Original Articles

Background. In India, 20 million workers are involved in the manufacturing of textiles. However, there are few epidemiological studies from India that have assessed the magnitude or the risk factors associated with byssinosis. In Pondicherry, textile mills have been in existence for over a century. This case–control study aimed to find the factors associated with the development of byssinosis in textile workers. Methods. The sample consisted of 761 men above the age of 30 years who had worked for at least 10 years in a textile factory. All the respondents were interviewed by a pretested questionnaire to gather information regarding the symptoms of byssinosis, certain personal characteristics and occupational history. Byssinosis was identified using the classification proposed by the World Health Organization. Two age-matched controls were selected for each case. Results. Univariate analysis of the factors for symptomatic byssinosis showed that dusty worksites, heavy smoking and duration of service 330 years were significant. Logistic regression analysis showed that working in the spinning (odds ratio 6.1) and weaving sections (odds ratio 1.9), heavy smoking (odds ratio 3.9) and 330 years of service (odds ratio 2.0) were independent significant risk factors. Conclusion. Efforts to reduce dust levels in the working environment and to discourage smoking among textile workers need to be strengthened to minimize the risk of developing byssinosis. Natl Med J India 2003;16:70–3 INTRODUCTION In 1956, an epidemiological study in the cotton industry in the UK documented the occurrence of byssinosis.1 Worldwide, India is the second largest producer of textile goods, which account for 20% of the national industrial output. Twenty million workers are employed in 1175 cotton mills across the country, representing a major occupational group.2 The Pondicherry region has around 8000 textile workers.3 Byssinosis has been reported from most countries with a textile industry. Its prevalence varied from 2% in the USA in the late 1970s4 to 63% in England in the late 1950s.5 While the prevalence is decreasing in developed countries, it continues to be high in developing countries. In Turkey it was 14.2% in the past decade.6 There are few studies on byssinosis among cotton textile workers in India.7–9 Murlidhar et al. examined 273 cotton textile workers in Mumbai and found that 54 of 179 workers (30%) in dusty sections and 16 of 94 workers (17%) in non-dusty sections had byssinosis. They also developed a questionnaire for the assessment of byssinosis.7 In Pondicherry, the textile industry is more than a century old but no study has assessed the magnitude of or the risk factors for byssinosis. We carried out a case–control study to find out the risk factors associated with the occurrence of byssinosis. SUBJECTS AND METHODS The Pondicherry Textile Corporation Limited has three textile mills. The largest and oldest is the AngloFrench Textiles, which has three units (A, B and C) with 6800 workers. We included all men >30 years of age who had been working in the factory for at least 10 years. The details of the sample studied are shown in Fig. 1. The analysis was done for 761 workers—96 from the spinning section, 503 from the weaving section and 162 from the non-dusty sections. We detected 150 cases of byssinosis, of whom 48 had associated chronic bronchitis. For the risk factor analysis, 102 cases with only symptomatic byssinosis were included. To choose controls a population of workers with neither byssinosis nor chronic bronchitis was selected (n=529). From this population, two age-matched (+2 years) controls were selected for each case of symptomatic byssinosis. Where more than two controls were available for a case, two controls were chosen by simple random sampling using the random number table. Chronic bronchitis was defined as ‘any person having cough with expectoration for >3 months in a year for >2 consecutive years’. All the sampled individuals were interviewed between October 1998 and March 2000 with the help of an interview schedule prepared by adopting the ATS-DLD-78 Questionnaire10 and the Byssinosis Questionnaire used by Murlidhar et al.7 Before the interview, an informed consent was obtained from each worker by explaining the nature of the study and the confidentiality of the information required. Information was collected on age, smoking behaviour, occupation, overcrowding and fuel used for cooking at home. Weight was accurately recorded using a standard weighing machine. Height was measured by a stadiometer. For the purpose of the study the WHO definition of byssinosis was used.9 For the type of fuel used, the predominant fuel used over the past year was considered. Those smoking >10 cigarettes or bidis per day for the last 20 years or more were considered heavy smokers (smoking index of 20 pack-years). Overcrowding was classified according to the number of persons per room. Pulmonary function tests done for all the workers included forced vital capacity (FVC), forced expiratory volume in the first second (FEV1) and FEV1/FVC. Three readings were taken after explaining and demonstrating the test procedure. The best of three readings was considered for analysis. The predicted value of FEV1 for the concerned population was calculated and 80% of the predicted value determined. Statistical analysis The data were analysed using EPI Info version 6.0 and SPSS (Statistical Package for Social Sciences) version 7.5. Chi-square and odds ratios (ORs) with 95% confidence intervals (CI) were calculated for univariate analysis. Subsequently, the significant factors on univariate analysis were entered into a logistic regression model and the adjusted ORs with 95% CI obtained. Independent sample t-test was used for the analysis of pulmonary function tests. Total workers in the factory=6800 Excluded=2800: Workers in C unit of factory, women, those <30 years of age and with a duration of exposure <10 years Remaining workers=4000 20% of this sample were taken=800 Distribution of this sample in different sections of the factory Spinning=110 Weaving=510 Non-dusty=180 Excluded=34: Those with chronic suppurative lung diseases such as tuberculosis and lung abscess, congestive cardiac failure and who refused consent Spinning=96 Weaving=508 Non-dusty=162 Died/retired=5