Smoking is the leading cause of preventable death in the United States. Tobacco use is the direct cause of more than 170,000 cancer deaths each year – or approximately one-third of all cancer-related deaths, according to the American Cancer Society (ACS).

In the United States, the number of smokers has declined over recent years, according to the U.S. Centers for Disease Control and Prevention (CDC). In 2003, 45.4 million Americans smoked – 21.6 percent of the population. The results of a survey conducted in 2004 indicated that the number of smokers dropped to 44.5 million (20.9 percent). Overall, more than one out of every five people still smoke in the United States.

Although smoking has been on the decline in the United States, it is rising in various areas of the world. The National Cancer Institute (NCI) estimates that 3 million people die each year from tobacco-related causes. By 2025, this number is expected to exceed 10 million.

In the United States, smoking incidence varies by ethnicity with the highest percentage among Native Americans. According to the ACS, the percentage of smokers per ethnic group is as follows:

Percentage of Smokers by Ethnicity

Cigarettes and tobacco products are directly responsible for the high incidence of certain cancers. Lung cancer is the most notorious example. Before the 20^th century, when cigarettes were not mass produced or readily available, lung cancer was rarely seen.

As cigarettes became widely available, cases of lung cancer rose dramatically. Today, smoking is responsible for about 87 percent of lung cancer cases in the United States, according to the ACS. In areas of the world where more people smoke, there has been a corresponding rise in lung cancer cases.

The risk for lung cancer increases by the length of time and the number of cigarettes a person smokes. Physicians often refer to this risk in pack years. Smoking a pack a day for one year is one pack year. Smoking two packs a day for a year equals two pack years, three packs a day for a year equals three pack years and so on. A person with 40 pack years or more has the greatest risk of developing lung cancer.

Tobacco smoke has been shown to contain approximately 4,000 chemical agents, including 60 known carcinogens (cancer-causing substances). These carcinogens can damage a person’s genes, including those that regulate the growth of cells. Without control, cells are free to grow abnormally or reproduce rapidly.

Some of the more toxic elements include carbon monoxide, tar, formaldehyde, benzene, arsenic and lead. These chemical agents and known carcinogens can cause harm to nearly every major organ of the body. Besides lung cancer, tobacco is implicated in many other cancers, including those of the following body areas:

• Oral cavity and throat
• Stomach
• Liver
• Pancreas
• Kidney
• Bladder
• Cervix
• Prostate
• Colon and rectum

Below is a chart that shows the increased risk of death of specific cancers for men and women who smoke. For instance, a man has 23 times the chance of dying from lung cancer as compared to a man who does not smoke.

Source: American Cancer Society’s Smoking and Cancer Mortality Table

Source: American Cancer Society’s Smoking and Cancer Mortality Table