Should interventions to reduce respirable pollutants be linked to tuberculosis control programmes?
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《英国医生杂志》
1 World Bank, Washington DC, USA, 2 Department of Population and International Health, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115, USA
Correspondence to: M Ezzati mezzati@hsph.harvard.edu
The potential benefits of linking tuberculosis control programmes with interventions to reduce smoking and indoor air pollution make research to improve our understanding of their relation a high priority
Introduction
The existence of a causal association alone, even if confirmed in subsequent studies, would have limited implications for public health interventions and policies. Even excluding tuberculosis, mortality and disease burden attributable to both smoking and indoor air pollution places them among leading global health concerns, persistently and increasingly affecting the poor.1 2 Therefore, establishing a causal link with tuberculosis will add little to the already strong arguments for reducing these two risk factors.
Neither can interventions for smoking and indoor air pollution be used as key elements of tuberculosis control, because tuberculosis control cannot rely on any single risk factor whose role in disease aetiology and transmission dynamics is highly dependent on multiple other factors, with heterogeneity across populations or over time. This is in contrast to diseases like chronic obstructive pulmonary disease, for which a reduction in exposure to airborne pollutants would reduce disease in nearly all circumstances. The core of national or regional tuberculosis control programmes therefore has unequivocally been, and should remain, interventions that can reduce and eventually interrupt transmission under relatively generalisable circumstances—that is, the directly observed treatment, short-course (DOTS) strategy.12 13
The effectiveness and coverage of DOTS, however, has been constrained by obstacles such as cost, physical and human infrastructure, and compliance of users or providers, which have limited case detection and completion of treatment.3 12-14 Hence, it is widely acknowledged that achieving higher case detection rates under DOTS requires participation outside health systems,12-14 but the nature of this participation needs to be better defined in different populations. A causal relation with respirable pollutants might provide a possible mechanism for such participation. Before attempting to link the two public health interventions, however, we need a better understanding of the aetiological relation between respirable pollutants and tuberculosis.
Implications of different possible mechanisms of association
China had an estimated 1.4 million new cases of tuberculosis in 2000, more than any country except India.16 China made substantial progress in expanding DOTS in the 1990s in 13 provinces, municipalities, and autonomous regions.16 Nevertheless, case detection and completion of treatment remain important challenges in poor rural areas.17
Nearly 80% of China's population relies on biomass (wood, crop residues, and animal dung) and coal for cooking and heating.18 China also has one of the highest levels of tobacco consumption in the world, with more than 60% of men smoking.8 The two risk factors, both increasingly concentrated in rural populations, magnify one another's effects, resulting in high levels of respiratory diseases among Chinese adults.1 2 8 The Chinese improved (high efficiency and low emissions) stove programme has primarily targeted exposure during cooking (figure).19 Home heating remains an important route of exposure, as does the absence of improved stove programmes in the poorest provinces and communities.
Biomass burning stove in rural China
Credit: HUAXI SCHOOL OF PUBLIC HEALTH, SICHUAN UNIVERSITY
Two important characteristics of new indoor air pollution programmes in poor communities are targeting solid fuel use and cigarettes as sources of airborne pollutants and combining clean fuels and stoves with health education among adults and children. Linking tuberculosis control to rural energy and health programmes as described above could in principle increase case detection and ultimately the coverage and community effectiveness of DOTS.
Research needs
World Health Organization. World health report 2002: reducing risks, promoting healthy life. Geneva: WHO, 2002.
Ezzati M, Lopez AD, Rodgers A, Vander Hoorn S, Murray CJL, Comparative Risk Assessment Collaborative Group. Selected major risk factors and global and regional burden of disease. Lancet 2002;360: 1347-60.
Frieden TR, Sterling TR, Munsiff SS, Watt CJ, Dye C. Tuberculosis. Lancet 2003;362: 887-99.
Gajalakshmi V, Peto R, Kanaka TS, Jha P. Smoking and mortality from tuberculosis and other diseases in India: retrospective study of 43 000 adult male deaths and 35 000 controls. Lancet 2003;362: 507-15.
Kolappan C, Gopi PG. Tobacco smoking and pulmonary tuberculosis. Thorax 2002;57: 964-6.
Lam TH, Ho SY, Hedley AJ, Mak KH, Peto R. Mortality and smoking in Hong Kong: case-control study of all adult deaths in 1998. BMJ 2001;323: 361-3.
Leung CC, Yew WW, Chan CK, Tam CM, Lam CW, Chang KC, et al. Smoking and tuberculosis in Hong Kong. Int J Tuberc Lung Dis 2003;7: 980-6.
Liu BQ, Peto R, Chen ZM, Boreham J, Wu YP, Li JY, et al. Emerging tobacco hazards in China: 1. Retrospective proportional mortality study of one million deaths. BMJ 1998;317: 1411-22.
Mishra VK, Retherford RD, Smith KR. Biomass cooking fuels and prevalence of tuberculosis in India. Int J Infect Dis 1999;3: 119-29.
Perez-Padilla R, Perez-Guzman C, Baez-Saldana R, Torres-Cruz A. Cooking with biomass stoves and tuberculosis: a case control study. Int J Tuberc Lung Dis 2001;5: 1-7.
Thomas P, Zelikoff J. Air pollutants: moderators of pulmonary host resistance against infection. In: Holgate ST, Samet JM, Koren HS, Maynard RL, eds. Air pollution and health. San Diego, CA: Academic Press, 1999.
Dye C, Watt CJ, Bleed DM. Low access to a highly effective therapy: a challenge for international tuberculosis control. Bull World Health Organ 2002;80: 437-44.
Raviglione MC, Pio A. Evolution of WHO policies for tuberculosis control, 1948-2001. Lancet 2002;359: 775-80.
Dye C, Watt CJ, Bleed DM, Williams BG. What is the limit to case detection under the DOTS strategy for tuberculosis control? Tuberculosis 2003;83: 35-43.
Squire SB, Wilkinson D. Strengthening "DOTS" through community care for tuberculosis. BMJ 1997;315: 1395-6.
China Tuberculosis Control Collaboration. The effect of tuberculosis control in China. Lancet 2004;364: 417-22.
Squire SB, Tang S. How much of China's success in tuberculosis control is really due to DOTS? Lancet 2004;364: 391-2.
Florig HK. China's air pollution risks. Environ Sci Tech 1997;31: 274-9A.
Smith KR, Shuhua G, Kun H, Daxiong Q. One hundred million improved cookstoves in China: how was it done? World Development 1993;21: 941-61.
Raviglione MC, Dye C, Schmidt S, Kochi A. Assessment of worldwide tuberculosis control. WHO global surveillance and monitoring project. Lancet 1997;350: 624-9.(Enis Baris, senior public)
Correspondence to: M Ezzati mezzati@hsph.harvard.edu
The potential benefits of linking tuberculosis control programmes with interventions to reduce smoking and indoor air pollution make research to improve our understanding of their relation a high priority
Introduction
The existence of a causal association alone, even if confirmed in subsequent studies, would have limited implications for public health interventions and policies. Even excluding tuberculosis, mortality and disease burden attributable to both smoking and indoor air pollution places them among leading global health concerns, persistently and increasingly affecting the poor.1 2 Therefore, establishing a causal link with tuberculosis will add little to the already strong arguments for reducing these two risk factors.
Neither can interventions for smoking and indoor air pollution be used as key elements of tuberculosis control, because tuberculosis control cannot rely on any single risk factor whose role in disease aetiology and transmission dynamics is highly dependent on multiple other factors, with heterogeneity across populations or over time. This is in contrast to diseases like chronic obstructive pulmonary disease, for which a reduction in exposure to airborne pollutants would reduce disease in nearly all circumstances. The core of national or regional tuberculosis control programmes therefore has unequivocally been, and should remain, interventions that can reduce and eventually interrupt transmission under relatively generalisable circumstances—that is, the directly observed treatment, short-course (DOTS) strategy.12 13
The effectiveness and coverage of DOTS, however, has been constrained by obstacles such as cost, physical and human infrastructure, and compliance of users or providers, which have limited case detection and completion of treatment.3 12-14 Hence, it is widely acknowledged that achieving higher case detection rates under DOTS requires participation outside health systems,12-14 but the nature of this participation needs to be better defined in different populations. A causal relation with respirable pollutants might provide a possible mechanism for such participation. Before attempting to link the two public health interventions, however, we need a better understanding of the aetiological relation between respirable pollutants and tuberculosis.
Implications of different possible mechanisms of association
China had an estimated 1.4 million new cases of tuberculosis in 2000, more than any country except India.16 China made substantial progress in expanding DOTS in the 1990s in 13 provinces, municipalities, and autonomous regions.16 Nevertheless, case detection and completion of treatment remain important challenges in poor rural areas.17
Nearly 80% of China's population relies on biomass (wood, crop residues, and animal dung) and coal for cooking and heating.18 China also has one of the highest levels of tobacco consumption in the world, with more than 60% of men smoking.8 The two risk factors, both increasingly concentrated in rural populations, magnify one another's effects, resulting in high levels of respiratory diseases among Chinese adults.1 2 8 The Chinese improved (high efficiency and low emissions) stove programme has primarily targeted exposure during cooking (figure).19 Home heating remains an important route of exposure, as does the absence of improved stove programmes in the poorest provinces and communities.
Biomass burning stove in rural China
Credit: HUAXI SCHOOL OF PUBLIC HEALTH, SICHUAN UNIVERSITY
Two important characteristics of new indoor air pollution programmes in poor communities are targeting solid fuel use and cigarettes as sources of airborne pollutants and combining clean fuels and stoves with health education among adults and children. Linking tuberculosis control to rural energy and health programmes as described above could in principle increase case detection and ultimately the coverage and community effectiveness of DOTS.
Research needs
World Health Organization. World health report 2002: reducing risks, promoting healthy life. Geneva: WHO, 2002.
Ezzati M, Lopez AD, Rodgers A, Vander Hoorn S, Murray CJL, Comparative Risk Assessment Collaborative Group. Selected major risk factors and global and regional burden of disease. Lancet 2002;360: 1347-60.
Frieden TR, Sterling TR, Munsiff SS, Watt CJ, Dye C. Tuberculosis. Lancet 2003;362: 887-99.
Gajalakshmi V, Peto R, Kanaka TS, Jha P. Smoking and mortality from tuberculosis and other diseases in India: retrospective study of 43 000 adult male deaths and 35 000 controls. Lancet 2003;362: 507-15.
Kolappan C, Gopi PG. Tobacco smoking and pulmonary tuberculosis. Thorax 2002;57: 964-6.
Lam TH, Ho SY, Hedley AJ, Mak KH, Peto R. Mortality and smoking in Hong Kong: case-control study of all adult deaths in 1998. BMJ 2001;323: 361-3.
Leung CC, Yew WW, Chan CK, Tam CM, Lam CW, Chang KC, et al. Smoking and tuberculosis in Hong Kong. Int J Tuberc Lung Dis 2003;7: 980-6.
Liu BQ, Peto R, Chen ZM, Boreham J, Wu YP, Li JY, et al. Emerging tobacco hazards in China: 1. Retrospective proportional mortality study of one million deaths. BMJ 1998;317: 1411-22.
Mishra VK, Retherford RD, Smith KR. Biomass cooking fuels and prevalence of tuberculosis in India. Int J Infect Dis 1999;3: 119-29.
Perez-Padilla R, Perez-Guzman C, Baez-Saldana R, Torres-Cruz A. Cooking with biomass stoves and tuberculosis: a case control study. Int J Tuberc Lung Dis 2001;5: 1-7.
Thomas P, Zelikoff J. Air pollutants: moderators of pulmonary host resistance against infection. In: Holgate ST, Samet JM, Koren HS, Maynard RL, eds. Air pollution and health. San Diego, CA: Academic Press, 1999.
Dye C, Watt CJ, Bleed DM. Low access to a highly effective therapy: a challenge for international tuberculosis control. Bull World Health Organ 2002;80: 437-44.
Raviglione MC, Pio A. Evolution of WHO policies for tuberculosis control, 1948-2001. Lancet 2002;359: 775-80.
Dye C, Watt CJ, Bleed DM, Williams BG. What is the limit to case detection under the DOTS strategy for tuberculosis control? Tuberculosis 2003;83: 35-43.
Squire SB, Wilkinson D. Strengthening "DOTS" through community care for tuberculosis. BMJ 1997;315: 1395-6.
China Tuberculosis Control Collaboration. The effect of tuberculosis control in China. Lancet 2004;364: 417-22.
Squire SB, Tang S. How much of China's success in tuberculosis control is really due to DOTS? Lancet 2004;364: 391-2.
Florig HK. China's air pollution risks. Environ Sci Tech 1997;31: 274-9A.
Smith KR, Shuhua G, Kun H, Daxiong Q. One hundred million improved cookstoves in China: how was it done? World Development 1993;21: 941-61.
Raviglione MC, Dye C, Schmidt S, Kochi A. Assessment of worldwide tuberculosis control. WHO global surveillance and monitoring project. Lancet 1997;350: 624-9.(Enis Baris, senior public)