Despite significant progress in reducing incidence and mortality, India’s fight against tuberculosis cannot succeed without addressing air pollution, a critical but overlooked driver of transmission and poor treatment outcomes.
Image Source: Freepik
India’s fight against tuberculosis (TB) spans from early mentions in ancient scriptures and foundational Ayurvedic literature to the 21st century. Despite being a preventable and treatable disease, its eradication is a challenge. TB is the largest contributor to deaths worldwide from a single infectious agent. Between 2015 and 2023, India saw an 18 percent decline in TB incidence from 237 to 195 cases per 100,000 population – outpacing the global average by double. Simultaneously, mortality declined by 21 percent from 28 to 22 per 100,000 population. However, India continues to have the highest (26 percent) TB burden globally.
According to the World Health Organization (WHO), several factors contribute to the burden of TB, including broader socio-economic determinants and other risk factors linked to health. The primary factors include the mycobacterium tuberculosis (MTB) strain factor (gene mutation, drug-resistant MTB), host factors such as genetics, history of contact, malnutrition, dual infections and co-morbid conditions, socio-economic factors including population density, immigration, stigmatisation, and health resources allocation among others, and environmental factors including temperature, pressure, and precipitation. However, emerging evidence points to another determinant of TB transmission, progression, and treatment outcomes – air pollution.
In 2025, the WHO acknowledged the link between air pollution and TB. The increasing exposure to pollutants above acceptable thresholds for the majority of the population worldwide can not only alter lung function by inducing oxidative stress and inflammation and weaken immune responses, but also allow particulate matter (PM) to act as carriers of airborne MTB, thereby increasing vulnerability to TB.
Various studies indicate that both short-term and long-term exposure to air pollutants increases the susceptibility to an MTB infection and progression to active disease. Research has long established the link between indoor air pollution (IAP) and the incidence of TB. Emerging evidence is increasingly recognising outdoor air pollution (OAP) as a contributor to TB as well.
In 2025, the WHO acknowledged the link between air pollution and TB. The increasing exposure to pollutants above acceptable thresholds for the majority of the population worldwide can not only alter lung function by inducing oxidative stress and inflammation and weaken immune responses, but also allow particulate matter (PM) to act as carriers of airborne MTB, thereby increasing vulnerability to TB.
1. Incidence
Research indicates that exposure to both IAP and OAP can contribute to an increase in active TB cases, particularly pulmonary TB (PTB). Of the total incidence of TB globally in 2024, an estimated 81 percent of cases were found to have PTB. A 2021 meta-analysis found that long-term exposure to air pollutants was associated with higher TB incidence. Specifically, for every 10 μg/m³ rise in particulate matter with an aerodynamic diameter ≤10 μm (PM10) concentrations, the relative risk of TB increased by 5.8 percent. Similarly, a 1 ppb increase in sulphur dioxide (SO2) and nitrogen dioxide (NO2) was associated with a 1.6 percent and 1.0 percent rise in TB incidence, respectively.
Air pollutants, such as PM2.5, PM10 and SO2, when inhaled, dampen natural defence barriers of the respiratory tract. IAP has been found to be associated with TB risk as well, with solid fuel and kerosene use for heating and cooking purposes associated with a higher likelihood of active TB.
A study from China found a lagged relationship between air pollution and PTB incidence. Increases in PM2.5, NO2, SO2 and carbon monoxide (CO) were associated with a rise in PTB incidence after a lag of three months, while exposure to ozone (O3) was linked to an increase within the same month. For PM10, the increase in incidence appeared after a lag of around nine months. A 2020 study from Korea further indicated that the relationship between exposure to PM10 and TB incidence strengthened with longer durations of exposure.
2. Treatment Outcomes, Disease Progression and Drug-Resistant Tuberculosis
Associations have been found between exposure to air pollutants and unfavourable treatment outcomes as well – including recurrent morbidity, disability, and mortality – limiting the effectiveness of TB treatment. Pollutants impairing the host’s lung immunity may also create a biologically favourable environment for the reactivation of MTB.
Additionally, a study found that high exposure to PM2.5, PM10 and CO was significantly associated with an increased incidence of MDR. Short-term exposure to air pollutants can aggravate drug-resistant tuberculosis (DR-TB) symptoms; particularly, NO2 exposure was associated with a 15.9 percent higher risk of a first-time outpatient visit for acute DR-TB exacerbations.
Women and children in solid-fuel-dependent households are particularly vulnerable and face higher susceptibility to TB. Climate change is expected to worsen these challenges, not only through higher exposure to pollutants, but also through extreme weather events and increasing outdoor pollution, driving people indoors, often in poorly ventilated spaces.
The cumulative risk of PM10 on TB-associated mortality can be seen even with exposure to concentrations as low as 15 μg/m³, and long-term exposure can be of significant harm to MDR patients, with effects varying with temperature and humidity levels. Additionally, a study found that higher concentrations of air pollutants in the living environment of newly treated TB patients were associated with greater risks of death as well.
3. Vulnerable Populations and Risk Stratification
According to the WHO, IAP from burning solid fuels disproportionately affects those from weaker socio-economic backgrounds. Women and children in solid-fuel-dependent households are particularly vulnerable and face higher susceptibility to TB. Climate change is expected to worsen these challenges, not only through higher exposure to pollutants, but also through extreme weather events and increasing outdoor pollution, driving people indoors, often in poorly ventilated spaces.
Stratified analysis also showed that elderly patients (≥65 years) and those with a history of TB treatment are more vulnerable to the effects of air pollution. Specifically, SO₂ exposure was linked to symptom flare-ups among the elderly. Other vulnerable populations may include communities that face the double burden of both high TB prevalence and exposure to air pollution, such as the urban poor. This is especially true for slum dwellers in megacities, who face a five-fold risk of TB in India and are regularly exposed to air pollutants.
Even though tribal populations comprise about 8.4 percent of India’s population, 63 percent of 170 tribal districts report TB rates above the national average, and continue to remain marginalised, despite schemes such as the Pradhan Mantri Ujjwala Yojana (PMUY) to reduce IAP, with Scheduled Tribes found to benefit the least from PMUY, limiting reductions in IAP.
All of India is exposed to unhealthy levels of PM2.5. In 2019 alone, 1.67 million deaths (17.8 percent of all deaths) in India were attributed to air pollution. Additionally, 40 percent of the Indian population is estimated to be infected with MTB. Decades of unrestrained transmission have left many Indians with latent TB infection (LTBI). Further, according to the WHO, India hosted 27 percent of the global multidrug-resistant tuberculosis (MDR) cases in 2023. Together, this presents a major obstacle for TB eradication, with poor air quality increasing the likelihood of LTBI reactivation.
While TB shares social determinants and comorbidity risks with a range of health conditions — including Human Immunodeficiency Virus (HIV) and diabetes — the relative burden in India underscores a policy gap. HIV dramatically increases the risk of developing active TB (by around eightfold), but People Living with HIV (PLHIV) account for just 5 percent of new TB cases each year (about 100,000 cases), even as TB contributes to 25 percent of deaths among this population. Diabetes is linked to 10 percent of TB cases globally.
Decades of unrestrained transmission have left many Indians with latent TB infection (LTBI). Further, according to the WHO, India hosted 27 percent of the global multidrug-resistant tuberculosis (MDR) cases in 2023. Together, this presents a major obstacle for TB eradication, with poor air quality increasing the likelihood of LTBI reactivation.
In contrast, approximately 26 percent of all TB cases are attributed to IAP. Meanwhile, the impact of OAP is still being studied. Although India’s response to HIV- and diabetes-associated TB, along with other determinants of TB, has been robust, the impact of air pollution on TB merits greater integration into elimination strategies.
India’s remarkable progress in combating tuberculosis can be attributed to the long-standing commitment of the state to eradicating it. In 1962, India launched the National TB Programme (NTP), followed by the Revised National Tuberculosis Control Programme (RNTCP) in 1997, which was renamed in 2020 as the National Tuberculosis Elimination Program (NTEP) after the government’s 2018 declaration of ‘TB-Mukt Bharat’ (TB-Free India) by 2025 – five years ahead of the United Nations Sustainable Development Goals (UN-SDGs) target of ending the TB epidemic by 2030, to which India is a signatory.
To bolster efforts and tackle the problem of missing cases, India launched the ‘100 Day TB Elimination’ campaign in December 2024, aimed at initiating early treatment and preventing deaths. Resultantly, 129.7 million vulnerable individuals were screened, and 0.719 million new TB cases were detected. While the overall progress in TB reduction has been commendable, in absolute numbers, the TB burden is still significant and far from the target of 44 new cases per 100,000 population.
As India develops its strategy for last-mile efforts in TB eradication, the approach should be broadened to consider TB within the context of wider lung health challenges – where air pollutants play a significant role in disease transmission, progression, and mortality.
Currently, the National Strategic Plan for Tuberculosis: 2017-15 (NSP 2017-25) lists indoor air pollution as a determinant of TB, and discusses efforts under the Pradhan Mantri Ujjwala Yojana (PMUY), which provides LPG connections to low-income households dependent on solid fuels to improve indoor air quality and reduce the incidence of TB. However, despite the increasing number of connections under PMUY, refill rates remain low among the beneficiaries. Moreover, there is no explicit framework to tackle TB in the context of air pollution.
As India develops its strategy for last-mile efforts in TB eradication, the approach should be broadened to consider TB within the context of wider lung health challenges – where air pollutants play a significant role in disease transmission, progression, and mortality.
Explicit and sustained integration of TB and air pollution policies is essential to reduce India’s TB burden. Embedding air quality considerations in TB elimination strategies, expanding surveillance for both IAP and OAP exposure, and prioritising high-risk populations are necessary. Given that TB is influenced by multiple intertwined health and environmental factors, adopting a ‘One Health’ approach that embeds environmental health, particularly air pollution, within TB frameworks can help address the disease comprehensively. In forthcoming work, a dedicated issue brief will explore cross-sectoral policies and innovative models that can operationalise this integration and accelerate India’s TB elimination efforts.
Nimisha Chadha is a Research Assistant with the Health Initiative at the Observer Research Foundation.
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Nimisha Chadha was a Research Assistant with ORF’s Centre for New Economic Diplomacy. She was previously an Associate at PATH (2023) and has a MSc ...
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