Air pollutants and the risk of TB

A study investigated whether exposure to household air pollutants (HAP), particularly fine particulate matter (PM2.5) and carbon monoxide (CO), from cooking and lighting behaviors is linked to an increased risk of active tuberculosis (TB). The researchers hypothesized that kerosene and biomass fuel use elevate HAP levels, which mediate TB risk. A hospital and community-based case–control study was conducted in five peri-urban, high-density suburbs of Lilongwe, Malawi. Cases included female TB patients on treatment, while controls were age-matched female cooks without TB from neighboring households. Data collection incorporated structured interviews, health measurements (e.g., BMI and HIV status), and personal exposure monitoring for PM2.5 and CO.[1] See also: https://tbreadingnotes.blogspot.com/2024/08/immunologic-metabolic-and-genetic.html

The study reported that PM2.5 exposure levels among participants (average 170 µg/m³) far exceeded the WHO guideline of 25 µg/m³, with even higher concentrations observed in cooking areas of case households. Kerosene lighting was significantly associated with TB risk (odds ratio [OR] 3.73), and this relationship was partially mediated by increased PM2.5 (16.8%). Conversely, while biomass cooking was linked to elevated PM2.5 and CO levels, no statistically significant association with TB was identified. Other factors, including lower BMI, HIV positivity, and advanced age, were independently associated with increased TB risk, and area PM2.5 emerged as a strong contributor to TB odds (OR 6.74).[1] See also: https://tbreadingnotes.blogspot.com/2024/10/type-2-diabetes-mellitus-and-recurrent.html

The findings suggest that reducing kerosene use and improving home ventilation could help mitigate TB risk by lowering HAP exposure, particularly PM2.5. Although no significant connection between biomass cooking and TB was observed, the study underscores the need for additional research with larger sample sizes to better understand these relationships. The results partially support the hypothesized mediating role of HAP in TB risk and emphasize the importance of addressing environmental exposures in TB prevention strategies.[1] See also: https://tbreadingnotes.blogspot.com/2024/10/quantifying-global-number-of.html

A study found that increased concentrations of PM2.5, PM10, and NO2 are associated with higher TB risk, with no significant modifying effects of sex or age. PM2.5 and PM10 facilitate Mycobacterium tuberculosis colonization in deep lung tissues, disrupt iron balance in respiratory cells, and promote alveolar cell senescence, reducing the effectiveness of antimicrobial peptides (HBD-2 and HBD-3) while enhancing intracellular M. tb growth. PM exposure also impairs antibacterial T-cell immune function. NO2 exposure damages airway mucosa and ciliary clearance, enabling pathogen entry, and prolonged exposure suppresses pro-inflammatory cytokine expression, weakening host resistance to M. tb. While satellite-based air pollutant data may not accurately represent individual exposure levels, the findings suggest that reducing air pollution could play a crucial role in TB prevention and control.[2] See also: https://tbreadingnotes.blogspot.com/2024/08/yield-and-efficiency-of-population.html

Progress toward ending tuberculosis (TB) has been highly uneven across countries, with some achieving substantial mortality reductions while others struggle due to frail health systems, underinvestment, and inflexible approaches. High-burden countries face persistent challenges in case finding and diagnosis, as only 38% of TB cases were tested using WHO-recommended rapid molecular diagnostics in 2021. Most TB deaths occur in just eight countries, with over half concentrated in India, Indonesia, and Nigeria. Despite these challenges, some sub-Saharan African countries have demonstrated that rapid declines in TB mortality are possible with existing tools, underscoring the importance of focused interventions and system strengthening.[3]

Innovations in TB diagnostics and treatments hold promise but face slow adoption due to barriers like cost, infrastructure limitations, and regulatory hurdles. Advances such as oral swabs, urine antigen tests, and AI-assisted chest x-rays could improve case detection, particularly in asymptomatic or high-risk populations. Shorter treatment regimens for drug-susceptible and multidrug-resistant TB have improved outcomes and reduced healthcare demands, yet high costs and limited access to essential drugs like bedaquiline hinder widespread adoption. Additionally, preventive treatment strategies such as shorter TPT regimens show potential to reduce TB incidence but are constrained by logistical and regulatory gaps.[3] See also: Lin TB Lab

Addressing social and environmental determinants of TB is critical, particularly in light of the role of air pollution, undernutrition, and food insecurity in increasing TB risk. Undernutrition has been identified as the leading risk factor since 2009, emphasizing the need for nutritional support for patients and households. Investments in TB programs, including the development of new vaccines and better diagnostic tools, could not only reduce TB-related mortality but also yield significant societal benefits. However, achieving the Sustainable Development Goals (SDGs) for TB will require sustained international funding, equitable resource allocation, and the integration of TB care into broader health and social development frameworks.[3]

Tuberculosis (TB) remains the leading infectious cause of adult deaths globally, with over 10 million new cases annually, largely driven by poverty, overcrowding, and poor living conditions. Advances such as rapid molecular testing and whole-genome sequencing have improved TB diagnosis and drug resistance detection, while new drugs like bedaquiline and delamanid have transformed drug-resistant TB care with shorter, all-oral regimens. However, treatment for drug-susceptible TB remains reliant on the standard 6-month regimen, and the BCG vaccine provides limited protection for adults, spurring the development of new vaccines and shorter latent TB treatments. WHO emphasizes patient-centered care, including socioeconomic support like cash transfers, to reduce barriers and improve outcomes. Despite technological advances, reducing TB morbidity, mortality, and stigma requires stronger political commitment, equitable access to high-quality healthcare, and targeted efforts to address the social determinants of the disease.[4]

References:

1. Jagger, P., McCord, R., Gallerani, A., Hoffman, I., Jumbe, C., Pedit, J., Phiri, S., Krysiak, R. and Maleta, K., 2024. Household air pollution exposure and risk of tuberculosis: a case–control study of women in Lilongwe, Malawi. BMJ Public Health, 2(1).

2. Lu, J.W., Mao, J.J., Zhang, R.R., Li, C.H., Sun, Y., Xu, W.Q., Zhuang, X., Zhang, B. and Qin, G., 2023. Association between long-term exposure to ambient air pollutants and the risk of tuberculosis: A time-series study in Nantong, China. Heliyon, 9(6).

3. Reid, M., Agbassi, Y.J.P., Arinaminpathy, N., Bercasio, A., Bhargava, A., Bhargava, M., Bloom, A., Cattamanchi, A., Chaisson, R., Chin, D. and Churchyard, G., 2023. Scientific advances and the end of tuberculosis: a report from the Lancet Commission on Tuberculosis. The Lancet, 402(10411), pp.1473-1498.

4. Furin, J., Cox, H., & Pai, M. (2019). Tuberculosis. Lancet (London, England), 393(10181), 1642–1656.