Chapter 6 
various smoking levels compared with smokers from a later period (1970 to 
1977). They interpreted this temporal pattern as indicating that cigarettes 
with lower tar and nicotine yields had less effect on lungs than did higher 
yield cigarettes. 
A number of studies have shown that smokers of lower yield cigarettes 
have comparatively lower rates of respiratory symptoms. Respiratory 
questionnaire data collected in the late 1970's from approximately 
6,000 Pennsylvania women are illustrative (Schenker et al., 1982). The brand 
of cigarettes currently smoked was determined and used with FTC tar yield 
information to classify the smokers by tar exposure. Tar yield was positively 
associated with cough and phlegm but not with wheezing or shortness of 
breath. For cough and phlegm, there were consistent exposure-response 
relationships with an approximate doubling of symptom frequency from 
the lowest to the highest exposure category (Table 3). The findings of other 
studies are similar. For example, a large study of civil servants in the United 
Kingdom, the Whitehall study, showed that the percentage of smokers 
reporting phlegm increased with tar yield within each stratum of cigarettes 
smoked per day, even the lowest (Higenbottam et al., 1980). 
Table 3 
Absolute and relative risks of chronic cough and chronic phlegm in Pennsylvania 
women by smoking status, cigarettes smoked per day (CPD), and tar yield of 
current brand 
Chronic Cough 
Chronic Phlegm 
Smoker 
Classification 
Risk 
Relative Risk 
Risk 
Relative Risk 
Never-Smokers 
0.038 
1.00 
0.033 
1.00 
Ex-Smokers 
0.056 
1.46 
0.052 
1.58 
Current Smokers 
1-14 CPD 
7 mg tar 
0.073 
1.92 
0.067 
2.04 
1 5 mg tar 
0.103 
2.71 
0.085 
2.56 
22 mg tar 
0.137 
3.61 
0.103 
3.12 
15-24 CPD 
7 mg tar 
0.136 
3.58 
0.155 
4.67 
1 5 mg tar 
0.185 
4.87 
0.190 
5.74 
22 mg tar 
0.240 
6.32 
0.226 
6.82 
25+ CPD 
7 mg tar 
0.273 
7.18 
0.234 
7.05 
1 5 mg tar 
0.353 
9.29 
0.281 
8.48 
22 mg tar 
0.430 
11.32 
0.327 
9.87 
Source: Schenker et al., 1982. 
83 
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