Curbing tobacco use and taking other steps to eliminate some of the most common risk factors for cancer could save millions of lives over the next few decades, US health officials said Monday.

Tobacco alone is predicted to kill a billion people this century, 10 times the toll it took in the 20th century, if current trends hold.

"In all of world history, this is the largest train wreck not waiting to happen," said John Seffrin, chief executive officer of the American Cancer Society.

Reducing tobacco use would have the single largest effect on global cancer rates, Seffrin and other health officials said Monday in unveiling two reference guides that chart global tobacco use and cancer.

Changing diets to contain fewer saturated fats and more fruits and vegetables, as well as reducing infection by cancer-causing viruses and bacteria, could also cut rates dramatically, they said.

"We know with cancer, if we take action now, we can save 2 million lives a year by 2020 and 6.5 million by 2040," said Dr. Judith Mackay, a World Health Organization senior policy adviser.

Today, tobacco accounts for one in five cancer deaths, or 1.4 million deaths worldwide each year, according to the new Cancer Atlas. When deaths from tobacco-related cardiovascular and pulmonary diseases are included, the yearly death toll rises to nearly 5 million and it's expected to keep going up.

An estimated 1.25 billion men and women currently smoke cigarettes, and more than half of them will die from the habit, according to the newly issued second edition of the Tobacco Atlas.

The two atlases were released Monday at an International Union Against Cancer conference. The two statistics-packed guides are meant as reference guides for doctors, politicians, academics, students and attorneys who work on cancer and tobacco control.

Lung cancer remains the major illness among the 10.9 million new cases of cancer diagnosed each year, according to the Cancer Atlas. And it is not likely to be bumped from its perch: In countries like China, where 300 million men now smoke, lung cancer could eventually kill a million smokers a year, Seffrin said.

The authors and researchers responsible for the atlases fear that a reduction in the global prevalence of smoking would do little to curb what they called the "tobacco epidemic."

"Even if smoking rates decline worldwide, there will be a constant or even slightly increasing number of smokers due to population increases," said Michael Eriksen, director of the Institute of Public Health at Georgia State University.

In 2002, besides the nearly 11 million new cancer cases worldwide, there were nearly 7 million cancer deaths. By 2020, officials anticipate there will be 16 million new cases a year and 10 million deaths. An estimated 70 percent of those deaths will occur in developing countries, according to the Cancer Atlas. The number of new cases is largely the result of the increasing proportion of older people in the world.

The risk of developing cancer is higher in the developed world, according to the Cancer Atlas. In the United States, for instance, the probability someone will develop cancer by age 65 is nearly 18 percent. In Oman, the probability is just shy of 6 percent. Still, cancers in developing countries are more often fatal.

The American Cancer Society published the two atlases with help from the International Union Against Cancer, WHO and Centers for Disease Control and Prevention. English, French and Spanish editions are now available; Chinese language versions are due later this year.