CONTENTS Introduction Influence of Cigarette Smoking on the Natural History of Byssinosis Cigarette Smoking Patterns Among Workers Exposed to Cotton Dust Acute Effects of Smoking and Cotton Dust Exposure on Respiratory Symptoms Effects of Smoking and Cotton Dust Exposure on Pulmonary Function Tests Chronic Clinical Effects of Cotton Dust Exposure Mechanisms of Cotton Dust Lung Injury Inflammation (Bronchitis) Airways Constriction Chronic Inflammatory Lung Destruction Cotton Dust Exposure and Mortality From Respiratory Disease and Lung Cancer Control of Cotton Dust Exposure Summary and Conclusions References 401 Introduction Exposures to cotton, hemp, and flax dust have been associated with two acute pulmonary responses: irritant (industrial) bronchitis and chest tightness (byssinosis). These symptoms, often accompanied by reduction in lung function, have occurred in 2 to 30 percent of cotton textile workers within hours of resuming exposure following a weekend or holiday @chilling 1956; Morgan et al. 1982). These elements of the acute cotton dust pulmonary response may not occur together, and may represent responses of distinct pulmonary mecha- nisms. The exposure variables or host characteristics that lead to cough rather than to bronchoconstriction are currently under careful study (Hogg and Eggleston 19841. The effects of cigarette smoking upon these different responses is also incompletely under- stood. In the manufacture of cotton textiles, cotton dust exposure occurs most intensely when the tightly packed bale is opened and when abrasive crushing and carding remove the "trash" (plant bracts and other parts, dirt, bacteria, and fungi) and align the fibers for spinning (Gideon and Johnson 1978). Normally, as the cotton fibers are spun, twisted, and woven into cloth, progressively less dust is generated. By the time cotton cloth is processed, the procedure is practically free of cotton dust (Kilburn 1983). Cross-sectional studies have shown that byssinosis prevalence is greatest among cotton textile workers in the dusty preparation jobs (e.g., carder, stripper, or grinder) (Figure 1). Byssinosis prevalence has been related to the duration of cotton dust exposure, to the quality of the raw cotton, and to the levels of lint-free cotton dust (Molyneux and Tombleson 1970; Merchant, Lumsden, Kilburn, O'Fallon et al. 1973b; Kamat et al. 1981). At a cotton dust level of 0.2 mg/m3 (lint-free dust of approximately 15 urn or less), approximately 15 percent of the cotton textile workers have some grade of byssinosis (Merchant, Lumsden, Kilburn, O'Fallon et al. 1973b). While a small sex-specific effect (male disadvantage) has been noted (Berry et al. 19741, no age effect has been shown after adjustment for exposure (Merchant, Lumsden, Kilburn, O'Fallon et al. 1973b; Berry et al. 1974). Cigarette smoke interacts with cotton dust exposure in cotton textile workers and has been associated with increased byssinosis prevalence and severity (Berry et al. 1974). The frequency of byssinosis has been closely correlated with the presence of chronic bronchitis, and both symptoms have been associated with ventilatory impairment (Imbus and Suh 1973). Cross-sectional studies have correlated cotton dust exposure with two components of ventilatory impairment: reduction in the baseline level of forced expiration and reversible loss of function across a work shift. The relationship of byssinosis and bronchitis with ventilatory impairment and its Z! 2( P 1 s 1t 6 1 3 h 1C 5 c 26.2 I cotlon [7 Cotton/Synthetic 16.2 Preparation Yarn production Slashing/Weaving Miscellanecus FIGURE l.-Byssinosis prevalence by work area and raw material use NOTE- Average prevalence- cotton. 5.7. percent. cotton/synrhetlc, 4 4 percent. SOURCE Imbus and Suh (19731. relationship to cigarette smoking is discussed in greater detail later in this chapter. Influence of Cigarette Smoking on the Natural History of Byssinosis Cigarette Smoking Patterns Among Workers Exposed to Cotton Dust The smoking patterns of cotton dust exposed workers have been reported by a number of authors and are presented in Table 1. In summary, current studies show that male cotton workers tend to smoke to a greater degree than do female cotton workers. Male textile workers in Western Europe and in Canada smoke with 404 TABLE l.-Prevalence of smoking in studies of cotton workers Study Number and type of population Smoking characteristica (percent) Comments Schrag and Gullett (1970) Kari-Koskinen and 967 female cotton workers, Hirvonen (1970) Finland Merchant, Kilbum. 435 cottonsynthetic blend et al. (1972) workers, North Carolina Kilburn, Kilburn 1,046 female textile et al. (1973) workers, North Camliia Szymczykiewin et al. (1970) For et al. (1973) 509 cotton textile workera 637 men, 2,530 women Cotton workers, 35 mills, Great Britain Age 17-29 30-39 4049 iw-60 CigslbY l-14 15-24 >24 2.6 SM EX NS 54.7 12.0 33.3 SM 45.2 35.6 Syn. wool workers Cottonmill workers Men Women 60.5 6.9 SM NS EX 62 31.6 6.3 36.2 21 SM 36 EX/NS Percent smoking ~1 pack/day not available 16.9 39.8 14.1 9.0 5.0 63.1 >53% began smoking at 15-19 years of age E TABLE L-Continued Number and type Study of population Smoking characteristics (percent) Cmnmenta Imbus and Suh 10,133 cotton workers. 11973) North Carolina Men 78 Women 43 Smokers include ever smoked 1 cig/day for 1 Y-r Berry et al. (1974) 14 cotton and 2 manmade fiber milla. Great Britain Men 75.6 Women 56.5 Former smokers not reported Zwkin et al. (1976) Wool workers and controls Workers Men 47 Women 0 Controls Men 55 Women 0 Khogali (1976) 271 ginnery workers, Sudan SM 36.5 Jones et al. (1977) 153 cottonmill workers, southeast United States SMIEX 70 Almost l/2 smoken said smoked <5 cigs/day Bouhuys et al. (1977) Card and weave room workers, South Carolina SM Men X-41 Women 15-25 TABLE l.-Continued Study Number and type of population Smoking characteristics (percent) Comments Palmer et al. (1978) Bouhuys et al. (1979) 203 gin workers Textile workers, aged 245, South Carolina Ginnera Pressmen Others Controls Women Carding SM EX 51.1 25.5 (16.0)' (9.6) 57.1 19.1 (7.3) (4.1) 45.5 15.1 (15.3) (8.0) 52.3 19.2 (11.4) (9.1) SM EX NS 18 14 68 20 10 70 17 14 69 20 10 69 15 11 74 Jones et al. Cotton and wool/synthetic (1979) mill workers &,rii,g Weaving Others' Men Carding . - Preparing Weaving Others' Mill 1 Mill 2 Mill 3 Mill 4 38.0 62.0 SM' NS 52.6 47.2 66.9 33.1 64.8 35.2 26 44 26 37 4.5 16 50 42 8 38 37 16 20 3.5 30 NS 23.4 23.8 39.4 28.5 `( )=mean pack-years (1 pk/day/year) * Includes cloth room workers and miscellaneous job CAgOrieS ' Smokers include ex-smokera TABLE k-Continued Study Number and type of population Smoking characteristics (percent) Comments Barman (1979) - 70 cottonmill workers MUI Women Sparks and Peters (1960) Grimard and Adams (1981) Becketal (19821 Cotton duetexposed workers Men Women Textile workers, Canada Men Women 118 male and 162 female cottm textile workers Men Workers Controls Women Workers Controls SM EX 44 28 58 44 28 55 - 76.6 60.4 27 16 31 43 NOTE SW Smoker; EX Exnmoker. NS. Nonrmoker greater frequency than do American workers, with many studies showing the proportion of smokers to be well over 70 percent. Acute Effects of Smoking and Cotton Dust Exposure on Respiratory Symptoms The symptoms 01 ?ilonddy ches t t;,htness begin gradually, S or 4 hours after the cotton texrile worker returns to work. A dry cough and shortness of breath on exertion frequently accompany the sensation of chest tightness. However. the physiologic reaction associated with Monday chest tightness is not confine2 to the chest. X low grade temperature. a 20 to 3n percen: increase in the peripheral white blood cell I polymorphonuclear ieukocyte 1 count, and a general malaise have been frequently reported These systemic symptoms suggest the presence of a host in!lammarory response; however, the relationship between these systemic symptoms and the symptom of che?t tightness is not well defined. By 1936, an association had heen recognized between Monday chest tightness and detectable loss of ventilatory capacity and increased breathlessness iPrausnltz 19361. Recognition that in sus- ceptible cotton mill workers. Monday chest tightness may be followed by permanent respiratory disabi!ity led to the evolution of a standard byssinosis case definition. Schilling and colleagues (19551 developed specific questions concerning Monday chest tightness for the British Medical Research Council's respiratory symptom survey questionnaire (British Medical Journal 1960). A positive response to the standardized questions regarding Monday chest tightness de- fined the presence of byssinosis. Molyneux and Tombleson (19701 conducted one of the first prospective studies of byssinosis. 4t the initial examination, these investigators interviewed 1.359 workers from 14 cotton spinning miZc and 227 -xorkers from 2 manmade fiber spinning mills in Lancashire. United Kingdom. Followup examinations were conduct- ed at 6-month intervals over 3 J.ears, from 1963 to 1966. Byssinosis and bronchitis prel-alence were :Ieterl..A ~;ned by the use of the Jledical Research Council's questionnaire on respiratory sy!:iptoms [British .Medicai .Journal 196Oi, to which :t.e Roach and Schilling t1960) questions on chest tightness wert- added. Bjs;inosis bvas graded as follows (Molyneux and Tombleson 197Oj.' Grade 0: No evidence of chest tightness or breathing diffi- culty on the first day of the workweek Grade 1 `2: Occasional chest tightness on !`rlondays Grade 1: Chest tightness or difficulty in breathing on Mondays only Grade 2: Chest tightness or difficulty in breathing on Monday and other days Age, length of exposure to cotton dust, and smoking habit were determined by questionnaire. Individuals were considered smokers if they regularly smoked one or more cigarettes per day. Hexlet and total dust air samplers were used to measure the mass concentration of the respirable, medium, and fly components of the total airborne dust. Byssinosis prevalence (adjusted for age, sex, and mill type) showed a progressive increase with increasing duration of cotton dust exposure (Table 2) (Molyneux and Tombleson 1970). A rearrange- ment of the data from this Lancashire mill workers study and calculation of the Mantel-Haenszel (weighted) odds ratios (Mantel 1963) shows an interesting relationship between smoking, byssinosis, bronchitis, and sex. A similar relationship is demonstrated by data from studies of American cotton mill workers (Merchant et al. 1972; Imbus and Suh 1973). Cigarette smoking was associated with an overall 2.21-fold excess risk of bronchitis in the Lancashire cotton mill workers (Table 3). Cotton mill workers of both sexes who smoked had a consistently greater prevalence of bronchitis than did non- smokers. The magnitude of the smoking effect was similar for men 12.2%fold) and women (2.16-fold). The presence of bronchitis con- ferred an approximately twofold excess risk of developing byssinosis (Table 4). This risk was significant for men and for women, for smokers as well as for nonsmokers. Once the presence of bronchitis had been controlled for, however (Table 51, cigarette smoking did not add significant additional risk for developing byssinosis. One may interpret these observations to show that among cotton mill workers both cotton dust exposure and cigarette smoking produced the symptoms of bronchitis. Bronchitis, in turn, seemed to confer additional risk for the development of acute chest tightness (byssinosis). Cigarette smoking, therefore, seems to facilitate the development of byssinosis in smokers exposed to cotton dust, perhaps by the prior induction of bronchitis. Applying an additive logit model (6 dust levels x 3 lengths of exposure x 4 combinations of sex and smoking habit) to these data, Berry and colleagues (1974) found that cigarette smokers had a modest (1.4-fold) increase in the adjusted prevalence of byssinosis when compared with nonsmokers and ex- smokers. Two years after the initial questionnaire survey, these investigators were able to reinterview about half of the original population (669 cotton workers and 127 manmade fiber workers). Incidence and remission rates were tabulated for byssinosis and bronchitis by length of exposure, sex, and smoking status. The incidence of both bronchitis and byssinosis was greater among 410 TABLE 2.-Prevalence (percent) of byssinosis in nine exposure groups Number in group Prevalence adjusted for age. mill type. and sex CL4 305 52 8.8 8.0 %9 155 23 3 20.5 19.2 l&14 168 28 0 22 3 21.0 15-19 187 35.8 29 5 27.5 20-24 117 36.8 30 9 31.1 2529 115 43.5 40 2 42 4 30-34 94 30.9 302 35 1 3639 99 35 4 36.5 414 140 119 33 6 37.7 418 SOURCE Malyneux and Tombleson (19701 TABLE 3.-Age-adjusted association of bronchitis and smoking, by byssinosis status and sex Smoker Bronchitis Bronchitis Chi square and with byssinosis without byssinosis odds ratio for the association of N Present Absent N Present Absent smoking/bronchitis' Yes 127 No 33 557c 554 45% 45% Men 301 46% 54% X*=15.20 105 21% 79% OR = 2.28 cp