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Indian Journal of Community Medicine

Effect of Smoking on Lung Functions of Workers Exposed to Dust and Fumes

Author(s): Viju T Mhase, P.S.N. Reddy

Vol. 27, No. 1 (2002-01 - 2002-03)

Deptt. of P.S.M, L.T.M. Medical College, L.T.M.G. Hospital, Sion, Mumbai - 400022

Abstract:

Research question: Is there any association between smoking behaviour and respiratory morbidity among workers exposed to dust and fumes in terms of pulmonary functions.

Objectives: 1. To study the prevalence of smoking and types of respiratory disorders among workers exposed to dust and fumes. 2. To assess lung functions of these workers in relation to their smoking behaviour.

Study design: Cross-sectional study.

Setting: Out patient departments of a large hospital in Mumbai.

Participants: 115 workers occupationally exposed to dust and fumes, irrespective of their present complaints. Outcome variables: FVC, FEV1, FEV1/FVC ratio, FEF25-75 (Values as percentage predicted), restrictive, obstructive and mixed (restrictive + ventilatory) disorders.

Statistical analysis: Chi square test, Z test.

Results: Prevalence of smoking was 50.4% among workers. Respiratory disorders were significantly higher in smokers and were related to their smoking behaviour. Smokers had more restrictive and ventilatory disorders as compared to those who had never smoked suggesting combined effect of smoke and dust or fumes.

Keywords: Ever smokers, Current smokers, Nicotine dependants, Quitters,

Introduction:

We are discovering the right things in the wrong order, which is another way of saying that we are learning to control nature before we have learnt how to control ourselves.
-Raymond Fosdick

One of the most important controls we need to exert is control on smoking behaviour. The use of tobacco products by workers and the general population continues to increase in all parts of the world. From 1920 to 1966, tobacco consumption in various forms increased as did the introduction into the work places of chemicals with unstudied biological effects1 . Tobacco smoke contains a large variety of compounds, some 4000 of which have been identified and many have been quantified 2 . Several ways have been identified in which smoking may act with physical and chemical agents found in workplace. The actions are not mutually exclusive and several may prevail at the same time 1.

The study was carried out in a large teaching hospital in Mumbai, to assess lung functions of workers exposed to dust and fumes in relation to their smoking behaviour. A hospital based study was taken up to eliminate healthy worker effect 3 (selection of workers with better health by means of pre-placement examination).

Material and Methods:

This was a cross-sectional study of workers over a period of two months. In this period 27,782 patients attended various general OPDs of the hospital. The patients included 15,169 males and 12,613 females. Out of these, 12,000 was the working population. When interviewed, 1609 workers gave history of continuous exposure to dust or fumes by means of their occupation. Types of dust included cotton, cement, silica and paper dust etc. Fumes included gases, chemicals, rubber etc. 10% of the workers were selected by simple random sampling method. Appointment cards were given to 160 workers, out of which 128 workers responded. Three subjects with cardiovascular diseases and ten with active tuberculosis were excluded from pulmonary function testing (PFT) as they secreted copious sputum and the spirometer could not give accurate PFT readings. Thus the final sample size came to 115, which included 11 women.

All these workers were subjected to an interview using a pretested, structured, close ended questionnaire and information was collected regarding socio-economic status and working conditions. Detailed smoking history was obtained. This was followed by careful general examination. Workers were then subjected to pulmonary function testing, using a computerized spirometer (Jaeger-Wuerzburg's flow mate). Tests were repeated thrice and the best reading was selected by the flow-mate. Workers' sex, height and weight were entered in the flow mate which used pre-fed Udwadia's standards 4 for comparison of pulmonary functions with normal values for given age, sex and height.

Socio-economic status was decided using Kuppuswamy's classification 5 . Covey's classification 6 was used to classify smoking behaviour of workers who smoked. The terms were defined as follows:

1. Ever smokers: Those who had ever smoked cigarettes at least once a day for 1 year.

2. Current smokers: Those who either were smoking at the time of interview or had stopped less than 12 months earlier.

3. Quitters: Previous smokers who had not smoked during the previous year.

4. Nicotine dependent smokers: Current smokers who smoked more than 25 cigarettes per day and who lit up in the morning within 30 minutes of awakening. Results of pulmonary function testing were correlated with smoking behaviour. Forced vital capacity (FVC), Forced expiratory volume in one second (FEV1), the ratio of FEV1/FVC and mid expiratory flow rate were taken into consideration. Reports were obtained to determine the lung function pattern, whether normal, restrictive, obstructive or mixed (restrictive + ventilatory) disorders.

Results:

The age range of the workers was 25 to 62 years. 68% of the workers belonged to the age group of 25 to 44 years. 70% of the workers were Hindu. 68% belonged to nuclear families. Most of the workers belonged to middle class (Grade IV - 72.1% and Grade III 18.26%). The workers mainly belonged to unorganised sector. Pre-placement examination was done in case of only 23% of the workers. 64% of the workers were occupationally exposed to dust while 36% were exposed to fumes. 67% of the workers were found to work for 48 hours per week. 25% of them were working for 60 hours while 8% were working for 72 hours a week. Prevalence of smoking was 50.4%. 70.4% of the workers had normal respiratory functions. 9.6% had restrictive disorders (FVC<75% of predicted value), 6.9% had obstructive disorders (FEV1<75% of predicted value) and 13.1% had mixed, i.e., restrictive as well as ventilatory disorders (both FVC and FEV1 reduced to <75% of predicted value).

Table I: Respiratory disorders in relation to smoking habit.

Smoking habit Normal
No.(%)
Disorders
No.(%)
Total
No.(%)
Non-smokers 50 (87.7) 07 (12.3) 57  
Smokers 31 (53.5) 27 (46.5) 58 (100)
Total 81 (70.4) 34 (29.6) 115 (100)

X 2 =15.74, p<0.001.

Among smokers 46.5% had respiratory disorders compared to 12.3% among non-smokers. The difference was statistically significant.

Table II: Smoking habit and respiratory disorders.

Smoking habit Normal
No.(%)
Disorders
No.(%)
Total
No.(%)
Ever smokers + current smokers 18 (75.0) 6 (25.0) 24 (100)
Quitters + nicotine dependants 13 (38.2) 21 (61.8) 34 (100)
Total 31 (53.5) 27 (46.5) 58 (100)

Age not stated (35) were excluded for application of test of significance. x 2 =7.71, p<0.01.

Among smokers, 24.2% were identified as 'ever smokers', 17.2% as 'current smokers', 29.3% were 'Quitters' while another 29.3% were 'Nicotine dependents'.

Respiratory disorders were significantly higher in quitters and nicotine dependants as compared to ever smokers and current smokers.

Table III: Type of disorders.

Smoking habit Restrictive
No. (%)
Obstructive
No. (%)
Mixed
No. (%)
Total
Non-smokers 3 (43.0) - - 4 (57.0) 07
Smokers 8 (29.6) 8 (29.6) 11 (40.8) 27
Total 11   8   15   34

Table III shows that smokers had significantly more restrictive and ventilatory disorders than non-smokers.

Table IV: Values of lung functions as per smoking behaviour (in percent predicted).

Lung function parameter Non-smoker mean ± SD Smoker mean ± SD P value
Forced vital capacity (FVC) 92.4±20.8 64.7±21.2 <0.001
Forced expiratory volume in one second (FEVI) 112.4±28.9 72.6±28.5 <0.001
FEVI/FVC ratio % predicted 106.1±13.5 103.5±18.9 NS
FEF25-75 (Mid-expiratory flow rate) 117.3±25.1 79.3±50.2 <0.01

NS-Not significant. There was no significant difference in prevalence of obstructive disorders in smokers and non-smokers.

Table V: Years of exposure and respiratory disorders in relation to smoking habit

Year of exposure Non-smoker(n=57) Smokers (n=58)
Normal Disorder Total Normal Disorder Total
0-5 16 (100) -   16 8 (73) 3 (27) 11
6-10 13 (93) 1 (7) 14 6 (60) 4 (40) 10
11-15 10 (91) 1 (9) 11 10 (62) 6 (38) 16
16-20 9 (82) 2 (18) 11 5 (42) 7 (58) 12
≥ 20 2 (40) 3 (60) 5 2 (22) 7 (78) 09
Total 50   7   57 31   27   58

Figures in parentheses show percentages.

Respiratory disorders went on increasing with years of exposure in both smokers and non-smokers. But disorders developed much earlier in smokers as compared to non-smokers.

Average number of symptoms per worker in non-smokers was 1.8, whereas, among smokers it was 2.32. In non-smokers prevalence of chronic bronchitis was low (3.5%). In ever-smokers and current smokers it was higher (20.8%). The prevalence of chronic bronchitis was highest (41.1%)in quitters and nicotine dependants.

The workers described the working conditions as 'not satisfactory', 50.4%described the ventilation as poor and only 11.3% described it as good. 88% of the workers did not use any protective device. There was no system of periodic examination of workers in any of the workplaces.

Discussion:

Both exposures to dust and fumes as well as smoking are known to cause respiratory disorders; but when the two co-exist, the effects could be more than additive. Half of the workers, in this study smoked. Most of them worked in unorganised sector under unsatisfactory working conditions and inadequate medical assistance as reflected by absence of periodic examination. Since human body has tremendous reserves to cope up with adversities, disability develops only when impairment has progressed upto certain levels. The occupational health problems which reach the OPDs is only the tip of the iceberg. For respiratory disorders, spirometer helps to explore the larger section of the iceberg. Though the present study can not detect the exposure response relationship between smoking and lung functions, it clearly indicates lower FVC and FEV1 and mid-expiratory flow rate (FEF25-75) in smokers as compared to non-smokers. Thus smokers had significantly more restrictive and ventilatory disorders.

These was no difference in prevalence of obstructive disorders in smokers and non-smokers. In absence of exposure to dust and fumes in general population, smokers are known to have more obstructive disorders than non-smokers. In present study, restrictive and mixed disorders were found to prevail more suggesting combined effect of smoking and workplace exposure.

Conclusion:

The respiratory morbidity was definitely higher in smokers than in non-smokers and disorders were higher in nicotine dependants and quitters.

References:

  1. Smoking and Health, A report of Surgeon General, U.S. department of Health, Education and Welfare, Washington, 1979; 7-18.
  2. Women and Tobacco, World Health Organisation, Geneva, 1992: 32.
  3. Helga FM, Levi BS. Physician based surveillance of occupational diseases, Developing a methodology. Journal of Occupational Medicine, 1987; 29(8): 688.
  4. Udwadia FE, Sunawala JD, Shetye VM, Jain PK. The maximal expiratory flow-volume curve in normal subjects in India. CHEST 1986; 89(6): 852-6.
  5. Park JE, Park K. Park's Textbook of Preventive and Social Medicine, Messers Banarsidas Bhanot publishers, Jabalpur, 7th edition, 1979: 81.
  6. Covey LS, Zang EA, Wynder EL. Cigarette smoking and occupational status 1977-1990. American journal of public health 1992; 82: 1230-4.
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