in the open air. However, the velocity of the airstream through the
chamber has considerable influence on the yields of individual
compounds in SS (Klus and Kuhn 1982). .

To collect the particulate phase of MS and SS, the smoke aerosols
are passed through a glass fiber filter (a Cambridge filter with a
diameter of 45 mm) that traps more than 99 percent of all particles
with a diameter of at least 0.1 jm (Wartman et al. 1959). The portion
of the smoke that passes through the glass fiber filter is arbitrarily
designated as vapor phase, although it is realized that this separa-
tion does not fully reflect the actual physicochemical conditions
prevailing in MS and SS. For the analysis of individual components
or a group of components, specific trapping devices and methods
have been developed (Dube and Green 1982).

Human Smoking

The standardized machine-smoking conditions used in the tobacco
laboratory were set up to simulate the parameters of human
smoking as practiced 30 years ago. The examination of current
smoking practices suggests that machine-smoking conditions no
longer reflect current practices. Human smoking patterns depend on
a number of factors, one of which is the delivery of nicotizie.
Dosimetry of smoke constituents has shown that low nicotine
delivery (<0.6 to 1.0 mg/cigarette) generally induces the smoker to
draw larger puff volumes (up to 55 mL per puff), to puff more
frequently (three to five times a minute), and to inhale more deeply
(Herning et al. 1981). Furthermore, many smokers of cigarettes with
perforated filter tips tend to obstruct the holes in these tips by
pressing their lips around them; thus, they inhale more smoke than
would be expected according to the machine-smoking data (Kozlow-
ski et al. 1980). Smokers of cigarettes with a longitudinal air channel
in the filter tip compress the tip in a similar manner so that the
mainstream smoke delivery is increased over that measured with the
laboratory methodology (Hoffmann et al. 1983).

These deviations from machine-smoking patterns cause a greater
amount of tobacco to be consumed during MS generation. Conse-
quently, the quantity of tobacco burned between puffs is diminished,
and lower amounts of combustion products are released as SS.
Because of the proximity to the burning tobacco product, the active
smoker usually inhales more of the SS and ETS than a nonsmoker.

It is not known to what extent the different constituents of inhaled
ETS aerosols can be retained in the respiratory tract of nonsmokers.
Studies with MS have shown that more than 90 percent of the

volatile, hydrophilic components are retained by the smoker (Dal-
hamn et al. 1968a) and that less than 50 percent of the volatile,
hydrophobic MS components are retained by the smoker (Dalhamn
et al. 1968b). On the basis of these data, it may be assumed that the

126
passive smoker retains a high percentage of the vapor phase
components of ETS and significantly less of its hydrophobic volatiles.

Sidestream Smoke
Formation and Physicochemical Nature

When nonfilter cigarettes are being smoked under standardized
conditions, approximately 45 percent of the tobacco column is
consumed during the generation of MS (puff-drawing), whereas the
remainder is burned between puffs and under conditions of a
strongly reducing atmosphere. In addition, MS and SS is generated
at distinctly higher temperatures than SS (Wynder and Hoffmann
1967). Thus, undiluted SS contains more tobacco-derived combustion
products than does MS, and contains especially greater quantities of
those combustion products that are formed by nitrosation or
amination. Consequently, the composition of SS differs from that of
MS.

The SS of a smoldering cigarette enters the surrounding atmo-
sphere about 3 mm in front of the paper burn line, at about 350° C
(Baker 1984). In Table 1, the MS and the SS from nonfilter cigarettes
are compared. Under standardized conditions, the formation of the
MS of a nonfilter cigarette (80 mm, 1,230 mg) is completed during 10
puffs, requires 20 seconds, and consumes 347 mg of tobacco. The
formation of SS from the same cigarette during smoldering requires
550 seconds and consumes 411 mg of tobacco (Neurath and Horst-
mann 1963).

The pH of the MS of a blended U.S. cigarette ranges from 6.0 to 6.2
and the pH of SS, from 6.7 to 7.5. Above pH 6, the proportion of
unprotonated nicotine in undiluted smoke rises; at pH 7.9, about 50
percent is unprotonated. Therefore, SS contains more free nicotine
in the vapor phase than MS. The reported measurements of the pH
of cigars were 6.5 to 8.5 for MS and 7.5 to 8.7 for SS; measurements
for the pH of SS from pipes have not been published (Brunnemann
and Hoffmann 1974).

Chemical Analysis

In order to establish reproducible chemical-analytical data, ciga-
rette SS is generated in a special chamber. This assures that the
cigarettes burn evenly during puff intervals when an airstream at a
velocity of 25 mL per second is drawn through the chamber. At this
flow rate in the chamber, MS generation is quantitatively similar to
that measured without the SS chamber (Neurath and Ehmke 1964;
Brunnemann and Hoffmann 1974; Dube and Green 1982). Through-
out this chapter the data refer primarily to MS, SS, and ETS
deriving from cigarettes and not from cigars or pipes, because

127
TABLE 1.—Comparison of mainstream smoke (MS) and
sidestream smoke (SS) of a nonfilter cigarette:
Some physicochemical data

 

Study Parameters MS ss
Neurath and Horstmann Duration of smoke production (sec) 20 550
“1963) Tobacco burned (mg) 347 411
ynder and Hoffmann Peak temperature during formation (°C) 900 =x600
967)
Brunnemann and pH of total aerosol 6.0-6.2 6.7-7.5
Hoffmann (1974)
Scassellati-Sforzolini Number of particles per cigarette? 10.5 x 10% 3.5 x 10"
and Savino (1968) ,
Carter and Hasegawa Particle sizes (nm)? 0.1-L.0 0.01-0.8
(1975); Hiller et al. Particle mean diameter (nm)* 0.4 0.32
(1982)
Wynder and Hoffmann Smoke dilution (vol %)?
(1967); Keith and "OO
Derrick (1960); Carbon monoxide 3-5 2-3
Baker (1984);
Hoffmann, Brunnemann Carbon dioxide 811 46
et al. (1984)
Oxygen 12-16 15-2
Hydrogen 3-15 0.8-1.0

 

NOTE: Data obtained under standard laboratory smoking conditions of 1 puff per minute of 2-second duration
and 35 mL volume. .

* Fresh and undiluted mainstream smoke and sidestream smoke.

*Four mm distant from the burning cone (gas temperature, 350° C).

cigarette smoke is the major source of ETS in public places. Few data
are available on the SS and ETS from cigars and pipes.

About 300 to 400 of the several thousand individual compounds
identified in tobacco smoke have been quantitatively determined in
both mainstream and 'sidestream smoke. A listing of selected agents
in the MS of nonfilter cigarettes with their reported range of
concentration and their relative ratio of distribution in SS compared
with MS is presented in Table 2. Values greater than 1.0 reflect the
greater release of a given compound into SS than into MS. The
grouping of the compounds in Table 2 into vapor phase components
and particulate phase constituents refers to the makeup of MS, but
does not represent the physicochemical distribution of these com-
pounds in SS. Some of the volatile compounds in MS and SS are
compared. On the basis of the amount of tobacco burned in the MS
and SS of a nonfilter cigarette (see Table 1), the ratio of SS to MS
should be 1.2 to 1.5 if the combustion conditions during both phases
of smoke generation were comparable. However, this is not the case,

128
as is indicated by the higher SS to MS ratios for carbon monoxide
(2.5-4.7), carbon dioxide (8-11), acrolein (8-15), benzene (10), and
other smoke constituents.

The high yield of carbon monoxide and carbon dioxide in SS
indicates that more carbon monoxide is generated during smoldering
than during puff-drawing. After passing very briefly through the hot
cone, most of the carbon monoxide gas in both MS and SS is oxidized
to carbon dioxide, most likely owing to the high temperature
gradient and the sudden exposure to environmental oxygen upon
emission..

The higher yields of volatile pyridines in SS compared with MS are
probably caused by the preferred formation of these compounds from
the alkaloids during smoldering (Schmeltz et al. 1979). In contrast,
hydrogen cyanide (HCN) is primarily formed from protein at
temperatures above 700° C (Johnson and Kang 1971), and the
smoldering of tobacco at about 600° C does aot yield the pyrosynthe-
sis of HCN to the extent that it occurs at the higher temperatures
present during MS generation. The very high levels of ammonia,
nitrogen oxide, and the volatile N-nitrosamines in SS compared with
the levels in MS is striking. Studies with “N-nitrate have under-
scored that the burning of tobacco results in the reduction of nitrate
to ammonia, and that the latter is released to a greater extent during
SS formation than during puff-drawing (Johnson et al. 1973). In a
blended cigarette, this higher level of ammonia in SS causes its
elevated pH to reach levels of 6.7 to 7.5, while the pH of MS is about
6 (Brunnemann and Hoffmann 1974).

The increased release of the highly carcinogenic volatile N-nitrosa-
mines into SS (20 to 100 times greater than into MS) has been well
established (Brunnemann et al. 1977). The carcinogenic potential of
SS may also be affected by the levels of the oxides of nitrogen (NO).
Four to ten times more nitrogen oxide (NO) is released into the
environment in sidestream smoke than is inhaled with the main-
stream smoke. The smoker inhales more than 95 percent of the NOx
in the form of NO, and only a small portion is oxidized to the
powerful nitrosating agent nitrogen dioxide (NO,). Only a fraction of
NO is expected to be retained in the respiratory system of smokers
by being bound to hemoglobin. The NO, gases released into the
environment are partially oxidized to NO, (Vilcins and Lephardt
1975). Therefore, sidestream smoke-polluted environments are ex-
pected to contain the hydrophilic nitrosating agent NO2.

Data for particulate matter and some of its constituents in MS and
SS are also listed in Table 2. The release of tobacco-specific N-
nitrosamines into SS is up to four times higher than that into MS.
Whether the distribution of these agents in the vapor phase and the
particulate phase of SS is of major consequence with respect to the
carcinogenic potential of SS needs to be determined. It is equally

129
O&T

TABLE 2.—Distribution of constituents in mainstream smoke (MS) and the ratio of sidestream smoke

(SS) to MS of nonfilter cigarettes

 

 

Vapor phase constituents! range eat Particulate phase constituents! range eco.
Carbon monoxide 10-23 mg 2.5-4.7 Particulate matter? 15-40 mg 13-19
Carbon dioxide 20-40 mg $11 Nicotine - 1-2.5 mg 26-33
Carbonyl! sulfide 18-42 pg 0.03-0.13 Anatabine 2-20 pg <0.1-0.5
Benzene? 12-48 pg 10 Phenol 60-140 pg 16-30 —
Toluene 160 pg 6 Catechol 100-360 pg 0.6-0.9
Formaldehyde 70-100 pg 0.1250 Hydroquinone 110-300 pg 0.7-0.9
Acrolein 60-100 pg 8-15 Aniline 360 ng 30
Acetone 100-250 pg 2-5 2-Toluidine 160 ng 19
Pyridine 16-40 pg 6.5-20 2-Naphthylamine? 17 ng . 30
3-Methylpyridine 12-36 pg 3-13 4-Aminobipheny]* 4.6 ng 31
3-Vinylpyridine 11-30 pg 20-40 Benz{ajanthracene* 20-70 ng 24
Hydrogen cyanide 400-500 pg 0,1-0.25 Benzofa]pyrene*® 20-40 ng 2.5-3.5
Hydrazine® 32 ng 3 Cholesterol 22 pg 0.9
Ammonia 50-130 pg 40-170 ; y-Butyrolactone‘ 10-22 pg 3.6-5.0
Methylamine 11.5-28.7 pg 4.2-6.4 Quinoline » 0.5-2 pg 811
Dimethylamine 78-10 pg 3.7-5.1 Harman 17-3.1 pg O.7-1.7

Nitrogen oxide 100-600 pg 410 N'-Nitroeonornicotine‘ 200-3,000 ng 0.5-3

 
TABLE 2.—Continued

 

MS

“SS/MS

 

MS SS/MS
Vapor phase constituents' range ratio Particulate phase constituents? range ratio
N-Nitrosodimethylamine* 10-40 ng 20-100 NNK* 100-1,000 ng 4
N-Nitrosopyrrolidine* 6-30 ng 6-30 N-Nitrosodienthanolamine* 20-70 ng 12
Formic acid 210-490 pg 14-16 Cadmium 100 ng 12
Acetic acid 330-810 pg 1.9-3.6 Nickel? 20-80 ng 13-30
Zinc 60 ng 6.7
Polonium-210? 0.04-0,1 pCi 1.0-4.0
Benzoic acid 14-28 pg 0.67-0,95
Lactic acid 63-174 pg 0.5-0.7
Glycolic acid 37-126 pg 0.6-0.95
Succinic acid 110-140 pg 0.43-0.62

 

’ Values are given for fresh and undiluted MS and SS.

2 Human carcinogen (IARC 1986).
® Suspected human carcinogen (IARC 1986).
* Animal carcinogen (IARC 1986).

SOURCE: Elliott and Rowe (1975); Hoffmann et al. (1983); Klus and Kuhn (1982); Sakuma et al. (1983); Sakuma, Kusama, Yamaguchi, Matsuki et al. (1984); Sakuma, Kusama, Yamaguchi,

Sugawara (1984); Schmeltz et al. (1975).
important to examine the significance of the abundant release of
amines into SS (levels are up to 30 times higher than in MS),
indicated by the data for aniline, 2-toluidine, and the alkaloids. This
is of concern because certain amines are readily nitrosated to N-
nitrosamines. However, analytical data on secondary reactions of
amines in polluted environments are lacking.

For a meaningful interpretation of the data on the distribution of
the compounds in cigarette smoke presented in Table 2, certain
aspects of the methodology should be emphasized. First, the data are
based on analyses of nonfilter cigarettes that were smoked under
standardized laboratory conditions. Second, the standardized ma-
chine-smoking conditions were established according to human
smoking patterns observed three decades ago and do not reflect the
smoking behavior of contemporary smokers. This caveat applies
particularly to smoking patterns observed with filter cigarettes
designed for low smoke yields. Most consumers of these cigarettes
inhale the smoke more intensely than smokers of nonfilter cigarettes
(Herning et al. 1981; Hill et al. 1983). This change in smoking
intensity affects the delivery of the sidestream smoke. The conven-
tional filter tips of cigarettes influence primarily the yield of MS and
have little impact on SS yield. However, in the case of cigarettes with
specially designed filter tips such as perforations, the yield of SS is
also affected (Table 3) (Adams et al. 1985).

Radioactivity of Tobacco Smoke

Naturally occurring decay products of radon are found in tobacco
and, therefore, also in tobacco smoke. These include the isotopes of
lead (Pb-210), bismuth (Bi-210), polonium (Po-210), and radon, which
originates from the decay of uranium through radium (Radford and
Hunt 1964; Martell 1975). Radon and its short-lived daughters (Po-
218, Pb-214, Bi-214, Po-214), which precede long-lived daughters in
the decay chain, are ubiquitous in indoor air and are largely derived
from sources other than tobacco smoke. Most of the radon daughters
are attached to particles in the air, but a small proportion, referred
to as the unattached fraction, is not (Raabe 1969; Kruger and
Nothling 1979; Bergman and Axelson 1983).

It has been suggested that the presence of Pb-210 and subsequent
decay products in tobacco is dependent upon an absorption of short-
lived radon daughters on the leaves of the tobacco plant, especially
where phosphate fertilizers that are rich in radium have been used
and have caused increased leakage of radon from the ground. These
attached short-lived radon daughters then decay to long-lived Pb-210
and subsequent nuclides found in the tobacco (Fleischer and Parungo
1974; Martell 1975). However, the origin of these decay products may

132
e&T

TABLE 3.—Distribution of selected components in the sidestream smoke (SS) and the ratio of SS to
mainstream smoke (MS) of four U.S. commercial cigarettes

 

 

 

Cigarette A Cigarette B Cigarette C Cigarette D

85 mm NF 85 mm F 85 mm F 85 mm PF
Components ss SS/MS Ss SS/MS SS SS/MS SS SS/MS
Tar (mg/g) 22.6 11 24.4 16 20.0 29 14.1 15.6
Nicotine (mg/g) 4.6 2.2 40 2.7 3.4 4.2 3.0 20.0
Carbon monoxide (mg/g) 28.3 2.1 36.6 2.7 33.2 3.5 26.8 14.9
Ammonia (mg/g! 524 7.0 893 46 213.1 6.3 236 5.8
Catechol qug/z) 58.2 14 89.8 13 69.5 2.6 117 129
Benzolalpyrene (ng/g) 67 2.6 45.7 2.6 51.7 4.2 448 20.4
N-Nitrosodimethyamine (ng/g) 735 23.6 597 139 611 50.4 685 167
N-Nitrosopyrrolidine (ng/g) 177 2.7 139 13.6 233 TA 234 17.7
N’-Nitrosonornicotine (ng/g) 857 0.85 307 0.63 185 0.68 338 5.1

 

NOTE: NF, nonfilter cigarette: F, filter cigarette: PF, cigarette with perforated filter tip: values given are for fresh and undiluted sidestream and mainstream smoke.

SOURCE: Adams et al. (1985)
also depend on the general occurrence of radon in the atmosphere
and not on the local emanation of radon (Hill 1982).

In recent years, it has been shown that relatively high levels of
radon and short-lived radon daughters may occur in indoor air, and
consistent observations in this regard have been made in several
countries (Nero et al. 1985). In the air with a very low concentration
of particles, the proportion of unattached radon daughters is
increased beyond that found with a higher concentration of particles.
The unattached daughters are removed more rapidly than those that
are attached by plating out on walls and fixtures. The addition of an
aerosol, such as tobacco smoke, increases the attached fraction,
elevates the concentration of radon daughters, and reduces the rate
of removal of radon daughters (Bergman and Axelson 1983). The
dose of a radiation received by the airway epithelium depends not
only on the concentration of radon daughters but also on the
unattached fraction and on the size distribution of the inhaled
particles. The interplay among these factors as they are modified by
ETS has not yet been fully examined.

Environmental Tobacco Smoke

The air dilution of sidestream smoke, and of other contributors to
ETS, causes several physicochemical changes in the aerosol. The
concentration of particles in ETS depends on the degree of air
dilution and may range from 300 to 500 mg/m‘ to a few g/m’. At
the same time, the median diameter of particles may decrease as
undiluted SS is diluted to form ETS (Keith and Derrick 1960;
Wynder and Hoffmann 1967; Ingebrethsen and Sears 1986). Further-
more, nicotine volatilizes during air dilution of SS, so that in ETS it
occurs almost exclusively in the vapor phase (Eudy et al. 1985). This
is reflected in the fairly rapid occurrence of relatively high concen-
trations of nicotine in the saliva of people entering a smoke-polluted
room (Hoffmann, Haley et al. 1984). Most likely there are also
redistributions between the vapor phase and the particulate phase of
other constituents in SS due to air dilution, which may account for
the presence of other semivolatiles in the vapor phase of ETS.
However, evidence of such effects needs to be established.

Comparison of Toxic and Carcinogenic Agents in Mainstream
Smoke and in Environmental Tobacco Smoke

The combustion products of cigarettes are the source of both
environmental tobacco smoke and mainstream smoke. Therefore,
comparisons of the levels of specific toxins and carcinogens in ETS
with the corresponding levels in the mainstream smoke are relevant
to an estimation of the risk of ETS exposure. Although ETS is a far

134
less concentrated aerosol than undiluted MS, both inhalants contain
the same volatile and nonvolatile toxic agents and carcinogens. This
fact and the current knowledge about the quantitative relationships
between dose and effect that are commonly observed from exposure
to carcinogens have led to the conclusion that the inhalation of ETS
gives rise to some risk of cancer (IARC 1986).

However, comparisons of MS and ETS should include the consider-
ation of the differences between the two aerosols with regard to their
chemical composition, including pH levels, and their physicochemi-
cal nature (particle size, air dilution factors, and distribution of
agents between vapor phase and particulate phase). Another impor-
tant consideration pertains to the differences between inhaling
ambient air and inhaling a concentrated smoke aerosol during puff-
drawing. Finally, chemical and physicochemical data established by
the analysis of smoke generated by machine-smoking are certainly
not fully comparable to the levels and characteristics of compounds
generated when a smoker inhales cigarette smoke. This caveat
applies particularly to the smoking of low-yield cigarettes, for which
the yields of smoke constituents in machine-generated smoking and
human smoking activities may be most divergent (Herning et al.
1981).

The levels of certain smoke constituents in the mainstream smoke
of one cigarette compared with the amounts of such compounds
inhaled as constituents of ETS in 1 hour at a respiratory rate of 10 L
per minute are presented in Table 4. Unaged MS does not contain
nitrogen dioxide (NO.<5 yg/cigarette) because the nitrogen oxides
generated during tobacco combustion in the reducing atmosphere of
the burning cone are transported in the smoke stream (=10 vol %
O,) to the exit of the cigarette mouthpiece in less than 0.2 seconds,
and it takes 500 seconds for half of the nitrogen oxide in MS to
oxidize to nitrogen dioxide (Neurath 1972). The relatively low values
for nicotine reported in ETS may be explained, in part, by the
inefficiency of the trapping devices for collecting all of the available
nicotine; the alkaloid is predominantly in the vapor phase, which
escapes retention by the filters of such devices.

The assignment of benzene as a “human carcinogen,” benzo-
{alpyrene as a “suspected human carcinogen,” and N-nitrosodi-
methylamine and N-nitrosodiethylamine as “animal carcinogens” is
based on definitions by the International Agency for Research on
Cancer (1986). Accordingly, a human carcinogen is an agent for
which “sufficient evidence of carcinogenicity indicates that there is a
causal relationship between exposure and human cancer.” A sus-
pected human carcinogen is an agent for which “limited evidence of
carcinogenicity indicates that a causal interpretation is credible, but
that alternate explanations, such as chance, bias, or confounding,
could not adequately be excluded.” An animal carcinogen is an agent

135
9ET

TABLE 4.—Concentrations of toxic and carcinogenic agents in nonfilter cigarette mainstream smoke
and in environmental tobacco smoke (ETS) in indoor environments

 

 

 

 

 

: Inhaled as ETS constituents during 1 hour

Mainstream Smoke Range Episodic high values’
Agent Weight Concentration Weight Concentration Weight Concentration
Carbon monoxide 10-23 mg 24,9000-57,300 ppm 1.2-22 mg 1-18.5 ppm 37 mg 32 ppm
Nitrogen oxide 100-600 pg 230,000~1,400,000 ppb 7-90 ug 9-120 ppb 146 pg 195 ppb
Nitrogen dioxide <5 ug <7,600 ppb 24-87 pg ‘21-76 ppb 120 pg 105 ppb
Acrolein 60-100 pg 75,000-125,000 ppb &72 ug 6-50 ppb 110 pg 80 ppb
Acetone 100-250 pg 120,000-300,000 ppb 210-720 pe 150-500 ppb 3,500 pg 2,400 ppb
Benzene? 12-48 pg 11,000-43,000 ppb 12-190 pg 6-98 ppb 190 pg 98 ppb
N-Nitrosodimethylamine* 10-40 ng 9-38 ppb 6-140 ng 0.003-0.072 ppb 140 ng 0.072 ppb
N-Nitrosodiethylamine® 4-25 ng 3-17 ppb <6-120 ng <0,002-0.05 ppb 120 ng 0.05 ppb
Nicotine 1,000-2,500 pg 430,000-1,080,000 ppb 0.6-30 pg 0.15-7.5 ppb 300 pg 75 ppb
Benzofa}pyrene * 20-40 ng 5-11 ppb 17-460 ng 0.0002-0.04 ppb 460 ng 0.04 ppb

NOTE: Values for inhaled mainatream amoke P ts were calculated from values in Table 2 and on a respiratory rate of 10 L per minute. Values for carbon monoxide and nicotine represent

the range in mainstream smoke of U.S. nonfilter cigarettes as reported by the U.S. Federal Trade Commission (1985). Data under ETS are derived from Tables 8 through 15, with data from the
unventilated interior compartments of automobiles excluded (Badre et. al. 1978).

The designation “episodic high values” was chosen to classify those data in the literature that require confirmation,

* Human carcinogen according to the IARC (Vainio et al. 1985) and suspected carcinogen according to the ACGIH (1985).

* Animal carcinogen according to the IARC (Vainio et al. 1985).

*Suspected human carcinogen, according to the IARC (Vainio et al. 1985) and according to the ACGIH (1986).
“for which there is sufficient evidence of carcinogenicity in animals
but for which no data on humans are available.”

Polonium-210 is not listed in Table 4 because there are no data on
the concentration of this isotope in ETS, although it is a component
of both MS and SS. Whereas in clean air the short-lived radon
daughters tend to plate out on room surfaces, in the presence of an
aerosol such as ETS, some of the short-lived radon daughters become
attached to particles and consequently remain available for inhala-
tion. Radon daughter background concentration may more than
double in the presence of ETS (Bergman and Axelson 1983).

Number and Size Distribution of Particles in Environmental
Tobacco Smoke

Environmental tobacco smoke consists of the combined products of
both fresh and aged sidestream smoke and exhaled mainstream
smoke. Coagulation, evaporation, and particle removal on surfaces
occur simultaneously to modify the physical characteristics of the
ETS particles; as a result, the “typical” particle size and chemical
composition of ETS may vary with the age of the smoke and the
characteristics of the environment. Other factors such as relative
humidity, particle concentration, and temperature may also affect
the characteristics of ETS.

The rapid dilution of SS smoke as it is emitted into a room leads to
a number of physical and chemical changes. For example, the
evaporation of volatile species as the ETS ages reduces the median
diameter of the smoke particles. Several studies have measured the
particle distribution of SS under controlled conditions (Table 5), and
indicate that the mass median diameter (MMD) of ETS is between
approximately 0.2 jm and 0.4 um. The differences among the studies
reflect the varying analytical methods. ETS particles are in the
diffusion-controlled regime for particle removal and therefore will
tend to follow stream lines, remain airborne for long periods of time,
and rapidly disperse through open volumes.

As indicated, a number of factors can produce variation in the
mean size of the particles in ETS; however, in considering transport,
deposition, and removal in the human lung, it is useful to assume
that the particle sizes of aged ETS will generally be between 0.1 and
0.4 um. Although the results presented in Table 5 do not permit the
assignment of a single value for the diameter of sidestream smoke
particles, the difference in deposition efficiency in the human
respiratory tract of 0.2 um particles and 0.4 un particles is negligible
(Chan and Lippmann 1980). Particles in this size range are not
efficiently removed by sedimentation or impaction. Although diffu-
sion is the major removal mechanism for particles of this size, it is
minimally efficient in the 0.2 to 0.4 tm range. The relatively low

137
8éT

TABLE 5.—Summary of sidestream smoke size distribution studies

 

 

 

 

 

 

Count Mass Geometric

Chamber median median standard Number
Study Cigarette Method concentration (yg/m*) diameter diameter deviation per cm’
Keith and Derrick Blended “Conifuge” Not reported 0.15 Not reported Not reported 3.8 x 10"
(1960)
Porstendérfer and Not reported CNC/diffusion tube Not reported 0.24 Not reported Not reported 3.3 x 107
Schraub (1972)
Hiller et ai. Not reported SPART analyzer 50-100 0.32 0.41 15 Not reported
(1982)
Leaderer et al. Commercial EAA 700 Not reported 0.225 21 Not reported
(1984)
Ingebrethsen and MC/CNC 0.2 16
Sears (1986)

 

NOTE: CNC ~ Condensation nucleus counter; SPART = Single particle aerodynamic relaxation time analyzer; EAA -: Electrical aerosol analyzer; MC = Mobility classifier
particle deposition efficiency for SS particles in human volunteers
observed by Hiller and colleagues (1982) is consistent with particles
in this size range.

Several investigators have measured the size distribution of MS
smoke (Table 6). As is the case with SS smoke, the different
instruments and methodologies employed yielded differing results.

For purposes of comparison, only two sets of studies utilizing
similar instruments are discussed. McCusker and colleagues (1983),
using a single particle aerodynamic relaxation time (SPART) analyz-
er to study highly diluted MS smoke particles, found a mass median
diameter of 0.42 »m with a geometric standard deviation (GSD) of
1.38. Hiller and colleagues (1982) used the SPART analyzer on SS
smoke particles and found a mass median diameter of 0.41 ym and
GSD of 1.5. Chang and colleagues (1985) used an electrical aerosol
analyzer (EAA) to measure MS for various dilution ratios and
reported a MMD of 0.27 pm (GSD 1.26) for the highest dilution.
Leaderer and colleagues (1984) used an EAA to determine the size
distribution for SS smoke particles in an environmental chamber
and determined an MMD of 0.23 um (GSD 2.08). These results also
show that studies utilizing similar instruments provide similar
results for the size distribution of both SS and MS particles. As
discussed in an earlier section, however, the chemical composition of
the MS and ETS particles can be quite different because of the very
different conditions of their generation and the subsequent dilution
and aging ETS undergoes before inhalation.

Estimating Human Exposure to Environmental Tobacco Smoke

Human exposure to ETS can be estimated using approaches
similar to those used for other airborne pollutants. The concentra-
tion of ETS to which an individual is exposed depends on factors such
as the type and number of cigarettes burned, the volume of the room,
the ventilation rate, and the proximity to the source. These factors,
along with the duration of exposure and individual characteristics
such as ventilatory rate and breathing pattern, dictate the dosage
received by an individual.

Ideally, the health effects of exposures to ETS might be assessed by
quantifying the time-dependent exposure dose for each of the several
thousand compounds in cigarette smoke and defining the dose—
response relationships for these compounds in producing disease,
both as isolated compounds and in various combinations. The
magnitude of this task, given the number of compounds in smoke,
and the limited knowledge of the precise mechanisms by which these
compounds cause disease have led to a simpler approach, one that
attempts to use measures of exposure to individual smoke constitu-
ents as estimates of whole smoke exposure. The accuracy with which

139
OFT

TABLE 6.—Summary of mainstream smoke size distribution studies

 

 

 

 

 

 

 

Count Mass
median median Geometric
Dilution diameter diameter standard Concentration
Study Cigarette Method ratio (um) (um) deviation (number/cm!)
Keith and Derrick Blended “Conifuge” 295 0.23 Not reported 16 5.3 x 10°
(1960) .
Porstendirfer and Not reported CNC/diffusion tube Not reported 0.22 Not reported Not reported Not reported
Schraub (1972)
Okada and Blended Light scattering 1500 0.18 0.29 15 3 x 10°
Matsunama
(1974)
Hinds (1978) Commercial Cascade impactor 10 Not reported 0.52 1.35 Not reported
Cascade impactor 50 Not reported 0.44 144 Not reported
Cascade impactor 100 Not reported 0.39 1.43 Not reported
Aerosol certifuge 100 Not reported 0.38 1.33 Not reported
Aerosol certifuge 320 Not reported 0.38 137 Not reported
Aerosol certifuge 500 Not reported 0.38 1,35 Not reported
Aerosol certifuge 700 Not reported 0.37 131 Not reported
McCusker et al. 2R1 SPART analyzer 1.26 x 10° 0.36 0.42 1.38 42 x 10°
(1983)
Chang et al. 2R1 EAA 6 0.25 0.30 1.27 42x 10°
(1985) 10 0.24 0.26 1.18 3.6 x 10°
18 0,22 0.26 1.26 7x10

 

NOTE: CNC = Condensation nucleus counter; SPART = Single particle aerodynamic relaxation time analyzer; EAA = Electrical aeroeol analyzer,
measurements of a single compound reflect exposure to whole smoke
is limited by the changes in the composition of ETS with time and
the conditions of exposure. For this reason, exposures to ETS are
often asseased using several measures as markers, including mark-
ers of the vapor phase and the particulate phase as well as reactive
and nonreactive constituents. Although biological markers show
promise as measures of exposure because they measure the absorp-
tion of smoke constituents, they too have limitations (discussed in
Chapter 4). An individual’s exposure is a dynamic integration of the
concentration in various environments and the time that the
individual spends in those environments.

In specifying an individual’s exposure to specific components of
ETS, consideration must be given to the time scale of exposure
appropriate for the response of interest. Immediate exposures of
seconds or hours would be most relevant for irritant and acute
allergic responses. Time-averaged exposures, of hours or days, may
be important for acute contemporary effects such as upper and lowe:
respiratory tract symptoms or infections; chronic exposures occur
ring over a year or a lifetime might be associated with increasec
prevalence of chronic diseases and risk of cancer.

The spatial dimensions or the proximity of the individual to the
source of smoke is important in assessing that individual’s exposure
to ETS. ETS is a complex, dynamic system that changes rapidly once
emitted from a cigarette. Physical processes such as evaporation and
dilution of the particles, scavenging of vapors on surfaces, and
chemical reactions of reactive compounds are continuously occurring
and modify the mixture referred to as ETS. An individual located a
few centimeters or a meter from a burning cigarette may be exposed
to a high concentration of ETS, ranging from 200 to 300 mg/m®, and
may inhale components of the mostly undiluted smoke plume and of
the exhaled mainstream smoke. Ayer and Yeager (1982) reported
cigarette plume concentrations of formaldehyde and acrolein in the
core smoke stream emitted from the cigarette of up to 100 times
higher than known irritation levels. Hirayama, as reported by
Lehnert (1984), cites the importance of this “proximity effect” in
assessing exposure. Distances on the order of a meter to tens of
meters from a burning cigarette are relevant for exposures in offices,
restaurants, a room in a house, a car, or the cabin of a commercial
aircraft. At these distances, the mixing of ETS throughout the
airspace and the factors that affect concentration are of importance
in determining exposure for people in the space. In many rooms,
mixing is not completely uniform throughout the volume, and
Significant concentration gradients can be demonstrated (shizu
1980). These concentration gradients will affect an individual’s
exposure by modifying the effectiveness of ventilation in diluting or
removing pollutants. The airborne mass concentration may vary by

141
a factor of 10 or more within a room. Short-term measurements in
rooms with smokers can yield respirable particulate concentrations
of 100 to 1,000 pg/m* (Repace and Lowrey 1980). Multihour
measurements average out variations in smoking, mixing, and
ventilation and yield concentrations in the range of 20 to 200 g/m‘
(Spengler et al. 1981, 1985, 1986). Finally, on a systems scale, as in a
house or building, concentrations are influenced by dispersion and
dilution through the volume. Most time-integrated samples are
taken on this larger scale.

Using a piezobalance, Lebret (1985) found significant variation in
respirable suspended particulate (RSP) levels between the living
room, kitchen, and bedroom in homes in the Netherlands during
smoking or within one-half hour of smoking. Ju and Spengler (1981)
studied the room-to-room variation in 24-hour average concentra-
tions of respirable particles in various residences. Although differ-
ences between some rooms were statistically significant, absolute
differences were relatively small, with a maximum difference of a
factor of 2.

Moschandreas and colleagues (1978) released sulfur hexafluoride,
a tracer gas, in the living rooms of several residences and observed
uniform concentrations in adjacent rooms within 30 to 90 minutes.
RSP, which is slightly reactive, and nonreactive gases would be
expected to rapidly migrate through adjacent rooms. Therefore, in a
setting such as the work environment, where the duration of
exposure is several hours or more, ETS would be. expected to
disseminate throughout the airspace in which smoking is occurring.
Smoke dissemination may be reduced when air exchange rates are
low, as may occur when internal doors are closed.

Time-Activity Patterns

Individual time-activity patterns are a major determinant of
exposure to ETS. The population of the United States is mobile,
spending variable amounts of time in different microenvironments.
Individual activity patterns depend on age, occupation, season, social
class, and sex. For example, Letz and colleagues (1984) surveyed the
time-activity patterns of 332 residents of Roane County, Tennessee,
and found that 75 percent of the person-hours were spent at home,
10.8 percent at work, 8.5 percent in public places, 2.9 percent in
travel, and 2.8 percent in various other places. As expected,
Occupation and age were strong determinants of time-activity
patterns. Housewives and unemployed or retired individuals spent
84.9 percent of their time at home, and occupational groups worked
21 to 24 percent of the hours. Students tended to spend the largest
percentage of their time in public places, presumably schools,
ranging from 14.7 percent for the youngest group to 19.17 percent for
the oldest group of students.

142
TABLE 7.—Mean percent and standard deviation of time
allocation in various locations by work or
school classification subgroup

 

Outdoor Office/ Industrial/ —Total, all
Location Homemaker Student worker Service Construction participants

 

Home 84.34 60.91 49.97 68.74 57.28 64.21
(2.02)! (13.92) (12.24) (8.72) (7.05) (13.99)
Outside 5.52 8.62 19.81 2.47 10.59 8.08
(3.27) (6.53) (8.55) (2.49) (10.74) (7.07)
Motor vehicle 4.28 5.1 8.67 4.69 1.64 5.51
(3.19) (3.74) (6.15) (2.33) (7.52) (4.29)
Other indoors 6.01 23.61 21.55 24.99 24.80 21.58
(3.27) (10.62) (5.32) (10.24) (12.86) (11.87)
Cooking 4.69 0.34 0.00 232 0.52 1.24
(1.88) (0.79) (0.00) (2,30) (0.86) (1.98)
Near smokers 2.84 5.20 2.75 11.73 12.03 6.89
4.32) (7.88) (3.38) (15.19) (10.05) (9.71)

Number 8 32 4 12 8 662

 

* Numbers in parentheses are the standard deviation.
* Two unemployed participants were included in the total, but not given a separate category.
SOURCE: Data from Quackenboss et al. (1982).

The time allocations for various population subgroups in Portage,
Wisconsin, are summarized in Table 7 (Quackenboss et al. 1982). The
data are consistent with the findings of Letz and colleagues (1984)
and show that the variability of individual nonsmokers’ exposure to
smokers can be quite marked between the various occupational
subgroups.

Infants have unique time-activity patterns; their mobility is
limited and the locations where they spend their time depend
primarily on their caretakers. The time-location patterns for 46
infants is illustrated in half-hour segments in Figure 1 (Harlos et al.
in press). Although infants spend most of their time in their
bedrooms, they are in contact with a caretaker while traveling or in
the living room or the kitchen for approximately half of the day.
These infant time-activity patterns presumably correspond to the
family patterns and may significantly influence the infants’ poten-
tial exposure.

Although most people spend approximately 90 percent of their
time in just two microenvironments (home and work) (Szalai 1972),
important exposures can be encountered in other environments. For
instance, commuting or being “in transit” accounts for about 0.5 to
1.5 hours per day for most people. Therefore, additional information

143
 

24

 

  
   

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22

J
20

   

CRS
Z

\

l
18

  

 
  

I
16

     
   
    

N

Sis
al

WS
y
7

]
14

 
  

Living room

    
  
   

LZ

i
AS

XX

J
12

Ue
x

Hour of the day

!
10

Bedroom

ZA Other room
HBB kitchen
[_] outside nouse
RSS Travel
iH Unknown

4.

 

| 1
3 8 &

SWUBJU! JO JOQUINN

10

FIGURE 1.—Time location patterns for 46 infants

SOURCE: Harlos et al. (in press).

on the time spent and the ETS concentration in various microenvi-
ronments may be useful in defining exposure. This exposure
information can be obtained by questionnaire and validated by
personal monitoring programs. The characterization of concentra-

144
tions or exposures or both in microenvironments should use time
scales appropriate for the health effect of interest. These variations
in location and time-activity patterns can make the reconstruction of
detailed ETS exposure difficult in studies of long-term health effects.

The limitations in utilizing this time-activity approach in charac-
terizing exposures to other environmental pollutants also apply for
ETS exposures. They include the following: the extent to which
overall population estimates can be generalized to individual pat-
terns is poorly understood; concentrations in various microenviron-
ments are only partially characterized; the variation in time and
activity patterns and their effects on concentration levels are not
established; extrapolation to longer time scales either prospectively
or retrospectively has not been validated; the differences within
structures, i.e., room to room variations, are not well established.

Temporal and Spatial Distribution of Smokers

Exposure to ETS can occur in a wide variety of public and private
locations. Approximately 30 percent of the U.S. adult population
currently are cigarette smokers. Nationwide, 40 percent of homes
have one or more smokers (Bureau of the Census 1985). In a survey
of more than 10,000 children in six US. cities, the percentage of
children living with one or more smoking adults varied from a low of
60 percent to a high of 75 percent (Ferris et al. 1979). Lebowitz and
Burrows (1976) reported that 54 percent of children in a study in
Tucson had at least one smoker in the home; Schilling and colleagues
(1977) reported that 63 percent of homes in a Connecticut study had
a smoker in the home. These data indicate that the population
potentially exposed to ETS in the home is greater than might be
inferred from aggregated national statistics on the prevalence of
smoking. A variation in the percentage of homes with smokers may
be observed among different regions. Furthermore, within house-
holds, smoking does not take place uniformly in time or space.
Smoking patterns may change with activity, location, and time of
day. These variables all serve to modify a nonsmoker’s exposure to
ETS.

Exposure to ETS at home may also correlate with ETS exposures
outside the home, possibly because nonsmokers married to smokers
may have a greater tolerance for ETS-polluted environments or may
be in the company of more smokers because of the spouses’ tendency
to associate with other smokers. Wald and Ritchie (1984) used a
biological marker and questionnaires to show that nonsmokers
married to smokers reported a duration of exposure to ETS greater
outside the home than was reported by nonsmokers married to
nonsmokers (10.7 hours and 6.0 hours, respectively).

Smoking prevalence varies widely among different groups (e.g.,
teenage girls, nonworking adults, and adults employed in various

145
occupations); this variation modifies the exposure of nonsmokers to
ETS. Smokers are present in nearly all environments, including
most workplaces, restaurants, and transit vehicles, making it almost
impossible for a nonsmoker to avoid some exposure to ETS. The
number of cigarettes consumed per hour by the smoker may vary at
different times in the day, and the rate and density of smoking will
also differ by the type of indoor environment and activity in such
locales as schools, autos, planes, offices, shops, and bars. ~
Although there have been numerous measurements of ETS
concentrations in various indoor settings, these data do not repre-
sent a comprehensive description of the actual] distribution of ETS
exposures in the U.S. population. Spengler and colleagues (1985) and
Sexton and colleagues (1984) demonstrated by the personal monitor-
ing of respirable particles and the use of time-activity questionnaires
that exposures to ETS both at home and at work are significant
contributors to personal exposures. However, additional data on the
distribution of smokers in the nonsmokers’ environment, as well as
the distribution of ETS levels in that environment, are needed in
order to characterize the actual ETS exposure of the U.S. population.

Determinations of Concentration of Environmental Tobacco
Smoke

Environmental tobacco smoke is a complex mixture of chemical
compounds that individually may be in the particulate phase, the
vapor phase, or both. ETS concentration varies with the generation
rate of its tobacco-derived constituents, usually given as micrometer
per hour. The generation rate for ETS has been approximated by the
number of cigarettes smoked or the number of people present in a
room who are actively smoking. Room-specific characteristics such
as ventilation rate, decay rate, mixing rate, and room volume also
modify the concentration. Because ETS particles have MMDs in the
0.2 to 0.4 4m range, convective flows dominate their movement in
air, they remain airborne for long periods of time, and they are
rapidly distributed through a room by advection and a variety of
mixing forces. Under many conditions, the ventilation rate of a space
will dominate chemical or physical removal mechanisms in deter-
mining the levels of ETS particles.

Nonreactive ETS components distribute rapidly through an air-
space volume, and their elimination depends almost solely on the
ventilation rate. For example, Wade and colleagues (1975) simulta-
neously measured carbon monoxide, a nonreactive gas, and nitrogen
dioxide, a reactive gas, in a house and determined their half-lives to
be 2.1 and 0.6 hours, respectively. This study demonstrates the need
for caution in extrapolating from one vapor phase compound to
another. Reactive gases and vapors may be rapidly lost to surfaces or

146
may react with other chemical species. Their removal may be
dominated by their reaction or absorption rates, Furthermore, the
decay of ETS-derived substances can be a function of the chemical as
well as the physical characteristics of room surfaces. For example,
Walsh and colleagues (1977) found that sulfur dioxide removal was
greater for rooms with neutral and alkaline carpets than for rooms
having carpets with acidic pH. Reactions with furnishings and other
materials may occur for some ETS components as well.

Microenvironmental Measurements of Concentration

As was discussed earlier, the complex chemical makeup of ETS
makes the measurements of individual levels for each compound
present in ETS impossible with existing resources; thus, some
individual constituents have been measured as markers of overall
smoke exposure. Because many of these constituents are also
emitted from other sources in the environment, the contribution of
ETS to the levels of these constituents is quantified by determini
the enrichment of specific compounds found in smoke-polluted
environments relative to the concentration measured in nonsmoking
areas. Various ETS components have been measured for this
purpose, including acrolein, aldehydes, aromatic hydrocarbons,
carbon monoxide, nicotine, nitrogen oxides, nitrosamines, phenols,
and respirable particulate matter. A summary of the levels found
and the conditions of measurement are presented in Tables 8
through 15. The major limitation of using most of these gases,
vapors, and particles is their lack of specificity for ETS. The presence
of sources, other than tobacco smoke, of these compounds may limit
their utility for determining the absolute contribution made by ETS
to room concentrations. Levels of nicotine and tobacco-specific
nitrosamines, however, are specific for ETS exposure.

Obviously, no single measurement can completely characterize the
nonsmoker’s exposure to ETS, and many studies have measured
several of these components in order to characterize the exposure.
Markers should be chosen both because of their accuracy in
estimating exposure and because of their relevance for the health
outcome of interest.

One widely reported marker of ETS is respirable suspended
particulate (RSP) matter. Although lacking specificity for tobacco
smoke, the prevalence and number of smokers correlates well with
RSP levels in homes and other enclosed areas.

A study of the RSP levels in 80 homes in six cities (Figure 2)
(Spengler et al. 1981) showed that indoor concentrations were higher
on average and had a greater range than the outdoor concentrations.
From these data, it is evident that even one smoker can significantly
elevate indoor RSP levels.

147
SPT

TABLE 8.—Acrolein measured under realistic conditions.

 

 

 

Levels
Type of Monitoring

Study premises Occupancy Ventilation conditions Mean Range
Badre et al. Cafes Varied Not given 100 mL samples 0.03-0.10 mg/m*
(1978) Room 18 smokers Not given 100 mL samples 0.185 mg/m*

Hospital lobby 12 to 30 smokers Not given 100 mL samples 0.02 mg/m?

2 train compartments 2 to 3 smokers Not given 100 mL samples 0.02-0.12 mg/m*

Car 3 smokers Natural, open 100 mL samples 0.03 mg/m?

2 smokers Natural, closed 100 mL samples 0.30 mg/m*

Fischer et al. Restaurant 50-80/470 m* Mechanical 27 x 30 min samples 7 ppb
(1978) and Restaurant 60-100/440 m* Natural 29 x 30 min samples 8 ppb
Weber et al. Bar 30 -40/50 m?* Natural, open 28 X 30 min samples 10 ppb
(1979) Cafeteria 80-150/574 m* 11 changes/hr 24 X 30 min samples 6 ppb (6 ppb

nonsmoking section)
6FT

TABLE 9.—Aromatic hydrocarbons measured under realistic conditions

 

 

 

 

Levels Nonsmoking controls
Type of Monitoring
Study premises Occupancy Ventilation conditions Mean Range Mean Range
Benzene (mg/m*)

Badre et al. Cafes Varied Not given 100 mL samples 0.06-0.15
(1978) Room _ 18 smokers Not given 100 mL samples 0.109

Train compartments 2 to 3 amokers Not given 100 mL samples 0.02-0.10

Car 3 smokers Natural, open 100 mL samples 0.04

2 smokers Natural, closed 100 mL samples 0.15
Toulene (mg/m*

Cafes Varied Not given 100 mL samples 0.04-1.04

Room 18 smokers Not given 100 mL samples 0.215

Train compartments 2 to 3 smokers Not given 100 mL samples 1.87

Car 2 amokers Natural, closed 100 mL samples 0.50

a /m*
Elliott and Rowe Arena 8,647-10,786 people Mechanical Not given ql
(1975) 12,000-12,844 people Mechanical Not given 9.9
13,000-14,277 people Mechanical Not given 21.7
Separate non- 0.68
activity days

Galuskinova Restaurant Not given Not given 20 days in summer 6.2
(1964) 18 days in the fall 28.2-144

 
OST

TABLE 9.—Continued

Type of
Study premises Occupancy

Just et al. Coffee houses Not given
(1972)

Perry (1973)* 14 public places Not given

''The correctness of the data is doubtful (Grimmer et al. 1977).

Levels Nonsmoking controls
Monitoring
Ventilation conditions Mean Range Mean Range

Not given 6 hr continuous 0.25-10.1 4.0-9.3 (outdoors)

Benzofe ne_(ng/m*,

3.3-23.4 3.0-5.1 (outdoors)
Benzofghi)peryiene (ng/m*)
5.9-10.5 6.9-13.8 (outdoors)
Perylene (ng/m*)_
0.7-1.8 0,1-1.7 (outdoors)
Pyrene (ng/m')
4.1-9.4 2.8-7.0 (outdoors)
Anthanthrene (ng/m*
0.6-1.9 0.5-1.8 (outdoors)
Coronene (ng/m’)
0.5-1.2 1.0-2.8
Phenols (u/m’)
TA-ALB
Benzofalpyrene (ng/m*) _

Not given Samples, 5 outdoor < 20-760 < 20.43
locations