paraplegics. this guy could stand up again. this is when an accident paralyzed five years ago and doctors said he would never walk again. a medical team implanted an electric stimulator and within months he was taking assisted steps on a treadmill. i'll be back at the top of the hour with more live news here. >> i'm dr. sanjay gupta. welcome to the show. today i'm taking a closer look at something that's become so closely woven into our lives it's hard to imagine what we would do without it. i'm talking about our cell phones. most of us take it for granted that they're safe and that may be the case. but i've also spent the last several months investigating and talking with people who say don't be so sure. some of you may already be rolling your eyes. i understand that. i want you to stick with me this half hour. we've been digging a little deeper to try to get a more definitive answer. i will tell you this, it wasn't easy. what surprised me is voices urging caution are not only getting louder, but they're getting more prominent. >> all right. i'm on my way. >> if you've ever put a cell phone for your ear, you should listen to what neurosurgeon dr. keith black has to say. >> there's no way to say that cell phone use is safe. i think the public has a right to know there could be a potential risk. the public generally assumes that if one is selling something on the market, that we have had assurances that that device is safe. >> to be clear, dr. black's message is at odds with headlines from the largest international study on cell phones and cancer. their conclusion, little or no evidence cell phones are associated with brain tumors. if you look just one layer deeper into the appendix of that same study, you'll see something unsettling. turns out participants in the study who use a cell phone for ten years or more had double the rate of a type of tumor. keep in mind cell phone use in the united states has only been popular for around 15 years. in 1996, there were 34 million cell phone users. today, nearly 300 million in use according to industry figures. >> environmental factors take decades to see their effect and not a few years. >> if it may take decades to get a clearer answer, what can we say about cell phone safety now? scientists here in san jose, california, are trying to answer that very question. >> one of the things we have to do first is literally put the brain inside the head. >> exactly. it's very light now. >> the fcc require that cell phones emit low levels of radiation. they try to mimic the human rain with salt, sugar and water. let me show you how they do this test. this is a model. this is an adult male. this is my phone attached there connected at the angle that most people would speak with. and inside over here very important this bubbly liquid inside that represents liquid brain. the phone makes a call after a period of time. this device will come over here and measure radiation at all sorts of different points in the brain. after that they will take all of those numbers and basically put it on a computer screen and tell us where the hot spots are and just how high the levels got. my cell phone measured within fcc limits. the whole process was surprisingly low tech. and what about different size skulls or children? >> in children their skull is thinner so microwave radiation can penetrate deeper into the brain of children and young adults and their cells are dividing in a much faster rate so the impact of microradiation can be much larger. >> there have been no studies on children and cell phone safety. here's something else that might surprise you. the cell manufacturers themselves advise against putting the cell phone right next to your head or really anywhere on your body. look with the iphone 4. safety instructions say when using the iphone near your body for voice calls keep it 15 millimeters away from your body. blackberry users specifically have safety guide lines saying keep it .98 inches or 25 millimeters from your body meaning your head or your pocket. dr. keith black has been talking about this longer than many but the voices joining him are becoming louder and more prominent. the city of san francisco pushed for radiation warning labels on cell phones. the head of a prominent cancer research institute sent a memo to all employees urging them to limit cell phone use because of possible risk of cancer. the european environmental agency has pushed for more studies saying cell phones could be as big a public health risk as smoking and leaded gasoline. the federal communications commission, the fcc, they set the guidelines for how much radiation a cell phone can emit and they say cell phones are safe. how can they be so sure? keeping them honest, we decided to come here to try to find out for ourselves but they declined an on-camera interview. the type of radiation coming out of your cell phone is called nine iedonnizing. it's not like an x-ray but more like a low powered microwave oven. >> what microwave radiation does in the most simplistic term is very similar to what happens to your food when you put your food in a microwave oven. it's cooking the brain. >> based on past statements, the fcc isn't convinced there's a real risk and maintain they do not endorse the need for consumers to take any precautions to reduce exposure. i tell you as a neurosurgeon and journalist and a guy that has three cell phones, i believe this is an important issue to investigate. for what it's worth, i haven't met anyone that says don't use a cell phone. that's not even realistic in today's age. there are things you can do, steps you can take to minimize your risk from radiation. if you are concerned about that, i'll show you those during the show. coming up first, we'll dig even deeper into this and you'll hear my conversation with a scientists studying this for over 20 years. i'll be right back with a special look at cell phone safety. granola bars made with crunchy oats and pure honey. nature valley -- 100% natural. 100% delicious. 8% every 10 years.age 40, we can start losing muscle -- nature valley -- 100% natural. wow. wow. but you can help fight muscle loss with exercise and ensure muscle health. i've got revigor. what's revigor? 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"not tonight, britta. not tonight." ♪ >> it brings your best minds and their brightest ideas together. it helps the largest of companies seize opportunity like the smallest of startups. it's the network-- the intelligent, secure cisco network that lets your employees, partners, suppliers and customers innovate and share so you can unleash the power of your most valuable asset: your people. we're talking about cell phone safety. there's been a lot of studies on this. the most recent study on cell phones is by researchers at the national institutes of health. they found something very interesting. the radiation emitted from your cell phone increased brain cell activity after 50 minutes of talk time. let me show you what i'm talking about here. these are natural scans of the brain looking at what's known as glucose metabolism. one way of measuring brain activity. this is with the cell phone on. look at the yellow around the brain compared to when the cell phone is off, very little yellow comparatively speaking. it shows there's an impact from using cell phones actually on the brain. we don't know if it's good or bad right now. these are preliminary findings. there may be concerns among people who already have some sort of brain problem. for example, someone has a brain tumor you can see increased glucose metabolism because cancer is high activity part of the brain and could that worsen it somehow. that's the questions that researchers at nih raised and that's part of the speculation overall. they say they are committed to studying it further. it all comes back to a question of safety. i should tell you now right off the bat what we're talking about today is highly controversial. we've talked to industry experts who say that scientific evidence has overwhelmingly indicated that wireless devices do not pose a public health risk. i talked to a lot of scientists and doctors who say, look, we just don't know and then there are people like a physician, researches are, former white house health adviser who founded a group called environmental health trusts. she studied the issues with cell phones for decades and the amount of radiation they give off and what your body might absorb trying to connect those dots. you may not agree with what you're about to hear and what she has to say, but i think it's important to hear. why did you get interested in cell phones? >> i knew about the history of tobacco and asbestos. >> it doesn't mean everything will become problematic. >> in this case i knew enough to look at effects that vent behav been appreciated and when i looked at the science, i learned the navy had warnings and had developed ways to protect personnel against exposures and i became curious. >> as you talk about and a lot of people do, everybody has one nowadays. young kids are using them. >> i prefer to think that we were naive and the reason we're talking about is that we're no long eer naive about this issue and governments of france and israel have issued warnings and those are not countries known to take these issues lightly. i'm particularly concern as a grandmother about the developing brain, about children who are using cell phones, about toddlers and infants whose parents are downloading white noise apps and lullabies and putting the phones by their heads. cell phones haveolutionized our lives. people have a right to know that cell phones are basically small two-way microwave radios and not kept directly on the brain or body and that's what the fine print warnings now tell you. >> a lot of people listening to us would say i thought this was studied and if there was something bad, we would know about it. >> we know that brain cancer did not show up at all as increased until 40 years after the bombing occurred. >> when you put it like that, it seems to make sense that we certainly just don't know, enough time has not passed to say anything definitive on this but the jury seems to be clear on this. >> i don't think the jury is clear in other nations right now. i think the answer so that has to do with the old fashioned issue, isn't it? the cell phone industry has been very, very powerful and is very influential on both sides of the aisle. all of us including me don't want to give up our phones. >> over ten years, the affect of using a phone as cumulative problem? are you accumulating the problems in your brain? >> it is. we are born with repair processes. we get damage to our dna every day by breathing, sunlight and what not. if we eat well and exercise and don't have too much exposure, that damage gets repaired. for cell phone radiation, young people today are growing up in a sea of radio frequency radiation that didn't exist even five years ago. >> we've been surrounded by radiation for a long time. you're saying this new radiation has changed the amount that we're exposed to? >> by billions and billions and billions of times. the amount of radio frequency radiation today is billions and billions of times greater than occurred at the big bang with which we evolved museum lihuman. i recognize that microwaves play an important role in many aspects of modern life. i think direct microwave radiation of the brain and that's why all of the fine print warnings advise don't hold the phone directly on the body. the test system for testing phones today which gives you the specific absorption rate uses a spacer here for every millimeter away from the brain you get a 15% reduction in radiation to the body. >> what's the worst case scenar scenario? if you extrapolate numbers you just talked about, how bad could this be? >> it would be a global epidemic. people have a right to know there are simple things to do. you have to have more of a public conversation about this. we are poorly served by reassurances that everything is okay by misuse of science. it's not helping us. it's not helping our children. >> i should say we had a long conversation with john walsh from the industry group that represents cell phone makers and maintain they are falling radiation guidelines enforced dy our own government and defer to fcc who say that cell phones are safe and we tried several times to ask the fcc how can we be sure cell phones are safe. they wouldn't speak to us about this and referred us to their websites by saying "the fcc does not endorse the need for any of these practices." a real estate agent who used a cell phone all the time. many of us do. he thinks in his case it gave him a brain tumor and he's fighting back. we'll tell you his story next on "sgmd." ♪ [ male announcer ] you've reached the age where you don't back down from a challenge. this is the age of knowing how to make things happen. so, why would you let something like erectile dysfunction get in your way? 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[ female announcer ] wake up to sweetness with honey nut cheerios cereal. kissed with real honey. and the 100% natural whole grain oats can help lower your cholesterol. you are so sweet to me. bee happy. bee healthy. we are back with sgmd. i'm dr. sanjay gupta. our focus on cell phone safety. we met alan marks. he is a successful businessman with a remarkable story. marks' battle with brain cancer led him on this journey to capitol hill, doing something he never expected to do. for alan marks, being in the real estate business for 30 years has been a passion. >> i like building homes and seeing people move into them, happy. >> but three years ago, his life changed. >> i had a seizure and i don't remember it. >> the cause of that seizure, a malignant brain tumor. surgeons were able to remove the cancer, but he says the recuperation was challenging. >> it took a long time. even now, i have some deficits, and you try to find ways to overcome them. >> and there's something else. marks feels responsible for his own cancer. >> i know what it is. it was my cell phone use. there's no way you could put something to your head for 20 years and not have it cause something. >> while there are some studies suggesting cell phones pose a health risk, many others do not. as the trade group representing cell phone manufacturers tell cnn, numerous experts and governments on cell phone organizations around the world have reviewed the studies on research and have concluded that the products meeting safety guidelines pose no health risk. but still, there are many manufacturers that recommend you do not put the phone next to your head. that is something marks and his family support. >> i still use my phone. i usually use a speakerphone or i use a headset. >> marks and his wife are urging lawmakers around the country to require manufacturers to put warnings directly on the phones. they believe having the safety information in the manual simply isn't enough. today marks is able to provide for his family again and is back on top in the real estate business. >> do you roll over or do you fight? i'm a fighter. >> now, we can't say for sure whether alan marks' tumor, in fact, was caused by cell phones, but as we said, he's certainly a fighter. good luck to him and his family. also moving forward in the condition of gabrielle giffords. she underwent surgery to replace a piece of her skull that doctors removed months ago because of brain swelling. surgeons took a bone substitute and actually placed it in her own native bone which was saved but actually thought to be contaminated. they put in little plates, two little screws in the native skull and affixed that to the skull and actually closed the skin over that, giving her normal contour back to her head again. we have another incredible story as well of recovery. a car hit rob summers and then drove off, leaving him paralyzed from the chest down. he did have some sensation in his legs, but that was it, and that was five years ago. this week summers and his doctors announced he's been able to stand up and even take steps under his own power with some assistance. he actually uses a harness that helps him along. doctors reestablished neuroconnections by stimulating rob's spinal cord. an amazing story. we'll see what answers it hopefully leads to for other spinal cord victims. coming up, i'm going to answer your questions about cell phone safety. you've got a lot of them. stick around. [ male announcer ] bridgestone is using natural rubber, producing products that save on fuel and emissions like ecopia tires... even making parts for solar panels that harness the sun's energy... working on social activities like clean up programs on beaches in many locations... and regional replanting activities that will help make a better world for all of us. ♪ one team. one planet bridgestone. to london starts with arthritis pain... and a choice. take tylenol now, and maybe up to 8 in a day. or...choose aleve and 2 pills for a day free of pain. enjoy the flight. we are back with fcmd. as you know now, we are talking about cell phone safety and apparently you have a lot of questions about this. they've been flooding in. i have to share this one with you. this is a question we've got many times over the years. it's about this viral video. i'll tell you off the top this is not real. this is a hoax. the question was, can cell phones really pop popcorn? no, they don't. that's not the type of radiation we're talking about. just a hoax, that video. but we do have important questions to get to. this one from our blog. if cell phones caused cancer, wouldn't we have seen a huge increase in brain cancer recently? very important question, and the answer is sort of the idea that not necessarily because it takes a period of time for cancers to develop. cell phones have just become popular in this country over the last 15 years. there were only about 30 million cell phones in 1996 in this country, and now there's three times as much, 300 million. it takes certain time for tumors to develop. we haven't had that time yet. this one says, i'm a parent with a child that keeps a cell phone stuck to her head. whael what's the greatest risk to her? first of all, you don't get to talk to your child as much. but children have thinner skulls and radiation may penetrate more greatly. there's been no studies so far on children and cell phones, nothing in the periodic journal we could look at. i find that alarming because children use it at an early age and they'll use it their entire life. also, cell phones may be distracting. their sleep patterns may be rearranged. they may stay up at night playing with their phones rather than winding down, so it could really throw that sleep pattern off. one says, i text on my phone more often than talking is radiation from texting the same as a phone call? here's the good news. it's not. texting is actually a much safer alternative. the radiation you absorb goes away exponentially as you move it away from your ear. you could use a wired earpiece or