Aromatic AMIN€S ............cceececesceeaeeneeeeeeeee 47

Alkanes and Alkenes ..............ccseeeeeseenereeees 48
Tobacco Isoprenoids ..............:sceseeeeereneeeeeees 48
Benzenes and Naphthalenes ...............cseeesees 49

Polynuclear Aromatic Hydrocarbons (PAH) dL
N-Heterocyclic Hydrocarbons (Aza-Arenes) ....52

 

 

Phenols ..........c.cccceccceeesenensneeseeeatenenesceeens 52
Carboxylic Acids ............ccceeeeeeeeseeneseeeee eens 57
Metallic Constituents .............cccceeteeeeeeeeeeeee 58
Radioactive Compounds .............ceeeeeeeeeseevees 60
Agricultural Chemicals ............:::sessesereeer eens 61
Tobacco Additives ...........cccsceeeeeseeeeeneeeeeenes 63
Toxic and Carcinogenic Agents—A Summary........... 64
References. ........cccceccececceecseeeneeneeseeneneneeeeneeaeneeees 66
Physiological Responses to Cigarette Smoke..............+++ 73
Animal Smoke Inhalation Exposure Methodology...... 73
Smoke Generation...........cccccceeeeeeeeeeeeneeensereees 73
Methods of Inhalant Delivery ...............-:seseeee 74
DOSimetry............csccceceeeenseceeeeeeenneeeeeseeeseneees 74
Limiting Factors in Smoke Exposure............... 75
Selected Animal Studies ............:.ccsceseeseneeeeeseseneens 76
Pulmonary Studies..........c:ccsseeeeseeseresereseeeeenes 76
Cardiovascular Studies............:.:sscecessesenenreeees 76
Exercise Tolerance ..........cccccccseeeeeceeceeteeneteeens 77
Toxicity of Specific Smoke Components ................++ 78
NiCOtiNe «0.0.0.0. . cece ec ee ne ecee ee esceceeecesseneneegeoeeeuees 78
Carbon Monoxide...........cecceceeeesceeeeee even en esoeees 79
Nitric Oxide ...........cccsceeceeeeeseeeeseeseeenseneneeeees 80
Nitrogen Dioxide .............:::eeseeeeceereenesseeene eens 81
Phen] ....... 0. ccc eccec eee ec eee e cess eeeenenseeenene nena ea eees 81
References. .........cccccececscenceceoncnaseesesenseeeeegeeneoueneas 82
Pharmacology of Cigarette Smoke ........-...::seseseeeereeeeene 85
Nicotine Absorption ...........:.:scceseceeeeeneeeeeeeeseneeeee es 85
Alteration of Enzyme Systems ...........-::ssessseeeeereres 87
Catecholamine Responses ............:ceseeeeeeeeceeeeeneeeenes 87
Cardiovascular and Related Effects ..............:ssseeeeee 89
Pulmonary Effects...........:cccceeeeeserecsssneeeeeeeneeeen eens 90
Fat Metabolism...............::ccceeesceenenseeneneneeseeneeaees 90
Hyperglycemic Effects ............:::ssessesesseeeeeeeeeeeeeees 90
Other Central Nervous System Effects ............-..06+ 92
Metabolism of Nicotine...............cecececeneneeeeveeneeeeees 92
Metabolic Products in Test Animals from Nicotine
in Cigarette Smoke...........ccccseeeesseeseeeeseeneaeeeeees 93

14—4
Related Alkaloids and Their Metabolites

 

 

in Cigarette Smoke................cccseeeeceeeeeeeneeeeresens 94
Pharmacodynamics ..............:.cccecececeeeteeeeeneneneneneees 94
SUMMaPy ......... ccc cecec ccc ee ee eec sense eeeeeeeneeeeeeeseneeenes 99
References. .........cccc cece ccececceeeceeenceeeneesneeeaeneeeeeees 100

Reductions of the Toxic Activity of Cigarette Smoke ... 104
Gas Phase ........... cc ccceeceeceec ences ce teeteeetseeseeestesaees 104
Carbon Monoxide............cccccecesceeveeeeeseeeeeenes 104
Reduction of Ciliatoxice Smoke Compounds...... 104

Volatile Phenols and Catechols ...................-- 106

Volatile N-Nitrosamines...............0:cceececeee eee 107
Particulate Phase .............ccccccceeeceeneeeceeeeceereeteees 108
TAY occ c cece cece s cece cc cesceeseeenauseeeepnaeenserenssaaees 108
Nicotine ............ cece eecesece cece eeceeeeeeeeneeceneeeaees 108
Polynuclear Aromatic Hydrocarbons............... 109
Nonvolatile N-Nitrosamines ...................0e0e00 112
Polomium-210..............cccccencececeeccscereeseteseenes 113
SUMMALY ...... 2.0 e cece cece eee eet e eee ee eeseaneenencneneeneeens 118
References..........ccccccecsccenceneeecesncencenteceeeeseeseeees 115
Future Considerations ..............c.ccececceeeseeeceeeneeneeeentes 119

LIST OF FIGURES

Figure 1.—Cigarettes: production and tobacco used,
1964 to 1975... 0... cece ce cec cee eec tent eec eeu eaeenenseesensesen sees 138

 

 

Figure 2.—Tobacco use, 1970 and 1975, men and women,
21 and OVE... 20... .cccccc cece e cece ne cee sec eeneeenece nesses seaeenaes 13

 

Figure 3.—Common tobacco alkaloids and tobacco—specific

 

 

 

nitrosamines in cigarette smoke...............ccceceeteeee sees 46
Figure 4.—Tobacco isoprenoids ...............ceccseeseseseseeenees 50
Figure 5.—Some tumorigenic PAH in tobacco smoke...... 53
Figure 6.—Carcinogenic aza-arenes in tobacco smoke ...... 55

 

Figure 7.—Weakly acidic compounds in cigarette smoke..56

14-5
 

Figure 8.—Residues of agricultural chemicals in tobacco
and cigarette SMOKE .............c.c:ececeeeceeeeceeestensneeneoeas 62

 

Figure 9.—Degree of protonation of nicotine
in relation to PH ............ceccesseeeseceeeeeeereeeeneeeseeneneees 86

 

Figure 10.—Carotid blood levels of nicotine in ng/ml, after
the presence in the mouth for 10 minutes of buffered
solutions of nicotine at pH 6, pH 7, and pH 8............ 86

 

Figure 11.—Mean plasma norepinephrine and epinephrine
concentrations in association with smoking and sham
SMOKING ....... cece ecce cece eee ecencncncnceeneetesacerseeeeeeeeeenenees 88

 

Figure 12.—Arterial blood levels of “C-nicotine and “C-
cotinine, heart rate, and blood pressure during and
after smoking a cigarette labeled with “C-nicotine, and
during and after intravenous administration of C-
MCOLING 2.0.0... cece cscs eee eececeseeenensedensceseeeeaeesssenesaeeres 91

 

Figure 13.—Nicotine metabolism..............:.:seceeeseseeseees 93

 

Figure 14.—Structural formulas of some tobacco
alkaloids .................c.00000 [oveesaeeetacsausncsuescoesersrsessueses 95

 

Figure 15.—Sales-weighted average “tar” deliveries of U.S.
cigarettes from 1957 to the present ............ceseeeeeees 109

 

Figure 16.—Sales-weighted average nicotine deliveries of
US. cigarettes from 1957 to the present.................- 111

 

Figure 17.—Benzo(a)pyrene in the smoke condensate of a
leading U.S. nonfilter cigarette....:...........::eceessee eens 112

LIST OF TABLES

Table 1.—U.S. tobacco production in 1964, 1968, and 1975
Dy tyP@s 2... ... cece cee eec es eee eee en ees eeeceeaeeneeeenenenneneen onesies 12

 

 

Table 2.—Classes and types of tobacco established by the
U.S. Department of Agriculture .............:.::eceeeeeeeeeeee 15

14—6
 

Table 3. Approximate composition of freshly harvested
tobacco leaves..........cccccececeeecenseeecec tesa nessenenenenseueeens 16

 

Table 4.Range of chemical composition of tobacco being

 

 

used in Cigarettes...........cccceeeceee eee tee eee nen rece eee eneneeeees 17
Table 5.—Stalk positions and leaf characteristics............ 18
Table 6.—Stalk positions and smoking properties............ 18

 

Table 7._Representative analyses of cigarette tobaccos...21

 

Table 8.—Representative analyses of cigar tobaccos........ 22

 

Table 9.—Correlations among smoke and leaf variables... 24

 

Table 10.—Correlations among selected leaf and biological
Variables ........cccccececececeeenencececenseeesseneeee eee eseeeasecaes 25

 

Table 11.—Correlations among selected smoke and

 

 

biological variables ..............:ccseeseesese seen eeee eee eecea enone 26
Table 12.—Percent distribution of cigarette smoke ......... 37
Table 13.—Typical mainstream smoke mixture............... 37

 

Table 14.—Major toxic agents in the gas phase of

 

 

 

 

cigarette smoke (unaged).............:csseseseseeneeeneeeeee eres 43
Table 15.—Tumorigenic PAH in cigarette smoke............ 54
Table 16.—Major phenols in cigarette smoke...............+. 57
Table 17.—Free fatty acids in cigarette smoke .............. 58
Table 18.—Metals in cigarette smoke particulate............ 59

 

Table 19.—Harmful constituents of cigarette smoke
particulate matter ...............:cceceeeeeneeeereeeeeeeeeeeteeeens 64

 

Table 20.—Known tumorigenic agents in cigarette smoke
Particulates ...........ccccee eee eeeeeeeee eee eee ete eeeenee een eeneenees 65

 

Table 21.—Relative molar potency of nicotine and other
cigarette smoke alkaloids..............-:.:::sseeeseeeeeeeeeee ees 96

14—7
c

Table 22.—Effects of various forms of air dilution on
carbon monoxide and carbon dioxide deliveries.......... 105

 

Table 28.—Vapor phase constituents with high ciliatoxic
potency—in Vitro... cece cece ce eeeeeeneneeeeeneeeenees 106

 

Table 24.—Removal of some gas-phase components of
cigarette smoke by an activated carbon filter........... 107

 

Table 25.—Some measures for ‘tar‘ reduction in cigarette
SMOKE. ........ececccccececeneee cece escneneeceeccsceesacessseeseeress 110

 

14—8
Introduction

Our understanding of cigarette smoke—its generation, physical
composition, toxicity, pharmacology, behavioral effects, and techniques
to modify its composition—has advanced considerably since the last
review on cigarette smoke in the 1972 report on The Health
Consequences of Smoking.

Technology has played an important role in advancing our under-
standing of cigarettes and their resulting smoke. One aspect in
particular that has improved our understanding is the development of
new instrumentation and miniaturization of analytical tools. For
example, Baker (1) reported on the use of a fiber-optic probe system
for determining and differentiating solid and gas temperatures within
the coal of a burning cigarette. The advance made it possible for
Osdene (5) to define more clearly the reaction mechanisms that occur
in the burning cigarette. Such information should make intelligible
modification of cigarettes and cigarette smoke more of a science and
less of an art. Another example has been the development and
refinement of the Thermal Energy Analyzer, which allows scientists to
quantify the level of N-nitrosamines in cigarette smoke (2, 3). The
development of reconstituted tobacco sheet technology, designed, at
least in part, for better utilization of the tobacco plant in cigarette
manufacture, has given manufacturers additional control over the
delivery of certain constituents of cigarette smoke, permitting
alteration of the combustion process and consequently the levels of
smoke condensate produced (4).

In this chapter we will consider the tobacco as a raw material, how it
is made into cigarettes, the cigarette smoke generation process, the
composition of cigarette smoke, physiological responses to cigarette
smoke, the pharmacology of nicotine as a component of cigarette
smoke, and efforts to define less hazardous cigarettes through
cigarette smoke modification. Also, consideration will be given to the
effects of smoke characteristics on smoking behavior and, therefore, on
the dose inhaled by man and experimental animals.

14-9
Introduction: References

(1) BAKER, R.R. Temperature distribution inside a burning cigarette. Nature 247:
405-406, February 8, 1974.

(2) BRUNNEMANN, K.D., YU, L., HOFFMANN, D. Assessment of carcinogenic
volatile N-nitrosamines in tobacco and in mainstream and sidestream smoke
from cigarettes. Cancer Research 37(9): 3218-3222, September 1977.

(3) FINE, D.H., RUFEH, F., LIEB, D., ROUNBEHLER, D.P. Description of the
thermal energy analyzer (TEA) for trace determination of volatile and
nonvolatile N-nitroso compounds. Analytical Chemistry 47(7): 1188-1191, June
1975.

(4) MATTINA, C.F., SELKE, W.A. Reconstituted tobacco sheets. In: Wynder, E.L.,
Hoffmann, D., Gori, G.B. (Editors). Proceedings of the Third World Confer-
ence on Smoking and Health, New York, June 2-5, 1975. Volume 1. Modifying
the Risk for the Smoker. U.S. Department of Health, Education, and Welfare,
Public Health Service, National Institutes of Health, National Cancer
Institute, DHEW Publication No. (NIH)76-1221, 1976, pp. 67-72.

(5) OSDENE, T.S. Reaction mechanisms in the burning cigarette. In: Fina, N. J.
(Editor). The Recent Chemistry of Natural Products, Including Tobacco:
Proceedings of the Second Philip Morris Science Symposium. New York, Philip
Morris, Inc., 1976, pp. 42-59.

14—10
The Cigarette: Composition and Construction

Tobacco, a member of the nightshade family (28), is an important
agricultural and economic crop that is produced in almost all parts of
the world and used in nearly every country. The tobacco plant
Nicotiana tabacum L. is a native plant of the Americas and is used
primarily for the manufacture of cigarettes, cigars, pipe tobaccos, and
to a lesser extent for oral consumption. Its dominance for smoking use
is generally attributed to a few of its combustion products which
induce physiological effects to be discussed later in this chapter. The
tobacco plant is an excellent material for research in plant and
biological science (24).

The characteristics of tobacco smoke are primarily functions of the
physical and chemical properties of the leaf; hence, one can approxi-
mate the levels of nicotine, tar, and other smoke components based on
certain physical and chemical properties of the leaf (32). Wide
variations in botanical, chemical, and physical characteristics of leaf
tobacco are found among the various species, types, varieties, strains,
and grades; the quality of the tobacco leaves is predetermined by
genetic makeup and subsequently influenced by weather conditions,
cultural practices, soil properties, curing, and other post-harvest
handling practices (27).

The relatively sweet Orinoco-type tobacco, Nicotiana tabacum L.
was successfully introduced for cultivation in Jamestown, Virginia in
1611 and into Europe, Asia, and South Africa by the early part of the
17th century. Worldwide production has increased in recent years (26).
During the years 1973 through 1975, worldwide total acreages of
tobacco harvested were 10.1, 10.5, and 10.7 million acres; yields per acre
were 1,054, 1,080, and 1,088 pounds; and total production was 10.7, 11.4,
and 11.7 billion pounds, respectively (26).

- Asian countries lead the world in tobacco production followed by
North America, Europe, and South America (26). The highest yield per
acre appears to be in the People’s Republic of China, followed by the
United States. The U.S. production for all types of tobacco in 1975 was
2.19 billion pounds. Table 1 summarizes U.S. tobacco production.

Since 1964, when the first Surgeon General’s Report on Smoking and
Health was published, there has been a gradual and continued increase
in the number of cigarettes manufactured in the United States (35). It
should be noted, however, that per capita consumption has decreased
from 11.53 pounds in 1964 to 9.14 pounds in 1975, and total tobacco
consumption has declined from 1.41 billion pounds in 1964 to 1.35
billion pounds in 1975. This reduction is due largely to the reduced
waste of the tobacco biomass. These results are described in Figure 1.

Figure 2 describes the tobacco use for men and women 21 and older
for the years 1970 and 1975. It should be noted that there was an

14—11
TABLE 1.—U:S. tobacco production in 1964, 1968, and 1975 by

 

 

types
Yield
Type and crop year Acreage per Production
acre
1,000 acres pounds million Ibs.
Flue-cured (Types 11-14)
1964 628 2,211 1,388
1968 533 1,841 981
1975 117 1,973 1,415
Fire-cured (Types 21-23)
1964 32 1,716 55
1968 23 1,689 39
1975 23 1,601 37
Burley (Type 31)
1964 307 2,022 620
1968 238 2,372 563
1975 282 2,265 639
Maryland (Type 32)
1964 39 1,085 42.
1968 2 1,100 32
1975 wa 1,050 25
Dark air-cured (Type 35-37)
1964 14 1,735 aA
1968 il 1,757 19
1975 9 1,690 15
Cigar filler (Type 41-44)
1964 31 1,683 52
1968 2 1,766 41
1975 4 1,663 23
Cigar binder (Type 51-55)
1964 14 1,862 26
1968 9 1,821 17
1975 1B 1,851 2
Cigar wrapper (Type 61-62)
1964 14 1,530 21
1968 13 1,348 19
1975 5 1,409 8
Puerto Rican Filler (Type 46)
1964 31 1,231 38
1968 6 1,271 8
1975 3 1,500 4
Total U. S. tobacco (Types 11-72*)
1964 1,109 2,044 2,266
1968 885 1,941 1,718
1975 1,090 2,008 2,189

 

*Includes Perique
SOURCE: U.S. Department of Agriculture ($5).

increase in the percentage consumption for males and females under 21
years old. Cigarettes are by far the largest single tobacco product.

14—12
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CIGARETTES: PRODUCTION
AND TOBACCO USED
BIL. CIGARETTES T T Ba. .B*
- Cigarette producson 4
600 J Xi 2a 16
450 po omen | = = ot 12
| ee tad MIPORTED OPNENTAL
300 Tobacco used MARYLANU 2% 15% —loe
150 TOBACCO USE los
BY KIND
Ss 4
0 i 1 1 1972-74| 1 i 1
1964 1966 1968 1970 1972 1974S
“UNSTEMMED PROCESSING WEIGHT = A PRELMANARY

 

 

 

FIGURE 1.—In the United States flue-cured tobacco is the most
important domestic type, with burley in second place. Note that
cigarette production has increased while the tobacco used has
remained about the same since 1964. This is due to use of stems,
reconstituted sheets and filters in cigarette manufacture in recent

years — formerly discarded as “waste”.
SOURCE: Tso, T.C. (27).

 

TOBACCO USE, 1970 AND 1975
Men and Women, 21 and Over

| MALE

  

DATA FROM HOUSEHOLD SUAVE ¥S FOH PUBLIC HEALTH SERVICE

 

 

 

FIGURE 2.—Use of tobacco by men for cigarettes, cigars, pipes,
chewing tobacco and snuff all showed a decrease in the 5-year period
1970-75. Use of tobacco by women also showed a slight drop in

cigarettes, but a slight increase in use of cigars and pipes.
SOURCE: Tso, T.C. (27).

Types and Classes of Tobacco
There are at least 65 species within the genus Nicotiana. The species

14—13
Nicotiana tabacum L. is the main commercially grown species. This
species has been established as a natural hybrid between W. Sylvestris
and N. Otophora (87).

The types of tobacco generally used in smoking products are bright
(flue-cured), Burley, Maryland, and cigar tobaccos, as well as oriental
(aromatic) tobaccos. These types make up the bulk of the tobacco
products (Table 1). Other types of tobacco exist, such as Perique,
Latakia, and several Indian types, but they are not generally used in
U.S. tobacco blends. Over the years, new varieties of bright, Burley,
and other tobaccos have been developed that are multiple-disease
resistant to specific tobacco diseases (23, 28).

Within the species of N. tabacum, many varieties and types show
wide differences in their chemical composition (28). Numerous germ
plasms are available in the USDA collection, including approximately
1,060 tobacco introductions, 400 established varieties, and 100 breeding
lines. Tso (30) reported that, in a preliminary examination of randomly
selected samples from tobacco introductions, there was a threefold
variation in sterol content, a tenfold variation in nitrate content, a
thirtyfold variation in alkaloid content, and a fivefold variation in
phenolic content. He concluded that greater variations probably exist
among types not yet studied.

Based on methods of curing and the cultivar (a variety of tobacco
within a tobacco type) used, leaf tobaccos produced in the United
States are separated into the major classes shown in Table 2. There are
five classes of air-cured tobacco including light air-cured, dark air-
cured, and three kinds of cigar tobaccos: filler, binder, and wrapper (26,
28). Filler is tobacco that makes up the bulk of a cigar, and wrapper is
used for the outside covering. Binder is now used primarily for scrap
chewing. Binding material for cigars is now made from reconstituted
tobacco sheet (RTS). (RTS is also used in the manufacture of
cigarettes, as will be discussed later.) Each of these tobaccos has
specific characteristics and is produced for a specific purpose.

Under class, the subdivision is “types” (26, 27), based on location of
production, method of culture, and in most cases, plant cultivar. The
cured leaf from each type is further subdivided into grade groups
named on the basis of either principal use in manufacture or stalk
position under the U.S. Government grading system. Each of the
subdivisions is composed of several grades, determined by several
elements of quality, such as body, texture, and color.

Physical and Chemical Characteristics

In addition to the genetic makeup, environmental factors, including
mineral nutrition, soil properties, moisture supply, temperature, and
light intensity, affect the chemical composition and physical properties
of the leaf (26, 28). The relationships among these factors and the

14-14
TABLE 2.—Classes and types of tobacco established by the U.S.
Department of Agriculture

 

 

Type of curing and class Type no. Type name or locality
Flue-cured, Class 1 1A Old Belt-Virginia and North Carolina
11B Middle Belt-Virginia and North Carolina
12 Eastern North Carolina
13 Border Belt-Southeastern North Carolina
and South Carolina
14 Georgia and Florida
21 Virginia
Fire-cured, Class 2 22 Eastern-Kentucky and Tennessee

Western-Kentucky and Tennessee

Air-cured
Class 3A (light air-cured) 31 Burley

32 Maryland
Class 3B (dark air-cured) 35 One-Sucker

36 Green River
Virginia Sun-Cured
Class 4 (cigar filler) Pennsylvania Seedleaf, or Broadleaf
Gebhardt
Zimmer Spanish
Little Dutch
Puerto Rico
Connecticut Broadieaf
Connecticut Havana Seed
New York and Pennsylvania Havana Seed
Southern Wisconsin
Northern Wisconsin
Connecticut Valley Shade-Grown
Georgia and Florida Shade-Grown
Louisiana Perique
Domestic Aromatic

Class 5 (cigar binder)

Class 6 (cigar wrapper)

Miscellaneous, Class 7

NBBSLRERRZSEESRES

 

SOURCE: U.S. Department of Agriculture (56).

tricarboxylic acid (TCA) cycle help define the smoking quality of
tobacco leaves (3).

‘Smoking quality of tobacco leaf is determined to a great extent by
the balance between the carbon and the nitrogen fractions (28).
Atmospheric CO: is assimilated by the tobacco leaf through photosyn-
thesis, while nitrogen is accumulated by the roots from the soil. The
net result of nitrogen assimilation is, therefore, the utilization of a
portion of newly photosynthesized carbon chains into the nitrogenous
pool. Thus, when the nitrogen supply is abundant, more amino acids
and nicotine and less sugar and starch will be synthesized. If the
nitrogen supply is limited, acetate will accumulate from the TCA cycle
and increase the production of carbohydrates, fats, volatile oils, resins,
and polyterpines (26, 28). These variations will effect the resulting leaf

14—15
TABLE 3.—Approximate composition of freshly harvested tobacco

 

 

leaves
Bright ; ;
Constituents cigarette Cigar filter
tobacco

tobacco
% %
Carbohydrates 23.0 3.0
Protein 12.2 17.3
Soluble N compounds 3.3 6.7
Inorganics 12.0 14.0
Cellulose and lignin 10.0 9.5
Pentosans 2.0 3.0
Pectins 7.0 10
Ether-soluble resins 15 10
Tannins ~ 2.0 . 25
Organic acids 13.0 18.0
Not identified 8.0 17.0

 

SOURCE: Frankenburg, W.C. (7).

texture, color, porosity, and combustibility. Examples include those
tobaccos used in cigarette production, Turkish and bright (flue-cured),
as well as cigar tobacco types. The Turkish tobacco is produced with
limited supplies of nutrients and water, thus giving leaves more
hydrocarbons and highly aromatic qualities (26). Cigar tobacco is
grown with an abundant nitrogen supply yielding leaves high in
protein and nicotine levels. Flue-cured tobacco is intermediary but
slightly toward the carbon side. Table 3 illustrates typical differences
among major constituents of bright and cigar tobacco leaves at
harvest, and Table 4 describes the ranges of various constituents of the
four main tobaccos used in cigarette produetion. Other environmental
factors, such as the time of topping and the amount of sunshine (27),
also play a role in the carbon-nitrogen balance.

The lower right portion of Figure 1 indicates that bright (or flue-
cured) tobacco is the most widely used domestic type in the United
States, while Burley, a light, air-cured type, ranks second in
importance. Together, they account for most of the tobacco used.
Typical values are flue-cured (45-75 percent), Burley (15-45 percent),
Turkish (5-18 percent), and Maryland (1-7 percent) tobaccos (26). Some
RTS is also used (15-17). The Standard Experimental Blend (SEB)
used in the National Cancer Institute’s experimental cigarettes, based
- on 1970 sales-weighted averages, are comparable (15-17).

The physical and chemical characteristics of tobacco leaf and smoke
are unavoidably related to one another. Recent studies, particularly
with bright tobaccos, show that characteristics such as leaf thickness,
rate of leaf burn, and moisture content are significantly correlated
with combustibility. Factors that promote good burning will generally

14—16 .
TABLE 4.—Range of chemical composition of tobacco being used

 

 

in cigarettes*
Constituents Flue-cured Burley Maryland Oriental

Total nitrogen 1.00-3.00 1.50-4.50 1.25-3.00 1.40-3.50
Protein nitrogen 0.40-1.30 0.50-2.40 0.70-1.50 0.75-1.30
a-Amino nitrogen 0.08-0.45 0.10-0.50 0.08-0.36 0.10-0.54
Nicotine 0.80-3.50 0.40-4.50 0.65-2.00 0.50-1.30
Petroleum ether extractive 3.00-7.50 2.50-6.00 3.50-6.50 3.50-7.00
Starch 1.75-8.00 0.50-3.00 1.00-3.50 1,90-10.00
Soluble sugars 6.00-32.00 0.10-1.50 0.50-1.50 3.00-10.00
Nonvolatile acids** 9.00-26.00 15.00-38.00 13.00-25.00 16.00-23.00
Water-soluble acids** 2.50-5.00 0.30-3.50 0.40-3.50 -

pH (not %) 4.40-5.70 5.20-7.50 5.30-7.00 4,90-5.25

 

“Ranges in %.
**Milliliters of 0.1.N alkali per gram tobacco.
SOURCE: Darkis, F.R. (2).

result in lower levels of TPM in smoke, lower nicotine, cresols, volative
phenols, hydrogen cyanide, and benz(a)anthracene, but will yield
higher levels of acetaldehyde, acrolein, and carbon monoxide. The
position of tobacco leaves on the stalk is known to influence greatly the
resultant smoke characteristics (37). Present evidence shows that for
higher leaf positions on the stalk, the combustibility is lower, the filling
value of the tobacco is less, and the TPM, nicotine, HCN, volatile
phenols, and polynuclear aromatic hydrocarbons in the mainstream
smoke are higher. Thus, stalk position is an important indicator of both
physical and chemical properties of the leaf and aids in interpreting
precursors of the final product between leaf and smoke components.
Table 5 shows some typical relationships between leaf characteristics
and position on the stalk (8, 26, 37). Table 6 relates the effect of stalk
positions and smoking properties (27). Similar data have been described
by Wolf (37).

Culture and Harvesting Practices

Wolf (37) has reviewed the practices employed in tobacco culture and
harvesting. A standard field practice with all domestic types of tobacco
plants (except shadegrown cigar wrappers) is topping (removal of
early blossoms) and suckering (removal of secondary buds) to promote
the proper development in leaf size and thickness.

Priming (the removal of mature leaves at successive intervals)
results in the maximum yield and quality from tobacco plants since
leaves at different stalk positions mature at different stages.
Depending on the type of tobacco plant and the weather conditions
during harvest, there may be as many as nine primings.

Stalk-cutting is another method of harvesting, involving cutting the
plant at the lowest stalk position and harvesting the entire plant at one

14—17
TABLE 5.—Stalk positions and leaf characteristics

 

 

 

 

Properties of Tobacco Types Lower Leaves Middle Leaves Upper Leaves*
Flue-cured tobacco
Cell membrane substances Comparatively Comparatively Comparatively
Higher Lower Lower
Total sugar Lower Higher Lower
Total acid Higher Lower Medium
a-amino N Higher Lower Higher
Nicotine Lower Medium Higher
Water-soluble N, total N Medium Lower Higher
Soluble ash Higher Lower Medium
Tannins, resins Lower Higher Higher
pH Higher Lower Lower
Air-cured Burley
Color Lighter Darker Darker
Porosity More Less Less
Density Lighter Heavier Heavier
Ammonium N, amino N,
amido N Lower Medium Higher
Nicotine N . Lower Medium Higher
*Not including uppermost tips.
SOURCE: Harlan, W.R. (8), Tso, T.C. (27).
TABLE 6.—Stalk positions and smoking properties
Upper and

Smoking properties Lower leaves

middle leaves

 

Strength (N compounds) relatively light
Aromaticity (tannins, resins) aromatic
Mildness (sugars, starch,

oxalic acid) and sharpness

(cell membrane substances,

ash constituents, citric

acid) somewhat sharp mild

relatively strong
highly aromatic

 

SOURCE: Harlan, W.R. (8), Tso, T.C. (27).

time. In general, Burley and Maryland tobaccos are harvested by stalk-
cutting.

The application of herbicides to control weeds, fertilizers to enhance
plant growth, pesticides to treat soil and control plant diseases, and
insecticides may directly or indirectly leave residues on plant material;
this factor must be considered when the characteristics of the tobacco
leaf and smoke chemistry are examined.

Curing and Aging

The green tobacco leaf primed from the plant goes through a process
known as “curing” in order to develop desirable taste and aroma for

14—18
smoke products. Several different curing processes are used to produce
leaf tobacco suitable for the manufacture of a variety of tobacco
products (37).

Curing is a process during which chemical conversions take place in
the tobacco leaf. During flue-curing or air-curing, chemical conversion
is dominated by hydrolytic enzymes. Disaccharides and polysaccharides
are hydrolyzed to simple sugars; proteins are hydrolyzed to amino acids
which undergo subsequent oxidative deamination; pectins and pento-
sans are at least partially hydrolyzed to pectic acid, uronic acid, and
methanol. A second step occurs only in air-cured tobaccos and includes
conversions such as the oxidation of simple sugars to acids, the
oxidation and polymerization of certain phenolic compounds, and some
decrease in alkaloids and dry weight (26).

As a result of years of research, numerous advances have been made
in the procedures used to harvest, cure, and process tobacco. One
particular development in the early 1950’s was the process of
manufacturing reconstituted tobacco sheets (out of tobacco scrap) in a
manner analogous to paper manufacture (13). The process will be
discussed later. The significance of the process lies in the fact that
tobacco need not be harvested and cured in whole leaf form, thus
suggesting new mechanized approaches to harvesting and curing.

A new curing procedure called homogenized leaf curing (HLC),
developed by scientists at the U.S. Department of Agriculture, involves
the homogenization, incubation, and dehydration of tobacco leaf (4, 33).
The fundamental concept is to cause the necessary chemical changes to
occur in a homogenized tobacco slurry instead of in the harvested
whole leaf. The process saves considerable hand labor normally
required for handling whole leaf, allows a mechanism for removal of
undesirable components, and permits better control and enhancement
of biochemical and chemical changes. Results have shown that the
HLC method may provide smoking quality that is comparable to
conventionally cured leaf but with a relatively lower biological
response (33). :

Cured, unaged tobacco is still unsuitable for manufacturing into
tobacco products because it has a sharp, disagreeable odor and an
undesirable aroma and produces irritating smoke with unacceptably
harsh flavor (26). To improve these conditions, cigarette tobaccos (flue-
cured, Burley, Maryland and Turkish) are subjected to a further
process called aging. Aging greatly improves the aroma and other
qualities desirable in smoking products. The aging process can be
natural or forced, depending upon time, temperature, and humidity. A
1- to 2-year aging period is not unusual for cigarette tobaccos.

The treatment of cigar tobaccos consists of two steps (7). The first
step is storage and the second is fermentation. Current knowledge of
the chemical conversions during aging and fermentation is rather
limited (26). The most noticeable chemical changes in the aging process

14—19
are an increase in volatile acids and a decrease in a-amino nitrogen.
Flue-cured and Turkish tobaccos also exhibit a loss of reducing sugars
and volatile bases other than nicotine. In fermentation, new chemical
reactions appear and ongoing reactions are intensified. A decrease in
tobacco alkaloids, especially nicotine, is evident (7). Large amounts of
ammonia are produced, and amide and a-amino nitrogen levels are
decreased. The pH increases because of the elimination of organic acids
through oxidation and decarboxylation. It is likely that enzymes,
microorganisms, and catalysts all play a part in the fermentation
process (26).

Representative analyses of aged and cured cigarette and cigar .
tobaccos are shown in Tables 7 and 8. These chemical variations are the
results of different varieties, cultures, fertilizers, soils, climates, and
post-harvesting practices as described above.

Other Factors

Leaves from different levels on the stalk possess considerably different
chemical and physical properties. For example, upper leaves possess
higher nicotine, lower total sugar, higher tannins and resins, lower ash,
and higher total nitrogen; lower leaves tend to contain higher total
acid, higher soluble ash, and higher pH. However, not all substances
are at their highest or lowest concentration in the upper and lower
leaves. The leaves at the middle stalk position, for example, have the
highest sugar, lowest a-amino nitrogen, lowest total acid, lowest total
nitrogen, and lowest soluble ash. Selecting mature leaves at various
time intervals (priming) allows maximum use of tobacco leaves and
selectivity in future blending.

Because of the chemical and physical differences, leaves from
various stalk positions also vary in smoke characteristics, as shown in
Tables 5 and 6. Lower leaves usually deliver a lighter “strength,”
somewhat sharper taste, and less aromatic smoke than the upper and
middle leaves (1). These smoking properties are largely functions of
chemical composition. For example, nitrogen compounds are believed
to be associated with strength; tannins and resins are associated with
aromaticity; sugars, starch, and oxalic acid are associated with
mildness; and cell membrane substances, ash constituents, and citric
acid are associated with “sharpness” (1). Certain physical quality
factors are also related to chemical components, as all these variables -
are interrelated. In a recent study with bright tobaccos (31), many
physical variables including leaf thickness, rate of burning, leaf color, -
moisture content, moisture equilibrium, specific volume, and trichome
numbers were found to be significantly correlated with many leaf
chemical variables.

The presence of radicelements, including radium-226, lead-210 and
polonium-210 have been reported in tobacco and tobacco smoke (19) .
and reviewed recently by Harley and coworkers (9). Contents of Po#!°in

14—20
TABLE 7.—Representative analyses of cigarette tobaccos (leaf
web after aging, moisture-free basis)

 

 

 

Component % ote tye a pale , Turkish?

Total volatile bases as ammonia 0.282 0.621 0.366 0.289
Nicotine 1.93 291 1.27 1.05
Ammonia 0.019 0.159 0.130 0.105
Glutamine as ammonia 0.033 0.085 0.041 0.020
Asparagine as ammonia 0.025 0.111 0.016 0.058
a-Amino nitrogen as ammonia 0.065 0.203 0.075 0.118
Protein nitrogen as ammonia 0.91 LT 1.61 1.19
Nitrate nitrogen as NOs trace 1.70 0.087 trace
Total nitrogen as ammonia 197 3.96 2.80 2.65
pH 5.45 5.80 6.60 4.90
Total volatile acids as

acetic acid 0.153 0.103 0.090 0.194
Formic acid 0.059 0.027 0.022 0.079
Malic acid 2.83 6.75 2.43 3.87
Citric acid 0.78 8.22 2.98 1,08
Oxalie acid 0.81 3.04 2.79 3.16
Volatile oils 0.148 0.141 0.140 0.248
Alcohol-soluble resins 9.08 9.27 8.94 11.28
Reducing sugars as dextrose 22.09 0.21 0.21 12.39
Pectin as calcium pectate 6.19 9.91 12.41 6.77
Crude fiber 7.88 9.29 21.79 6.63
Ash 10.81 24.53 21.98 14.78

calcium as CaO 2.22 8.01 4.79 4.22

potassium as K2O 247 5.22 440 2.33

magnesium as MgO 0.36 1.29 1.03 0.69

chlorine as Cl 0.84 0.71 0.26 0.69

phosphorus as P20s 0.51 0.57 0.53 047

sulfur as SO. 1.23 1.98 3.34 1.40
Alkalinity of water-soluble

ash © 16.9 36.2 36.9 25

*In % except for pH and alkalinity.

»Blend of Macedonia, Smyrna, and Samsun types.
eMilliliters of IN acid per 100 g tobacco.
SOURCE: Harlan, W.R. (8).

leaf tobacco and tobacco soil vary with the origin of the sample and
methods of culture and curing (24). Polonium seems not to be entirely
derived from radium. The plant probably takes it up from the soil or
air. The general range of Po in tobacco leaf varies from 0.15 to 0.48
pCi/g (102 Curies per gram); in tobacco-growing soil, it varies from
0.26 to 0.55 pCi/g. The amount of Ra-226 in tobacco-producing soil
appears to be related to phosphorus fertilization. Soils having high
available P continuously used for tobacco crops usually have a higher
Ra-226 content, the range being 0.52 to 1.53 pCi/g (24). The
significance of these radioelements in tobacco and tobaeco smoke is
being extensively studied with Pb#°-enriched leaf tobacco by USDA.

14—21
TABLE 8.—Representative analyses of cigar tobaccos (leaf web
after fermentation, moisture-free basis)

Conn.

 

shade- Northern Penn Fuerte Cuban Sumatra
Wisconsin . Rican
Component* grown : filler. filler. wrapper.
wrapper. binder. Type 41 filler. Type 81 Type 82
Type 61 Type 55 Type 46
Total volatile
bases as ammonia 1.293 1.055 0.874 0.707 1.478 0.670
Nicotine 1.47 2.68 2.04 0,90 2.23 1.42
Ammonia 0.914 0.575 0.495 0.348 1.012 0.313
Total amide as :
ammonia 0.225 0.199 0.165 0.264 0.232 0.208
Protein nitrogen
as ammonia 2.20 214 2.88 3.26 281 3.01
Total nitrogen
as ammonia 5.78 4.75 5.16 4.65 5.83 5.17
pH 6.27 6.33 6.10 721 6.56 1.25
Ash 23.79 24.94 250 22.45 22.57 22.34
Alkalinity of
water-soluble ash> 90.4 45.5 47.0 62.7 43.0 93.6

 

*In % except for pH and alkalinity.
>Milliliters of IN acid per 100 g tobacco.
SOURCE: Harlan, W.R. (8).

Aflatoxin B:, the most toxic of the four known aflatoxins, is
produced by Aspergillus flavus Lk. ex Fr. The binding of aflatoxin Bi
to both native and denatured deoxyribose nucleic acid (DNA) partially
explains its extreme toxicity and carcinogenicity. Aflatoxins have been
reported to occur in many commodities, but its presence in leaf tobacco
has not been positively confirmed, although A. flavus was known to be
present in various grades of air-cured Burley tobacco. Certain types of
tobacco contain higher populations of fungi than other types (6). These
differences probably result from culture, curing, and handling
practices as well as from the chemical composition of tobacco leaf and
the climate in which it is grown. An examination of samples of leaf
tobacco and of cigarette smoke condensate by Tso, et al. (26) failed to
show aflatoxin Bi. Pure aflatoxin B: added to cigarettes was not
recovered in the smoke condensate, indicating that aflatoxin Bi, even if
present, was changed or decomposed during the smoking process.

Relationships Among Tobacco Leaf, Smoke, and Biological
Response

Recent reports have been published dealing with precursor-product
relationships among specific leaf tobacco components and smoke
constituents (20, 26, 31, 34). One comprehensive study was conducted to
examine the relationships among leaf, smoke, and biological responses
using well-defined bright tobacco samples specially produced for this

14—22
purpose. This study involved a total of 151 variables, including 102 leaf
and agronomic characteristics, 42 cigarette and smoke components,
and 7 biological responses (31). The results clearly indicated that
certain leaf characteristics could be used as “markers” to predict total
smoke delivery or individual smoke components. These findings
demonstrated that modification of these markers through genetic,
cultural, or curing procedures might lead to the development of leaf
tobacco of more desirable quality and usability.

The correlations made by Tso and coworkers may be interpreted in
the sense of precursor-proautt relationships between specific leaf and
smoke components and between certain smoke components and
biological responses. Table 9 gives the correlations among some
selected leaf and smoke variables.

Using the same selected leaf characteristics, the correlations with
the results of seven short-term bioassay systems were determined as
shown in Table 10. The sebaceous gland suppression system showed
many significant and interesting correlations with certain leaf
characteristics (34). In examining all these variables, the authors
commented that one significant factor appeared to be the one which
affects leaf combustibility and thus the formation of components that
affect suppression. Variables that promoted combustion were general-
ly negatively associated with suppression, and variables that inhibited
combustion were generally positively associated with suppression. In
addition, phenolic compounds were positively associated with suppres-
sion. These compounds may serve as precursors of smoke constituents
with tumor-promoting activity.

In addition to the sebaceous gland suppression system, the E. coli.,
virus-infected quail, and mixed cell-culture systems also used cigarette
smoke condensate. These three systems did not demonstrate any
meaningful correlations with the variables examined. Correlations
among selected smoke and biological variables are shown in Table 11.
For example, static burning rate was negatively associated, whereas
total phenols, benzo(a)pyrene (BaP), benz(a)anthracene (BaA), and
smoke pH were positively associated with sebaceous gland suppression.
Tso, et al. (34) commented that it is somewhat surprising that dry total
particulate matter, cresols, acetaldehyde, acrolein, and hydrogen
cyanide did not show any statistically significant correlation with the
biological data employing whole smoke in these studies.

Smoke delivery and smoke composition thus seem to depend on the
characteristics of leaf tobacco (26). The effects of genetic and stalk
position differences are reflected in botanical, physical, and chemical
properties of leaf tobacco, which in turn are clearly illustrated in the
smoke constituents of these experimental samples. These results agree
with those of parallel studies using leaf “markers” for identification of
leaf quality and usability as described by Tso and Gori (32). Usability in
their definition represents the state of being usable without adverse

14—23
veo—F1

TABLE 9.—Correlations among smoke and leaf variables

Nicotine-

 

Static. NOUN Dry TPM free dry fonds Acrolein BaP = BaA HCN Phenols ™ total vol.
burning (mg/100 g (g/100 g TPM (mg/i00 g (mg/100 g (ug/100 g (ug/100 g (mg/100 g (mg/100 g (mg/100 g phenols Smoke pH
rate tobacco tobacco = (g/100 g tobacco tobacco tobacco = tobacco §=— tobacco (ug/g tob. (last puff)
{mg/min.} smoked) smoked} oe smoked) smoked) smoked) smoked) smoked) smoked) smoked) smoked)
Trichoine -.604°° 450°" -105°° 719°" -.122 -.484°* 588°* agaee 665° T44e* 826°" 142 99°
Leaf thickness ~.403° S87" A62°° 399° -5TT°° ~.5ode* 353° 08 43"* 686°° .530°* +088 6R6°*
Fire-holding capacity 6B4t* -.612"* ~.799"* ~.T928* 407° .663°* -668°* ~548** ~.T55°* ~B2T°* -.20°* -1T9 -599""
Moisture equilibrium 671°" 468°* 672"* 675°* 0e9 +158 oeare SBT" A88°° 668** T° 1a ww
PH (leaf tobacco) 60°" -.538"" -.601°° ~.5T5S* 382* 548° ~.597°* -5T1°* ~6aae* -.608°* 671°" ~.688°" -.599"*
K S15** -.T5At* -.804°° -.161°" 550" 60B°* ~,662°* -.566°* -.166%* -.o01°* -. Tope? +. TTBO* 99°"
Cell-wall substance 398" +212 406° -A25¢ -.095 144 -.460°* - 480°" 278 +433° ~.565°* -511°* -199
Total N -.662°* 205°* aa" Bier - 8 --426° “TB°° -Ten** 31°° Sag" Bae S19°" 862°"
Nitrate N 367° -.280 -451°* -461°* 167 382° -224 -4 -A81* --498** -.543°° 8 -261
Total alkaloid (dist.) ~.526"" .984"" T1Oe* 595** -.368 297 656°* 631° A6T** 882°" 581** 4a** $°°
Total vol. bases ~513°* 985°" 158°" .650"* +359" -.333 &T2°° -650°* ‘Tage? Bea" 625°° Tale" S2are
a amino N 603°" AT5°* AT2°* 439° 078 +175 AB 450°" 5° 496°* Az +090 483°°
Total free amino acids ~.445°* 263 555** S88" 268 ~535¢* 44g* zie 606°" 552"° 622°° 591°" 312
Arginine ~410° 23 ATBP* ogre 233 -.690"* OM 02 587** MT 511? Age 20
Aspartic acid .609"* +358" -520e* ~.584°° 32 459°" -AT1°* ~.436"* 466" 488° ~.561°* -.5ag** - 294
Proline -.560°* 364° 382° 360° +192 -.530°* 8 319 356° Aa5° .530°° 508°" ZL
Dimethylamine ~.559°* ST3** 4g7° AM 113 ~-195 Sze 522° AB" Sa" .460°* 5gB°* ABP
Total polyphenols -ATae* BY som seors 161 -.169 sage 514e* gape Agere gaRee SRE 168
Chlorogenic acid -.585°* 561°* 63are 610°" ~084 +100 60°" 45°" 468** 668°" .550°* Bare 527°*
Rulin -.444° MT 495"° 548** 2 - 036 Ase 364° 38 Ab2°° 610°" Soar OTT
Scopoletin ~TRB°* .620°° -748** T27°* ~.466** ~.T35** 620°" 54" .T3B°* oles -T35** S21*¢ SA5e°
Lignin +140 378 528°" 529°" O16 -.086 392 83° Si" 388 328 Bad AL
Oxalic acid 545e* 516" 596°° 5T5"* -.623°* ~T2B°* sae AT ~.T3g¢* 646°° 618°* 626°* STB**
Malic acid a52"* -AB1** -.148°* ~.163** -112 412" ~683°* -510°* -.857°* ~.T29°* -.T328* ~.165°* -A8T*
Pentadecenoic acid ~ 4499 410° 659°" Bi5** 085 -.140 .6g0°° Sage 5eTe* oor Sager Sear 22
Stigmaaterol 520*° -.565** -.543°* ~.501** -161"* 820°" -4ear* ~ Azar" --B27** ~.596°* ~.508°* -558** -.659°*
p,p-TDEE -.366* 46T°* .636°* bear? -.205 -.321 Aba? mM 633°" 6m" 584"? -665°* 550"
Total DDT + TDE 2B B78 Jase? o34"* 034 0710 ATO" 460°" 519** 485°* 51Te* 519°* 2
Aroma -364 531°* 58° 332 21 086 566°" 527°" 328 525°" 501" Sze 358°
Flavor ~21 470°" 566"* 430° 313 212 533°" 5g0°* 20 boge* -512"* 538°" 284
Strength 416° 627"* T14** S5laer 64 023 5a5°* 14s" Abe" -bB°* 628°° -100°* AsBe*

 

*- 50/0 significance
**-18/0 significance
SOURCE: Tao, T.C. (34).
TABLE 10.—Correlations among selected leaf and biological

 

 

   
 
 
  
 
 
 
 
  
 
  
  
 
  
 

variables
E. Coli Virus- Mixed eae
Variable Sehaceous “zone infected cel wa Rhee a
8 inhibition quail culture y y oP
Stalk position............-:.cseeeeeee 0.506** -0.090 0.009 0.316 0.087 0.076 0.023
Trichome wees -.169 .007 327 -.158 -A11 -.088
Leaf thickness............c0::seee : .060 156 -.313 295 -.873* -.004
Rate of burn.............ceeeeneeee z 011 -.083 193 -.034 017 091
Moisture equilibrium. ceed -.100 056 -460°* 048 080 -.054
pH (leaf tobacco) ...............06+ . .104 -.2BA 209 -.039 154 -.152
Potassium .........2--2:ecceeereeeeees x -.106 -.221 .070 -.066 -.016 043
Total nitrogen...... tees 086 .200 -.194 037 -.096 171
Nitrate nitrogen ........ seas O15 148 205 085 083 082
Total alkaloids........... see -.053 219 -.124 205 -.150 166
Total volatile bases.. wo -.081 229 -.089 -140 -.130 175
a-Amino nitrogen ....... wo -.303 204 064 -.306 -.100 247
Total free amino acids... ve. 855" -.239 -.012 ~.087 -.304 -111 053
Aspartic acid ............ weve 2837 048 -.107 172 -.168 002 1A
Dimethylamine ..... wo. §=4519* 894-042 330 017 -.133 185
Total polyphenols ............-.--+++ 382* = -. 228 148 -353* = -.197 001 -.046
Chlorogenic acid...........--..--.0+ 509" = -.025 .160 -.326 086 -.050 098
Scopoletin ........ we. ASB" 076044 8 TTT 085
Oxalic acid... ......cee reece reece eens 397 -.089 AOl* 028 -.130 -.014 104
Malic acid............ccccseeseeeeeeee -5OT** = -.117 -.072 224 223 020 .105
Pentadecenoic acid. 196 123 148 064 -.315* 274 -.106
Stigmasterol ..............0.:00eeeee -361* —--.070 “171 -.101 -171 28 -.043
030 .180 ~.186 -271 -102 -159
-.126 -.010 ~.249 ~.065 020 -.178
47 048 -212 -.126 144 126

 

 

* and ** = significantly different from 0 at 5 and 1 percent, respectively.
SOURCE: Tao, T.C. (26).

Usability index 9 =
B

If chemical, physical and botanical characteristics are considered:

 

Usability index = 4. + O*?
B E
where
A = nitrate + K + total ash + cellulose,
B = nicotine + TVB + a-amino nitrogen + starch + polyphenols
+ PEE + lipid residues + waxes + phytosterols + fatty acids,
c filling value + combustibility,
D = stem/lamina ratio,
E_ =_ thickness.

(TVB = total volatile bases, PEE = petroleum ether extracts
and K = potassium)

14—25
TABLE 11.—Correlations among selected smoke and biological

 

 

 

variables
E. Coli Virus- — Mixed a).
Variable! Sebaceous zone infected cell we woe Mae TO
Blane’ inhibition quail culture mrcty xicity Phage
Static burning rate per
Minute...........ccseee eee eee eee , 0.010 0.145 0.390* = -0.128 0.030 -—0.132
Dry total particulate
matter? ......0... ce ceecee eran : 234 073 104 212 -017 -.104
Nicotine in smoke? .......... Tl 204 -.013 AT2** — -.152 -.196
o-, m-, and p-Cresols? .116 -074 085 293 -.167 -314
Total volatile phenols? ....... mg .542** = -.165 054 -.322 O11 -.142 .080
Acetaldehyde! ................. mg -.104 112 -.829 -.083 ~216 180 -.018
Acrolein! .............:ccceeeee mg .073 ~.109 -.089 109 -.308 263 145
Hydrogen cyanide’............ mg .138 152 230 163 125 -.078 -.130
Benzofa]pyrene? ............... ng = .388* 249 .205 019 21 -014 057
Benzofa]anthracene? .......... we 446" = -.098 291 -.024 -.170 -.064 025
Smoke pH (last puff) ........ pH .468** = -.034 213 -.108 345 -.362° 228
Carbon monoxide? ............ mg .285 .105 373* 002 -.444* 264 -128
Carbon dioxide? ............... mg .323 .136 312 031 -.335 194 -.178

 

'* and ** = significantly different from 0 at 5 and 1 percent, respectively.
*per gram tobacco burned

per 100 grams tobacco burned

SOURCE: Tso, T.C. (26).

effects. Markers were used to establish a “usability index.” High
emphasis was placed on the chemical constituents. Physical factors
were next in importance because they can be improved through
reconstitution. Botanical factors were considered only when natural
leaf was used and entire stems were returned for cigarette manufac-

ture.
Thus, the potential is there to assume that modification of the

markers identified in this type of analysis may lead to the improve-
ment of the smoke products as well as the biological effects of the
smoke.

Modification of Tobacco and Tobacco Products

It has been reported by Tso and coworkers (33) that the labor of
tobacco harvest and post-harvest handling may account for 50 to 55
percent of the total required to produce the crop. Consequently, many
attempts have been made to reduce use of hand labor. It is not
essential that the tobacco leaf be kept whole in order to be useful to
the tobacco industry (14). Tso and coworkers (4, 33) recently reported
the results of a new procedure for curing leaf tobacco through
homogenization, incubation, and dehydration, called homogenized leaf
curing (HLC). The objectives of the HLC process were threefold: to
reduce production labor costs, to reduce or eliminate undesirable
factors that may be associated with the smoking and health problem,

14—26
and to improve tobacco usability by enhancing certain physical and
chemical factors. Preliminary results (4, 33) suggest HLC advantages
are the capability for more complete mechanization and the enhanced
potential for reduction or elimination of substances found to be
hazardous to health. Reductions in total volatile bases, nicotine,
reducing substances, total particulate matter, and nitrosamines have
been reported (33).

Another method of modifying tobacco and tobacco products involves
development of the reconstituted tobacco sheet (RTS); this method has
been reviewed by Moshey (14) and Mattina and Selke (13). The original
impetus for developing a reconstitution process was purely economical.
For each pound of auction weight tobacco, only about 63 percent was
usable shredded leaf tobacco, although approximately 6 percent of the
stem material was also blended in smoking tobacco. The remaining 31
percent, consisting of sand (2 percent), discarded stems (18 percent),
manufacturing fines (1 percent), and moisture and aging loss (10
percent) was lost to the manufacturer. A process that could utilize the
lost stems and fines and control moisture would increase the amount of
usable tobacco from a harvest, cut costs, and offer some manufactur-
ing control over the physical and chemical properties of the resultant
product (73).

Several processes were developed in the early 1950’s. These were of
two general type groups; in one group, the tobacco is ground into fine
particles, mixed with a hydrocolloid gum, and cast on an endless steel
belt. The other, more widely used group of processes, involves
mechanically working the insoluble portion of the tobacco into a
fibrous mass and forming it, via papermaking techniques, into a web.
In one variation of the paper process, the soluble portion is diverted
prior to the papermaking and then added back to the self-supported
web. In another variation, the soluble portion remains with the fibrous
material throughout the processing. For all processes, the finished
product is in the form of leaflets which are then blended with natural
tobacco and shredded.

The significance of the sheet process lies in the ability to chemically
and mechanically produce desired changes during the pulping process.
For example, chemical extractions can be performed to reduce nicotine
and other constituents. Tar-yield levels can be reduced to some extent,
and additives can be put into the material. The structural modifica-
tions which can be effected through reconstituted sheet technology
could result in considerable differences in the burn properties and in
the smoke. Produced tobacco sheet with a 10 mg/cigarette tar yield
without filtration is now available using RTS technology. Lower
figures are possible but may cause the sheet to be undesirable as a
tobacco product. Flavorings and other additives can also be added at
selective stages during the process if necessary, depending upon the
solubility and volatility of the additive.

14-27
The components of leaf tobacco can be classified into three different
categories. Some components are essential for smoke quality and
desirability, others have either little or no effect, and a third category
consists of components that serve as precursors of undesirable smoke
constituents such as HCN and aza-arenes (5, 28).

One class of components in the third category is fraction-1-protein
(12, 28, 29). This and other proteins do not contribute in any significant
way to smoke aroma or flavor. Removal of fraction-1-protein achieves
two purposes—improved leaf quality and usability, and fraction-1-
protein as a potential food source. It is estimated that up to 6 percent
of the tobacco yield could be used for feed and food purposes (28).

Fraction-1-protein is the major soluble protein of green plants and
may account for 50 percent of the soluble protein fraction and 25
percent of the total protein (26, 28). The protein is an enzyme called
carboxydismutase (21) that catalyzes the first step in the transforma-
tion of COzinto carbohydrates during photosynthesis (28).

Tso (33) and DeJong (4) have reported that the fraction-1-protein
can be removed for beneficial use by the above-mentioned HLC
process, and could be used as a food source for millions of people
annually (28). The protein has been evaluated as a food source (28, 29)
and found to compare favorably with egg and human milk for essential
amino acid content.

Cigarette Engineering

The tobacco blend can vary in the amount of Burley, bright (Virginia),
Maryland, and oriental leaf and in the amount of reconstituted tobacco
sheet used. Casing solutions are used to hold the tobacco blend
together. Humectants (moisture retainers) are added to maintain the
necessary body and moisture qualities and to contribute to the
flavoring of the blend. Flavor-enhancing additives are used to make
the smoke pleasant and more acceptable to the smoker. To maintain
the physical integrity of the product, a paper wrapper is used. Fach of
these ingredients may affect the burn rate, puff number, pyrolysis
products, and ultimately the chemical constituents of mainstream and
sidestream smoke and smoke condensate.

Typical casing materials that may be u: «1 are sugars, sirups, licorice
and balsams. These additives improve or change the flavor characteris-
tics and burning qualities and impart important binding qualities to
the blend. However, additives, when pyrolyzed, may yield undesirable
as well as desirable products. Licorice, for instance, could be a
precursor of polyaromatic hydrocarbons (PAH). Sugars used in casings
cause an increase in furfural, nicotine, and tar in resulting smoke and a
decrease in volatile acids (21).

Flavoring agents are added at different steps in the cigarette
manufacturing process, depending upon volatility. Volatile flavors.
such as alcohol-soluble fruit extractives, menthol oils, and aremai

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