According to the World Health Organization: 90% of lung cancer, 75% of emphysema, 25% of coronary heart disease is caused by smoking. Smoking reduces life expectancy: When it comes to the dangers of smoking, we have to talk about life expectancy, according to some surveys, the average life expectancy of each cigarette will be shortened by 11 minutes, of course, this number may not be accurate, but one thing is certain, non-smokers than smokers to live longer.