The three-year AIRCARE study, underway for three months already, will compare lung cancer patients with their family and look for the biological footprint of PM2.5 in Indians

India’s first population-level study of how long-term exposure to polluted air contributes to lung cancer, including among people who have never smoked, has begun at the All India Institute of Medical Sciences (AIIMS), New Delhi.

The study, AIRCARE (Air Pollution and Cancer Research Ecosystem), commenced about three months ago, will run for three years and involves public and private healthcare institutions. It aims to build India-specific evidence on the link and to understand the biological mechanisms through which pollutants such as PM2.5 may trigger cancer. Researchers involved in the study are urging lung cancer patients in Delhi-NCR and their families to take part—a sign of how little Indian data exists on the question.

The study comes as the Capital’s air slides deeper into the ‘very poor’ range. Delhi’s Air Quality Index (AQI) stood at 323 on Thursday, according to Central Pollution Control Board (CPCB) data. Delhi-NCR is under Stage II of the Graded Response Action Plan (GRAP), and Indian Institute of Tropical Meteorology (IITM) forecasts show air quality could turn ‘severe’ by Friday.

“Lung cancer is no longer a disease that we can associate only with smoking," Dr Abhishek Shankar, principal investigator (PI) of the study, from the Department of Radiation Oncology at Dr BR Ambedkar Institute Rotary Cancer Hospital (Dr BRAIRCH), AIIMS, told News18.

The same AIIMS team has registered a second study, the Indian Lung Screening Trial (ILST). This trial is not about pollution. It tests whether low-dose computed tomography (LDCT) scans can catch lung cancer early in people at high risk from smoking. The pollutant at the centre of the AIIMS study is PM2.5. Particles smaller than 2.5 micrometres that can travel deep into the lungs and enter the bloodstream.

“Environmental and occupational exposures, particularly prolonged exposure to air pollution, deserve much greater scientific attention. Through AIRCARE and ILST, AIIMS New Delhi is working towards understanding the disease better, identifying people at risk and strengthening opportunities for early detection."

What The Study Will Do

AIRCARE will be conducted at AIIMS and in parts of Delhi and the National Capital Region (NCR) with varying levels of PM2.5 exposure, according to the registry entry.

Researchers plan to enrol about 3,230 people: 1,615 lung cancer patients and 1,615 of their family members, who will serve as controls. Relatives were chosen, the registry at Clinical Trials Registry – India (CTRI) says, to get a group matched to the patients in PM2.5 exposure. Patients will be drawn from the AIIMS outpatient department and the Delhi Cancer Registry, and will include both smokers and non-smokers.

Participants must be adults aged 18 or older who live in Delhi or NCR. There is no upper age limit, and both men and women can take part. Patients need a lung cancer diagnosis confirmed by examining tissue under a microscope, known as histological confirmation.

The design combines a cohort followed for three years, with repeated exposure measurement, and a case-control comparison. Exposure will be estimated from satellite data, ground-level monitors and land-use modelling, along with indoor sensors and wearable monitors that track what individuals actually breathe.

A laboratory arm will expose blood cells to PM2.5 samples and use gene sequencing to look for a ‘PM2.5 gene signature’, early genetic changes that could flag people at risk. The team also plans to build a risk model to help decide who in India should be screened for lung cancer.

The project runs from September 2025 to August 2028 with a budget of about Rs 8.6 crore, roughly $1 million, according to the study protocol filed on the registry.

“The AIRCARE study commenced approximately three months ago and is planned over three years," said Dr Shankar. “It aims to generate important India-specific evidence on the relationship between air pollution and lung cancer, including understanding the biological mechanisms through which exposure to pollutants such as PM2.5 may contribute to cancer development. This is an important research initiative involving collaboration across public and private healthcare institutions."

“We are not merely asking whether polluted air increases lung cancer risk, but also how it does so," he said. “We are studying lung cancer patients alongside their family members as controls, who may share similar household and neighbourhood environmental exposures. We are assessing exposure to air pollution at home and outdoors, alongside tobacco use, occupational and other environmental factors. We are also investigating molecular and genetic signatures that may help explain why some individuals develop lung cancer despite never having smoked."

The team is also seeking participants. “An important appeal is that any adult diagnosed with lung cancer in Delhi-NCR, irrespective of smoking history, can potentially participate along with an eligible family member," Shankar said. “We encourage patients and their families from different neighbourhoods, socioeconomic backgrounds and exposure settings across Delhi-NCR to come forward. Their participation will help us better understand the contribution of environmental pollution to lung cancer in India."

Why Non-Smokers Are A Concern

Lung cancer is the second-most common cancer among Indian men and the fourth most common overall. The protocol cites 81,784 new cases and 75,031 deaths in India, based on GLOBOCAN 2022 estimates from the International Agency for Research on Cancer (IARC).

The registry summary states: “Air pollution, particularly fine particulate matter (PM2.5), has been identified as a significant risk factor for lung cancer in never-smokers." It adds that India “is showing an increasing incidence of lung cancer and there is a need to understand air pollution given many cities in India have been reported to be the most polluted in the world."

IARC classified outdoor air pollution and particulate matter as cancer-causing in humans in 2013. The AIIMS team’s sample-size calculation assumes that people exposed to PM2.5 above 37 micrograms per cubic metre face at least twice the odds of lung cancer. That cut-off is close to India’s national annual standard of 40 µg/m³, and far above the World Health Organization’s (WHO) annual guideline of 5 µg/m³. Delhi’s winter levels routinely run several times higher.

Risk May Not Stop At The Lungs

“When examining the link between pollution and increased cancer incidence, it is important to emphasise that the risk extends well beyond lung cancer," said Dr Pragya Shukla, head of department, clinical oncology, Delhi State Cancer Institute (DSCI).

“While lung cancer comes to mind first because the respiratory tract is directly exposed, pollutants also cross the alveolar-capillary barrier, allowing carcinogens to enter the bloodstream. Furthermore, swallowing carcinogen-laden mucus exposes the gastrointestinal tract—and subsequently the urinary tract—to these toxins. Recent studies have even detected pollutants directly within breast cancer tissue, establishing a clear connection between environmental pollution and breast cancer."

What The Study Can And Cannot Show Yet

The protocol says the project will generate “the first population-level evidence" on PM2.5 and lung cancer in India. Smaller Indian studies have looked at parts of the question before. A single-centre case-control study at AIIMS Bhubaneswar examined risk factors among non-smokers with lung cancer, including outdoor PM2.5 and AQI exposure based on residential address.

Because the controls are family members, they will share much of the patients’ outdoor air. The study will rely on indoor sensors, wearable monitors and genetic testing to capture differences between individuals.

“Such studies will take time to give data. But there is no doubt in my mind that age-adjusted lung cancer risk will be increased by pollution," said Dr Anurag Agrawal, former director, CSIR Institute of Genomics and Integrative Biology. “Total cancer burden may not show the increase, simply because other diseases may kill before cancer gets diagnosed at older age," he added.

A Parallel Trial On Screening

The second study, the Indian Lung Screening Trial (ILST), has its official title “Evaluating the Effectiveness of Low-dose CT Based Lung Cancer Screening Among High-risk Individuals and Availability and Impact of Lung Cancer Care Pathways."

This trial is not about pollution. It tests whether low-dose computed tomography (LDCT) scans can catch lung cancer early in people at high risk from smoking.

It is open to people aged 50 to 80 with at least 20 pack-years of smoking who still smoke or quit within the past 15 years. One pack-year equals smoking a pack a day for a year. The trial is assessing screening across 10 centres in India, which have not been named publicly.

“Through the Indian Lung Screening Trial (ILST), led by AIIMS New Delhi, we are evaluating low-dose computed tomography (LDCT) for early detection of lung cancer among high-risk individuals across multiple participating sites in India," said Dr Shankar. “The study aims to generate evidence on the feasibility and effectiveness of lung cancer screening in the Indian context and strengthen pathways for early diagnosis and appropriate treatment."

“We appeal to eligible high-risk individuals across participating centres in India to come forward and participate in the Indian Lung Screening Trial. Greater participation across different regions and population groups will help generate evidence relevant to India’s diverse environmental and risk profiles," he said.

The registry lists the trial as not yet recruiting, with an estimated completion date of September 2028.

“Currently, lung cancer screening recommendations are largely based on age and smoking history. Consequently, individuals who have never smoked but have experienced prolonged exposure to polluted air may not be adequately identified for screening," said Dr Shankar.

“We need to move beyond a smoking-only approach to lung cancer risk assessment," he said. “Evidence from research on air pollution, together with screening studies, could help inform future risk-stratification models incorporating environmental, occupational, household and tobacco-related exposures. This may eventually help identify individuals, including never-smokers with substantial pollution exposure, who could benefit from targeted screening."

Dr Agrawal said the evidence for such screening comes largely from a different population. “LDCT is proven to help in mostly smoker COPD in the West. India will be interesting to see." Chronic obstructive pulmonary disease (COPD) is a long-term lung condition commonly linked to smoking.

What Doctors Advise

“Air pollution is emerging as an important risk factor for lung cancer, even among individuals who have never smoked," said Dr Pritpal Kaur, Senior Consultant, Pulmonology, Apollo Spectra Hospital, Delhi.

“Prolonged exposure to fine particulate matter, especially PM2.5, can trigger chronic inflammation and cellular damage in the lungs, increasing cancer risk over time."

“Meanwhile, people should avoid tobacco exposure, minimise outdoor activity during severe pollution, use appropriate respiratory protection and seek medical evaluation for persistent respiratory symptoms rather than ignoring early warning signs," she said.

Similarly, Dr G Mehar, director of medical oncology at Gorakhpur-based Regency Healthcare, believes lung cancer often develops silently, with early symptoms such as persistent cough, unexplained breathlessness, chest discomfort or recurrent respiratory infections being mistaken for common respiratory conditions. “Initiatives such as AIRCARE and the Indian Lung Screening Trial are important steps towards understanding the relationship between air pollution and lung cancer within the Indian population."

Mehar added that the findings could help oncologists identify vulnerable groups, strengthen risk-based screening strategies and improve opportunities for early detection. “It is equally important that persistent respiratory symptoms are investigated promptly, even in non-smokers, as timely diagnosis can significantly influence treatment options and patient outcomes."