The recipients' findings and subsequent research have established that alterations in genes are the initial step in producing human cancer.

Prolonged exposure to nickel and its compounds have been shown to produce cancer.

Of course, a mechanism would have to be devised to prevent them from producing cancer.

Although the virus does not act alone in producing cancer, Dr. Broker said, it is the primary factor in the disease.

"It's the dose that makes the difference," he said, and large doses or chronic exposure could produce nerve inflammation, skin allergies or even cancer.

The researchers did not expect to find cancer in the baseball players because it takes three to five decades for smokeless tobacco to produce cancer, she said.

The larger danger in processing uranium is chemical poisoning from the heavy metal, which does not produce cancer.

The research confirmed an independent study that found in 1953 that painting cigarette tars on the shaved backs of mice produced cancer.

In 1915, Yamagawa and Ichikawa showed that repeated application of coal tar to rabbit's ears produced malignant cancer.

In an interview in a medical journal, he said that is second-most-important work was showing that even small doses of ionizing radiation could produce cancer.