“But I don’t smoke!” This is often the first reaction I hear when diagnosing a patient with lung cancer who has never smoked. As an oncologist, I’ve noticed increasing concern among non-smokers about their lung cancer risk, especially with recent headlines like “Lung cancer in non-smokers is on the rise” and “Exposure to cooking oil fumes may increase the risk of lung cancer.”
In this article, I’ll address these concerns and explain why non-smokers and never-smokers – people without any smoking history – might develop lung cancer. More importantly, I’ll discuss the hidden risks in our environment and what you can do to protect yourself. For a more detailed discussion, you can listen to my full interview on CNA’s Asia First program.
The Truth About Rising Cases of Lung Cancers among Non-Smokers
A 2018 study by the National Cancer Centre Singapore found that nearly half of lung cancer patients were never smokers. But let me offer two reassurances here.
First, the age-adjusted standardised incidence rate of lung cancer has actually fallen over the years, according to data from Singapore Cancer Registry Annual Report 2022. When we mention “age-adjusted standardised” rate, what we mean is that comparing absolute numbers over a long period of time needs to account for our ageing population. As we live longer, we naturally see more cancer cases overall, not just lung cancer. It’s part of the ageing process. Our bodies’ natural defence mechanisms, including our ability to repair DNA damage and fight off abnormal cells, become less efficient over time.
When we make this adjustment, here’s what the numbers tell us:
- In the 1970s, the rate was about 60 cases per 100,000 people
- By the 2020s, this rate has nearly halved
Second, our success in reducing smoking rates has brought down the rates of lung cancer patients who used to be smokers or who are existing smokers. Statistically speaking, those who are non-smokers or never-smokers will form an increasing proportion of the total lung cancer cases. But this doesn’t mean that their actual risk has increased.
Why Would a Non-Smoker Get Lung Cancer?
“Doctor, I’ve never smoked in my life – how could this happen?” This is one of the most heart-wrenching questions I hear in my clinic. While it is true that smoking remains the leading cause of lung cancer, unfortunately, it is not the only risk factor.
In my previous blog article “Lung Cancer – A Quick Essential Guide”, I explained secondhand smoking can be as harmful as first-hand smoking, if not more so. When you are around smokers, you inhale the smoke from the burning cigarette, as well as the smoke exhaled by the smokers. This means that even if you have never smoked, regular exposure to smokers can significantly increase your lung cancer risk.
In addition to second hand smoking, there are several well-established risk factors:
- Pollution (both indoor and outdoor)
- Genetic predisposition
- Age (cancer risk increases significantly after 50 years old)
- Exposure to harmful substances like radon or asbestos (though these are less common in Singapore)
Recently, there are emerging concerns among scientists as well as the general public. In this article, I’ll address three critical questions:
- Thirdhand smoke: What is it, and how harmful is it?
- Vaping: Is it really safer than traditional cigarettes?
- Cooking fumes: Can they contribute to lung cancer risk?
Let’s examine each of these, based on current available medical evidence.
Beyond Secondhand Smoke: The Hidden Danger of Thirdhand Smoke
While secondhand smoke (inhaling others’ smoke) is well-known, thirdhand smoke poses a less obvious but significant risk.
Thirdhand smoke refers to passive inhalation of toxic residue from smoking that:
- Settles on furniture, carpets, and walls
- Lingers long after smokers have left, even when fans are used
- Can interact with other compounds to form carcinogens called nitrosamines
These toxins can persist for months or even years. Decontaminating is challenging and impractical – we don’t routinely deep-clean our leather upholstery, sofas, chairs, or car interiors.
This is particularly concerning for children who might touch contaminated surfaces. For instance, a toddler’s toys exposed to thirdhand smoke can harbour these substances for extended periods, and toddlers often put these toys in their mouths.
In Singapore, we have taken important steps by banning indoor smoking, significantly reducing this risk in public spaces. In private settings, responsibilities fall on individuals. The best way to protect yourself and your children from thirdhand smoke is to maintain a strict no-smoking policy at home and in your car, and to keep children away from areas where people smoke.
Vaping: Not a Safe Alternative
If we apply the same logic to vaping as traditional cigarette smoking, there are clear risks.
Vaping devices contain nicotine and other substances which can potentially cause damage to the lungs, such as formaldehyde, carbonyls, benzene, etc. The heating process in vaping devices can produce carcinogens similar to traditional cigarettes. When e-liquids are heated to create vapour, they undergo chemical changes that can form harmful compounds.
Vaping can also cause secondhand and thirdhand exposure, just like traditional cigarettes. While it doesn’t produce smoke per se, it does release secondhand fumes – that visible cloud you see. In fact, it can be more insidious because it often has a pleasant smell. But this appealing scent doesn’t make it safe. When that smell lingers on someone’s body, hair, or clothes after vaping, it indicates the presence of thirdhand exposure risk, similar to traditional smoking.
Data aren’t yet available to establish a clear association between vaping and lung cancer. But this is primarily because vaping is relatively new. In Singapore, vaping is illegal, yet it is quite rampant. Because it has gone underground, it is difficult to determine exactly how widespread vaping is. In my opinion, the rising prevalence of vaping could potentially negate decades of progress in reducing smoking-related cancers.
Are Cooking Fumes Really Dangerous? Here’s What We Know
Recent headlines about cooking fumes and lung cancer have caused unnecessary alarm, particularly regarding wok cooking. Let me share my perspective on this as both a doctor and someone who understands the cultural importance of Asian cooking methods.
A study found that women who cook with woks more than five times a week showed higher levels of carcinogenic metabolites in their urine compared to those who cooked less frequently or used different methods. However, we need to understand the research context and interpret these findings carefully:
- While the study showed presence of certain metabolites, earlier studies have shown inconsistent results.
- An association with carcinogens doesn’t automatically mean increased cancer risk. Let me use a simple analogy: We have seen rising computer sales and falling birth rates, but does this mean computers cause lower fertility? No! Correlation does not imply causation.
- Studies conducted on professional chefs found the same result, but when adjusted for smoking rates, the association between cooking fumes and lung cancer is relatively weak.
- Humans have been cooking for millennia, and wok cooking has been central to Asian cuisine for centuries. If cooking fumes were a major risk factor, we would have seen dramatic increases in lung cancer rates among cooking populations throughout history.
If you are reading this as a professional chef or someone who cooks regularly, please be assured that there is no need to abandon your wok or change careers. The risk from cooking fumes, when proper ventilation is used, is minimal compared to other known risk factors for lung cancer. You can take practical precaution, such as:
- Install and maintain good ventilation systems
- Use appropriate exhaust fans while cooking
- Consider alternative cooking methods for some dishes
- Keep kitchen windows open when possible
Symptoms & Early Detection of Non-smoker Lung Cancer
Symptoms of non-smoker lung cancer are not different from those of smoker lung cancer. They may include a persistent cough, chest pain, wheezing, changes in a person’s voice, loss of weight. I discussed these symptoms in my general guide to lung cancer here.
Unfortunately, these symptoms often appear when the cancer has reached a later stage, which brings us to a critical question: how can we detect it earlier?
For current and former smokers who undergo annual screening, medical evidence shows that low-dose CT scans are the most effective screening tool. But we don’t recommend them for all non-smokers. Population-wide studies haven’t shown the same benefits for never-smokers or non-smokers.
This might seem frustrating, but it leads us to an important conclusion: for non-smokers, prevention remains our most powerful tool. As the old saying goes, “prevention is better than cure”, and this is especially true for lung cancer in non-smokers. Rather than relying on detection methods alone, focusing on preventive measures like avoiding secondhand smoke and ensuring good ventilation at home offers the best protection.
Treatment Options for Non-Smoker Lung Cancer
Non-smokers typically develop a specific type of lung cancer – Non-Small Cell Lung Cancer (NSCLC), with adenocarcinoma being the most common subtype. (More about lung cancer types here.) While adenocarcinoma tends to be less aggressive than other forms of lung cancer, treatment decisions don’t depend on smoking status. From the doctor’s point of view, we recommend treatment based on cancer stage, the patient’s general health, as well as how well they respond to different therapies, among other factors.
Surgery offers the best chance for cure, but timing is crucial. It’s most effective when cancer is detected early and the tumour can be completely removed.
At later stages when cancer has spread beyond the lung, to the lymph nodes, bones or distant sites, treatment is less effective and there is a risk of relapse. For advanced stage lung cancers, we typically don’t use the word “cure”. Instead, we focus on controlling the disease and maintaining quality of life. A combination of therapies can be recommended, including:
- Chemotherapy: Uses drugs to kill rapidly dividing cancer cells throughout the body. While effective, it may cause side effects as it can also affect healthy cells.
- Targeted therapy: Addresses specific mutations driving cancer growth. It can be very effective, though resistance may develop over time.
- Immunotherapy: This helps your immune system fight cancer and can work exceptionally well in some patients. However, not everyone responds to this treatment.
Takeaway Message
While lung cancer in non-smokers is concerning, it’s important to understand these risks in context. Like all cancers, our best defence lies in understanding the risks, knowing how they apply to us personally, and taking appropriate preventive measures.
As your doctor, I encourage you to focus on what you can control. Here are some of the important steps you can do to reduce your risk:
- Avoid exposure to secondhand and thirdhand smoke
- Ensure proper ventilation while cooking
- Do not ignore persistent respiratory symptoms
- Seek medical attention if you have concerns
Remember, letting go of unnecessary worry and stress is also part of taking care of your health. Stay informed, take sensible precautions, and maintain regular check-ups with your healthcare provider.
Dr Donald Poon
[This article is adapted from my interview with CNA’s Asia First program. For additional insights, please listen to the full interview here.]