Editor's note: This report is part two of a two-part series.

TAMPA, Florida (CNN) -- For Rick Kelly, the first sign of cancer was a feeling of discomfort in his chest.

Jim Fontella, diagnosed with cancer in 1998, was based at Camp Lejeune in 1966-67. Read his story in Part 1.

"My wife would hug me, and it became almost unbearable," he said. "I went to a doctor, and they sent me to the oncologist, and they did biopsies on both sides. And then I ended up with a double mastectomy."

Kelly is one of 20 retired U.S. Marines or sons of Marines who once lived at Camp Lejeune, North Carolina, and who are now suffering from breast cancer, a disease that strikes about one man for every 100 women who get it. Each of the seven men CNN interviewed for this report has had part of his chest removed as part of his treatment, along with chemotherapy, radiation or both.

All 20 fear that water contaminated with high levels of toxic chemicals may have caused their illnesses, but the Marine Corps says no link has been found between the contamination and their diseases. Without that link, the men are denied treatment by the Department of Veterans Affairs, which says it can't treat them for a condition that hasn't been shown to have been "service-related." Watch "That's when I was shocked" »

Kelly was diagnosed with breast cancer in 1998, 16 years after he served at Camp Lejeune. Now a single father of a 7-year-old boy and without health insurance, he filed a claim with the VA to help pay his medical bills.

Kelly said his VA representative told him, "It's not the VA's problem, it's the Marine Corps' problem." Watch Marine Corps general respond to some of the allegations »

And Peter Devereaux, who was stationed at Camp Lejeune in the early 1980s, was told in writing that his breast cancer "neither occurred in nor was caused by service."

But Kelly, Devereaux and other stricken men CNN interviewed say the Marine Corps knew about the contamination in tap water years before it shut down tainted wells in the mid-1980s. Now they want the service to acknowledge that the water from those wells made them sick, which could make them eligible for VA benefits.

"They want it to go away, and it kind of just makes you sick with disgust," Devereaux said.

The men with breast cancer are among about 1,600 retired Marines and Camp Lejeune residents who have filed claims against the federal government. According to congressional investigators, they are seeking nearly $34 billion in compensation for health problems they say stemmed from drinking water at the base that was contaminated with several toxic chemicals, including some the federal government has classified as known or potential cancer-causing agents.

Jerry Ensminger is a former Marine Corps drill instructor who was stationed at the base in 1976, when his daughter, Janey, was born. She died of childhood leukemia at age 9.

"We were being exposed when we went bowling," Ensminger told CNN. "We were being exposed when we went to the commissary. We were being exposed when we went to the PX. And then when we went home, we were being exposed over there."

Ensminger helped start a Web site, "The Few, The Proud, The Forgotten," which was set up to organize people who believe they have been affected by the contamination. He also testified at a 2007 congressional hearing on the issue.

He and others say the Marine Corps waited too long to test and shut down the wells after learning the drinking water was contaminated.

"Five years they knew they had this stuff in the tap water," Ensminger said. "They never went and tested the wells. I think it's just criminal."

In 1980, the Navy hired experts to test for trihalomethanes, a byproduct from chlorination, in the base tap water. The experts reported that some of the base tap water was "highly contaminated," according to a test report.

In 1981, the lab again found "water highly contaminated" -- and added the word "solvents," with an exclamation point. In August 1982, the experts found one sample with levels of trichloroethylene, a degreaser believed to cause cancer, of 1,400 parts per billion. Today's EPA safe level for the substance is five parts per billion.

"We've never seen 1,400 parts per billion of trichloroethylene, so that is very high," said Frank Bove, an epidemiologist with the federal Agency for Toxic Substances and Disease Registry.

"These are very toxic chemicals we're talking about," Bove said.

But it would take until late 1984 and early 1985 for the Corps to begin widespread testing of wells on the base and shutting down ones that had been polluted. In addition to trichloroethylene, chemicals eventually identified in the drinking water included benzene, which the federal government identifies as a known cancer-causing agent; and the dry-cleaning solvent perchloroethylene, a suspected carcinogen.

The Marine Corps said two independent studies have found no link between water contamination and later illnesses. And in a statement to CNN, the Marine Corps wrote, "Once impacted wells were identified, they were promptly removed from service."

A fact-finding panel created by the Corps in 2004 ruled that officials acted properly and that the water was "consistent with general industry practices" at the time. And investigations by the Bush administration's Justice Department and Environmental Protection Agency found no criminal conduct by Marine Corps officials and no violations of the Safe Drinking Water Act.

Tyler Amon, an EPA investigator, told a House committee in 2007 that some employees interviewed during the criminal investigation appeared coached and were not forthcoming with details. The Justice Department decided against filing charges based on his concern, however.

The Corps told CNN that its actions "must be considered in the context of the state of science at the time" and should be viewed with a "contemporary understanding" of the chemicals involved and the "evolving regulatory structure" of the time.

But while chemical solvents may not have been tightly regulated back then, there was a clear general awareness on base about the need for proper handling.

In June 1974, the base commander issued an order calling for the "safe disposal" of organic solvents, warning that improper disposal could create "hazards" such as "contamination of drinking water." And as far back as 1963, the Navy's Bureau of Medicine outlined similar guidelines.

Two years ago, Congress ordered the Marine Corps to notify all Marines and their families who might have been exposed -- an estimated 500,000 people. The Marines say they have worked with environmental and health agencies "from the beginning" to determine whether the contamination resulted in any illness, and "this collaboration continues to the present day."

"I think if cancer of the breast in men or other kinds of cancer have been linked to this exposure, that we ought to know about that," said Richard Clapp, a nationally recognized epidemiologist who has studied clusters of cancer cases at toxic sites. "The families deserve that. The veterans themselves should know about that, and they should be compensated if the link can be made."

But for now, there is no proven link -- just Marines and their families who say they are suffering.

"Having been a former drill instructor where I trained over 2,000 brand new civilians and made them into Marines, I instilled in those Marines our motto, which is Semper Fidelis -- our slogan, that we take care of our own," Ensminger said.

"Nobody in this world has been more disillusioned than I've been. I feel like I've been betrayed."

All About U.S. Marine Corps • Camp Lejeune • U.S. Department of Veterans Affairs