associated solely with the combustion of tobacco (e.g., nicotine and tobacco-specific nitrosamines) while others are emitted by a number of other sources in the outdoor and indoor environment (e.g., carbon monoxide and suspended particle mass). Given this complex mix, one necessary task is the identification of an air contaminant or class of air contaminants for monitoring that would be indicative of the presence and amount of ETS. Over the past several years a number of marker or proxy compounds have been used to represent ETS concentrations in both field and chamber studies. Nicotine, carbon monoxide, 3-ethenylpyridine, nitrogen dioxide, pyridine, aldehydes, nitrous acid, acrolein, benzene, toluene, myosmine, and several other compounds have been used or been suggested for use as markers or proxies for the vapor-phase constituents of ETS (1-7). Tobacco-specific nitrosamines, particle-phase nicotine and cotinine, solanesol, polonium-210, benzo[a]pyrene, potassium, chromium, and respirable suspended particle (RSP) mass are among the air contaminants used or suggested for use as markers for particle-phase constituents of ETS (1-3, 8-10), Vapor-phase nicotine is a strong candidate as a marker for ETS. It is specific to tobacco combustion and emitted in large quantities in ETS. Approximately 95% of the nicotine in ETS is in the vapor phase (1, 2 , 4 , 5, 11). In addition, measurements of nicotine and one of its metabolites, cotinine, (in blood, urine, and saliva) are used extensively as a biomarkers of exposure to ETS and active smoking (1, 2). Recent advances in air sampling have resulted in the development of a variety of inexpensive and accurate active (4,5,12,13) and passive (14) monitors for measuring nicotine in indoor environments and for personal monitoring. ETS is a particularly important indoor source of respirable suspended particle mass (RSP particle diameter 1 2 . 5 pm). ETS particles contain a number of known and suspected carcinogens, which have also been used as proxies for ETS in both chamber and field studies (I,2). Studies of personal exposures to RSP and of RSP levels in indoor environments have shown elevated levels of RSP when ETS exposure was reported ( I , 2). Efforts to model ETS exposures for the purpose of assessing risks and the
0013-936X/91/0925-0770$02.50/0
0 1991 American Chemical Society
impact of various mitigation measures have focused on predicting ETS-associated R S P concentrations (e.g., ref 15). However, RSP encompasses a broad range of particles of varying chemical composition and size, emanating from a number of sources both outdoors and indoors, and therefore, RSP is not unique to ETS. Before the utility of either vapor-phase nicotine or RSP as a marker for ETS can be fully evaluated, data are needed on (a) the variability of vapor-phase nicotine and RSP concentrations from a variety of brands of cigarettes, tested under realistic conditions; (b) the ratio of vaporphase nicotine and RSP concentrations to each other and to other ETS constituents; and (c) a demonstration of the feasibility of vapor-phase nicotine and RSP as E T S markers in a field evaluation. The most extensive study of variability by brand was reported by Rickert et al. (IO), where smoking machine generated sidestream (SS) emissions of nicotine, carbon monoxide, and RSP were evaluated for 15 brands of Canadian cigarettes in a 1-ft3container. Little, however, is known about the variability of E T S nicotine emissions and their relation to other E T S constituents emitted from various brands of cigarettes when the emissions are generated under realistic conditions, that is, when ETS is generated by smokers smoking at typical smoking rates and is dispersed in large chambers. In this report vapor-phase nicotine is evaluated as a marker for ETS in a combined environmental chamber and field study. The chamber study evaluated concentrations of vapor-phase nicotine relative to particle mass concentrations for a variety of cigarette brands. The field study assessed 1-week-average vapor-phase nicotine concentrations and particle mass concentrations in residences as a function of the number of cigarettes smoked and the presence of other sources.
Methods Chamber Studies. The chamber studies were designed to determine the emission rates for total particle mass for a number of different brands of cigarettes and to determine the variability of the particle mass/nicotine air concentrations as a function of brand of cigarette. The experiments were carried out in a 1200-ft3(34 m3) aluminum-lined chamber (16) equipped with an efficient ventilation system that ensured very rapid mixing of outdoor air with the air contaminants generated in the chamber. Air entered the chamber through a plenum beneath a perforated floor and flowed upward through the floor to the ceiling. The volume flow (recirculation rate) was set a t 1900 ft3/min (950 L/s) or 95 air changes/h. Ventilation air could be brought into the chamber a t 0-400 ftg/min. The ventilation rate was calibrated by introducing a predetermined concentration of C 0 2into the unoccupied chamber and then measuring the decay of the concentration with an infrared C 0 2 analyzer. The chamber had excellent control of dry bulb (hO.1"C) and wet bulb (f0.2 "C) temperature. Four smokers from a pool of six occupied the chamber for each experiment. Fifteen minutes after entering, the occupants began to smoke serially a t the prescribed rate of a total of eight cigarettes per hour. The smokers were asked to smoke in their normal manner. Each cigarette was smoked for 7.5 min; this provided a continuous source. After 7.5 min of smoking the cigarette was placed in a small capped vial to be extinguished and stored. Smoking continued for 5 h at which time the smokers left the chamber. Ventilation was set at 2.4 air changes/h for all experiments. A total of 12 different brands of cigarettes and one cigar were evaluated for vapor-phase nicotine and particle mass concentrations in the chamber experiments. Ten of the
cigarettes were American brands, one a Danish cigarette, and one a University of Kentucky (U.K.) test cigarette (1R3F). Only one was a nonfilter cigarette. The cigarettes tested represented approximately 48% of the US.market (17). One cigarette was tested in three separate chamber runs on nonconsecutive days, while the U.K. cigarette was tested twice. The US.cigarettes were purchased locally and conditioned for a t least 24 h a t a temperature of 23 "C. Particle- and vapor-phase measurements were made under steady-state chamber conditions. One hour after smoking had begun and for the remaining 4 h of each experiment, integrated particle mass and vapor-phase nicotine measurements were made. Vapor-phase nicotine was measured typically in three separate locations in the chamber for each experiment by an active filter pack sampling method ( 4 ) . This method employs a sampling pump, which draws air through a filter cassette. The cassette contains two filters in series: the first collects particles, and the second is treated with sodium bisulfate to collect vapor-phase nicotine. The nicotine is then desorbed from the second filter and analyzed by gas chromatography for vapor-phase nicotine. Particle mass was measured typically in four to six separate locations in the chamber for each experiment by use of a 37-mm sampling cassette and a medium-flow pump sampling a 1.7 L/min. Teflon-coated glass fiber filters were used to collect the particle mass. The filters were equilibrated at 23 "C and 50% relative humidity before weighing. A Miniram Model PDM-3 (light-scattering aerosol monitor) was used to measure particle concentrations continuously before, during, and after smoking. The decay rate of particles was measured by the Miniram for 1h after cessation of smoking. The total particle removal rate was compared to the C 0 2 decay rate to determine particle deposition (18). The amount of tobacco consumed was determined by weighing the unburned tobacco from the cigarettes smoked during steady-state conditions when integrated air sampling occurred (4 h) and comparing it to the weight of tobacco in a sample of those cigarettes without filters. Emission rates for RSP were calculated from measurements made under steady-state conditions as given by the following equation: E = CV/R where E is the emission rate of RSP in milligrams per gram of tobacco consumed, C is the steady-state chamber concentration measured over the 4-h sampling period (mg/ m3), V is the effective removal rate (ventilation surface deposition) (m3/min),and R is the tobacco consumption rate (g/min). Since no real-time measurements of the decay of vapor-phase nicotine were available, emission rates for nicotine could not be calculated. Field Study. As part of a study to investigate the relation of infiltration and indoor air quality, the New York State Energy Research and Development Authority (NYSERDA) investigated the impact of combustion sources on indoor air quality (19). During the winter of 1986, extensive questionnaires were administered and field measurements were made in over 410 homes to collect data on infiltration rates and concentrations of NO2, SOz, CO and respirable suspended particles in homes with gas ranges, unvented kerosene space heaters, wood-burning stoves, cigarette smoking, and various combinations of the above sources. Approximately half the 410 residences sampled were chosen from Onondaga County and half from Suffolk County in New York State. Random digit dialing was used to select the houses for inclusion in the study. A telephone
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Table I. RSP Emission Factors and Steady-State Chamber Concentrations for RSP and Nicotine for Environmental Tobacco Smoke
type Cigb Cig Cig Cig Cig Cig Cig cig C% Cig Cig' Cigd
mainstream emission,o mg/cigarette tar nicotine 23 17 16
1.3 1.3 1.0
16
1.1 0.8 0.7
10
10 5 5 5 1
RSP emission factors, mg/g smoked
0.4 0.4
0.4 0.1
15
cigar
30 f 1.9 28 f 3.7 33 f 0.5 33 f 3.7 30 f 1.6 27 f 3.0 23 f 2.5 27 f 4.3 31 f 1.6 28 f 2.4 27 f 1.5 21 f 2.3 35 f 3.7 24 f 1.1 25 f 1.7 48 f 9.1
steady-state chamber concn, m / m 3 RSP nicotine 1789 1261 1609 1561 1530 1277 1190 1251 1459 1270 1295 953 1702 1241 1331 2532
steady-state chamber concn ratios, mg RSP/mg nicotine
120
15
104
12
96
17
111
14 16 17 15 15 12 12 13 13 9
81 70 85 99 107 106 74 132 137 134 138
10
18
FTC Rating 1985. bNonfilter cigarette. 'Danish Cigarette. dUniversity of Kentucky test Cigarette 1R 3F.
screening interview was conducted with all households to determine eligibility of the household to participate in the study. To be eligible, the housing structure must have been an occupied, single-unit house and have been located in one of the two counties. Eligible households were interviewed (telephone questionnaire) to determine building characteristics and the existence and use rate of the four major combustion sources under study (gas ranges, kerosene heaters, cigarettes, and wood-burning stoves or fireplaces). A factorial design was used to select homes for inclusion in the study from the eligible households based upon the presence and use of the sources. The factorial design allows estimation of interactions, physical and behavioral, that are important in determining effects of combined sources. A personally administered questionnaire was used to obtain detailed information on building characteristics, the presence and use of sources, and contaminant removal potentials in all 410 residents sampled. House volumes were determined by the field technicians. One-week integrated levels for NOz [Palmes diffusion tubes (ZO)], SOz [permeation passive sampler (2111, and RSP, 3-day CO levels (electrochemical monitor), and 1-week infiltration rates [perfluorocarbon tracer technique (22)]were obtained for all houses. A daily source use diary was kept by all households during air sampling. Nicotine was sampled in approximately 100 houses over the 1-week period. Outdoor concentrations of all monitored air contaminants were obtained and meteorological data were gathered from a local airport on a time scale consistent with the measurements. The respirable suspended particulate fraction of airborne particulates was measured through the use of a portable impactor developed a t Harvard University (23). The device samples a t a rate of 4 L/min. The sampler was operated under line power. Teflon filters were used to collect the sample with temperature and humidity conditioning of the filters before and after weighing samples. The impactors were placed near the other monitors in the house (i.e., 2-3 m from the combustion source, and/or in an area of major human activity). When the combustion source and the primary living area were different and both were sampled, a dual-head sampler was utilized with samples collected from each area in alternating 15-min intervals. Outdoor RSP measurements were obtained for every third 772
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house for which indoor measurements were made. Vapor-phase nicotine was measured by using a recently developed passive monitor (14). The monitor is based on passive diffusion of nicotine to a filter treated with sodium bisulfate. The nicotine is then extracted from the filter and analyzed by gas chromatography. The monitors sample at a rate of 24 mL/min. The passive nicotine monitors were collocated with the RSP samplers in the homes where they were used. Field blanks and duplicates were obtained for 10% of the samples. This paper will present and discuss the data collected for the residences for which vapor-phase nicotine samples were obtained. Only RSP and nicotine as they relate to source use, particularly tobacco combustion, will be discussed. The results of mass concentration measurements made in the full sample of approximately 410 residences and the trace element composition determinations made on the collected filters are presented elsewhere (24).
Resu 1t s Chamber Studies. The measured emission rates for RSP, the steady-state concentrations of RSP and vaporphase nicotine, and the RSP/vapor-phase nicotine concentration ratios for each experiment are shown in Table I. Also listed in Table I are the Federal Trade Commission rated total tar (dry particulate matter) and nicotine mainstream emissions for the cigarettes tested. Chamber particle mass concentrations for the cigarette experiments ranged from 1 to 1.9 mg/m3 while vapor-phase nicotine concentrations ranged from 60 to 150 pg/m3. Emissions of RSP from the one cigar tested were approximately twice the levels seen for cigarettes, while the steady-state nicotine concentration was comparable to those from cigarettes. The highest RSP cigarette emission was from the Danish cigarette. No trend in RSP emission rates by FTC tar and nicotine rating was observed. The reproducibility of RSP emissions for two cigarettes for which there were multiple runs was good, varying by only lo%, despite the fact that the same four smokers were not used for all runs. Repeat tests on the same brand of cigarette also resulted in vapor-phase nicotine concentrations within 16% of each other. The 10 U.S. brands of cigarettes emitted similar amounts of RSP. The average RSP emission rate for these cigarettes was 27 f 3.4 pg/g of tobacco consumed. The
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Figure 1. Cumulative frequency distribution and arithmetic means of vapor-phase nicotine levels, measured over a 1-week period in the main living area in residences in Onondaga and Suffolk Counties in New York State between January and April 1986.
% (pg/m3) 29.4 (25.9) Nicot1ne:O.O (Ns49) 15.2 (7.4) n Nicotine,O.O(N=47) 44.1 (29.9) A l l data (Nc96)
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average steady-state RSP and nicotine chamber concentrations for the U.S. cigarettes was 1331 f 227 and 95 f 16 pg/m3, respectively. The average ratio of steady-state chamber R S P to nicotine concentrations for the U S . cigarettes was 14.1 f 1.9. The RSP emission rate and RSP/nicotine ratio for the nonfilter U.S. cigarette was similar to the filter cigarette. The RSP/nicotine ratio for the cigar was only 28% higher than the average RSP/ nicotine ratio for U.S. cigarettes. An average 0.63 f 0.023 g of tobacco was consumed per cigarette smoked. On a per cigarette basis, the average RSP emission rate across all brands of U.S. cigarettes tested was 17 f 2.1 mg/cigarette. Field Study. Vapor-phase nicotine was sampled during 1week in the main living area (living room or family room) in 96 residences. Field blanks showed no detectable nicotine (limit of detection was 0.02 pg of nicotine). Duplicates were obtained over the full range of measured concentrations. A comparison of the duplicate samples (10 sets of samples) produced an r2 of 0.99, intercept of 0.0, and slope of 0.9 with a standard error of 0.03. RSP samples were collected during the same week and in the same locations. The cumulative frequency distributions of RSP, nicotine, and number of cigarettes reported smoked in the residences during the air sampling period for residences with nicotine concentrations equal t o zero, greater than zero, and for all 96 residences are shown in Figures 1-3. A zero nicotine concentration here is taken to mean below the detection limit of the passive nicotine monitor, which for these sampling conditions is 0.1 pg/m3. Cigarette and other tobacco consumption was obtained from the source use diary maintained by a resident of each home. Cigar or pipe smoking was reported for five of the residences.
Number of Cigarettes SmokedIWeek
Figure 3. Cumulative frequency distribution and arithmetic means of questionnaire-reported number of cigarettes smoked per week by vapor-phase nicotine levels, measured over a 1-week period in main living area in residences in Onondaga and Suffolk Counties in New York State between January and April 1986.
Each cigar or pipe reported smoked was counted as a single cigarette in this analysis, and these points are indicated in Figures 5 and 6. The figures also show the mean concentrations of RSP and nicotine measured and the mean number of cigarettes reported smoked. Thirty-four of the residences in the sample were reported to have none of the four sources, (cigarettes, kerosene heaters, gas stoves, and wood-burning stoves or fireplaces) while the remaining 62 were reported to have a mix of the four source categories. Detectable levels of nicotine were measured in 47 (49%) of the 96 residences. In these homes there is a considerable shift in the RSP distribution toward higher concentrations with the average concentration (RSP = 44 pg/m3) 3 times those in homes without measurable nicotine levels (RSP = 15 pg/m3). The number of cigarettes reported smoked in a residence were clearly associated with homes in which nicotine concentrations were greater than zero, although no nicotine was detected in a number of residences that reported cigarettes smoked. Nicotine was measured in 13% of the residences that reported no smoking, while nicotine was not detected in 28% of the residences that reported smoking. A comparison between the RSP concentrations measured in the main living area and the number of cigarettes reported smoked in each residence via the source diary is shown in Figure 4. A similar comparison for nicotine is shown in Figure 5. The association between RSP and nicotine (r2 = 0.64 for those with detectable nicotine and r2 = 0.71 for the full sample) is shown in Figure 6. House volume and measured air-exchange rate, when considered as independent variables in the regression equations shown in Figures 4 and 5, occasionally proved to be significant a t the 0.05 level but added little additional explained variation to the observed relationships.
Discussion An ideal marker or proxy compound chosen to represent the contribution of a chemically complex source to indoor air contaminants should be (a) unique to the source, (b) similar in emission rates for a variety of source products, (c) easily detected in air a t low concentrations, (d) in a consistent ratio to individual source contaminants of health or comfort interest, and (e) easily, accurately, and costeffectively measured. The results of the chamber and field studies reported here suggest that vapor-phase nicotine meets many of the above criteria to serve as an adequate marker for assessing the contribution of ETS to indoor air quality in the residential indoor environment. The chamber experiments were designed to assess the variability in RSP emissions and variability in the ratio of steady-state RSP to vapor-phase nicotine for a variety of brands of cigarettes smoked under conditions that would approximate those encountered in actual use and to determine the feasibility of using vapor-phase nicotine (VPN) Environ. Sci. Technol., Vol. 25, No. 4, 1991 773
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Flgure 4. Week-long respirable suspended particle mass levels, measured in the main living area of residences, vs the number of questionnaire-reported cigarettes smoked during the air sampling period. The left-hand panel is for all 96 residences with a mix of indoor combustion sources while the right-hand panel represents those residences with reported cigarette consumption. Numbers 1-9 refer to the number of observations at the same concentrations. Closed circles indicate that cigar or pipe smoking was reported, with each cigar or pipe smoked set equal to a cigarette. Data from residences in Onondaga and Suffolk Counties in New York State between January and April 1986.
Nicotine: 0.081+0.028T
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;;c;0.334+0.026T
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8
T o t a l number of cigarettes (T)
T o t a l number of cigarettes
Figure 5. Week-long vapor-phase nicotine levels, measured in the main living area of residences, vs the number of questionnaire-reported cigarettes smoked during the air-sampling period. The left-hand panel is for all 96 residences with a mix of indoor combustion sources while the right-hand panel represents those residences with reported cigarette consumption. Numbers 1-6 refer to the number of observations at the same concentrations. Closed circles indicate that cigar or pipe smoking was reported in the house, with each cigar or pipe smoked set equal to a cigarette. Data from residences in Onondaga and Suffolk Counties in New York State between January and April 1986. 200
-
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R S P822.9 t 9.8 Nicotine N.47 r e = 0.64 I
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Figure 6. Week-long respirable suspended particle mass levels, measured in the main living area of residences, vs corresponding vapor-phase nicotine levels. The left-hand panel is for all 96 residences with a mix of indoor combustion sources while the right-hand panel represents those residences with reported cigarette consumption. Numbers, 1 to 9, refer to the number of observations at the same concentrations. Closed circles indicate that cigar or pipe smoking was reported in the house, with each cigar or pipe smoked set equal to a cigarette. Data from residences in Onondaga and Suffolk Counties in New York State between January and April 1989.
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as a marker for ETS. The relatively small variations observed in RSP emissions as a function of cigarette brand and the high quantities emitted suggest that RSP is a strong potential marker for ETS. The consistency in the RSP/VPN ratios observed in the chamber suggests that VPN is a good predictor of ETS-associated RSP. Because nicotine is highly specific to tobacco combustion with no other important known sources, it is particularly attractive as a potential marker for ETS. Nicotine is used also as a pesticide, but this is not likely to occur in the environment sampled for ETS. It is not known if vapor-phase nicotine is in a constant ratio with other important gasand particle-phase ETS constituents (e.g., nitrosamines) among various cigarette brands. Additional chamber experiments to address this question are currently underway. The data also indicate that cigars, while considerably higher in RSP emissions, do not result in a substantially different RSP/VPN ratio. The chamber has been well characterized for ETS-related RSP, particularly for ventilation rates and particle deposition rates (18,25, 26). Thus, RSP emission rates could be calculated. No measurements of the deposition rate of vapor-phase nicotine for the chambers were made in these experiments and hence VPN emission rates could not be calculated. However, since the chamber conditions were identical for each experiment, the RSP/VPN ratios could be determined from measured concentrations and compared for each cigarette. As noted earlier, no studies have been reported that evaluate RSP and nicotine emissions for E T S (SS plus exhaled mainstream, MS) for a variety of brands of cigarettes smoked by smokers under realistic conditions. One study ( I O ) , utilizing a single-port smoking machine and a small container, measured SS and MS tar (RSP) and nicotine emissions from 15 Canadian cigarettes. The study found the average SS tar emissions to be 24.1 mg/cigarette with a range of 15.8-36 mg/cigarette. This compares to a value of 17.1 mg of RSP/cigarette measured in this study of American cigarettes. The experimental design (small chamber vs large chamber, smokers vs smoking machine, amount of tobacco per cigarette consumed, differences in Canadian and American brands, etc.) may explain part of the differences for RSP emissions; RSP differences may also be accounted for by the potential for greater mass of gas condensation in the small chamber study because of the considerably denser aerosol with a higher mass median diameter. A field test of a marker or proxy compound is required to demonstrate its effectiveness. Such a field test should evaluate both the ease with which the marker compound can be measured, including the sensitivity and the expense, and how well the measured concentration of the marker compound corresponds to recorded source use and other source-related contaminants. Recently developed methods for measuring vapor-phase nicotine (4,5,12-14)make it possible to measure nicotine accurately in field studies. Passive nicotine monitors ( 1 4 ) make it particularly easy to obtain accurate average nicotine concentrations in indoor spaces or for personal exposures in an unobtrusive and inexpensive way and for large sample sizes. The passive nicotine monitors were found to be useful in this study. Accurate RSP measurements can be obtained by using a variety of well-accepted measurement methods. The gravimetric RSP samples obtained in this study required considerably more effort, expense, and subject burden than did the nicotine measurements. No small inexpensive passive monitors exist for measuring RSP level either for personal exposures or for indoor concentrations.
The ease of measurement of airborne nicotine adds to its usefulness as a marker for ETS, particularly in large field studies. Air contaminant concentrations in any environment are the result of a complex interaction of several interrelated factors. In the indoor nonindustrial environment, these factors include such variables as (a) the type, nature (factors affecting the generation rate of the contaminants), and number of sources, (b) source use characteristics, (c) building characteristics, (d) infiltration or ventilation rates, (e) air mixing, (f) removal rates by surfaces, chemical transformation, or radioactive decay, (8) existence and effectiveness of air contaminant removal systems, (h) outdoor concentrations of the contaminants, and (i) meteorologic conditions. Given this complex set of factors, the concordance of the observed interactions of the concentrations of nicotine and RSP and the number of cigarettes smoked in the field study is particularly striking. Measured nicotine concentrations were found to be good predictors of both RSP and the reported number of cigarettes smoked in the residences. The dominance of the source in controlling RSP and VPN concentrations in the residences is demonstrated in the very small additional explained variation in RSP and VPN attributable to other factors (house volume, infiltration, etc.). The slope of the plot of RSP vs VPN observed in the field study (Figure 6) was 9.8-11 and compares well with the average RSP/VPN ratio of 14 observed in the chamber studies, which indicates that VPN is a good marker for RSP-related ETS. Presumably once the contribution of other residential sources of RSP (kerosene heaters, wood-burning stoves) are included in the model, the correlation between RSP and VPN will improve. The measured intercept for RSP of 18-23 vg/m3 for the RSP/VPN regression (Figure 6) compares well with the average indoor RSP concentration of 23 f 15 pg/m3 measured for residences without any known combustion sources (24). The measured nicotine concentrations were also good predictors of number of cigarettes smoked. Whether this relationship would be observable in other indoor environments (airplanes, nonindustrial occupational environments, etc.) is not known. Other indoor environments exhibit a different relationship between RSP and VPN due to such differences as mixing and surface deposition. It is also not known whether this relationship will be observed for short sampling periods (on the order of minutes), where ETSrelated RSP and VPN may be very dynamic. Similar relationships between nicotine and RSP have been found in other field studies. In a study of railroad workers, 44 samples were collected by active sampling in offices over an 8-h workday on several different days (27). The RSP/VPN regression yielded a slope of 8.6. A regression of 14 samples collected for 4-14 h from offices, bars, restaurants, a hospital waiting room, and a subway station produced a slope of 9.0 (28). Samples collected in offices in Japan had a slope of approximately 10 (29). The relationship between RSP and VPN was very similar for all these real-world samples, despite the wide variability in environments, smoking rates, ventilation, mixing, and surface to volume ratios. The impact of smoking on RSP levels in this study is pronounced. Residences that reported smoking had RSP levels on average 3 times those that reported no smoking. The increase in RSP levels related to smoking occurs in a background of RSP associated with other indoor sources and an outdoor contribution. Due to these other RSP sources, the contribution of ETS to RSP is difficult to assess from an RSP measurement alone. Such a meaEnviron. Sci. Technol., Vol. 25, No. 4, 1991
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surement should be supplemented with source use diary information on number of cigarettes smoked. The strong observed relation among nicotine, RSP, and number of cigarettes smoked, however, suggests that a measurement of nicotine by itself would be a good predictor of both ETS-related RSP and the number of cigarettes smoked. This analysis did not control for the location of smoking in the house (bedroom, main living area, basement, etc.) relative to the sampling location. Presumably better information on the location of smoking would improve the observed relation between number of cigarettes smoked and measured levels of nicotine and RSP. Misclassification of respondents by exposure group can introduce a bias in environmental epidemiologic studies. In studies of associations between exposure to ETS and health and comfort, exposure status is often determined by response to questionnaires. Failure of the respondents to report exposure status accurately leads to misclassifications of subjects by exposure. Reported exposures in the residential environment are particularly important because of the time individuals spend there and because of the importance of the residential exposures for sensitive individuals (the elderly, the young, and the infirm). The results of the passive nicotine monitor and the daily source diary in this nonrandom sample of 96 residences enabled a validation of questionnaire responses on smoking reported in the residences with actual measurements of nicotine. The results indicate that as much as 28% of residences whose occupants would be reported as having ETS exposure would in fact have little or no exposure (perhaps due to smoking in the basement, outdoors, or in rooms remote from the family room), while 13% of those reporting no exposure would be misclassified. The impact of the detection limit of the passive nicotine monitor on the percent misclassified is not known. If the degree of misclassification here is assumed in an epidemiologicstudy in which exposure status is determined from questionnaire alone, there would be a tendency toward underestimating or masking the effect under study.
Conclusion The results of chamber and field studies reported here indicate that vapor-phase nicotine is a suitable qualitative and quantitative marker for environmental tobacco smoke in the residential indoor environment. Nicotine is specific to tobacco, exhibits emission rates that are similar among different cigarette brands, and is emitted in sufficient quantities to measure easily in indoor spaces even a t low smoking and high ventilation or infiltration rates. Active sampling methods can collect detectable levels of nicotine in just a few hours. Passive sampling methods exist for vapor-phase nicotine, so personal exposure measurements for large populations or in a variety of indoor spaces can be obtained over several days. Vapor-phase nicotine measurements in the residential environment are closely related to the number of cigarettes smoked and highly predictive of respirable suspended particle mass generated by tobacco combustion. The observed field association between vapor-phase nicotine and RSP was consistent with chamber studies. It is not known how well vapor-phase nicotine can predict other gas-phase E T S or specific particle-phase E T S air contaminants. Respirable suspended particle mass emissions are similar among brands of cigarettes. RSP is emitted in quantities that can be measured indoors even a t low smoking and high infiltration/ventilation rates if high-volume samples are collected over sufficiently long time periods. However, there are a number of other sources of RSP indoors. A determination of the ETS contribution to RSP when in776
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door levels of RSP are low requires detailed source use information or vapor-phase nicotine measurements.
Acknowledgments We thank Mr. Joseph Rizzuto of NYSERDA for permitting the passive nicotine monitors to be placed in the residences sampled and for providing access to the air sampling and questionnaire data collected, Drs. Linda Sheldon and Tye Hartwell of RTI for their considerable cooperation in collection of samples and for providing access to the collected field data, and Colya Woskie and Jo Anne Shatkin for their laboratory work.
Literature Cited (1) Environmental tobacco smoke. Measuring exposure and assessing health effects;National Research Council, National Academy Press: Washington, DC, 1986; p 337. (2) The health consequences of involuntary smoking. A Report of the Surgeon General; U S . Dept. of Health and Human Services, U.S. Government Printing Office: Washington, DC, 1986. ( 3 ) Indoor pollutants; National Research Council, National Academy Press: Washington, DC, 1981; p 537. (4) Hammond, S. K.; Leaderer, B. P.; Roche, A. C.; Schenker, M. Collection and analysis of nicotine as a marker for environmental tobacco smoke. Atmos. Enuiron. 1987,21, 457-462. (5) Eatough, D. J.; Benner, C.; Mooney, R. L.; Bartholomew, D.; Steiner, D. S.; Hansen, L. D.; Lamb, J. D.; Lewis, E. A. Gas and particle phase nicotine in environmental tobacco smoke. Proceedings, 79th Annual Meeting of the Air Pollution Control Association, Minneapolis, MN, June 22-27, 1986, 1986; Paper 86-68.5. (6) Lofroth, G.; Burtin, R.; Forehand, L.; Hammond, K.; Selia, R.; Zwiedinger, E.; Lewtas, J. Characterization of genotoxic components of environmental tobacco smoke. Enuiron. Sci. Technol. 1989,23, 610-614. (7) Eatough, D. J.; Benner, C. L.; Tang, H.; Landon, V.; Richards, G.; Caka, F. M.; Crawford, J.; Lewis, E. A.; Hansen, L. D.; Eatough, N. L. The chemical composition of environmental tobacco smoke 111. Identification of conservative tracers of environmental tobacco smoke. Enuiron. Znt. 1989, 15, 19-28. (8) Benner, C. L.; Bayona, J. M.; Caka, F. M.; Tang, H.; Lewis, L.; Crawford, J.;Lamb, J. D.; Lee, M.; Lewis, E. A,; Hansen, L. D.; Eatough, D. J. Chemical composition of environmental tobacco smoke. 2. Particle-phase compounds. Enuiron. Sci. Technol. 1989, 23, 688-699. (9) Hammond, S. K.; Smith, T. J.; Woskie, S. R.; Leaderer, B. P.; Bettinger, N. Markers of exposure to diesel exhaust and cigarette smoke in railroad workers. Am. Ind. Hyg. Assoc. 5-1988, 49, 516-522. (10) Rickert, W. S.; Robinson, J. C.; Collishaw, N. W. Yields of tar, nicotine and carbon monoxide in the sidestream smoke from 15 brands of Canadian cigarettes. Am. J. Pub. Health 1984, 74, 228-231. (11) Eudy, L. W.; Thorne, F. A.; Heavor, D. L.; Green, C. R.; Ingebrethsen, B. J. Studies on the vapour-phase distribution of environmental nicotine by selected trapping and detection methods. Presented at the 39th Tobacco Chemists Research Conference, Montreal, October 1985. (12) Muramatsu, M.; Umemura, S.; Okada, T.; Tomita, H. Estimation of personal exposure to tobacco smoke with a newly developed nicotine personal monitor. Enuiron. Res. 1984, 35, 218-227. (13) Koutrakis, P.; Fasano, A. M.; Slater, J. L.; Spengler, J. D.; McCarthy, J. F.; Leaderer, B. P. Design of a personal annular denuder sampler to measure atmospheric gases. Atmos. Enuiron., in press. (14) Hammond, S. K.; Leaderer, B. P. A diffusion monitor to measure exposure to passive smoking. Enuiron. Sci. Technol. 1987, 21, 494-497. (15) Repace, J. L.; Lowery, A. H. Indoor air pollution, tobacco smoke, and public health. Science 1980, 208, 464-472.
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(16) Leaderer, B. P. Air pollution from kerosene space heaters. Science 1982,218, 1113-1115. (17) Maxwell, Tobacco Int. January 1987. (18) Bluyssen, P.; Van De Loo, H.; Leaderer, B. P. Chamber and field studies of respirable suspended particulate deposition rates indoors. Proceedings of the 4th International Conference on Indoor Air Quality and Climate;Institute for Water, Soil and Air Hygiene: Berlin, 1987; Vol. 1, pp 549-553. (19) An investigation of infiltration and indoor air quality. Final report to the New York State Energy Research and Development Authority prepared by the Research Triangle Institute, January 1990. (20) Palmes, E. D.; Tomczyk, C.; March, A. W. Relationship of indoor NOz concentrations in use of unvented gas appliances. J. Air Pollut. Control Assoc. 1979, 29, 392. (21) Reiszner, K. D.; West, P. W. Collection and determination of sulfur dioxide incorporating permeation and West-Gaeke procedure. Environ. Sci. Technol. 1973, 7, 526. (22) Dietz, R. N.; Cote, E. A. Air infiltration measurements in a home using a convenient perfluorocarbon tracer technique. Enuiron. Int. 1982, 8, 419. (23) Turner, W. A.; Marple, V. A.; Spengler, J. D. Indoor aerosol impactor. Presented a t Third International Conference on Indoor Air Quality and Climate, Stockholm, Sweden, August 20-24, 1984. (24) Leaderer, B. P.; Koutrakis, P.; Briggs, S. L. K.; Rizzuto, J. The mass concentration and elemental composition of indoor aerosols in Suffolk and Onondaga Counties, New
York. Submitted for publication in Atmos. Environ. (25) Leaderer, B. P.; Cain, W. S.; Isseroff, R.; Berglund, L. G. Ventilation requirements in buildings. 11. Particulate matter and carbon monoxide from cigarette smoking. Atmos. Environ. 1984, 18, 99-106. (26) Leaderer, B. P.; Cain, W. S.; Isseroff, R.; Berglund, L. G. Tobacco smoke in occupied spaces: Ventilation requirements. Proc.-APCA, 74th Annu. Meet. 1981, 81-22.6, 1-14. (27) Schenker, M. B.; Samuels, S. J.; Kado, N. Y.; Hammond, S. K.; Smith, T. J.; Woskie, S. R. Markers of exposure to diesel exhaust in railroad workers. Research Report 33, Health Effects Institute: Cambridge, MA, 1990. (28) Miesner, E. A,; Rudnick, S. N.; Hu, F.; Spengler, J. D.; Preller, L.; Ozkaynak, H.; Nelson, W. Particle and nicotine sampling in public facilities and offices. JAPCA 1989, 39, 1577-1582. (29) Muramatsu, M.; Umemura, S.; Okada, T.; Tomia, H. Estimation of personal exposure to tobacco smoke with a newly developed nicotine personal monitor. Environ. Res. 1984, 35, 218.
Received f o r review August 20, 1990. Accepted November 26, 1990. This work is supported by EPA cooperative Agreements CR-814150, CR-813594, and CR-813610. The field portion of this study was conducted by the Research Triangle Institute ( R T I )f o r the New York State Energy Research Development Authority (NYSERDA).
Oxidation of Chlorobenzene with Fenton's Reagent David L. Sedlak and Anders W. Andren" Water Chemistry Program, University of Wisconsin, Madison, Wisconsin 53706
w The degradation of chlorobenzene and its oxidation products by hydroxyl radicals generated with Fenton's reagent was studied. In the absence of oxygen, chlorophenols, dichlorobiphenyls (DCBs), and phenolic polymers were the predominant initial products. In the presence of oxygen, DCB yields decreased markedly and chlorobenzoquinone was also formed. Chlorophenol isomers were further oxidized by OH's to form chlorinated and nonchlorinated diols. DCBs and the phenolic polymers were also oxidized. The highest yield of product formed per mole of H 2 0 zconsumed was observed in the pH range of 2-3. The pH dependence and product distributions suggest that complexes of aromatic intermediate compounds with iron and oxygen may play a role in regulating reaction pathways. A t pH 3.0, approximately 5 mol of Hz02/mol of chlorobenzene were required to remove all of the aromatic intermediate compounds from solution. Introduction
Chlorinated aromatic hydrocarbons (CAHs) have been introduced to the environment from a variety of sources. Many of these compounds do not readily degrade and pose a threat to biota and human populations. Concern about the potential hazards associated with these compounds has resulted in laws and policies that require the cleanup of contaminated soil, sediments, surface water, and wastewater ( I ) . Treatment of these wastes necessitates the development of technologies to effectively degrade many types of CAHs. One potentially important method of destroying CAHs is through chemical oxidation by hydroxyl radicals generated with Fenton's reagent ( 2 , 3 ) . Fenton's reagent is 0013-936X/91/0925-0777$02.50/0
a mixture of hydrogen peroxide and ferrous iron (Fez+), which produces OH's according to reaction 1 ( 4 ) : Fez+ + H20, Fe3+ OH- + OH' (1)
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The OH's produced in reaction 1 are capable of reacting with a variety CAHs (5-7). Preliminary studies for the design of waste treatment systems employing Fenton's reagent (2,3,8-10) indicate that the reaction is effective in the degradation of phenols, chlorophenols, formaldehyde, and octachloro-p-dioxin. However, none of these studies have focused on either the nature of intermediate products or factors affecting product yields and distributions. Furthermore, mechanistic studies on CAHs are mainly limited to systems in which oxygen is excluded and high H 2 0 2and substrate concentrations are present. Understanding the reaction mechanism for the oxidation of CAHs under conditions relevant to waste treatment is an essential step in the design of efficient, cost-effective Fenton's reagent treatment systems. These factors are especially important for this oxidation system because product yields and distributions may be drastically affected by environmental conditions such as pH and oxidant concentrations (11,12). Furthermore, identification and quantification of intermediate products is important because hydroxylated aromatic and dimeric intermediates may be recalcitrant and/or toxic. In this study we have evaluated reactions of Fenton's reagent with chlorobenzene and its intermediate oxidation products as a function of pH, and in the presence or absence of oxygen. Through determination of intermediate products and the effect of environmental variables on product yields and distributions, we have identified possible reaction mechanisms and optimal conditions for
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