Indoor Air Pollution and Susceptibility to Tuberculosis Infection in Urban Vietnamese Children

Abstract

Rationale: The Southeast Asian tuberculosis burden is high, and it remains unclear if urban indoor air pollution in this setting is exacerbating the epidemic. Objectives: To determine the associations of latent tuberculosis with common urban indoor air pollution sources (secondhand smoke, indoor motorcycle emissions, and cooking) in Southeast Asia. Methods: We enrolled child household contacts of patients with microbiologically confirmed active tuberculosis in Vietnam, from July 2017 to December 2019. We tested children for latent tuberculosis and evaluated air pollution exposures with questionnaires and personal aerosol sampling. We tested hypotheses using generalized estimating equations. Measurements and Main Results: We enrolled 72 patients with tuberculosis (27% with cavitary disease) and 109 of their child household contacts. Latent tuberculosis was diagnosed in 58 (53%) household contacts at baseline visit. Children experienced a 2.56-fold increased odds of latent tuberculosis for each additional household member who smoked (95% confidence interval, 1.27-5.16). Odds were highest among children exposed to indoor smokers and children <5 years old exposed to household smokers. Each residential floor above street-level pollution decreased the odds of latent tuberculosis by 36% (adjusted odds ratio, 0.64; 95% confidence interval, 0.42-0.96). Motorcycles parked inside children's homes and cooking with liquid petroleum gas compared with electricity increased the odds of latent tuberculosis, whereas kitchen ventilation decreased the effect, but these findings were not statistically significant. Conclusions: Common urban indoor air pollution sources were associated with increased odds of latent tuberculosis infection in child household contacts of patients with active tuberculosis.

Keywords: built environment; cooking; motorcycles; smoking water pipes; tobacco smoke pollution.

Figure 1.

Study catchment area in Hanoi, Vietnam. Shown are participant residences by LTBI diagnosis, together with DHC recruitment sites. Residences are jittered randomly up to 300 m in any direction, to protect confidentiality. DHC = District Health Center; LTBI = latent tuberculosis infection.

Figure 2.

Unadjusted odds (top) and adjusted odds (bottom) of LTBI by air pollution continuous exposure variables (n = 109). We fit a separate generalized estimating equation model for each indoor exposure, with LTBI as the outcome and each model adjusted for age, sex, body mass index z-score, and household employment. Two interactions were also tested with this model: 1) the interaction between HS and age of household contacts, P-interaction 0.12; and 2) the interaction between LPG cooking hours per day and active kitchen ventilation (hood above the cooking stove or fan in the kitchen window), P-interaction also 0.12. Units were expressed in number of HS; number of cigarettes or waterpipes smoked per day (in increments of 10); floor level lived and slept on; and hours of LPG use per day. Zero was the referent value for all variables except floor level, where ground (first floor) was the referent. The aOR represented the adjusted odds of LTBI for each unit increase of continuous exposure variable. For instance, for each additional household member who was a smoker, there was a 2.56-fold higher odds of LTBI in the household contact; and for each higher floor the household contact’s bedroom was located on, there was a 37% lower odds of LTBI. Continuous models should not be interpreted outside the range of observed exposure values (see Table 2 for observed exposure value ranges). aOR = adjusted odds ratio; CI = confidence interval; HS = household smokers; LPG = liquid petroleum gas; LTBI = latent tuberculosis infection; OR = odds ratio.