Biomass fuel and risk of tuberculosis: a case-control study from Northern India

Background Although a known risk factor for several respiratory diseases, the relationship between cooking smoke and tuberculosis has not been conclusively established. Hence, a case-control study was conducted among adult women of Chandigarh Union Territory in India. Methods Physician-diagnosed cases of sputum positive pulmonary tuberculosis (n=126) and age-and residence area-matched controls (n=252) were enrolled from clinics in urban, rural and slum areas. Interviews were conducted in the clinic using a pretested questionnaire to collect information on type of cooking fuel, education, occupation, socio-economic status, smoking, overcrowding and type of kitchen, etc. The conditional logistic regression model was used for control of confounding. Results The study population was predominantly in the 20-29-year-old age group (58%) and lived in urban areas (67%). The majority were illiterate (52%) and housewives (93%), and nearly half (46%) had an income of no more than Rs 25 000. Among the cases, 20.6%, 27% and 52.4% used biomass fuel, kerosene and liquid petroleum gas (LPG), respectively, whereas among controls, the respective figures were: 12.3%, 26.2% and 61.5%. The unadjusted OR for biomass fuel compared with LPG was 2.33 (95% CI 1.18 to 4.59, p 0.01). Adjustment for confounding factors (education, type of kitchen, smoking tobacco and TB in a family member) and interaction between cooking fuel and smoker in family revealed an OR of 3.14 (95% CI 1.15 to 8.56, p=0.02) for biomass fuel in comparison with LPG. Conclusions Cooking with biomass fuel increases the risk for pulmonary tuberculosis.