70

60

  50

E
5 40
9
2
n
cs 30





  20




  10




  0

Males

1-14   15-34

.:.:
F,{
v.
::::
v.
:.:.
.::
Q
A
1
0::
2*
`s:
y
0.'
:::
:-
.
)
.
.

35+          1-14    15-34
Cigarettes/Day

FIGURE l--Age-standardized rates (percent) of chronic
       nonspecific respiratory disease* by inhaling and
       current cigarette smoking

*Criteria for diagnosis were as follows:
(1) Chronic bronchitis: Affirmative response to the question-Do you bring
up phlegm from chest six or more times a day for four days a week for three
months a year for the past three years or more?
(2) Asthma: Affirmative response that bronchial asthma had been diagnosed
and was still present.

(3) Chronic obstructive lung disease: Affirmative response to one or more of
the following: wheezing or whistling in the chest occurred most days or nights;
the subject had to stop for breath when walking at his own pace on the level;
FEVI less than 60 per cent of the FVC.
These could occur in various combinations and were not mutually exclusive.
SOURCE: Ferris, B.G., Jr. (22).

smoking histories were comparable. Rawbone et al., in a ques-
tionnaire survey of 10,498 secondary school children aged 11 to
17 in London, found a significantly higher frequency of cough,
                                        151


TABLE lO.-Respiratory symptoms and diseases in male (M) and
      female (F) participants in Charleswood
       (C)-urban-and in Portage La Prairie
      (P&rural-expressed as percent of respondents

Respiratory           Nonsmokers    Ex-Smokers     Smokers
  Symptom/Disease      C     P     C     P     C      P

Cough on most
days, at least 3
months/year
M
F
Phlegm on most
days, at least 3
months/year
M
F

Wheezing apart
from colds
M
F

Attack of short-
ness of breath
and wheezing
M
F

Shortness of breath
compared to per-
sons of same sex
and age
M
F

8.3
-






-
-




4.2
3.5






4.2
-








8.3
7.0

SOURCE: Manfreda, J. (39).

4.0     8.1     2.9    25.4    31.5
4.0     -     10.0    20.3    31.7

4.0    10.8     5.7    16.9    24.7
4.0     -     5.0    10.2    25.4

8.0    10.8    14.3    26.8    31.5
8.0    12.1    20.0    25.4    30.2

8.0
12.0







4.0
12.0

13.5    11.4    11.3    17.8
6.1    15.0    13.5    20.6

5.4     5.8     5.6    12.3
6.1     5.0    22.1    17.5

colds, and exertional dyspnea in regular smokers as compared
to nonsmokers (45). There was no appreciable difference in the
frequency of cough between male and female smokers or be-
tween male and female nonsmokers. Colley et al. examined the
influence of smoking, lower respiratory tract illness under 2
years of age, social class of father, and air pollution on respira-
tory symptoms in a cohort of 20-year-olds followed since birth
(15). Their data (Table 12) suggest that respiratory symptoms
were closely related to current smoking. Symptoms were also
related to a history of lower respiratory tract infection in the
first 2 years of life but were not related to social class or air
pollution.

152


TABLE ll.-Smoking and the prevalence of respiratory symptoms in girls from two different cities in England

                                         Prevalence of Symptom With Each Group       -
                                            Experimental
                                           Smoker +      Smokert     Nonsmoker
Symptom                           Residence     N     %      N      %     N      %   Significance*

Cough in the morning                     Kent       10    31.3     51     9.8     73     6.9    P <O.OOl
                            Derbyshire     14     18.9     50     8.4    138     6.7    P <O.OOl
Cough day or night                       Kent       17     53.1     148    28.0    195    18.4    P <O.OOl
                          Derbyshire     35     47.3    176    29.5    458    22.1    P <O.OOl
Cough for 3 months of year                  Kent        5     15.6     43     8.2     55     5.2    P <0.01**
                           Derbyshire     10     13.5     32     5.4     82     4.0    P <O.OOl

+ Smoker = a child who smoked at least one cigarette a week.
tExperimenta1 smoker = a child who had smoked at sometime but less than one cigarette a week.
*Test for significant association of cough and smoking habit. Chi-square 2 x 3 table.
**Smokers and experimental smokers combined to give chi-square on a 2 x 2 table.
SOURCE: Bewley, B.R. (9).


z
h TABLE 12.-Prevalence (percent) of respiratory symptoms by sex and smoking habit in cohort of 3,898
        20-year-old$ followed since birth

                                                                           Persistent
                      Winter    Cough Day   Cough 3     Winter   Phlegm Day   Phlegm 3   Cough and
                 Morning    or Night    Months in   Morning    or Night    Months in    Plegm
History of             Cough     in Winter     Winter     Phlegm     in Winter     Winter     Q.l(d
Cigarette     Population    &.1(a)+     Q.l(b)+     Q.l(c)+     6.2(a)+     Q.Wd +     Q.%c)+      +2(c) +
Smoking      M F M F M F M F M F M F M F M F


Never
smoked
cigarettes      802   1093    1.6    4.0    5.2    6.5   1.5    3.2    4.8    5.2    6.4    3.9   3.7    3.2    0.9    1.9

Ex-smokers
of cigarettes    101    57    3.0    1.8    7.1   10.5   3.0    1.8   11.0    1.9   10.2    9.1   6.0    0.0    2.0    0.0

Present
smoker of
cigarettes     1009   678   13.0   13.2   13.9   16.0   8.1    7.5   14.1   11.9   11.6   11.2   8.3    5.5    4.9    3.5

No data on
cigarette
smoking       92    48    8.7   11.8    9.1   18.8    4.5    0.0    0.0    6.7    4.8    0.0   4.8    0.0    4.8    0.0


  All       2022   1876    7.7    7.4    9.8   10.2   5.0    4.7    9.9    7.6    9.3    6.7   6.2    3.9    3.0    2.4

+ 1. (a) Do you usually cough first thing in the morning in the winter?
(b) Do you usually cough during the day or at night in the winter?
If "Yes" to either question l(a) or (b)
  (c) Do you cough like this on most days for as much as three months each winter?


`2. (a) Do you usually bring up any phlegm (spit from the chest) first thing in the morning in the winter?
(b) DO you usually bring up any phlegm (spit from the chest) during the day or at night in the winter?
  If "Yes" to either question 2(a) or (b)
(c) Do you bring up phlegm (spit from the chest) on most days for as much as three months each winter?
SOURCE: Colley, J.R.T. (15).

TABLE 13.-Percentages of nonsmokers and smokers with abnormal test results in three North American
      cities, using combined reference values*

Upper limit +
Lower limit +
1. Abnormal test
FEV-FVC
CVNC
CC/TLC
ANIL
RV/TLC

             Men                               Women
   Nonsmokers          Smokers           Nonsmokers           Smokers
AS     S    Total AS     S    Total AS     S    Total AS     S    Total
c951*   (27)   ww   (12)   (115)   (236)   (145)   (46)   (191)   (107)   (98)   (205)


1.6     0.2     1.8     1.8     1.8     2.6     2.1     0.6     2.4     1.7     1.7     2.4
11.6    20.0    10.6    10.6    10.9     8.7    10.0    15.0     9.1    11.1    11.5     9.0


6     11      7      5      7      6      4     20      8      7     25     16
2      7      3     13     17     15      6     11      7     23     26     25
2      7      3     20     32     26      8     17     10     20     29     25
1      7      3     17     13     15      7     24     11     27     37     32
6     11      7      9      9      9      8      9      8      11     13     12

  *Reference values for nonsmokers derived from asymptomatic nonsmokers in the three cities.
  **Numbers in parenthesis = number of subjects in each group.
  +Upper and lower limits in the expected 5 percent abnormal results.
G  AS = asymptomatic; S = symptomatic
v1   SOURCE: Buist, A.S. (11).


In a longitudinal study of elderly Edinburgh residents aged
61 to 90, Millne and Williamson found the prevalence of persist-
ent cough and sputum production was significantly greater in
smokers of both sexes than in their nonsmoking counterparts
(40). Male prevalence rates were three times higher than those
in females; however, no attempt was made to determine the
relationship of respiratory symptoms to life-time tobacco expo-
sure.

In summary, many recent studies demonstrate a higher fre-
quency of respiratory symptoms in women who smoke as com-
pared to women who do not smoke. This is true in surveys in-
cluding children, adolescents, young adults, working age, and
elderly women. The effect of cigarette smoking is related in
terms of both the number of cigarettes and years smoked. The
majority of studies indicate a greater prevalence of respiratory
symptoms among men who smoke than among women who
smoke; however, these differences often disappear when the
study is carefully controlled for smoking history.

Smoking and Pulmonary Function

The insensitivity of cough and sputum production in the adult
as a predictor of future development of COLD has been empha-
sized by Fletcher and Peto (29). Pulmonary function testing of-
fers an objective method for measuring the adverse effects of
smoking. However, current tests of pulmonary function display
a marked variability between individuals and may not detect
the development of COLD until irreversible damage of the lung
has occurred. Also, none of the presently used pulmonary func-
tion tests can predict which of those individuals with slightly
abnormal pulmonary function will progress to debilitating and
life-threatening emphysema and chronic bronchitis. Becklake
and Permutt have recently reviewed the objectives and prob-
lems of the tests of lung function commonly used for early de-
tection of COLD (7).

A large number of studies have established a higher fre-
quency of pulmonary functional abnormalities in smokers as
compared to nonsmokers. These studies have examined (a) the
relationship of smoking to abnormal tests of small airway func-
tion and (b) the relationship of smoking to measurements of
standard spirometry. The majority of epidemiologic surveys in-
vestigating the prevalence of functional abnormalities in smok-
ers have employed spirometric measurements, usually the
forced expiratory volume (FEV) and vital capacity (VC). Meas-
urements of airway resistance, diffusing capacity, lung volume,
and nitrogen mixing have been used much less frequently.
156


I Portage la Prairie
0 Charleswood

60 Females
1

RV%TLC   CV %VCE  CC %TLC-   Sip III  FEV,, % FVC

FIGURE 2.-Prevalence of lung function abnormalities among
      smokers in an urban (Charleswood) and a rural
      (Portage La Prairie) community
SOURCE: Manfreda, J. (39).

SMOKING AND "EARLY" FUNCTIONAL
ABNORMALITIES

The most widely used measurements for detecting early
change of chronic airflow obstruction are the single-breath ni-
trogen washout curve or a maximum forced expiratory volume
curve.
A limited number of recent studies using tests of small airway
function have included appreciable numbers of female subjects.
They have demonstrated a higher frequency of abnormalities in
tests of small airway function in smokers than in nonsmokers or
ex-smokers. A definite dose-response relationship has been
found in some of these studies but not in others (10,11,12). Table
13 shows the data from one of these studies (11). For all meas-
ures of small airway function, the frequency of abnormalities
was higher among smokers than nonsmokers in both men and
women. The frequency of abnormal measurements was consid-
erably higher in female smokers than in male smokers except
for closing capacity, in which equal proportions of male and

157


female smokers performed abnormally. However, the frequency
of abnormalities among female nonsmokers was also greater
than among male nonsmokers. The authors speculate that the
traditional view of chronic airflow obstruction as being predom.
inantly a disease of males may be accurate only when male
smokers outnumber female smokers and when males smoke
more cigarettes than females. They suggest that when women's
smoking habits become comparable to those of men, the effect
on lung function may be similar.
Manfreda et al. used the single-breath nitrogen test in a large
group of subjects in two Canadian cities (Figure 2) (39). Almost
all smokers (85 percent) reported that they inhaled their
cigarettes. Smokers had a greater prevalence of abnormalities
than nonsmokers regardless of sex. The prevalence of abnormal
values in women who smoke was slightly less than in male
smokers.
In a volunteer population of 530 cigarette smokers attending
an emphysema screening center, Buist and Ross found an
equivalent frequency of abnormalities of the slope of phase III
among male and female smokers of less than 20 cigarettes per
day (Figure 3) with both sexes having significantly higher pre-
valence of abnormalities among smokers of more than 20
cigarettes per day (12). In the groups smoking more than 20
cigarettes a day, a greater proportion of females demonstrated
abnormalities than males. However, the age composition of
each group (male and female) was not identical.
A recent study of small airway function in 205 young volun-
teer smokers aged 18 to 25 has suggested that smoking may
exert its effects at different anatomic locations in the lungs of
men and women (21). All subjects smoked fairly heavily (more
than 20 cigarettes per day) for a short period of time (average:
2.4 pack-years). Male smokers showed frequent abnormalities in
tests of small airway function but female smokers did not ex-
hibit these abnormalities. Both male and female smokers
showed decreased forced expiratory flows at high lung volumes,
suggesting the presence of large-airway dysfunction in young
smokers. Male and female smokers differed significantly in
their response to He-02 inhalation. Female smokers showed at
least as great an improvement in forced expiratory flows with
He-O, as did female nonsmokers. In contrast male smokers
showed a much smaller response to the He-O, at high lung vol-
umes. Thus, the predominant female response to habitual
cigarette smoking appears to have been involvement of the
large airways, but men who smoked appeared to have developed
abnormalities in small airway function. The reason(s) for the
differences in the data derived from this study and previously
158


Males $$$
m Females
n=350 .x    n=173

n=   21  19      137 74      173 77

     < 10        1 O-20        20-40

           Cigarettes/Day

J

FIGURE X-Percentage of male and female cigarette smokers
      with an abnormal change in nitrogen concentration
      ( ANz) per liter according to their daily cigarette
      consumption

*Indicates a significant difference between groups using 20 to 40 cigarettes
per day as the reference group (P ~0.05).
+ Indicates significant differences between males and females (P ~0.05).
SOURCE: Buist, AS. (12).

cited reports relating smoking to small airway dysfunction
(11,12,39) is unclear.
In summary, a limited number of recent studies have demon-
strated a higher frequency of abnormalities in tests of small
airway function in female smokers as compared to female
nonsmokers and ex-smokers. It is not clear whether these ab-
normalities are dose-related. Female smokers may have more
frequent abnormalities in the slope of phase III than male
smokers. Male smokers may have more frequent abnormalities
in closing volume than female smokers. The meaning of these
differences is unclear. One study has suggested that the earliest

159


effects of smoking on lung function may occur in the large air-
ways in women and small airways in men.

SMOKING AND VENTILATORY FUNCTION

The majority of studies examining the relationship of smok-
ing to ventilatory capacity have used some measurement of
forced expiratory volume. Most of these studies have focused on
male populations and have found a close relationship between
cigarette smoking and the presence of abnormal pulmonary
function (2,6,16,20). Furthermore, the decrement in perform-
ance measured by simple spirometry is dose-related to the
numbers of cigarettes smoked (6,16,20). Relatively few studies
have included appreciable numbers of females.

Woolf examined pulmonary function in 500 women volunteers
(65). Smokers demonstrated significantly lower values for FVC,
FEV, FEF 25-75 percent, and specific conductance than
nonsmokers and ex-smokers who had not smoked for over a
year; this suggests that at least some abnormalities of pulmo-
nary function are reversible with smoking cessation.

Higgins and Keller examined the relationship of smoking to
seven derivatives of the forced vital capacity curve in 3,109
males and 3,256 females aged 10 and older (35). Nonsmokers
performed better than smokers in both sexes. Values consis-
tently decreased with increasing cigarette consumption. The
largest differences were in FEV and FEF 25-75 percent.

Seltzer et al. examined the relationship of smoking to FVC in
65,086 white, black, and Asian subjects aged 20 to 79 who had
attended a Kaiser-Permanente multiphasic health clinic (49).
The authors found a significant reduction in FVC among white
women who smoked as compared to nonsmoking white women.
No such differences were found for black and Asian subjects,
however. No explanation for this racial difference was apparent
from their data.

In a study by Buist et al., the prevalence of abnormalities of
FEVl/FVC was higher in female smokers than nonsmokers (11).
The frequency of abnormalities in FEVl/FVC among female
smokers was twice that of male smokers (Table 12). Gibson et al.
examined the relationship of smoking to measurements of the
forced vital capacity in 18,359 men and women in Australia (30).
Nonsmokers had better lung functions than smokers. Among
smokers of 10 or more cigarettes a day, men showed a greater
decrement in lung function than women.

Burrows et al. examined the relationship of smoking to
measurements of forced expiratory volume in 883 men and 1,166
women in Tucson, Arizona (13). Nonsmokers performed better
160


        (34)
F;*"b-s *(39) .

2.0 -

      o Nonsmoker -qk
     A Heavy Smoker

1.0           I           1           I           I          I
30       40        50        60        70        80

Age - Years

FIGURE 4.-Changes in forced vital capacity (FVC) by age in
       various female cohorts

Results have been standardized to 155 cm and are body temperature and
pressure saturated (BTPS).

Numbers in parentheses are number in that cohort.

Heavy smokers are those who smoke 25 or more cigarettes per day.
SOURCE: Ferris, B.G., Jr. (23).

than ex-smokers or smokers, and ex-smokers performed better
than smokers in both sexes. Smokers of more than 20 cigarettes
per day performed worse than smokers of fewer than 20 cigar-
ettes per day. There were no significant differences in the re-
gression for FEVl/FVC on pack years in men and women,
suggesting that men and women with equivalent smoking
habits have similar decrements in FEVl/FVC.
The long-term effects of smoking on pulmonary function have
been scrutinized in two prospective studies. In the Framingham
study, 5,209 adults have been followed since 1948 with biennial
examinations including measurements of forced vital capacity
(3). Longitudinally, cigarette smokers showed a more rapid de-
cline in forced vital capacity than nonsmokers. Men and women
who continued to smoke had a more rapid decline in FVC than
those who had stopped. The rate of decline in pulmonary func-
tion was appreciably steeper in male smokers than female
smokers. The authors suggest that these differences could be
due to differences in smoking habits.
In a longitudinal study of residents of Berlin, New Hamp-
shire, Ferris examined the changes in pulmonary function by
smoking status in the various age cohorts (23). Among females,
heavy and moderate smokers had lower values for FVC and
FEVl as compared to nonsmokers, and the values fell more
                                       161


3.0r

FE", o

(38)

2.0

* Nonsmoker
A Heavy Smoker

1           I
30       40

I           I           I           1
50       60       70        80
Age-Years

FIGURE 5.-Changes in forced expiratory volume in 1 second
      (FEV,.,) by age in various female cohorts

Results have been standardized to 155 cm and are body temperature and
pressure saturated (BTPS).
Numbers in parentheses are number in that cohort.
Heavy smokers are those who smoke 25 or more cigarettes per day.
SOURCE: Ferris, B.G., Jr. (23).

rapidly with age. These relationships for heavy smokers (25 or
more cigarettes a day) are presented in Figures 4 and 5.

In summary, women smokers perform worse on spirometric
testing than do female ex-smokers or nonsmokers. This rela-
tionship appears to be dose-related to the number of cigarettes
smoked. The differential effects of smoking on pulmonary func-
tion in males and females is unclear. One study demonstrated
that men and women with equivalent smoking habits have simi-
lar decrements in FEVl/FVC. The long-term effect of smoking
on pulmonary function has been evaluated in two studies which
included appreciable numbers of females. Longitudinally,
women who smoke show a more rapid decline in forced vital
capacity than women who do not smoke. Women who continue to
smoke have a more rapid decline in forced vital capacity than
those who stop; however, men who continue to smoke have an
even more rapid decline in pulmonary function than women
who continue to smoke. The long-term, relationship between
respiratory symptoms and airflow obstruction in women is un-
known. One large prospective study could not find a relation-
ship between symptoms and the ultimate development of
chronic airflow obstruction in men (29).
162


Summary
1. Recent statistics indicate a rising death ra.te due to chronic
obstructive lung disease (COLD) among women. The data avail-
able demonstrate an excess risk of death from COLD among
smoking women over that of nonsmoking women. This excess
risk is much greater for heavy smokers than for light smokers.
2. Women's total risk of COLD appears to be somewhat lower
than men's, a difference which may be due to differences in
prior smoking habits.
3. The prevalence of chronic bronchitis varies directly with
cigarette smoking, increasing with the number of cigarettes
smoked per day.
4. There is conflicting evidence regarding differences in the
prevalence of chronic bronchitis in women and men. Several
recent studies suggest that there is no significant difference in
the prevalence of chronic bronchitis between male and female
smokers. This may be the result, however, of increasingly simi-
lar smoking behavior of women and men.
5. The presence of emphysema at autopsy exhibits a dose-
response relationship with cigarette smoking during life.
6. There is a close relationship between cigarette smoking
and chronic cough or chronic sputum production in women,
which increases with total pack-years smoked.
7. Women current smokers have poorer pulmonary function
by spirometric testing than do female ex-smokers or nonsmok-
ers, a relationship which is dose-related to the number of
cigarettes smoked.

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167


INTERACTION BETWEEN SMOKING
AND OCCUPATIONAL EXPOSURES.


INTERACTION BETWEEN SMOKING AND OCCUPATIONAL
EXPOSURES
The 1979 Surgeon General's Report on the health conse-
quences of smoking (18) examines the interaction of smoking
and occupational exposure. Ways in which smoking may inter-
act with the occupational environment are described and
examples of these interactions are discussed. Briefly, these
types of interaction are:
1. Tobacco products may serve as vectors by becoming con-
taminated with toxic agents found in the workplace, thus
facilitating entry of the agent by inhalation, ingestion, and/or
skin absorption of the agent.
2. Workplace chemicals may be transformed into more harm-
ful agents by smoking.
3. Certain toxic agents in tobacco products and/or smoke may
also inhabit the workplace, thus increasing exposure to the
agent.
4. Smoking may contribute to an effect comparable to that
which can result from exposure to toxic agents found in the
workplace, thus causing an additive biological effect.
5. Smoking may act synergistically with toxic agents found in
the workplace to cause a much more profound effect than that
anticipated simply from the separate influences of the agent
and smoking added together.
5. Smoking may contribute to accidents in the workplace.
Although few of the studies discussed in the 1979 Surgeon
General's Report included enough women to adequately deter-
mine the health risks of smoking and the occupational environ-
ment, it is reasonable to hypothesize that women with the same
occupational exposure and smoking behavior as men would de-
velop health effects similar to those demonstrated in men. How-
ever, the interaction of smoking and the occupational environ-
ment and its effect on women differs in at least two ways:
First, smoking patterns among women are different from
those among men-women are less likely to smoke, and if they
do, they smoke fewer cigarettes per day, inhale less, and are
more likely to smoke lower "tar" and nicotine cigarettes
(7,14,18). Second, smoking and occupational exposure may ad-
versely affect the fetus or the health of the mother during preg-
nancy. Smoking and occupational exposure may also interact
with methods of contraception chosen by women.
This chapter reviews each of these reasons for a differential
health impact on men and women and examines two occupa-
tional exposures where interactions with smoking have been
clearly demonstrated for women workers.
                                         171


TABLE l.-Smoking habits of working women by title and
      industry

Industry

Percent
  of
Current            Percent
Female
Labor    Non-     Ex-
Force*  Smokers Smokers Present Smokers

Professionals
Health
Teachers
Other

Managerial, incl.
office, rest.,
sales,
administrator

Sales

Clerical
Bookkeepers
Office machine
operators
Secretaries
All other

Crafts

Operatives

Service
Cleaning
Food
Health

Private Household
Workers

4.4     51.2     16.6     25.2      6.9
6.8     63.5     14.0     19.8      2.7
4.6     53.4     15.1     24.0      7.5

6.7     42.7     16.4

6.2     46.0     16.2

4.6     53.1     12.2

1.3     52.8     15.7
13.3     52.0     14.7
14.2     50.6     13.6

2.4     46.4     13.1

11.8     52.8     10.1

2.5     51.9     12.8
6.6     40.0     13.4
6.9     52.1     10.5

2.8     62.4     10.1

s 1 pack  2 1 pack
per day  per day
            -

28.0     12.1

30.0      8.0


26.5      8.2


23.1      8.4
26.3      7.0
27.5      8.3

31.8      8.6

31.6      5.5


31.2      4.1
39.8      6.8
32.2      5.2


24.7      2.8

*Figures are subject to sampling errors and may therefore not agree with
those in other tables.
SOURCE: National Center for Health Statistics (6).

Smoking Patterns in Women

The male-female differences in smoking behavior and the
change in patterns of smoking behavior in women over time are
reviewed in other sections of this report. It is important, how-
ever, to consider the impact of these trends when evaluating the
interaction of smoking and the environment. Regular cigarette
smoking is a behavior that usually begins between the ages 12
and 25 (18). It is unusual to begin regular smoking after the age
172


TABLE 2.-Estimates of the percentage of current, regular
      cigarette smokers, adults ages 20 years and over,
      according to labor force status and occupation and
      sex, U.S., 1976

        Female              Male
Total               Total
20+    20-44   45-64   20+   20-44 45-64

Total

Currently employed
White collar total
Professional
technical
and kindred
Managers &
administrators
except farm
Sales workers
Clerical &
kindred workers

Blue collar total
Craftsmen &
kindred workers
Operatives and
kindred workers
Laborer, except
farm

Service

Farm
Unemployed
Usual activity-
homemaking

32.0    36.9    34.8    41.9    47.6    41.3

35.9    37.0    36.1    43.4    46.8    39.7
34.3    33.8    36.9    36.6    38.6    35.3

29.1    28.6    32.7    30.0    31.1    29.9

41.6    42.7    40.8
38.1    37.0    42.6

34.8

39.0

37.6

34.7

43.7


46.9


42.5


52.6

42.8

51.0

41.0

36.0

33.6

40.5

35.6

31.2    52.3

56.3

39.0

32.2

40.0

29.0

41.0
39.9


40.4

50.4


48.0

46.4
42.6


40.1

54.1

36.1
38.0

44.2

44.3

52.1


55.3


56.9

51.1

45.4

59.9

41.6

46.2

*     53.7

37.2    47.2

*     36.9

39.2    56.8

51.7

44.8

35.0

53.8

37.1    32.2    NA     NA    NA

NOTE: Unknown if ever smoked excluded from calculation.
*Figure does not meet standards of reliability or precision.
SOURCE: National Center for Health Statistics (6).

of 25 (7). In a cohort of individuals born in the same year, a
certain percentage of them will begin smoking by age 25. The
prevalence of smoking in any birth cohort after age 25 is pre-
dominantly determined by the rate at which people stop smok-
ing or die. The prevalence changes over time for each 10 year
birth cohort since 1910 for both men and women are presented
in the part of this report titled Patterns of Cigarette Smoking.
Women first began smoking cigarettes in large numbers im-
mediately before and during the Second World War (18). Thus,
the observed upswing in smoking among women occurred 25 to
30 years after that among men. The birth cohorts with the high-
                                         173


TABLE 3.-Occupational distribution of men and women, 1978, by
     percent of each sex employed in each category

Women        Men

Professional, Technical
Sales
Clerical
Operatives & Transport
Service
All Other
Crafts
Managers

Total

SOURCE: Rones, P. (14).

15.6          14.7
6.9          6.9
34.6          6.2
11.8          17.7
20.7          8.7
2.5          11.7
1.8          21.1
6.1         14.0

100          100

est peak smoking prevalence were born from 1910 to 1930 (men)
and from 1920 to 1950 (women). As these cohorts with high pre-
valence of smoking grow older, they replace cohorts with lower
smoking prevalence. Since both occupational diseases and
smoking related illnesses increase separately with age, any in-
teraction between the two also could be expected to increase
with age. Men in the birth cohort from 1910 to 1930 are now in
the age range at which a high incidence of disease would be
expected, while those women born from 1920 to 1950 are just
beginning to enter the ages at which there is a high prevalence
of disease. As a result, the adverse effects of smoking and occu-
pational exposure would be expected to occur more frequently
in men, reflecting this difference in the age of the average male
and female smoker. This "cohort effect" might lead to the er-
roneous conclusion that women are protected from occupation-
smoking interactions, just as it has been used to suggest that
women are protected from the lung cancers induced by
cigarette smoking.

A second difference between male and female smoking habits
which must be considered is the prevalence of smoking by occu-
pation. Table 1 shows that the prevalence of smoking is rea-
sonably uniform among women employed in many different oc-
cupations (the exceptions are education and household area
workers with low prevalence and food area workers with high
prevalence). There is not the marked difference in smoking
habits between female blue collar and white collar workers that
has been observed in men (13) (Table 2). A slightly lower preva-
lence of smoking among professional women compared to other
white collar workers occurs similar to that seen in men (7).

The section on behavior in this report discusses the smoking
habits of several groups of health professionals. It shows that
174


women physicians and psychologists smoke more heavily than
their male counterparts. Thus, the relative levels of smoking
observed in the two sexes are reversed for these two occupa-
tional groups in comparison to the general population (14).
Nurses also have been shown to have a much higher prevalence
of smoking than women of the same age in the general popula-
tion (18). A final notable difference is that, among women, smok-
ing prevalence does not show the same marked inverse correla-
tion with socioeconomic status (7). The reasons for these dif-
ferences are beyond the scope of this section. However, an un-
derstanding of them forms part of the background for any dis-
cussion of the interaction of smoking and occupational expo-
sures among women.

Patterns of Employment

The percentage of women in the United States work force is
steadily growing. In 1973 women represented 38.4 percent of the
United States work force and in 1978 that percentage had risen
to 41.2 percent (15).
Approximately 39 million women are employed outside the
home. Table 3 clearly indicates that the distribution of women
in the labor force by category of work does not parallel that of
men. Women are more likely than men to be employed in the
clerical and service categories. Men are more likely to be em-
ployed in the management, crafts and operatives/transport
categories than women. Table 4 lists the number of women em-
ployed in a wide variety of occupations, including many of those
traditionally believed to be hazardous for men. In spite of this
diversity, the bulk of women are employed in a narrow range of
jobs. Over one-third of women in the paid labor force are em-
ployed in one of the 10 job categories listed in Table 5. All of
these categories have been traditional employment areas for
women. Thus, the recent gains by women in employment oppor-
tunity have not yet had a substantial impact on the actual dis-
tribution patterns of the female labor force. If a shift does occur
in employment patterns involving greater proportions of
women in occupations with significant exposures, we would ex-
pect a cohort effect to be apparent in the development of occu-
pational illness. That is, those women entering hazardous occu-
pations traditionally limited to male workers would be expected
to be women newly entering the work force and, thus, predomi-
nantly in the younger age groups. As these cohorts age, the
duration of both occupational and smoking exposures would in-
crease. It is only after these newer cohorts reach the ages where
disease is prevalent that we would be able to observe the full

175