Smoking cigarettes can seriously harm your health in several ways. It increases the risks of various cancers like lung cancer and heart disease, which are among the leading causes of death in the UK. Over 100,000 people die each year from smoking-related illnesses. Smoking also reduces life expectancy by about 10 years on average compared to non-smokers. The chemicals in cigarettes are addictive and can damage the lungs and blood vessels long-term in ways that lead to chronic illnesses and early death.