Lung cancer in non-smokers on the rise: what does this mean?

Lung cancer is one among other respiratory ailments which have long been associated with smokers.
Lung cancer in non-smokers on the rise: what does this mean?
Lung cancer in non-smokers on the rise: what does this mean?

“He was one of the most active people I knew,” Bengaluru-based Divya* recollects of her uncle. “Definitely fitter than most of the adults in the family. He never drank or smoked… he had an exemplary healthy lifestyle.”

“So, when he was diagnosed with lung cancer, none of us could really come to terms with it,” the 24-year-old narrates.

Krishna* was 43 when he was diagnosed. He succumbed to the disease 8 months later. The doctors could not say why he developed the cancer.

There have been several studies which have shown a direct correlation between lung cancer and smoking. According to the Center for Disease Control (CDC), up to 90% of lung cancer patients in the US are smokers. However, new reports suggest a rising incidence of lung cancer in non-smokers.

“We are seeing an increase in the prevalence of lung cancer in non-smokers. There could be a number of reasons for this,” says Dr Vijay Agarwal, an Oncologist with Aster CMI Hospital in Hebbal, Bengaluru.

Are non-smokers becoming more susceptible to lung cancer and respiratory issues?

While experts admit there is a lack of large-scale and long-term research on this, they admit seeing more non-smokers complaining of respiratory issues, including lung cancer.

Dr Anant Mohan, Professor in the Department of Pulmonary Medicine at AIIMS, Delhi and Dr Avneet Garg of AIIMS collated data of roughly 1800 lung cancer patients from 2008 to 2017. As per analysis, there appears to be an increasing trend of non-smokers also developing lung cancer. For instance, in 2008, if almost 20% of the 61 male lung cancer patients were non-smokers, in 2017, almost 30% of the 371 men with lung cancer were non-smokers.

Chronic obstructive pulmonary disease (COPD), characterised by poor airflow to the lungs, has been associated with smokers. But, many experts told TNM, there has been an increasing number of non-smokers with COPD in the past few years.

Dr Anant says that while most cases continue to be detected in people who smoke, it is no longer just limited to them.

“Our youngest patient was a 13-year-old boy,” he recounts. “Besides, compared to Western countries, the age group susceptible to lung cancer here is 10 years younger – the early 50s, that is. That could also be because we have shorter average lifespans. But we definitely have more people coming with complaints of respiratory issues who are below 35 years of age also.”


Experts say that the lifestyle we lead these days can be a big factor contributing towards the rising incidence of lung cancer and respiratory illnesses.

“More people are leading sedentary lifestyles,” Dr RP Ilango, a senior consultant in Respiratory Medicine at Apollo Hospital in Chennai, says. “Increased stress levels are also responsible,” he notes, describing the lifestyles today as ‘artificial.’

Dr Karan Madan, who is a pulmonologist and Assistant Professor in the Department of Pulmonary medicine in AIIMS, Delhi, says that certain dietary factors can also increase the risk.

Both agree, however, that it is difficult to establish a direct correlation. “Often, we give labels, but with a host of possible factors, it is tough to pinpoint exact reasons,” Dr Ilango says.


With 11 of the 12 most polluted cities as stated by the World Health Organisation being in India, pollution was a strong contributory factor in every expert’s list. The International Agency for Research on Cancer (IARC), associated with the WHO, has also linked outdoor air pollution as a leading environmental cause for cancer deaths.

The levels of pollution in Indian cities, especially in metros, are alarming. For instance, breathing Bengaluru's air has been equated to smoking six cigarettes a day; Mumbai’s air has the same effect on your body as smoking four cigarettes, and Delhi air, as many as 7.7 cigarettes.

Dr Karan notes that the number of people complaining of respiratory issues goes up every year when pollution levels peak.

Dr Mohan explains that the particulate matter in the air can enter the airways and cause irritation. “Once inhaled, these get deposited in the airway. Hypotheses suggest that some of the microparticles may even get absorbed into the lungs and the airway and cause more serious problems,” he says.

Further, indoor pollution can also contribute to lung cancer and other respiratory issues.

In rural areas or where people do not use LPG or electricity to cook, exposure to fumes of biomass fuels affects the lungs as well. Experts say that because women are predominantly working in the kitchen, they are at higher risk.

“You must also keep in mind that what is outside is also inside,” Dr Karan notes. “Air purifiers can only help to an extent and works when the room is sealed. But this is hardly possible because the doors and windows will be opened at some point.”

Further, passive smokers are also as much at risk as smokers, warns Dr Ilango.

Occupational hazards

Being in certain occupations can also put you at a greater risk of cancers and respiratory issues. Experts say that people who work in the sand mining industry, coal industry, brick kilns, iron ore industries and so on, are exposed more to harmful substances which can become irritants to the respiratory system and cause illnesses.

Many working in industrial factories are often exposed to harmful radiation. “Radon is one such radioactive gas which is actually present in a higher proportion in the environment now due to increase in industrial pollution. It contains radioactive particles which can cause lung damage,” explains Dr Vijay.  

Biological factors

There are also biological factors which can increase the risk. One such reason is genetic susceptibility.

“Lung cancer, like a number of other types of cancers, has a hereditary factor to it, too,” says Dr Vijay, “Someone who has a history of it in the family does automatically have a little higher risk of developing it.”

In January 2016, Dr Paul Kalanithi’s book When Breath Becomes Air was published posthumously after his battle with stage four lung cancer and it was specifically noted that his cancer developed as the result of a mutation in the ‘epidermal growth factor receptor (EGFR),’ a protein found in the body, the genetic mutations of which have been known to result in cancer.

“It’s true that certain mutations can result in cancer, but we can’t say what might be causing the mutation as such. While an environmental factor, such as prolonged exposure to radiation, is definitely something which could result in a mutation, we can’t say that is the reason for a particular mutation to have taken place,” explains Dr Karthik R, a Chennai-based pathologist.

Increase due to better detection?

While many smaller studies have shown that there is a rise in the number of lung cancer in non-smokers, experts say that there is a lack of data about other contributory factors.

“We have enough evidence to suggest a direct correlation between smoking and lung cancer, but we don’t have the same kind of studies done for lung cancer in non-smokers,” Dr Vijay observes.

“There are questions about whether the incidence is really increasing or are more people just coming forward, getting correctly diagnosed and getting treated? These need to be studied long term to have a better understanding,” he states.

Precautions you can take

What must one do to decrease the risk of developing lung cancer and respiratory illnesses, apart from avoiding active and passive smoking?

Dr Ilango says that lifestyle habits such as exercising, eating healthy and sleeping well are crucial, even if they may not appear to be directly related to the illnesses.

And while exercise is essential to maintaining health, Dr Karan warns that when pollution levels peak, people should avoid too much exertion.

Dr Anant says that people should practice wearing pollution masks. “Employers should ensure that employees are not exposed to harmful substances and carcinogens. And if it is unavoidable, they should at least provide protective masks and gear,” he says.

“Also go for more frequent checkups. Be aware of early symptoms like persisting breathing difficulty, cough, wheezing and blood in sputum,” he adds.

*Names changed on request

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