By 2005, the number of cell-phone users worldwide had reached 2.4 billion. A recent Pew survey found that 75 percent of US adults own cell phones, and that more Americans would have trouble giving up their cell phones than any other piece of technology they owned, including their television, land line, or computer. Cell phones are everywhere, and we use them a lot.

If your cell has become as close to you as your wallet, here's something to consider. According to videos circulating on the net, cell phones emit enough radiation to pop corn. Seriously! Watch this video to see for yourself. Don't believe your eyes? Then watch another clip and then ask yourself: if a phone can make the corn go sizzle, what's it doing to your brain? Are the videos real or a hoax? It doesn't matter. They serve to focus attention on a serious issue.

As you may know, there's a disturbing body of evidence indicating a link between cell phone use and brain cancer--but many sources discount that evidence. In their corner, they have several impressive studies indicating that cell phones pose no dangers at all. But look closely at that research, and you'll typically find flawed methodology. For instance, a Danish study of 420,000 cell-phone users found no evidence of cancer risk, but the subjects included people who made just one call per week, and the study also included data from 1982 when calls tended to be very brief because they were so expensive, unlike today. It also excluded commercial cell phone users --in other words, the heaviest users.

On the other side of the argument is research linking cell phone use to genetic damage. A study last year at the Weizmann Institute of Science in Israel determined that even 10 minutes of cell-phone use led to changes in how brain cells divide, triggering the formation of tumors and leading to a 58-percent increased risk of parotid gland tumors . And a 2006 study out of the Swedish National Institute for Working Life discovered that heavy cell-phone users stood a 240-percent increased risk of developing a cancerous tumor on the side of the head where they used their phone. A 2005 study at Guru Nanak Dev University, in India, found heightened risk of genetic damage, and ditto for a 13-nation study sponsored by the World Health Organization.

Because of the weight of evidence on both sides, most sources consider the jury still out on the safety issue. If you want to believe cell phones are safe, you can find supporting data. If you choose to believe they pose a threat, there's plenty of evidence, too. But meanwhile, there's the popcorn video to consider, and the evidence of your own senses. Some of us, at least, notice tingling or headaches after even brief cell-phone use. Still, we've developed the cell-phone habit and kicking it seems unthinkable -- head tingling be damned. So we hope for the best and use headsets just in case.

And Bluetooth headsets do indeed emit much lower levels of radiation than the phones. If you hold your phone far from your body when using a Bluetooth, you're probably better off than if you hold the phone right to your ear or against your body, as your internal organs absorb radiation too. Some sources, though, say even Bluetooth poses significant dangers, perhaps even greater than the phones themselves since the transmitter sits closer to the brain than the phone does.

It seems wise, given the conflicting evidence, to be prudent about using your cell. Use it only when you must, use the speakerphone if at all possible, and keep it far away from your body. Certainly, keep it out of your pants pocket next to anything you may value. You can invest in a relatively inexpensive product to shield you from cell-phone radiation. Don't give a cell to your kids, for goodness sakes, until the results are in about long-term effects. And take a cue from a June 3 article in the New York Times that quotes three prominent neurosurgeons who recently appeared on Larry King Live.

Dr. Vini Khurana, an associate professor of neurosurgery at the Australian National University, says, "I use it on the speaker-phone mode. I do not hold it to my ear." His less-cautious colleague, Dr. Keith Black of Cedars-Sinai Medical Center in Los Angeles, says, "I think the safe practice is to use an earpiece so you keep the microwave antenna away from your brain."

I tend to agree that any device capable of popping corn (even as a joke) belongs nowhere near my little gray cells, lest my brain end up fried, just like in the old anti-drug commercial. And indeed the drug commercial seems apropos, because cell-phones may well be the addiction of our era. We won't give up the phone even though we suspect it might be bad for us, we want it above other toys, we want it attached to us every day, all day, and we get the shakes if we find ourselves without it.