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Introduction Elevated levels of indoor air pollutants may cause cardiopulmonary disease such as lower respiratory infection, chronic obstructive lung disease and lung cancer, but the association with tuberculosis (TB) is unclear. So far the risk estimates of TB infection or/and disease due to indoor air pollution (IAP) exposure are based on self-reported exposures rather than direct measurements of IAP, and these exposures have not been validated. Objective The aim of this paper was to characterize and develop predictive models for concentrations of three air pollutants (PM 10 , NO 2 and SO 2 ) in homes of children participating in a childhood TB study. Methods Children younger than 15 years living within the eThekwini Municipality in South Africa were recruited for a childhood TB case control study. The homes of these children (n=246) were assessed using a walkthrough checklist, and in 114 of them monitoring of three indoor pollutants was also performed (sampling period: 24 h for PM 10 , and 2–3 weeks for NO 2 and SO 2 ). Linear regression models were used to predict PM 10 and NO 2 concentrations from household characteristics, and these models were validated using leave out one cross validation (LOOCV). SO 2 concentrations were not modeled as concentrations were very low. Results Mean indoor concentrations of PM 10 (n=105) , NO 2 (n=82) and SO 2 (n=82) were 64 μg/m 3 (range 6.6–241); 19 μg/m 3 (range 4.5–55) and 0.6 μg/m 3 (range 0.005–3.4) respectively with the distributions for all three pollutants being skewed to the right. Spearman correlations showed weak positive correlations between the three pollutants. The largest contributors to the PM 10 predictive model were type of housing structure (formal or informal), number of smokers in the household, and type of primary fuel used in the household. The NO 2 predictive model was influenced mostly by the primary fuel type and by distance from the major roadway. The coefficients of determination (R 2 ) for the models were 0.41 for PM 10 and 0.31 for NO 2 . Spearman correlations were significant between measured vs. predicted PM 10 and NO 2 with coefficients of 0.66 and 0.55 respectively. Conclusion Indoor PM 10 levels were relatively high in these households. Both PM 10 and NO 2 can be modeled with a reasonable validity and these predictive models can decrease the necessary number of direct measurements that are expensive and time consuming. [ABSTRACT FROM AUTHOR]

Background: Crude measures of exposure to indicate indoor air pollution have been associated with the increased risk for acquiring tuberculosis. Our study aimed to determine an association between childhood pulmonary tuberculosis (PTB) and exposure to indoor air pollution (IAP), based on crude exposure predictors and directly sampled and modelled pollutant concentrations., Methods: In this case control study, children diagnosed with PTB were compared to children without PTB. Questionnaires about children's health; and house characteristics and activities (including household air pollution) and secondhand smoke (SHS) exposure were administered to caregivers of participants. A subset of the participants' homes was sampled for measurements of PM 10 over a 24-h period (n = 105), and NO 2 over a period of 2 to 3 weeks (n = 82). IAP concentrations of PM 10 and NO 2 were estimated in the remaining homes using predictive models. Logistic regression was used to look for association between IAP concentrations, crude measures of IAP, and PTB., Results: Of the 234 participants, 107 were cases and 127 were controls. Pollutants concentrations (μg/m 3 ) for were PM 10 median: 48 (range: 6.6-241) and NO 2 median: 16.7 (range: 4.5-55). Day-to-day variability within- household was large. In multivariate models adjusted for age, sex, socioeconomic status, TB contact and HIV status, the crude exposure measures of pollution viz. cooking fuel type (clean or dirty fuel) and SHS showed positive non-significant associations with PTB. Presence of dampness in the household was a significant risk factor for childhood TB acquisition with aOR of 2.4 (95% CI: 1.1-5.0). The crude exposure predictors of indoor air pollution are less influenced by day-to-day variability. No risk was observed between pollutant concentrations and PTB in children for PM 10 and NO 2 ., Conclusion: Our study suggests increased risk of childhood tuberculosis disease when children are exposed to SHS, dirty cooking fuel, and dampness in their homes. Yet, HIV status, age and TB contact are the most important risk factors of childhood PTB in this population.