I% .8
. ..........
THE RELATIONSHIP BETWEEN TOBACCO
PYROLYSIS AND HEALT14
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717LE
Thermodynamic and Kinetic Variables in Tobacco
Pyrolysis and their Influence an the Relationship
Between
Smoking and Health
AUTHdRS
J. A. E. Bell NIASc. , PhD Senior Research Eng.
International Nickel Company of Canada, Limited,
J. Roy
Gordon Rescarch Laboratory, Clarkson, Ontario.
D. H. Laing Senior Technologist, University of
Toronto, Department of Metallurgy and Material
Science,
Toronto, Ontario.
ACKINOWLEDGMENTS
None
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BATCo document for Province of BritiSh Columbia 14
April 1999


Thorn-todynarnic and Kint-tic Variables in Tobacco
Pyrolysis and
thoir influence on the Relationship between
Smoking and lbealth.
J. A. E. Bell, PhD D. H. Laing
ABSTRACT
Statistical analysis of recent data on the
mortality rates
of pipe, cigar and cigarette smokers showed that
the mortality ratio
of smokers could be best described in terms of the
dose rate (volume
of si-nokc per day), length of exposure and
toxicity of the smoke. When
the toxicity of cigarette smoke was defined as
one, the toxicity of pipe
smoke was found to be 0. 07 . 11 and of cigar
smoke 0. 28 t . 13. No
reasonable explanation of this difference in
toxicity has been proposed.
A hypothesis that the toxicity of the smoke is
controlled by the com-
bustion conditions during pyrolysis of the tobacco
is advanced.
The mode of the combustion of cigarettes, pipes
and
cigars and some of the chemical properties of
their smoke were studied.
Substantial differences between the composition of
their respective
gaseous constituents and that of their particulate
phase is demonstrated.
There appears to be a quantitative link between
the optical tar density
and the toxicity of the smoke to mortality. It is
also demonstrated that
by altering the combustion characteristics of a
cigarette that the pro-
perties of the smoke can be changed so that the
expected mortality ratio
of male cigarette smokers aged 45 to 65 should be
reduced from 2. 1 to
less than 1. 1 for an average daily dose of 28
cigarettes at 25 cc/puff
with an average age of starting to smoke of 19
years.
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April 1999


int.- oduct ion
Bell
A statistical analysis of recent observations (1),
(2),
(3) and (4) on the influence of pipe, cigar and
cigarette smoking on
health is undertaken in the appendix. This
analysis showed that
the toxicity of pipe smoke was 15 times lower than
the toxicity of
cigarette smoke, and that cigar smoke was 3 times
less toxic at
the same smoke dose rate and length of exposure.
No really satisfactory expla nation of this
difference
in toxicity has been advanced and it is
hypothesized in the appendix
that the toxicity of the smoke is controlled by
the combustion
conditions of the pyrolysis of the tobacco. This
portion of the
paper describes an experimental investigation of
the influence of
the pyrolysis conditions of the tobacco on the
properties of the
smoke.
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-3-
Description of Tests
The combustion of tobacco is a complex process
Bell
involving both destructive distillation and
oxidation reactions.
T\.,.-o maJor phases are present in the smoke - a
gaseous phase
and a liquid particulate phase. From thermodynamic
consid-
erations it is well known that the time -
temperature relation-
ships which exist during the combustion are the
important
variables governing the composition of both the
particulate
and gaseous phases.
In order to minimize the influence of tobacco type
on
the combustion mode, the same tobacco was employed
in the
pipe as in the cigarette. The measurements on
cigars, of course,
precluded the possibility of the use of the same
tobacco. Chromel-
Alurnel (0. 006 " Diameter) thermocouples were
used to continually
record the time- temperature relationships in the
combustion of
the tobacco. Readings of the maximum temperature
attained during
the draw cycle are difficult to obtain, and
admittedly even the
temperature during the idle (no puff) cycle shown
in Table I are
low because fine enough thermocouples were not
employed (5). The
temperature differences are however, quite
significant.
In the cigarette the maximum temperature of over
7300C
in the fire ball occurs at a point approximately
0. 6 cms ahead of the
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(3 a) Bcll
TAB LE I
Combustion Charac,~eristics and Smoke Produced
from Principle Smoking Devices
"
(l) Avg.Cig.
,
1 Cigar Pi e
9 COMD. Cig.4
Reconst. Cig.5
ortality Ratio
Avera&e .
(o 1.05 1.
1 ?
Avera.e idle Te7.p.(2)*C 730 620 47o 720 61o
Avg. Rate of Heating
of Tobacco during puff
cycie *C/sec. - 130 79 47 70 60
Gr=s of Tobacco
burned per puff .024 .043 .009 .017 .015
Avg. Rate of Feating of
Tobacco at Idle *C/min.
at 0 Puffs/Min - 570 Neg. Neg. 290 Neg.
620 230 Neg 250
2 700 330 Neg: 480
8 510 250
Avg. Ilo. of Puffs
Der Device - (std) 15 67 go 17 20
Velocity of Burning
Interface in/min.
at idle - .17 Decrease& Decrease .091
at 25 cc/sec. puffing 1-9 1.1 .25 .72
Gas Analysis in.% H2 2.5 3.0 .1-2 1.5
Normal Pluffing
Conditions Co 4.7 4.0 .5-2 .5 3
02 13.5 8.o 8-14 12
C02 8.7 15.0 5 7
CH, .52 .5 .3 .8
-LATIVE OPTICAL TAR DENSITYM .
:OMPARED ON PER PUFF BASIS ~00 40-50 3-8 20-30 11
CAMBRIDGE FILTER TEST 24 11
TOTAL PARTICULATE MATTER Mg
~lj AGe adjusted ratio of deaths of smokers to
non-srokers.
2 Maximum temperature in fireball-normal smoking
conditions.
3 Based on relative absorbance of solutions
obtained by scrubbing
smoke in methyl hydrate. Applies over entire
visible spectrum.
(4) Cigarette with tobacco longitudinally
compressed and having a
centrally located passage parallel to the
longitudinal axis.
(5) Cigarette rolled with a high tobacco density
and a passage as in (4);
(6) Pcrformcd in major Tobacco Co. Laboratory
sample size = 100 cigarettes
comparcd on equiv. puff basis.
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April 1999


-4- Bell
, intcrface of the paper. The particulate phase in
the
burr, ing
smoke is not produced near this maximum
temperature zone
an,i the particulate phase of the smoke becomes
gaseous if
heated over 5000C and substantially gaseous over
300 0C. Thus
the maxin-itiri-i temperature in the fire ball can
not be the primary
factor controlling the composition of the
particulate phase.
Under uniform puffing conditions or at idle the
rate
heating of the tobacco is constant from
approximately 1500C
to 5000C i. e. the time versus temperature trace
on a recorder
is a straight line.
The linearity of the time - temperature trace
during
puffing or idling is also shown by Touey and
Mumpower (5). In
the study of reaction rate kinetics and in
irreversible thermo-
dynarn,,c.c;. it is well known that the products
from any reaction
are controlled by the time and temperature
variables. The only
parameter reflecting a ti me - temperature
relationship in smoking
which can be measured in the 1500C - 5000C range
is the rate of
heating of the tobacco; and this parameter should
be the major
thermodynamic or kinetic variable controlling the
particulate
phase composition. The rate of heating of the
tobacco found in
various ways of smoking tobacco is shown in Table
I as a function
of the number of puffs per minute at idle and also
during the puff
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-5-
Bell
cycle. Each reading is averaged from 10 to 30
measurements
covering a wide variety of brands. The rate of
heating of the
tobacco in dic range 1500C - 5000C will be more
independent
of the thermocouple size than the absolute
temperature
i-ricasurcment and th,- ;;ccuracy of the couples
used in these
experiments should be quite sufficient.
The velocity of the burning interface is shown in
Table 1 at idle and during puffing. as well as the
mass of tobacco
burned per puff cycle.
The number of puffs per device was measured under
standard conditions - the cigarette and cigar at
two puffs per
minute, and the pipe at eight puffs per minute.
The puff rate
during pipe smoking must be measured at a puff
rate over two
puffs per minute or the combustion of the tobacco
will terminate
as indicated in Table 1.
Analysis of the gaseous phase composition was
under-
taken using normal gas chromatographic procedures
and the
results are shown in Table I.
A detailed study of the particulate phase was not
under-
taken. Indeed, it is not possible to know which
combination of
compounds is important from a health standpoint.
The major
purpose of these tests was to indicate that
alteration of the variables
of combustion changes the properties of the
particulate phase.
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Bell
Total Particulate Matter (TPM) tests were carried
out
;In a inajor Canadian tobacco company on
conventional cigarettes
an(i cigarettes modified by compression as
described below. Both
cigarettes had the sarne overall pressure drop and
samples of 100
cigarettes were employed. The results had to be
compared on a,
per puff basis as the compressed cigarette burned
longer ( see
Table 1). Another indication of the hydrocarbons
content of the
smoke is what may be termed the optical tar
density (OTD). The
smoke from the smoking device was scrubbed by a
given amount
of a methyl hydrate (in these tests 25 cc's) and
the absolute
absorbance of the solution compared to pure methyl
hydrate was
measured on a recording spectophotorneter. The
absorbance of
the solution in the visible spectrum is directly
proportional to
the amount of coloured hydrocarbons in the smoke.
Fortunately.
the relative absorbance between all types of smoke
studied is
constant across the entire visible spectrum so
that the absorbance
of the solutions can be compared at any wave
length in the visible
spectrum. In Table I the relative absorbance
measured at 450
millimicrons is shown on a scale with the value
for smoke from
the cigarette adjusted to a value of 100. The
results were mea-
sured after smoking each device to approximately a
normal butt
length and reported on a per puff basis.
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-7-
Bell
As noted in Table I the optical tar density in the
smoke
from the pipe and cigar is remarkably lower than
the smoke from
cicarettes. In addition it should be noted that
the rate of heating
in tiio tobacco is correspondingly lower. To
further experimentally
substantiate t1iis apparent relationship,
cigarettes were altered to
chanze the rate of heating of the tobacco.
Compression of the
tobacco and -Pfacing of a small longitudinal hole
down the cigarette
in order to secure proper Alrawing"
characteristics appears to be
the most effective method to produce the change.
Cigarettes were compressed by 1/3 in a
longituciinal
direction without changing the cross sectional
area or wrinkling
the paper, pierced longitudinally by a 3/32 inch
rod, and subjected
to the same tests as the usual smoking devices and
the results
indicated in Table 1 under "Comp. " cigarette.
Cigarette tobacco
was also rerolled to a density 1/3 greater than
normal cigarettes,
pierced longitudinally, and tested as shown in
Table 1 under
"Reconst. '' cigarette.
Discussion
In the introduction it was postulated that the
properties
of the smoke from tobacco should depend on the
thermodynamic and
kinetic variables of the pyrolysis to which the
tobacco is subjected.
If this postulate is correct then there should be
a quantitative
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-8- Bell
rciationship, between the smoke properties and
these variables. The
rate of heating of tobacco during the puff cycle
was shown to be one
of the r-nost important thermodynamic and kinetic
properties. The
-at,- of heating of the tobacco at idle could have
been selected to
nnake a similar demonstration. From Table 'I the
mobt signifi,~ant
6 ifference in the smoke produced was shown to be
the optical tar
censity. Thus the relative optical tar density
(ROTD) should bear
a functional relationship to the rate of heating
of the tobacco (HR)
or:
ROTO (HR)
The amount of colourcd hydrocarbons per puff
should also be ex-
pected to be linearly related to the mass of
tobacco burned per puff
(M/P) thus:
ROTD (H R) x (M / P)
Statistical analysis of the results shown in Table
I
indicate that the simple best fit equation is:-
ROTD -0 - 22 + 0. 225 x ( (HR) 2 x (M/P) ) + 10.8
This equation is shown graphically in Figure 1.
along
with the experimentally determined points. The
probability that
there is no statistical correlation between ROTD
and (HR) 2 x M/P
is less than 1 in 100. The standard error of the
best fit equation is
10. 8 and the correlation coefficient between ROTD
and (HR)2 x (M/P)
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-9-
Bell
is 0. 976 (a pericct correlation is I . 0). The
above equation also
satisiics the criteria that when the tobacco is
not burning. i. e.
M/P = 0 or HR = 0. then ROTD = 0.
The relative optical tar density per puff is only
an .:n-
dicativc property of the particulate phase. From
thermodynamic
reasoning it is possible to assert that there will
be similar rnath-
eniatical relationships between the combustion
variables i. e. the
rate of heating of the tobacco. HR, and any of the
compositional
variables. Thus. the conclusion is of general
validity that the
composition of smoke produced by tobacco pyrolysis
is dependent
upon the thermodynamic variables of the pyrolysis
and the
hypothesis propounded in the introduction is
substantiated.
In the appendix the best fit equation which fits
all of
the mortality data of all male smokers aged 45 to
65 was found
to be:
MR = .93 + .03 2 (TOXICITY) (DOSE RATE x 10-4) 1/3
X (55 - AS)
where:-
MR = Morlatily ratio (ratio of deaths of smokers
to non-
smokers of the same age)
DOSE RATE = cc of smoke inhaled per day
AS = age started smoking.
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Bell
The best values of the toxicity were found to be;
for
cigarette smoke - 1. 00 1 .07 (defined). for pipe
smoke - 0. 07 11
and for cigar smoke - 0. 28 13.
1 f the optical tar density issuing from the
smoking
device per puff signUicantly affects the
inorLctliLy ratiu uf the
smoker then there should be a relationship between
the relative
tar density and the toxicity. This comparison is
indicated in
.able 2.
Thus with a high degree of confidence it can be
stated
that the toxicity of the smoke is equal to the
relative optical tar
density.
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-10a- Bell
TABLEZ
Comparison of the Relative Optical Tar Density to
the Relative
Snioke Toxicity
Device Relative Optical Tar Density/100 Relativt:
Simoke Toxicity
Cigarette 1.00 1.00 .07
Cigar 0.40 to 0.50 0.28 13
Pipe 0.03 to 0.08 0.07 + I I
Reconst.
Cigarette 0. 11
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- 11 -
Bell
The optical tar density is only one indication of
the
potential hoalth hazard to the smoker and a more
general hy-
pofficsis that the smoke toxicity is a function of
the thermodynamic
variables alone is more fitting. Since a
relationship between the
rate oi heating and the burning rate with the
optical tar density
%vas shown to exist at the 99% confidence level
and since the optical
tar density is directly related to the smoke
toxicity it is possible
to state with a large degree of confidence that
there is a relation-
ship between the health hazard or toxicity of
smoking and the
thermodynamic and kinetic variables of the
pyrolysis of tobacco.
In addition, it can be asserted that the important
variables control-
ling the composition of the particulate phase are
the rate of heating
of the tobacco and the rate of burning of the
tobacco. It is inter-
esting to note that if cigarettes were produced so
that they exhibit
similar properties to those shown in columns 4 and
5 of Table I
then the expected mortality ratio of male
cigarette smokers aged
45 to 65 with an average daily dose rate and
length exposure would
be lowered from 2. 1 to 1. 1.
Summary
As shown in the appendix cigarette smoking is a
serious
health hazard while pipe and cigar smoking is not.
No evidence has
been advanced which can explain this difference as
discussed in the
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appendi.%. The only possible reason was shown to
be a variation
of smoke composition produced by different burning
conditions in
the cigarette. pipe and cigar.
Some of the chemical properties of the cigarette,
cigar
anc' pipe smoke were stucied and a large
difference was found. For
instance, the optical tar density of cigarette
smoke was found to be
20 times higher than in pipe smoke. A direct
relationship between
the optical tar density and the toxicity for all
t~rpes of smokers was
established. Thus it can be concluded that:
- the greater health hazard of cigarette smoking
corn-
pared to pipe and cigar smoking derives from a
different smoke
composition, and that:
- the optical tar density is an important index of
the
health hazard or smoke toxicity.
The amazing difference in optical tar density
between
pipe and cigarette smoke was shown to depend
quantitatively on
the rate of heating of the tobacco and the rate of
burning during
combustion.
By altering the construction of a cigarette it was
possible
to approach the burning conditions in the pipe.
Smoke from the
altered cigarettes had optical tar densities
similar to that of pipe
smoke. From these observations it can be concluded
that:
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Bell
the combustion conditions control the smoke
composi-
tion. anc! that:
- cigarettes can be altered so that the smoke and
corn-
bustion conditions are substantially the same as
pipes and that:
- the modified cigarettes should be 10 times less
toxic
than conventional cigarettes and should not
represent a health
hazard.
It is important to note even if a filter were
produced
which could remove all of the coloured
hydrocarbons or tar from
the sT-noke it would not be possible to claim that
the smoke re-
presented no health hazard or even that it was
"safer". Until
all of the potentially hazardous components and
groups of com-
ponents are discovered (a very formidable
undertaking) the only
method of producing a "safe" cigarette is to
correct the combus-
tion variables. which are responsible for
producing the hazardous
substances. so that they are similar to those of a
known safe
method of smoking. From thermodynamic
considerations it is
then possible to claim that such an altered
cigarette would be
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_14-
Rcf(- rcnc cs
(1) Advisory Con-,mittc to the Surgeon (,eneral on
Srnoking and Health, U. S. A. Public Health
Service Publication #1103.
(2) E. C. Hammond Smoring in Relation to the
Death Rates of One Million Men and Women,
National Cancer Institute Monograph No. 19
127-204, 1966.
Bell
(3) E. C. Hammond Smoking in Relation to Mortality
and Morbidity, Journal of the National Cancer
In stitute Vol. 32, No. 5. May 1964.
(4) E. C. Hammond and L. Garfinkel The Influence
of Health on Smoking Habits, National Cancer
Institute Monograph, No. 19, P. 269-285, 1966.
(5) G. P. Tauey and R. C. Mumpowder Measurement
of the Combustion-Zone Temperature of Cigarettes,
Tobacco Vol. 144, No. 8, PP. 18-22, 1957.
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Appendix
Beli
Statistical Analysis of Mortalitv Rates of
Cigarctte, Pipe and Cigar
Smokers
A proper correlation between the mortality rates
of
cigarette, pipe, and cigar smokers as a function
of the three
exposure variables, amount smoked, depth of
inhalation, and
ge at which smoking started, has not been carried
out. The
purpose of this appendix is to develop the best
fit equations
-elating the mortality ratio and the exposure
variables. Such
an analysis permits a comparison between the
toxicity of smoke
from cigars, pipes and cigarettes. In addition,
the possibility
of explaining the mortality ratios in terms of a
more conventional
dose rate and length of exposure concept is
investigated.
For a proper investigation the mortality rate
should
be tabulated as a function of two of the exposure
variables at
-zvery level of the third variable. For
instance,the mortality rate
of cigarette smokers as a function of the number
of cigarettes
smoked per day and the depth of inhalation should
be shown for
every age of started smoking for a given age group
i. e. 40 to 69 years.
However, the mortality rates (1), (2). (3) and (4)
have
not been so tabulated. Table 3 reference (3) shows
the mortality
of cigarette smokers as a function of the depth of
inhalation and
the amount smoked at the average age of starting
to smoke (19 years).
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--:-0:,i this table the best fit equation of the
mortality ratio (easily
calculatcd irorn the mortality rate) can be found
by multinornial
rogrossion.
To convert the depth of inhalation which is
expressed by
1), j2), (3) and (4) as nono, slight, moderate, or
deep, to a more
ma-,*-ematical form; the volume of air inhaled by
smoking through a
cic,arette filter was measured when ten male
sub*ects were requested
to give the above depths of inhalation ten times.
The rounded off
avorage values were; none - 14 cc, slight - 20 cc,
moderate - 26 cc,
and deep - 33 cc. It should be noted that it is
physically impossible
to inhale deeper without taking a larger volume of
smoke into the
6 ody. While it can be argued that these values do
not represent
the population,they are al.most certainly more
representative than
the subjective classification by smokers into one
of four depth of
inhalation groups.
Thus the best fit multinornial equation relating
the
mortality ratio, (MR), to the number of cigarettes
smoked per
day (NG), and the depth of inhalation (DR) at the
average age of
starting to smoke for men aged 40 to 69 was found
to be,
2 +
MR = .983 + .028(NC) + .0209(DR) - .00031(NC) 11
(1)
where . 11 is the standard error.
mortality ratio is the ratio of death rates of
smokers to
non-smokcrs in the same age group.
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-17- Bell
Each of tho above torms is significant at the 99%
confidence level.
T'he i-nialtiple correlation coefficient of this
equation is . 97(a perfect
correlation is 1. 0) and the F value for analysis
of variance is 86.
While equation (1) ii the best fit equation for
this data
it does not have a physicai interpretation. A more
meaniful
method of analyzing the results would be to
postulate that the
mortality rate was proportional to the "dose rate"
of the smoke.
Thus for cigarette smokers the daily dose rate
would correspond
to the number of cigarettes per day times the
number of puffs per
cigarette times the volurne inhaled per puff or,in
other words,the
volume of smoke inhaled per day. Analysis of the
data in Table 3
reference (3) for rnale smokers ager! 40 to 69
indicates the best
fit equation is of the form:
-4 1/3 +
M R 1. 0 1 + .983 (Dose Rate x 10 13 (2)
where Dose Rate = (NC) x 15 x (DR) ccSmoke/Day.
The
multiple correlation coefficient for this
relationship is . 96, the
dependence with (dose rate) 1/3 is significant at
a confidence level
over 99. 99%, and F value for analysis of variance
is 105. Three
extra data points for all the cigarette smoking
relationships at
MR = 1. 0. DR = 0. NG = 0. were added as it is the
best known
point and represents the zero value for each
variable. Thus
expressing the mortality ratio as a function of
the dose rate gives
as good a fit to the data as the best fit
multinomial equation.
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Bell
As nientioned a proper multinornial regression on
all
z'-.ree exposure variables is not possible because
the information
:~ ;-.,)t tabtilatec! in a convonient form.
However, the mortality
-ates are expressed as a Ifunction of the three
variables when the
other two are averager-, ri), (2) and (3). A
multinomial regression
or, this grouped data is thus possible. If a
comparison between
smokers of cigars, pipes and cigarettes is to be
made,it is
necessary to consider the mortality of men over 45
years of age
m orrier to have enough observations in each
grouped data point.
The mortality rates were calculated from tables
presented in
reference (2) in the age group 45 - 65 as this
group contains a
higher number of excess deaths from smoking than
an older group.
The mortality rates were normalized on the
standard pop-
ulation distribution (Table 1, Appendix of
reference (Z)) as was done
in that work. The average values for amount
smoked. age started
smoking and depth of inhalation were averaged from
the appropriate
tables in (2) over the 45 to 65 age group.
The best fit equations were found to be:
Male Cigarette Smokers Only Aged (45 - 65)
MR = 3. 18 + . 0156(NC) - . 134(AS) + 00017(AS) +
.00059(DR) + .087 (3)
multiple correlation coeff. = . 99 F 126. 5
where AS = age started smoking.
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-19-
Ma'.o C:,-,arette + Cicar Pioc Srnokers:~ A q ed
(4 5 - 6 5)
BclI
2.05 + .0101(NC) 113(AS) + .0363(DR) + .00023(NC)
2
2 +
+ .00171(AS) - .096 (4)
multiple correlation coeff. 98 F =: 6 0. 5
'Ihe corresponding best iit dose rate equations
are
.\,Iale Cigarette Smokers Only Aced 45 - 65
-4 1/3 +
MR = .93 + .032(NC x 15 x DR x 10 ) x (5 5 - ASI
13 (5),
-,,,-'r-LereNC -, 15 x DR = doserate =
volumesmoke/day
multiple correlation coeff. = .97 F = 207.
N.'alle Cigarette Plus Pioe and Cicar Smokers Aged
(45 - 65)
-4 1/3
MR = .92 + .0272 ((NIC) x 15 x (DR) x 10 x (5 5 -
AS)
+ . 19 (6)
multiple correlation coeff. = .91 F = 66.
For pipe and cigar smokers there are not enough
data points
to cvaluate the best fit multinornial equations so
only the mortality
ratio as a function of the dose rate equations can
be calculated. No
data is available for the age started smoking for
pipe and cigar smokers.
Male Pipe Smokers Only Aged(45 65)
MR = 1. 02 16 (7))
multiple correlation coeff. = .08 F = .01.
::,classified by number of cigarettes smoked per
day
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April 1999


-20-
CiL,ar Smokers Onlv Aced (45 - 65)
Bell
-3 113 +
MR 82 + .208 (NtCIG x 60 x DR x 10 13 (8)
v,-here INCIG = number of cigars per day
MkLItiple correlation coeff. = .7 F = 1. 8Z.
The average number of puffs per cigar is 60 and
for pipeb 90 afi
shown in Table (1) of this report.
Discussion
An excellent correlation (correlation coefficient
99)
rclating the mortality ratio of cigarette smokers
and the exposure
variables of arnount smoked, depth or volume of
inhalation, and age
started smoking, has been found by multinornial
regression. The
mortality ratio is linearly related to the dose
rate (volume of smoke
per day) to the one third power times the average
length of exposure
to the smoke.
Lf the mortality ratio of men who smoke cigars and
pipes
in addition to cigarettes is compared to that of
men- who smoke only
cigarettes by utilization of the respective best
fit equations (3) and (4)
an irftportant conclusion can be drawn. The best
value of the
mortality ratio for male cigarette smokers aged 45
to 65 at 24
cigarettes per day, an inhalation volume of 25 cc,
and an age of
started smoking of 19, is 2. 00 087,while the
corresponding
value for cigarette plus cigar and pipe smokers is
1. 80 096. C=>
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April 1999


_21-
Bell
one of the two following conclusions can be made
depending
,.-.'iethor the smokers smoked cigars and pipes
concurrently with
~:,,~,arottos L)i*. at sonic unie.switchcd mode of
smoking:
Cigar and pipe smoking in addition to cigarette
smoking
pro-L'uces a sigrill"CajIL luwering of the
mortality ratio of the smoker;
0 r:
Cigar and pipe smoking did not induce mortality as
readily as cigarette smoking over the period when
those devices
smoked.
. The most important conclusion is derived from
the
analysis of pipe smoking; namely, pipe smoking is
not dangerous
.o health and there is no correlation between the
dose rate or
exposure and the mortality ratio. Cigar smoke is
only slightly
toxic and the relationship between the mortality
ratio and the
(lose rate is not highly significant.
The lower mortality ratio of pipe and cigar
smokers
compared to cigarette smokers is often linked to a
lower volume
of inhalation. For example; 7076 of pipe smokers
(45 to 65 years)
inhale only approximately 1.4 cc per puff, 807c of
cigar smokers
inhale only 14 cc per puff, while the average
cigarette smoker
inhales approximately 25 cc per puff (see appendix
of reference (2)).
When converted in terms of dose rates the average
daily dose of
C71.
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April 1999


-22-
Bell
these three modes of smoking are: cigarette -
11,000 cc/day,
pipe - 11, 500 cc/day, cigar - 3, 000 cc/day.
Calculation of the
mortality ratio from equations (5, 7. 8) at
equivalent dose rates
clearly indicate at a confidence level of better
than 99. 9% that
the lower mortality ratio of pipe and cigar
smokers cannot
primarily be caused by a small depth of inhalation
or dose rate.
,\o 6ata is available for the age started smoking
of pipe and
c1 gar smokers so the effect of this variable
cannot be checked.
However, even if the average age of starting to
smoke cigarettes
was 24 years instead of 19 years the same
conclu6i0n would result.
A more fundamental way of expressing the data is
to calculate the relative toxicity of pipe and
cigar smoke compared
to cigarette smoke. If the toxicity of the smoke
is defined by the
equation:
MORTALITY RATIO (MR) = a + b (TOXICITY) (DOSE;
RATE) 1/3
x (LENGTH OF EXPOSURE)
then the relative toxicity of pipe and cigar smoke
can be easily
calculated from a comparison of the respective
martality ratio
versus dose rate equation (5, 7, 8).
Let the toxicity of cigarette smoke be 1. 0; then
the
mortality ratio for all male smokers aged 45 to 65
is expressed
by the equation:
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-23- Bell
.93 + .032(TOXICITY)(CC SMOKE/DAY x 10-4 )1/3 x
(5 5 - AS) (9)
where AS is the age started smoking.
Comparison of eqn. (9) with eqn. (7) and (8)
yields
the following toxicity values.
DEVICE SMOKED TOXICITY OF SMOKE
CIGARETTE 1.0 + .07 (Defined)
CIGAR .28 + . 13
PIPE . 07 + .11
Placing the appropriate toxicity value in equation
(9) allows the
calculation of the mortality ratio of a male
smoker ages 45 to 65
for any smoking device.
Conclusions
The mortality ratio of cigarette smokers is highly
corrclated (multiple correlation coefficient =
.97) to the dose
rate of the smoke (volume of smc?ke inhaled per
day) and the
length of exposure to the dose. The increase in
mortality ratio
with dose rate is large for cigarette smokers and
represents a
doubling of the death rate of male smokers from 45
to 65 at
average dose rates.
The mortality ratio of pipe smokers is independent
of the dose rate of the smoker.
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April 1999


-24- Bell
The mortality ratio of cigar smokers is correlated
to the dose rate oi the smoke but the increase in
mortality with
dose rate is not large.
The mortality ratio of cigarette smokers who also
sr-..o.'-,c pipc_- and c1gars is significantly
1,:~wer than smokers who
smoke only cigarettes at the same cigarette smoke
dose rate
and length of exposure. -
The lower mortality ratio of pipe and cigar
smokers
compared to cigarette smokers cannot be explained
by a differ-
ence in amount smoked, depth of inhalation. or age
started
smoking.
If the relative toxicity of smoke from a cigarette
is defined as 1. 0 then the toxicity of pipe smoke
is 0. 07 11
and cigar smoke .28 13. No factors mentioned in
current
reports on smoking and health (1). (2), (3) and
(4) can satis-
factorily account for the lower toxicity of pipe
and cigar smoke.
The only hypothesis which might satisfactorily
explain the smoke
toxicity differences is a difference in smoke
composition
produced by different combustion conditions in the
pipe, cigar
and cigarette. It is somewhat disturbing that this
hypothesis has
not apparently, received the widespread attention
which it would
appear to merit.
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BATCo document for Province of BritiSh Columbia 14
April 1999


100
90
So
70
60
50
40.
30 -
CL 20-
0
10/
PIPE
0
0 100 200 300 400
(RATE OF HEATING OF TOBACCO) 2 x MASS/PUFF
2
(,C/SEC) x GM/35ML VOL
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BATCo document for Province of British Columbia 14
April 1999


LEGEND
FIGURE: I
The relationship between the colourcd Hydrocarbons
yielded per
puff and the Thermodynamic and Kinetic Variables
of Tobacco
Pyrolysis.
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BATCo document for Province of BritiSh Columbia 14
April 1999