After reading a memo yesterday from the director of the University of Pittsburgh Cancer Institute warning about the potential hazards of cellular phones, Anne Kisak decided she might want to pay an extra $5 a month for an unlimited text messaging plan.

Text messaging, Dr. Ronald Herberman advised in his memo to about 3,000 faculty and staff, is much safer than calling and holding the phone to one's ear.

"If texting saves my children from talking on the cell phone during this development stage in life, maybe it's a good thing," said Ms. Kisak, who works at the Hillman Cancer Center as a director of clinical pathways and special projects.

In the memorandum, Dr. Herberman, who also is director of UPMC Cancer Centers, outlined possible risks associated with cell phone use. He advised that people keep cell phone conversations brief, use a hands-free device, and keep cell phones far from children, whose thin skulls and scalps make them especially vulnerable to the electromagnetic fields.

Dr. Herberman is believed to be the only cancer center director in the country to release an advisory about the possible hazards of cell phone use. Evidence supporting the theory that cell phones might cause brain tumors is inconclusive, and other studies cited by the U.S. Food and Drug Administration have found no correlation between the two.

Still, said Maryann Donovan of Pitt's Cancer Institute, it's better to act now rather than wait for absolute proof.

"If you wait to be 100 percent sure, a lot of people could be dead," she said, noting that the enormous popularity of cell phones could mask their dangerous side effects, the same way cigarettes were once thought to be harmless.

Ms. Donovan rarely holds a cell phone to her ear, she said. She prefers to use a hands-free device, speaker phone or a land line -- all of which are safer alternatives than holding a phone to one's ear, according to Dr. Herberman's memorandum.

Word of Dr. Herberman's advisory was spreading around Pittsburgh yesterday.

Julia Morley, a 20-year-old college student from New Hampshire, said her cell phone is a calculator, alarm clock, calendar and vital communication tool.

"Unless the research was overwhelming, I wouldn't be too worried about holding it," she said. "If the studies were true, I might invest in a headset. It depends what the risk is."

Even if there was stronger evidence that cell phones caused brain tumors, Shelby Melrose, 16, of Squirrel Hill, said, it wouldn't keep her from using hers.

"I don't think I'll ever change the way I talk on my cell phone because it's more convenient than using another phone. ... It's so much easier to talk on the cell phone than to use a pay phone or wait until you get home," she said.

Scientific evidence proving -- or even strongly indicating -- that cell phones might cause brain tumors is very weak, said Dr. Arlan Mintz, a neurosurgeon at UPMC. But the evidence is noteworthy enough to take preventive measures just in case, he said.

"We don't want to be in a position where, 10 or 20 years from now, we find out [for certain] that there is an association between cell phones and brain tumors," he said.

The ubiquity of cell phones in America makes precautionary measures that much more imperative, Dr. Mintz said. Dr. Herberman's warning should cause people to take a second look at their cell phone, he said, and possibly spur scientists to research the issue further.

One way to do that, he suggested, would be to ask cell phone companies for their usage data, and use that information to study brain tumor patients at a hospital. A 20-year study comparing the health of cell phone users with that of non-cell phone users would be all but impossible, since nearly everyone has a cell phone, he said.

Ben Johnson, 17, of Edgewood, is among those who admits he uses his cell phone more than he'd like to, but also points out that it's a handy tool, for use as a calendar and keeping track of appointments.

"I don't really like talking on the phone, but I do it maybe three times a day. If I knew it caused cancer, I would try to use it less. If it was possible for me to get a cheap headset, I might look into doing that."