Smoking kills over 400,000 people a year -- more than one in six people in the United States -- making it more lethal than AIDS, automobile accidents, homicides, suicides, drug overdoses, and fires combined.

It is estimated that the U.S. spends an astounding $50 billion each year on smoking-related health costs. Smoking may be even more dangerous now than 30 years ago, most likely because the lower tar and nicotine levels in most cigarette brands cause people to inhale more deeply.

In one study only 42 percent of male lifelong smokers reached the age of 73 compared to 78 percent of nonsmokers. People who are exposed to second-hand or side-stream smoke are also at risk. Smoke that is exhaled not only contains the same dangerous contaminants as inhaled smoke, but the exhaled smoke particles are smaller, so that they can reach distant sites in the lungs of involuntary or passive smokers and do great harm.

Quitting smoking is one of the most important things you will ever do: You will live longer and live better. Quitting will lower your chance of having a heart attack, stroke, or cancer. If you are pregnant, quitting smoking will improve your chances of having a healthy baby. The people you live with, especially your children, will be healthier. You will have extra money to spend on things other than cigarettes.

The Centers for Disease Control and Prevention says cigarette smoking is responsible for 151,322 cancer deaths annually in the United States. Most of those -- 116,920 -- are from lung cancer. The CDC says men who smoke are 22 times more likely to die from lung cancer than non-smokers. Women who smoke are 12 times more likely to die from the disease. Statistical studies have long shown that people who don't smoke live longer than people who do, and scientists have seen statistically the correlation between smoking and incidences of lung cancer since the 1950s.

Smoking also has been linked time and again to cardiovascular diseases. Among these, the biggest killer is heart disease: according to the CDC, smoking triples the risk of dying from heart disease among middle-aged men and women. Studies also show an increased risk of death from stroke, aneurysms, high blood pressure, and other cardiovascular illnesses.

Smoking is cited as a risk for dying of pneumonia, chronic bronchitis, or emphysema. The CDC says people who smoke increase their risk of death from bronchitis and emphysema by nearly 10 times.

According to the CDC, 400,000 Americans die each year because they smoke cigarettes, making it the single most preventable cause of premature death in the United States. Quitting doesn't necessarily help, according to another University of Birmingham study -- at least not if the smoker waits too long. Stroke risk is high for up to 20 years after a smoker quits, according to that study, published in the Journal of Epidemiology and Community Health. The CDC says that on average, if you smoke, you will die seven years earlier than if you don't.