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Air Pollution Is Making TB Deadlier
A large population survey of tuberculosis patients in Delhi has linked exposure to fine particulate air pollution with a higher likelihood of death in those receiving treatment for the disease, highlighting the challenge posed by poor air quality in the Indian capital.
The study, which the authors call the largest ever global research study exploring the relationship between air pollution and tuberculosis mortality, looked at data from 61,925 people who started treatment for TB in Delhi between September 2022 and August 2023. It was conducted by scientists at the All India Institute of Medical Sciences (AIIMS), the Central Tuberculosis Division of the Union Ministry of Health and Family Welfare, and the South Asian Institute of Health Promotion, in partnership with researchers at Boston Medical Center and Boston University in the U.S., Cornell University and the University of Virginia, HydroSciences Montpellier in France, and Maastricht University in the Netherlands
Researchers discovered that the risk of dying during treatment was closely linked to the level of exposure to particulate matter (PM2.5) in the month preceding the initiation of therapy. Those exposed to between 40 and 80 micrograms of PM2.5 per cubic metre had a three per cent higher likelihood of dying during treatment than those who had been exposed to less than 40 micrograms. The risk increased progressively with higher pollution levels, peaking at 22 per cent, 31 per cent and 66 per cent among those exposed to 80 120, 120 160 and more than 160 micrograms, respectively.
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In simple terms, people who were exposed to the highest levels of air pollution before they began their treatment for tuberculosis were significantly more likely to die during therapy than those who were exposed to less polluted environments.
To do this, the team cross-referenced nationwide tuberculosis treatment records from Nikshay, India's national TB database, with estimates of PM2.5 air pollution levels obtained from satellite data, to identify the level of pollution for each person before he or she began his or her treatment.
They focused their attention on the period of 30 days leading up to the beginning of treatment for tuberculosis. Because, as Pranay Sinha of the Boston University School of Medicine notes, this is a crucial period in the course of the disease.
"TB deaths tend to come early, and the weeks just before treatment starts are a dangerous window. The disease is at its peak, and the patient has no protection from treatment yet. We expected pollution during that period to hit hardest, so that is where we looked," Sinha explained.
Importantly, the association between air pollution and mortality was maintained even after adjusting for potential confounding variables such as age, sex, HIV, diabetes, patient's nutritional status, tobacco and alcohol use, treatment setting (public or private), and type of TB (pulmonary or extra-pulmonary).
The researchers note that the fact that the association persisted after adjustment provides further confidence that it is real, rather than due to chance.
Yet, the researchers were careful to point out that the study cannot establish a causal relationship between air pollution and death.
"This is an observational study, so we cannot claim to have proven cause and effect. What we can say is that the link is strong and biologically plausible," Sinha said. "People with TB are already in a fragile state. When air pollution spikes, they may struggle to breathe and sustain more lung damage, and it is reasonable to think this raises their risk of dying. Readers should treat this as a serious warning signal, not as final proof."
The finding is of special importance to India, which has the world's largest tuberculosis problem despite intensive efforts to identify cases and provide treatment to those who need it.
"The study suggests that air pollution may be an important, neglected factor influencing tuberculosis epidemiology," he states.
"For India, this is a serious finding. India carries the world's largest TB burden, and the country has invested enormous effort and resources into finding people with TB and getting them onto treatment. That work saves lives," he said.
He added that the study suggests that polluted air may increase the risk of dying by almost two-thirds for a patient who has received adequate care, saying that such environmental factors may contribute to treatment outcomes by reducing the effectiveness of control measures for TB.
Although the researchers note that more studies are needed before considering formal adjustments to clinical practice guidelines, they feel that it is reasonable to advise TB patients that they should do their best to avoid serious air pollution if at all possible.
The team feels that the implications of their research could go beyond TB. Air pollution has been linked to chronic respiratory and cardiovascular diseases; their research suggests it could also interfere with the body's ability to fight infections.
The researchers noted that particulate matter tiny particles in the air that cause pollution can infiltrate the lungs. They cause inflammation, which can lead to constricted air passages, but the body uses some of this inflammation to fight off infection and disease, especially those related to the respiratory system. However, too much can be damaging to lung tissue, restricting the person's ability to breathe normally and recover from diseases like TB.
The research adds weight to the belief that working to minimize air pollution has far-reaching benefits, including lowering the risk of chronic respiratory and cardiovascular diseases, while also being vital in helping the body fight infections.
Disclaimer: This report is auto-generated from PTI news service. Thehealthsite holds no responsibility for its content. Readers are advised to seek professional medical consultation for diagnosis, treatment, and personal health decisions. TB treatment should only be taken under medical supervision.