Due to many years of dedicated research conducted by experts all over the world, the dangers of smoking are now well known, and there is a scientific consensus on a large list of diseases caused by smoking, which include some very serious and dangerous complications and conditions, including multiple forms of cancer, most notably lung cancer. Just in the UK, smoking is directly related to one in four cancer deaths and accounts for up to a fifth of documented cancer cases.

However, medical experts agree that possibly the grimmest part of this statistic is the fact that most of those deaths were preventable – simply by quitting smoking. However, since nicotine is a highly addictive substance, smokers cannot abandon their bad habit that easily, in fact, while some do manage to quit “cold turkey”, others need to rely on nicotine replacement therapies or other medication to help them cope with nicotine withdrawal and cravings associated with quitting smoking. Still, the statistics clearly show that giving up smoking has no alternative when it comes to health and the longer you smoke the odds of developing some of the diseases caused by smoking are greater.

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What diseases are caused by smoking?

Smoking is related to many medical conditions including numerous infections which can appear as a result of adverse effect smoking has on the immune system, many different respiratory and pulmonary diseases, impotence in men, reduced fertility, cardiovascular diseases and conditions, as well as multiple forms of cancer.1

Lung cancer is most often associated with smoking due to obvious reasons – not only that the smoke has the most direct impact on the lungs, but the statistics clearly show that smoking is the prime cause of lung cancer worldwide. In fact, while smokers have a 22% of dying of lung cancer before year 85, non-smokers have much better odds at just 1%.

However, the lungs are not the only organ which is endangered by this bad habit. Due to the fact that nicotine and other harmful chemicals found in tobacco smoke enter the bloodstream, they can affect the whole body. Still, the organs which are directly exposed to smoke are at the highest risk. So it comes as no surprise that cancers of the mouth, upper and lower throat, nose and sinuses, larynx and oesophagus are noticeably more common in smokers than in non-smokers. But aside from this, studies have shown a direct link between smoking and increased chance of developing anomalies in the cells of the liver, pancreas, stomach, kidneys, bowels, ovaries, bladder and cervix. There are also some indications that diseases caused by smoking also include some types of leukaemia as well as breast cancer.

Lung cancer causes

Aside from nicotine and carbon monoxide, cigarette smoke contains over sixty cancer-causing compounds including benzene, polonium-210, nitrosamines, beryllium and even lead, cyanide and arsenic. All of these chemicals damage the DNA inside lung cells while some others, also present in cigarette smoke, like chromium and benzopyrene, stick to the DNA molecules, increasing the chances for long-term damage.

While cellular repair mechanisms do try to mitigate all the damage to DNA and stop the copying and reproduction of the damaged genetic code, this process isn’t 100% perfect and chemicals like nickel and arsenic can even interfere with the pathways for repairing and containing damaged DNA. When all these dangers of smoking are combined, the chance for a mistake on a cellular level increase and there is a possibility that a damaged DNA code can be copied and reproduced, thus turning the cell cancerous.

But, there is another risk factor, a less direct way in which smoking can cause this serious disease, and that is by weakening the immune system and lowering the body’s ability to cope with toxins which might be completely unrelated to cigarette smoke. Due to this mechanism, smokers can reduce their biological ability to mitigate damage caused by secondary sources.

While the human body is remarkably good at repairing the damaged DNA and stopping its reproduction, scientists estimate that for every 15 cigarettes smoked, there is a DNA change in once cell that could lead to cancer if natural repair mechanisms don’t fix the problem. Since they mostly do, medical experts believe that the “true” cause of lung cancer is the build-up of damage in a single cell which first alters the DNA and then interferes with the repair mechanisms so that the damaged DNA ends up being reproduced and copied into new cells, thus leading to disease. For most, it takes years, even decades before this kind of damage occurs, but there is no guarantee that everyone can have that much time. In fact, cases where people got lung cancer from exposure to second-hand smoke prove that there is no safe limit in either amount or time when it comes to tobacco smoke.

Smoking and mouth cancer

Another type of cancer that is proven to be in direct relation to smoking is mouth cancer or oral cancer. Although there are other identified causes, including the Human papilloma virus (or HPV for short), cigarette smoking and tobacco chewing are still the leading risk factor in the world.

Since mouth cancer can develop in different areas of the mouth, it can be somewhat hard to identify and is, most of the time, discovered by a dentist and not a doctor. However, the mechanism by which smoking leads to this serious disease is the same as in lung cancer – namely, cancer-causing chemicals in tobacco smoke damage the DNA in mouth cells, leading to accumulation of damage which in turns leads to reproduction and replication of the cancerous cell.

Both these types of cancer clearly demonstrate that those organs that are directly influenced by tobacco smoke are more likely to be affected. However, since inhaled compounds also enter the bloodstream and are thus transported throughout the body, the risk is greater as cancer can appear on other organs and parts of the body.

Exactly because of the fact that cigarette smoke is undoubtedly harmful and there is no safe way to filter it, passive smoking can also lead to these conditions, although in a noticeably smaller percentage of patients.


  1. Cancer Prevention – WHO