Passive smoking raises TB risk

Passive smoking increases the risk of Mycobacterium tuberculosis infection in children living with a tuberculosis patient at home. Tuberculosis and smoking are both significant public health problems. The possible association between passive smoking and TB infection in children is a cause of great concern, considering the high prevalence of smoking and tuberculosis in most developing countries. The researchers from the KNCV Tuberculosis Foundation, The Hague, Netherlands, conducted a community survey that included 15 percent of the addresses in two adjacent low- to middle-income suburbs in Cape Town. All children younger than 15 years of age and their adult household members living at the addresses were included in the study. All of the children received a tuberculin skin test, with a positive test defined as a subcutaneous response of at least 10 mm. The team defined passive smoking as living in a home with at least one adult who smoked for at least 1 year. A total of 1344 children were included in the analysis. Of these, 432 (32 percent) had a positive tuberculin skin test and 1170 (87 percent) were classified as passive smokers. The rate of a positive tuberculin skin test was 34 percent in children with a smoker at home compared with 21 percent in those who were not passive smokers; but this difference was not statistically significant. However, there was a significant association between passive smoking and a positive tuberculin skin test in the 172 households that had with a patient with tuberculosis. Children living in these conditions were nearly five-times as likely to test positive for exposure to TB bacilli. Passive smoking might affect the immune system of the child, thus increasing the risk of getting infected. Tobacco smoke exposure alters cell function, such as lowering the rate of clearance of inhaled substances and abnormal permeability of cells and blood vessels. In many developing countries with a high burden of tuberculosis, the prevalence of smoking is rapidly increasing, especially among women, and this is particularly worrisome, because they expose their children to tobacco smoke.