LAUSR

Occupational exposure to dusts and smoke is an important cause of chronic obstructive pulmonary disease (COPD) all over the world, including in the Indian subcontinent. A recent joint statement of the American Thoracic Society and European Respiratory Society on the burden of nonmalignant respiratory diseases indicates a population attributable factor of 14% for spirometry-defined COPD and 13% for chronic bronchitis (CB). The authors of a recently published systematic review and meta-analysis from India reported a 7% prevalence of COPD among the population aged 50 years and above; among others, biomass fuel exposure was an important risk factor. There was a 6.3 times higher risk of COPD among workers such as mechanics, cleaners and others with self-reported exposure to vapours, gas, dust, fume and smoke in their workplace than the non-exposed group in a small hospital-based study from Bangladesh. Recent reports from developed countries list industrial exposures to metal dusts, sand and synthetic resins and other dusts generated due to activities such as smelting, machine maintenance, casting and finishing as causes of occupational COPD. On the other hand, reports from India and several other countries in the subcontinent show exposures to household work, occupational and agricultural dusts and indoor and outdoor pollution as having a significant association with COPD (Table 1; Figure 1). Workers engaged in coal and silica mining, metal and foundry industries and textiles and cotton spinning are also reported to have a greater risk of COPD, in addition to the risks of pneumoconioses and other occupationally related lung diseases. COPD risk is also high among ad hoc workers engaged in unorganized sectors such as construction and other roadside works. There are occasional reports on spirometric and other lung function abnormalities as well as symptoms of CB in some categories of workers chronically exposed to fumes and smoke. Hindu priests working in the temples are exposed to the burning of incense sticks and other fire rituals (e.g., havan) almost constantly on a long-term basis. Transport workers, traffic police and street hawkers, chronically exposed to vehicular exhausts and fumes, may also suffer adverse effects. There are however limited data on these groups at present. Household work is often identified as a routine chore for women and therefore may not be listed as an important occupation. As per the national Census of India, it is a major occupation engaging about 160 million women and 6 million men in India. The Supreme Court of India has identified the value of women’s work at home as equal to that of office-going men. Household work often involves exposure to combustion of solid biomass fuels for cooking and heating in the Indian subcontinent and other lowand middle-income countries. In various global estimates, over one third of the total world population use these biomass fuels. This is particularly so in the rural and tribal areas, crowded suburban and slum areas of bigger cities and remotely located and hilly regions. Combustion of biomass fuel is an important risk factor of COPD. This is of particular concern among non-smoking subjects, especially women. In an earlier multicentre study from India, about 30% of patients with COPD were nonsmokers and most were exposed to the burning of biomass fuels such as crop residue and dried cattle dung in their kitchens. Several other studies report higher risk with an odds ratio greater than 1.5 associated with biomass fuels. In a large multi-country, prospective cohort, the Urban Rural Epidemiology (PURE) study on 91,350 adults aged 35–70 years, higher odds were reported for respiratory deaths or non-fatal COPD among people exposed to household air pollution after a median follow-up period of 9.1 years. A significant number of industrial and agricultural workers are exposed to both occupational dusts and tobacco smoking, thereby making it difficult to distinguish the clinical and morphological characteristics of occupationalrelated COPD from those of smoking-related COPD. Occupational COPD in non-smoking women has some distinct clinical and therapeutic features, predominantly suggesting a small airway disease which can be considered as a different clinical phenotype. Biomass and other non-smoking related occupational COPD is more likely to show eosinophilic T A B L E 1 Some of the important occupational causes of chronic obstructive pulmonary disease in the Indian subcontinent