State health officials have hired a Johns Hopkins University epidemiologist to investigate why a number of Anne Arundel County firefighters have developed cancer.

In the last decade, as many as 20 have died, and more than 20 current or former firefighters have the disease, said Cindy Ell, a former firefighter who works in a law firm representing some of the families.

Many in the department fear that the cases may be linked to a toxic oil used to ignite fires at its Millersville training facility in the late 1970s and early '80s, she said. The oil was laced with small amounts of polychlorinated biphenyls, the toxin commonly known as PCBs.

Nelson Sabatini, the state's health secretary, said he was concerned enough about the cancer reports to launch the investigation.

"One of the common links appears to be this question of the training that occurred while they were at the academy," he said. "But we don't know the answers. We need to have an honest gathering of the facts to find out what kinds of cancer we are talking about. What's the common linkage? What is it that these firefighters may have done and may have been exposed to?"

The matter was referred to the state this month by Katherine Farrell, Anne Arundel's acting health officer, who said the county had tried to investigate the illnesses on its own but lacked the resources to do a full inquiry. Farrell, who worked at the state health department in the late 1970s, said she remembers that health officials were concerned about the use of the oil and had urged fire officials not to burn it. But because the concentrations of PCBs in the oil were so small, they "didn't have the authority to order [the fire department] to stop using it," Farrell said.

Capt. Michael Cox, a spokesman for the fire department, declined to comment except to say, "We are cooperating fully with the state Department of Health and Mental Hygiene in their efforts."

The U.S. Environmental Protection Agency considers PCBs a "probable human carcinogen." The toxin has been proved to cause cancer in animals, according to the EPA. Its production was banned in 1977.

Finding the causes of cancer can often be very difficult, Sabatini said, especially in cases going back several years. It is possible, he said, that the six-month probe by Jonathan Samet, the chairman of the department of epidemiology at the Johns Hopkins Bloomberg School of Public Health, will yield no definitive answers.

"We have to be very careful not to jump to any conclusions," Sabatini said.

Last year, however, the State Workers' Compensation Commission ruled that David Fowler, a former firefighter, contracted non-Hodgkin's lymphoma as a result of working on the force. But the commission did not specifically identify how he got the disease.

Samet said that during his investigation, he will pore over the state's cancer registry, which lists cases of the illness; review any studies involving cancer and firefighters; and, at some point, attempt to "identify all the firefighters and try to track them in a way over time to see what the cancer rate really is."

Farrell said the number of sick firefighters may sound like a lot. "But the question is whether that's unusual when compared to the rest of the population," she said. "And that's really what the study will be about."

Firefighters "face a multitude of risks every day," she said. "Anyone who faces smoke on a daily basis has a multitude of substances that are risky to inhale."

But Ell and others are becoming convinced that the oil burning is linked to the illnesses. Ell has started to compile a database of firefighters who have been diagnosed with cancer and said she already has come across multiple types of the disease.

Kim Bettis, who has served as a firefighter for 23 years, was diagnosed with melanoma two years ago, not long after her husband, John Dull, a battalion chief in the fire department, died of a brain tumor.

"I know at least four battalion chiefs that have died from brain tumors, and they all worked together," Bettis said. "It's overwhelming."

Health secretary Nelson Sabatini said that although PCBs may be to blame, "we have to be very careful not to jump to any conclusions."