Smoking is the single-largest risk factor for lung-cancer worldwide, with as much as 80 percent of all lung-cancer cases coming from tobacco smokers. However, the remaining 20 percent of the cases come from people who do not currently smoke or smoked very little in the past (fewer than 100 cigarettes), as well as those who have never smoked in their life. So, what causes them to develop lung cancer? In this article, we will discuss why non-smokers are as much at risk of lung-cancer as smokers.
As is well-known, a tumour or cancerous growth is uncontrolled growth of body-cells which rob healthy cells of their nutrition and hinder the normal functioning of cells, tissues and organs in the body. Changes in DNA of lung-cells can trigger the growth of cancerous tissue there. But it’s good to understand how the mechanism works.
DNA is important as they make up the chemical composition of our genes. We inherit genes from our parents and the DNA in them decides how we look. They also influence the risk or onset of various diseases including cancer in any part of the body.
Some of these genes help regulate or manage when new cells must be generated, when they must grow, divide or multiply, and finally die. Again, there are 2 types of such genes:
In some people, DNA changes (called mutations) in a certain part of the body turn-on the oncogenes while at the same time turning off the tumour suppressor genes. As a result, there is uncontrolled or abnormal growth of cells in that part of the body. When it comes to lung-cancer, there are several gene mutations that can increase the risk. We will examine them in a later section.
Non-smoker is a generic word but there are actually 2 types of people here:
The symptoms of lung-cancer are the same in both smokers and non-smokers:
If the cancer has spread (metastasized) to other parts of the body, the person may notice more symptoms such as:
There are different types of lung-cancers that affect non-smokers:
Secondary smoke: Being constantly exposed to tobacco-smoke from a friend, partner, family-member or co-worker increases the risk of lung-cancer. In fact, a significant number of lung-cancer deaths in non-smokers, every year, comes from this category.
Radon: Radon is a radioactive metal that is naturally found in nature. When uranium, which is a heavier radioactive metal than radon starts decaying or decomposing, radon is one of the metals formed. Uranium present in the soil or water bodies is decaying constantly, so radon makes its way into the soil, into the water we consume, in the air we breathe, and in to homes that are constructed at such sites. That is why, in recent years, governments around the world are encouraging citizens to get radon testing for their homes and offices. In India too, several agencies that provide indoor air quality (IAQ) testing cover radon, among other parameters.
Toxic chemicals: There are various industries that use toxic chemicals like arsenic, chromium and asbestos for their products, so workers in such factories are at risk of developing lung-cancer over time. While asbestos was heavily used in the construction industry in the past, in recent years, its use is banned or severely restricted due to this risk. However, when it comes to other toxic chemicals, there is limited to no regulation. People who work at, or live close to – nuclear reactors are also at the risk from uranium that is used at these reactors. While there is some form of protection for workers, and restrictions for living close to a reactor, the risk is still there.
Air pollution: Excessive dust, smoke from industries, landfills where waste is dumped and burnt, and vehicle exhaust (especially diesel exhaust) increases the risk of lung-cancer for people who are constantly exposed to the same. People who live in highly polluted cities, neighbourhoods or industrial layouts should use good-quality face-masks. This is the best form of protection, as currently, lung-cancer screening is not done unless one has a history of smoking, or works in hazardous industries, or is showing any sign of lung-cancer.
The fifth major risk-factor is genetic changes which deserves a detailed mention.
Certain gene mutations or changes happening in our DNA structure can increase the risk of lung cancer. These abnormal mutations can either be inherited from parents/grand-parents or acquired over time.
Genetic changes happening in the following genes can increase the risk of either SCLC or NSCLC.
Consult a qualified doctor at a reputed hospital on how to reduce your risk of lung cancer in-spite of being a non-smoker or never-smoker. Broad guidelines include:
Reviewed by Dr Suresh S Venkita, Group Medical Director, Kauvery Hospitals
Kauvery Hospital is globally known for its multidisciplinary services at all its Centers of Excellence, and for its comprehensive, Avant-Grade technology, especially in diagnostics and remedial care in heart diseases, transplantation, vascular and neurosciences medicine. Located in the heart of Trichy (Tennur, Royal Road and Alexandria Road (Cantonment), Chennai, Hosur, Salem, Tirunelveli and Bengaluru, the hospital also renders adult and pediatric trauma care.
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