Some studies have found a possible link. For example, several studies published by the same research group in Sweden have reported an increased risk of tumors on the side of the head where the cell phone was held, particularly with 10 or more years of use. It is hard to know what to make of these findings because most studies by other researchers have not had the same results, and there is no overall increase in brain tumors in Sweden during the years that correspond to these reports.

The exact source of radiation in a cell phone is from the transmitter, a device located near the antenna that converts audio data into electromagnetic waves. The amount of radiation a cell phone can emit is limited by legal restrictions in the U.S., Canada and Europe. Additionally, the average radiation levels of most mobile phones are available to the public, courtesy of the Federal Communications Commission in the U.S.
RadiArmor’s anti-radiation material blocks over 99% of EMF radiation. However, since covering your entire phone with this material would result in no reception, only the front cover is lined with this material. This still provides an effective EMF reduction of 91% with no loss in reception. The front cover has a hole for sound to pass through so that you can close the case and talk at the same time.
Laptop computers are best placed on a table at as much of an arm’s length away as possible to minimize radioactive contact. If you must use your laptop on your lap, you can purchase a laptop cooling pad which will add a bit of extra space between the device and your body. Even better are laptop cases specifically designed to shield against radiation.
Many mobile phone protection stick on shields, chips or buttons make claims to manage the radiation problem in ways that are not verifiable by recognised scientific methods. We have evaluated a number of such products and have found in many cases that many of them simply do not work. On the other hand, our Anti-radiation phone covers, headsets and other solutions offer outstanding levels of protection (up to 100%) and are proven by verifiable SAR testing in accredited laboratories. In fact we are proud to say that our range includes some of the most effective radiation reducing solutions available anywhere in the world.
There are fears that the electromagnetic radiation emitted from mobile phone handsets may harm health. In particular, there have been claims that it could affect the body’s cells, brain or immune system and increase the risk of developing a range of diseases from cancer to Alzheimer’s. Laboratory tests on mice have shown that radiation from mobile phones can have an adverse effect on their overall health. It is still not clear whether those findings can be applied directly to humans. A study by scientists in Finland, published in 2002, suggested that the electromagnetic radiation did affect human brain tissue. But they played down their findings saying more research was needed to see if the effects were the same in living people. Another study by scientists in Sweden, also published in 2002, claimed to have found a link between analogue mobile phones and brain tumours. It suggested users of “first generation” phones had a 30% higher risk of developing tumours than people who did not. However, the findings were controversial and there have been no similar studies into the effects of modern GSM phones. There have also been reports of people suffering from headaches, fatigue and loss of concentration after using their mobile phones. However, these claims have not been scientifically substantiated.
The reason we’re talking about cellphones and cancer — why there’s a concern here — is because they emit radiation, the invisible waves of electric and magnetic energy, of varying power, organized on the electromagnetic spectrum. You can see in the graphic below that less powerful (or lower-frequency) types of radiation are on the left, moving to the more powerful (or higher-frequency) types of radiation on the right.

Dr. Carlo and his team developed new exposure systems that could mimic head-only exposure to EMR in people, as those were the only systems that could approximate what really happened with cell phone exposure. Those exposure systems were then used for both in vitro (laboratory) and in vivo (animal) studies. The in vitro studies used human blood and lymph tissue in test tubes and petri dishes that were exposed to EMR. These studies identified the micronuclei in human blood, for example, associated with cell phone near-field radiation. The in vivo studies used head only exposure systems and laboratory rats. These studies identified DNA damage and other genetic markers.
Although common sense, spending as little time on your computer as possible, and when you’re not using it, disabling the Wi-Fi connection or even turning your computer off completely, is recommended to help keep EMF pollution to a minimum. These devices emit a constant stream of EMFs when plugged in and “synced” up to a router or other wireless device.
Can cellphone radiation cause cancer in humans? There’s no scientific consensus on this issue, but there is “some evidence” that exposure to radiation equivalent to that emanating from 1990s-era cellphones is associated with brain tumors in male rats, according to results of a US National Toxicology Program (NTP) study released last week (November 1). 

The government, however, does not require phone manufacturers to consider the effect of cases when they conduct compliance tests to meet the FCC’s allowable radiation exposure limits. The significance of this omission was underscored by tests commissioned by case-maker Pong Research and submitted to the FCC in May 2012. Those tests showed that three models of cases made by competing companies and used with an iPhone4 increased the phones’ Specific Absorption Rate, or SAR – the amount of radiation absorbed by the user’s body – by 20-to-70 percent (Table 1).
So of course now that we understand that the cases are not tested and just the material--it makes sense! We measured power density levels all around the case-the shielding material most likely isn't used "all over" because then the phone couldn't receive signal and wouldn't be able to engage in a call.  That's why we did not see even close to a 99% reduction when some cases were on the phone.  In fact, watch the video and you'll see some readings are more than 20% higher with a case on vs the naked phone.
In the US, a small number of personal injury lawsuits have been filed by individuals against cellphone manufacturers (including Motorola,[28] NEC, Siemens, and Nokia) on the basis of allegations of causation of brain cancer and death. In US federal courts, expert testimony relating to science must be first evaluated by a judge, in a Daubert hearing, to be relevant and valid before it is admissible as evidence. In a 2002 case against Motorola, the plaintiffs alleged that the use of wireless handheld telephones could cause brain cancer and that the use of Motorola phones caused one plaintiff's cancer. The judge ruled that no sufficiently reliable and relevant scientific evidence in support of either general or specific causation was proffered by the plaintiffs, accepted a motion to exclude the testimony of the plaintiffs' experts, and denied a motion to exclude the testimony of the defendants' experts.[29]

“The evidence so far doesn’t prove that cell phones cause cancer, and we definitely need more and better research,” says Michael Hansen, Ph.D., a senior scientist at Consumer Reports. “But we feel that the research does raise enough questions that taking some common-sense precautions when using your cell phone can make sense.” Specifically, CR recommends these steps:
The guidelines recommend keeping phones away from the body when they’re not in use—in a backpack, for example, rather than a pocket—and sleeping with phones away from the bed. People may also choose to use speakerphone or a headset to make calls, rather than holding the phone to their heads. (They should remove their headsets when they’re not in use, though, as these devices also emit small amounts of RF frequency.)
It’s true that cellphones do emit radiation. And radiation is a scary word for a lot of people, thanks in part to the horrific aftermath of nuclear accidents and photographs of victims of the nuclear bombs the US dropped on Japan in World War II. People hear radiation and they associate it with nuclear radiation and the bomb, says Geoffrey Kabat, a cancer epidemiologist at the Albert Einstein College of Medicine and author of the book Getting Risk Right. “There are all these associations and those are deeply ingrained in people. But it doesn’t apply here.”
Laptop computers are best placed on a table at as much of an arm’s length away as possible to minimize radioactive contact. If you must use your laptop on your lap, you can purchase a laptop cooling pad which will add a bit of extra space between the device and your body. Even better are laptop cases specifically designed to shield against radiation.
Cell phone radiation emissions present the greatest potential health risks when directly touching the body, especially the head, breasts and reproductive organs. This is referred to as zero distance to the body. Moving your cell phone away from your body just a few inches reduces the health risks. As a rule of thumb, when a cell phone is moved at least one foot away from the head or body, cell phone radiation is reduced by as much as 80%.
EWG met with representatives of Pong Research and fully agrees with its business premise that cell phone cases should decrease, not increase, radiation exposure. Pong hopes to carve out a niche by selling cases that lower the phones’ radiation exposure. We anticipate that as awareness of the potential risks of cell phone radiation grows, Pong and other companies will respond by marketing cell phones and cases that offer users good communication with less radiation.
In addition, the findings might be influenced by the fact that the study subjects owned cell phones that were in some cases manufactured two decades ago. The way we use cell phones and the networks they’re operated on have also changed since then. Last, cancer can develop slowly over decades, yet the studies have analyzed data over only about a five- to 20-year span.
The energy of electromagnetic radiation is determined by its frequency; ionizing radiation is high frequency, and therefore high energy, whereas non-ionizing radiation is low frequency, and therefore low energy. The NCI fact sheet Electromagnetic Fields and Cancer lists sources of radiofrequency radiation. More information about ionizing radiation can be found on the Radiation page.