What makes cigarettes really harmful is the cigarette smoke, which contains 7,000 chemicals produced when the cigarette is burned. This is what turns a seemingly plain stick of tobacco into the notoriously addictive and harmful substance that we know cigarettes to be.
Every stick of cigarette contains about 600 ingredients that when burned produces about 7,000 different chemicals, most of which are poisonous, with 69 of them known to cause cancer. Most of these chemicals are actually found in things like insecticides, lighter fluid, battery acid, mothballs, and our pavements. So, if you consider insecticides harmful, then imagine how much harmful cigarettes are. Together, all these chemicals can cause damage to almost every organ in the human body from our lungs down to our reproductive organs. And it has also been directly linked with deadly diseases like cancer and heart disease.
Perhaps the most dangerous substance found in cigarette smoke is carbon monoxide. Given that in most cases of fire, it's actually smoke inhalation and carbon monoxide poisoning that kills victims and not the fire itself, then you can see why the cigarette smoke produced when smoking, which also contains carbon monoxide, is really harmful to health.
However, to make things worse, cigarettes don't just harm the person smoking. What really makes them dangerous is the harm it could cause through second hand smoke, which affects the people around the smoker, and through third hand smoke, which affects even those who don't directly come in contact with smokers.
Studies have shown that second-hand smoke actually exposes non-smokers to the same chemicals as the smoker, himself. It's actually worse, because there are more toxins in the burning end of the cigarette, than the filtered end that smokers use. Third-hand smoke is just as bad. They may contain only about 250 chemicals that are harmful to health, but they can cause damage longer because it seeps into curtains, rugs, furniture, and every porous surface of your house or car and can be especially harmful to children.
Hope this helps.
Sources:
- What's In a Cigarette. http://www.lung.org/stop-smoking/smoking-facts/whats-in-a-cigarette.html
- The reasons why smoking is bad for you. https://www.medicalnewstoday.com/articles/10566.php
- What is Second and Third-hand Smoke? https://www.thoracic.org/patients/patient-resources/resources/second-hand-smoke.pdf