GWEN IFILL: Now, an international panel of scientists is raising questions about whether there's a link between cell phones and cancer.
Jeffrey Brown has the story.
JEFFREY BROWN: The news led to provocative headlines, all triggered by an announcement from a panel of the World Health Organization.
A team of 31 scientists from 14 countries said radiation emitted by cell phones is -- quote -- "possibly carcinogenic" and may be associated with some risk for brain cancer.
But the group also said that evidence is a -- evidence of a direct link is still far from clear, and it called for more study.
A cell phone industry group put out a statement that today's news doesn't mean cell phones cause cancer.
So, to walk through what is and isn't known, we're joined by Dr. Keith Black, chair of neurosurgery and neuroscience at Cedars-Sinai Medical Center in Los Angeles.
Dr. Black, welcome to you.
So, what does "possibly carcinogen" mean exactly?
DR. KEITH BLACK, Cedars-Sinai Medical Center: What it means is that the World Health Organization panel of scientists looked at the current available evidence that's been published, as well as some unpublished data that should be coming out shortly from the Interphone, which is a multinational study, and concluded that the evidence suggests that there is a possible link between cell phone use and brain cancer.
This is looking at multiple studies, but the best conclusion at this point would suggest that there is the possibility for a link.
JEFFREY BROWN: Now, the issue is the radiation, right? Explain what researchers are concerned about and what they're studying.
DR. KEITH BLACK: So, essentially, a cell phone is a microwave antenna which generates microwave radiation.
And we know that microwave radiation can penetrate into the brain when you hold the cell phone next to your ear. In fact, it's related to the square of the distance. So, the closer, you get a much, much greater amount of radiation going into the brain.
That radiation and energy, when it hits biological tissues, there is some concern that it may actually cause cells, over a long-term time period, to transform from normal cells into cancer cells.
JEFFREY BROWN: Well, to be clear now, this is a shift for the WHO, but as I said in the introduction, at the same time, researchers said that they have -- they have not found a direct link so far.
So, tell us, what is it that we don't know, and what makes this hard to make a direct link?
DR. KEITH BLACK: So, what we don't know currently is whether cell phone use is safe, and we don't know that it is unsafe.
The problem that we have is that about half of the studies have shown that there is no correlation to brain cancer and cell phone use, and half of the studies that have been done have shown a correlation.
The problem that we have is that the studies that tend to show no correlation tend to be studies that look at people that have had very short time periods of cell phone use and very low amounts of minutes of using a cell phone. The studies that do show a correlation tend to be studies that have looked at people that have used cell phones for a period of 10 years, for example, and are using cell phones, say, for 30 minutes a day, higher-term use.
So, the longer-term studies, the studies that have been somewhat better-designed, although still flawed, have tended to show this correlation.
The problem we have is that we know that most environmental agents that cause cancer don't cause cancer after a month or a year or two years of exposure. The best example I can give to illustrate this is that, if one was to start smoking cigarettes when they were 12, we don't expect them to develop lung cancer when they're 22. We expect them to develop lung cancer when they're 42 or 52, three or four decades of exposure.
We just don't have that long period of study with people that have used cell phones.
JEFFREY BROWN: Well so of course people wonder what they should do.
And I -- this group didn't propose guidelines or regulations. As to advice to consumers, I noted that one of the researchers said, "Pending the availability of additional research, it is important to take pragmatic measures to reduce exposure, such as hands-free devices or texting."
So, fill in that picture for us. What advice would you give people, given what we know and what we don't know?
DR. KEITH BLACK: So, you know, the best thing is to be informed.
I think the best thing for consumers and the best thing about the WHO statement is that at least consumers can be aware that there is the potential risk, and they can -- therefore, they can begin to sort of take measures to use a cell phone more safely.
Even if you read the insert in the cell phone, it will tell you to hold the cell phone an inch or so away from your ear, so that the radiation doesn't go directly into the brain. Best to use an ear piece, best to use it on speaker mode, best to use text, if you're driving, best to use hands-free, and not to put the cell phone, you know, right adjacent to your brain.
The other thing to be aware of is that we haven't had any good studies in the pediatric population. A child's skull is much thinner. The scalp is much thinner. And the amount of radiation that goes into the pediatric brain is much higher than in the adult. So, we should be cautious with how we allow our children to use a cell phone. They're going to be the ones not only using it at a much younger age, but using it over a much longer duration.
JEFFREY BROWN: And just -- just briefly...
DR. KEITH BLACK: So...
JEFFREY BROWN: Oh, I'm sorry.
No, just briefly, I can't resist asking you, Dr. Black, what about you yourself? You use a cell phone -- or does this change how you see it?
DR. KEITH BLACK: No, I use a cell phone. But I always use it either on speaker mode or use it with an earpiece or text. I don't put it next to my brain.
You know, I think to -- also just to put this in context for your viewers, you know, the risk of developing brain cancer is about six per 100,000 in a population per year. So, even if the risks were to double, you're looking at about 12 cases for 100,000 in the population.
It doesn't mean that, you know, we're going to be walking down the streets and people are going to be falling over dying of brain cancer. You know, the overall number of people that develop brain cancer, you know, it is not like lung cancer or breast cancer. It's a little smaller.
But what's important to recognize is that, if you do develop brain cancer, it's one of the most devastating illnesses that you can have. So, if you want to take precautions, at least you're aware that your cell phone is not necessarily a safe device, and using the things that we have outlined...
JEFFREY BROWN: OK.
DR. KEITH BLACK: ... earpiece, speaker mode, you know, can be a safer way of using it.
JEFFREY BROWN: Alright, Dr. Keith Black, thanks so much. Thank you very much for joining us.
DR. KEITH BLACK: Thank you.