"I was really healthy," he says. "In fact, about two or three years before I was diagnosed, we climbed Mount Adam, a mountain in the state of Washington, and I can't even climb the steps of my house right now."
Leth's challenge now is staying alive long enough to try and prove that his cancer came from exposure to toxic chemicals at the IBM computer chip plant in San Jose.
"Is there a relationship? I think there is," Leth tells CBS News Correspondent Sandra Hughes.
Leth is not alone. A total of 130 former IBM workers and surviving relatives are suing Big Blue. But with no scientific evidence to prove that the process used in making chips causes cancer, they're fighting an uphill battle.
"The worker exposure levels, we don't know, because the industry doesn't share the data," explains Dr. Joe LaDou, who has tracked the health of Silicon Valley workers for 30 years. He claims that every time a health study is proposed that might link the manufacture of computer chips to cancer, it goes nowhere.
"The long-term health effects on the workers, we don't know, because the industry refuses to let us look at them," Dr. LaDou adds.
The California Department of Health requested a study of cancer rates among semiconductor workers. The idea had the support of several occupational health experts, and the Environmental Protection Agency was willing to pay for it.
"Everything was ready, funding and all," Dr. LaDou recalls. "But the industry simply marched in, with Intel and IBM leading the pack, and said, 'No.' No explanation, no nothing. It just won't happen."
Intel executive Howard High, speaking on behalf of the Semiconductor Industry Association, says, "This industry has always done the right thing when it comes to worker safety." But, he adds, the industry will not agree to a study until someone brings it evidence to prove a link between chip-making and cancer.
"We keep looking," says High, "and we don't see the scientific, the medical evidence that makes you believe that that is, in fact, the case."
The booming industry employs 160,000 people nationwide, and it's growing so fast, government health agencies can't keep up.
While occupational health experts fear a potential cancer epidemic is being ignored, not one government agency is currently studying the cancer claims, even though some see a real danger.
"I am alarmed," says Charles Jeffress, assistant U.S. labor secretary, "at the chemical use in this industry and alarmed at the number of illnesses that are being reported by people working in this industry."
The government may claim to be alarmed. But when Dr. LaDou wrote to the National Institute for Occupational Safety and Health, asking it to force the industry to participate in the California health study, he was told that the agncy did not have the authority to "compelÂ…industryÂ…to participate in research for such a study."
So who is responsible for worker safety?
"It's very clear by law in this country that employers are required to provide a workplace free of safety and health hazards," says Jeffress.
Try telling that to Lee Leth, whose claims until now have been ignored by an industry that seems to answer only to itself.