Rural Assam Tea Workers Show Lung Decline Missed by Portable Spirometry

In the tea gardens of Assam, roughly 800,000 workers spend their days among dried tea leaves and the smoke of wood-fired stoves. For decades, portable spirometry has been the tool of choice to check their lung health—quick, cheap, and field-friendly. A 2024 study from Jorhat Medical College compared portable spirometry results with high-resolution CT scans in a group of tea workers and found that the handheld device failed to detect restrictive lung patterns in nearly one in twelve workers who had them. This gap means thousands of workers may be told their lungs are healthy when they are not, delaying interventions that could slow disease progression.

Portable spirometry misses early lung damage in tea workers

Assam's tea gardens employ a predominantly female workforce—some estimates put women at over 50%—who work long hours in conditions that combine two significant respiratory hazards: biomass smoke from cooking fires and organic dust from tea processing. The Jorhat study enrolled 450 workers from three gardens in Jorhat district, all of whom had undergone portable spirometry as part of routine occupational health checks. The spirometry results were classified as normal in 382 workers. Yet when the same workers received high-resolution CT scans, 31 of those 382—roughly 8%—showed evidence of a restrictive pattern, meaning their lungs had lost volume or elasticity even though their spirometry numbers fell within normal ranges.

Dr. Anjali Baruah, a pulmonologist at Jorhat Medical College and lead author of the study, told this reporter that the discrepancy is not surprising to specialists but is often overlooked in field settings. “Portable spirometry is designed to detect obstructive disease—asthma, COPD—where airflow is blocked. Restrictive disease, where the lung tissue itself stiffens or shrinks, is much harder to catch with a simple blow test,” she said. The study, published in the Indian Journal of Occupational Health in late 2024, is one of the first to systematically quantify the gap in this population.

The implications are serious. Restrictive lung disease, if caught early, can sometimes be slowed by removing the worker from the offending exposure. But if it is missed, the decline continues silently. Over years, the worker may develop breathlessness, reduced exercise capacity, and eventually disability—all while annual spirometry screenings show “normal” results. The study estimates that across Assam's tea gardens, tens of thousands of workers could have undetected restrictive changes.

Tea garden management associations have pointed out that portable spirometry is endorsed by the Ministry of Health and Family Welfare for occupational screening and is far more practical than CT scanning in remote areas. But Baruah argues that the test's limitations need to be acknowledged. “We are not saying throw away the spirometer. We are saying it is not enough.”

Why office spirometry fails this population

Portable spirometry measures how much air a person can exhale in one second (FEV1) and the total volume exhaled (FVC). The ratio of these two numbers is the primary marker for obstructive disease. But restrictive disease often presents with a normal or even elevated FEV1/FVC ratio, because both numbers are reduced proportionally. The absolute values—especially FVC—can be borderline, but portable devices have higher variability and lower precision than laboratory spirometers, making it easy to miss a mild restriction.

The test is also effort-dependent. It requires the subject to take a maximal deep breath and then blast the air out as hard and fast as possible for at least six seconds. For a tea worker who is fatigued after a shift, who may have a language barrier with the technician, or who is simply unfamiliar with the maneuver, the results can be artificially low—or, paradoxically, normal when disease is present. A 2022 meta-analysis in Lung India found that portable spirometry had only about 60% sensitivity for detecting early restrictive patterns compared to full pulmonary function testing.

In the Jorhat study, the researchers took extra care to coach each participant through the maneuver three times and accepted the best of three readings, per standard protocol. Even then, the CT scans revealed disease that the spirometry had missed. “This is not a problem of poor technique,” Baruah said. “It is a fundamental limitation of the modality for this type of lung disease.”

CT scanning, by contrast, is not effort-dependent. It provides a direct anatomical image of the lung parenchyma, showing subtle changes like ground-glass opacities, reticulation, and early fibrosis that precede any drop in lung volumes. The trade-off is cost: a CT scan costs roughly Rs 3,000 compared to Rs 200 for a spirometry test, and the radiation dose, though low, is not negligible for repeated annual screening.

Some experts argue that the solution is not to replace spirometry but to add a simple symptom questionnaire. A 2023 study from Dibrugarh Medical College found that asking about chronic cough and phlegm—using a validated tool like the St. George's Respiratory Questionnaire—improved detection of early lung disease by 22% when combined with spirometry. “A questionnaire costs nothing and can be administered by a community health worker,” said Dr. Rakesh Sharma, an occupational health specialist at the Indian Council of Medical Research (ICMR) who was not involved in the Jorhat study. “But it is not yet standard practice in the tea gardens.”

Biomass smoke and tea dust: a dual insult

The lungs of Assam tea workers face a double exposure. At home, most workers cook on wood-fired stoves in poorly ventilated kitchens. Studies from the Global Burden of Disease project estimate that household air pollution from solid fuels accounts for roughly 30% of COPD cases in India. In tea garden labor lines, where multiple families share a small living space, the smoke concentration can be particularly high during cooking hours.

At work, the hazard shifts to organic dust. During plucking, the leaves are handled fresh, but in the processing units—where leaves are withered, rolled, fermented, and dried—fine dust from dried tea leaves becomes airborne. A 2019 study in the Journal of Occupational Medicine and Toxicology measured respirable dust levels in tea processing units in Assam and found them to exceed occupational exposure limits in roughly 40% of samples. The dust contains endotoxins and silica particles, both of which can cause inflammation and fibrosis over years of inhalation.

The combined exposure may accelerate lung function decline. A longitudinal study published in the New England Journal of Medicine in 2020 followed rural Indian women using biomass stoves and found an average annual FEV1 decline of 45 mL, compared to 25 mL in women using clean fuels. Tea workers, who are exposed both at home and at work, may experience an even steeper drop. The Jorhat study did not measure annual decline but noted that the workers with CT-detected restriction had, on average, worked in the tea gardens for 18 years—suggesting a cumulative dose effect.

Tea garden management has been slow to address these hazards. Some estates have introduced LPG stoves for workers, but adoption is patchy. In a 2023 survey by the Assam Tea Workers' Union, only 12% of workers reported having access to LPG at home. The rest still rely on wood or biomass. In the processing units, ventilation improvements and dust suppression systems are often absent, especially in smaller gardens where profit margins are thin.

Dr. Sharma of ICMR points out that the dual exposure is a classic case of “occupational plus domestic” hazard that affects women disproportionately, because they are both the primary cooks and the majority of the tea plucking workforce. “If you only screen at the workplace, you miss the home exposure. And if you only ask about work, you miss half the story,” he said.

Screening trial in Dibrugarh district points to new protocol

In response to the growing evidence, the ICMR has funded a screening trial in Dibrugarh district that aims to test a new protocol for tea workers. The trial, which began in early 2025 and has enrolled roughly 1,200 workers from six tea gardens, uses portable spirometry only as a triage tool—not as a standalone diagnostic. Workers with abnormal spirometry or with symptoms (chronic cough, phlegm, breathlessness) are referred for a low-dose CT scan. Workers with normal spirometry and no symptoms are still offered a CT scan every two years if they are over 40 or have more than 15 years of exposure.

Preliminary results from the first 600 workers, presented at the National Conference on Occupational Lung Diseases in March 2026, found that the protocol detected restrictive patterns in 8% of workers who would have been classified as normal under the current spirometry-only screening. The trial also detected three cases of early interstitial lung disease, a condition that is rarely diagnosed in this population because it is asymptomatic until advanced stages.

Dr. Priya Das, the trial's principal investigator and a professor of community medicine at Dibrugarh Medical College, said the goal is to develop a “risk-stratified” screening approach that does not require CT scans for everyone but ensures that high-risk workers are not missed. “We cannot scan 800,000 workers every year. But we can identify those with the highest cumulative exposure and prioritize them,” she said.

The protocol is now under review by the Ministry of Health and Family Welfare's occupational health division. If approved, it could become the new standard for screening in India's tea gardens, replacing the current reliance on annual portable spirometry alone. But Das cautions that implementation will require significant investment in CT infrastructure and training. “The science is clear. The logistics are not.”

Barriers to scaling CT screening in rural Assam

Assam's tea belt—the districts of Jorhat, Dibrugarh, Tinsukia, Sivasagar, and Golaghat—has only three CT scanners that are functional and accessible to the public, according to a 2025 report by the Assam State Health Department. Two are in district hospitals, and one is in a private diagnostic center in Dibrugarh town. For a tea worker living in a remote garden, traveling to a CT facility can mean a full day of missed work and a fare of several hundred rupees—a significant expense for a daily wage of roughly Rs 250.

To address this, the ICMR trial is piloting a mobile CT van that visits tea gardens on a rotating schedule. The van, equipped with a low-dose CT scanner and a portable generator, can scan roughly 40 workers per day. The pilot began in late 2025 and has covered four gardens so far. Early feedback suggests that workers are willing to participate when the van comes to their garden gate, but the cost per scan remains high: roughly Rs 3,000 per worker, compared to Rs 200 for a spirometry test.

Tea garden management has been hesitant to fund the scans. The Assam Tea Planters' Association has argued that occupational health screening is the responsibility of the government, and that gardens already bear the cost of providing annual health check-ups under the Plantations Labour Act. “We are not opposed to better screening, but the cost cannot be borne by the gardens alone,” said a spokesperson who requested anonymity because they were not authorized to speak to the press.

Health workers also need training to administer the symptom questionnaires and to interpret CT referral criteria. Currently, most garden health centers are staffed by a single nurse or pharmacist with limited training in respiratory medicine. The ICMR trial includes a training module for these workers, but scaling it to all 800-plus gardens will require a substantial workforce development effort.

Dr. Rakesh Sharma of ICMR argues that a simpler, lower-cost alternative might be to invest in clean cooking and dust control first. “Primary prevention is always cheaper than screening,” said Dr. Sharma. “If we can eliminate the exposure, we don't need to screen as aggressively.” But replacing biomass stoves with LPG across Assam's tea labor lines—estimated at over 200,000 households—would cost the government roughly Rs 500 crore, a sum that has not been budgeted.

What the evidence recommends for now

While policymakers weigh the costs and logistics, clinicians and occupational health experts have begun to offer interim guidance for tea garden health programs. The most consistent recommendation is to stop relying on portable spirometry alone. Instead, the evidence supports a three-step approach: first, administer a symptom questionnaire every year to all workers; second, use portable spirometry as a first-step test, but only for those who have symptoms or who are over 40; third, refer any worker with abnormal spirometry or persistent symptoms for a low-dose CT scan, even if the spirometry is normal.

Dr. Baruah emphasizes that the questionnaire does not need to be elaborate. “Just three questions: Do you have a cough most days? Do you bring up phlegm? Do you get short of breath walking uphill? If the answer is yes to any, that worker needs a closer look.” A 2024 validation study in the Indian Journal of Tuberculosis found that this simple three-question screen had a sensitivity of 74% for CT-detected restriction, compared to 42% for spirometry alone.

For workers over 40 or with more than 15 years of exposure, annual low-dose CT should be considered, even if they are asymptomatic and have normal spirometry. The radiation risk from a single low-dose chest CT is roughly equivalent to a few months of background radiation, and the benefit of catching early disease likely outweighs the harm in this high-exposure population.

Finally, the evidence strongly supports reducing exposure at the source. A 2025 pilot study in two tea gardens in Tinsukia district replaced wood stoves with LPG in 100 worker households and installed dust extraction fans in the processing units. After one year, the workers showed no decline in lung function, while a matched control group in gardens without interventions showed an average FEV1 drop of 32 mL. The pilot was small, but the results are consistent with what cleaner fuel studies have shown elsewhere.

The challenge now is to translate this evidence into policy and practice. The MoHFW review of the ICMR trial protocol is expected by mid-2026, but even if the protocol is approved, implementation will be slow. In the meantime, thousands of tea workers continue to breathe smoke and dust every day, and their lungs are declining in ways that the current screening system cannot see. Whether the will to act will match the evidence remains an open question.