Why smoking is harmful to health?

Because tobacco contains a variety of irritating and toxic substances. Among them, nicotine is the most toxic. Can make people's nervous system chronic poisoning, dizziness, insomnia and dreaminess, memory loss, inattention, mental decline, muscle weakness, affecting work and study. It can also narrow the contraction of blood vessels, increase blood pressure and accelerate the heartbeat, causing or aggravating coronary atherosclerotic heart disease. For young people, it may also cause or aggravate thromboangiitis obliterans. In recent years, according to the research of scientists, smoking is still the main cause of lung cancer. In addition, smoking is also an important factor causing chronic bronchitis. Therefore, there are too many dangers of smoking. Moreover, it's time for us teenagers to learn and grow up, and we shouldn't smoke at all.