Household fuel use and pulmonary tuberculosis in central
Household fuel use and pulmonary tuberculosis in central Nepal: A case-control study. Michael N. Bates, Ph. D School of Public Health University of California, Berkeley
Household solid fuel use v For cooking and space-heating, about 3 billion people, mainly in developing countries and rural settings, use solid fuels: v 2. 4 billion--biomass (wood, charcoal, crop residues and animal dung) v 0. 6 billion—coal v About 1. 1 billion smokers worldwide 2
Traditional Biomass Stoves 3
TB risk factors include: n n n n n HIV Immune suppression Diabetes mellitus Crowding Contact with TB case Alcoholism Silicosis Malnutrition Active tobacco smoking Household solid fuel use? 5
Published biomass and TB disease study results, 2010 Biomass-TB study results 6
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Overall study objectives To determine whether the following are risk factors for (1) M. tuberculosis infection or (2) pulmonary TB disease: 1. biomass fuel used for cooking or heating indoors 2. kerosene used as a cooking or lighting fuel indoors 8
Study design n Case-control study in Kaski and surrounding districts, central Nepal. n Cases: 581 pulmonary TB disease Controls: 1, 226 frequency matched by VDC or urban ward, population-based (both men and women). n n Anyone previously diagnosed with TB excluded from both case and control groups. n Comprehensive investigation of household fuel use: u u u n cooking (LPG, wood, biogas) and secondary stoves heating lighting Extensive questionnaire to all participants. 9
Conditional logistic regression results for cooking (women only: 191 cases and 649 controls) Odds ratio* 95% Confidence interval Primary stove LPG 1. 00 - Biogas 0. 21 0. 05, 1. 00 Wood 0. 17 0. 07, 0. 41 No 1. 00 - Yes 1. 55 0. 44, 5. 46 Biogas No 1. 00 - Yes 0. 47 0. 13, 1. 71 No 1. 00 - Yes 0. 80 0. 34, 1. 90 Secondary stoves LPG Wood *Adjusted for age, marital status, income, worked overseas, education, literacy, religion, caste, land ownership, kitchen location, home ownership, household crowding, smoking status, household owns means of transport, use of non-fuel lights, alcohol consumption, family member with TB in last 10 years. 10
Random-effects meta-analysis of all other TBcookstove studies, ordered by publication year, 2017.
Meta-analysis of other studies of cookstoves and pulmonary TB n Restricted to studies comparing biomass with gas (reference category) That is, excluded studies: u Where different frequencies of biomass cooking were compared (N=2) u When almost all participants used solid fuel (N=1) u When either fuel category contained kerosene (N=2) n n Results for women used if available; if not, used combined results for men and women. Stratified according to whether prior TB cases excluded or not. 12
Random-effects meta-analysis of studies stratified by prior TB exclusion status Prior TB excluded Prior TB not excluded
Possible reasons for the difference between LPG and biogas n Composition u LPG is propane and butane u Biogas is methane and CO 2 n Time of cook in kitchen when cooking 14
Women-time in kitchen during cooking, by primary stove type (data from a different ongoing study in Kaski district). Time in kitchen LPG stove Biogas stove Wood stove Total N (%) All or most. 112 (29. 5) 3 (5. 1) 32 (35. 6) 147 (27. 8) Some. 245 (64. 5) 53 (89. 8) 51 (56. 7) 349 (66. 0) Little or none. 22 (6. 1) 3 (5. 1) 6 (6. 7) 32 (6. 0) Outside kitchen. 0 0 1 (1) 1 (0. 2) Total. 380 (100) 59 (100) 90 (100) 529 (100) 15
Women-time in kitchen during cooking, by primary stove type (data from a different ongoing study in Kaski district). Time in kitchen LPG stove Biogas stove Wood stove Total N (%) All or most. 112 (29. 5) 3 (5. 1) 32 (35. 6) 147 (27. 8) Some. 245 (64. 5) 53 (89. 8) 51 (56. 7) 349 (66. 0) Little or none. 22 (6. 1) 3 (5. 1) 6 (6. 7) 32 (6. 0) Outside kitchen. 0 0 1 (1) 1 (0. 2) Total. 380 (100) 59 (100) 90 (100) 529 (100) 16
Main conclusions n Cooking with LPG appears to be a risk factor for TB in people who have not previously had (pulmonary) TB. The mechanism is unclear, but might involve ultrafine particles. n Lung damage from previous TB appears to increases pulmonary TB risk from biomass smoke. n Cooking with biogas seems to be less of a TB risk factor in people without prior TB than cooking with LPG. 17
Funding National Institute of Environmental Health Sciences of the National Institutes of Health (grant number R 01 ES 019624). n 18
Thanks to the following: United States Nepal n Ellen Eisen n Ambika Baniya n Laura Flores n Avash Bhandari n Phil Hopewell n Dirgha Ghimire n Nick Lam n Krishna Ghimire n Ajay Pillarisetti n Birenda Kunwar n Amod Pokhrel n Madhu Maya Pahari n Karl Pope n Ramesh Kumar Rijal n Lee Riley n Tula Ram Sijali n Kirk Smith n Sharat Verma 19 And many more…
Thank you!
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