Section_ⅠWelcome_to_the_unit_&_Reading_-_Pre­reading

　　Do you know how many diseases smoking can lead to?

　　Smoking causes nearly 1 in 5 deaths each year. About 8.6 million Americans suffer from smoking­related health problems.

　　Cancer

　　The smoking­cancer link is well­known to most people: Smoking causes at least 30% of all cancer deaths and 87% of lung cancer deaths, according to the American Cancer Society. Smoking increases the risk of at least 15 cancers, including those of the throat, lip, mouth and stomach.

　　Diabetes (糖尿病)

　　Diabetes and smoking don't mix. Tobacco use can increase blood sugar levels. The more you smoke, the bigger your risk is. More than 20 cigarettes a day almost doubles a smoker's risk of developing diabetes, compared with nonsmokers'. "People with diabetes already have higher cardiovascular (心血管的) risks, "says David Kendall of the American Diabetes Association. "Smoking just adds to the burden of that risk."

　　Heart

Smoking can double the risk of dying from coronary heart disease (冠心病), the leading cause of death in the USA, the American Heart Association says. Each year, nearly 900, 000 people die of coronary heart disease. That's because smoking narrows blood vessels supplying the heart and other parts of the body; it also raises blood pressure.