This 2009 meta-analysis, published in the Journal of Clinical Oncology, looked at 23 case-control studies of the risk of both malignant and benign tumors from mobile phone use. When the authors included all 23, they found no increased risk of tumors. When they crunched certain subsets of the data — like looking only at studies that were blinded, or people who used cellphones for 10 or more years — they did find increases in tumor risks. Confusingly, when they divided up the analysis by tumor type, they found no increase in risk for glioma and acoustic neuroma, and a decrease in risk of meningioma.
Today, the computer and phone have merged into one device that fits in the palm of your hand. A smartphone is essentially a small computer, yet has many times the computing power of traditional computers. There are no cords to connect you to a base. When turned on in your pocket or being used against your head, the cell phone touches some of the most sensitive parts of the body. Although the cell phone produces lower levels of radiation then past computers, they are now used much closer to the body and for longer periods of time, thus creating more health risks than in the past.
A large, long-term study has been comparing all of the people in Denmark who had a cell phone subscription between 1982 and 1995 (about 400,000 people) to those without a subscription to look for a possible increase in brain tumors. The most recent update of the study followed people through 2007. Cell phone use, even for more than 13 years, was not linked with an increased risk of brain tumors, salivary gland tumors, or cancer overall, nor was there a link with any brain tumor subtypes or with tumors in any location within the brain.
The pacemaker studies were a harbinger of bad things to come. Results showed that cell phones do indeed interfere with pacemakers, but moving the phone away from the pacemaker would correct the problem. Amazingly, the industry was extremely upset with the report, complaining that the researchers went off target. When Dr. Carlo and his colleagues published their findings in the New England Journal of Medicine in 1997,11 the industry promptly cut off funding for the overall program. It took nine months for the FDA and the industry to agree on a scaled-down version of the program to continue going forward. Dr. Carlo had volunteered to step down, since he was clearly not seeing eye-to-eye with the industry, but his contract was extended instead, as no one wanted to look bad from a public relations standpoint.
But this study also has some drawbacks. First, it is based only on whether or not people had a cell phone subscription at the time. It didn’t measure how often these people used their phones (if at all), or if people who didn’t have a subscription used someone else’s phone. There are also limits as to how well this study might apply to people using cell phones today. For example, while the cell phones used at the time of the study tended to require more power than modern cell phones, people also probably used the phones quite a bit less than people use their phones today.
We did not simply measure energy coming from the front of the case which is the area of the case where the phone would be "shielded" from radiation. If we had taken readings with a directional meter, specifically measuring energy coming from only the front or flap cover where the shielding material is, we assume as the manufacturers claim, that we would have seen a drop in the radiation readings.
Users were defined as anyone who made at least one phone call per week for six months between 1982 and 1995. So any person who made 26 calls was a cell phone user and therefore considered exposed to radiation. Those with less than 26 calls were non-users. In reality, the radiation exposure between users and non-users defined in this manner is not discernable.
An analysis of an "eagerly anticipated" study using rats and mice by the National Toxicology Program indicates that due such issues as the inconsistent appearances of "signals for harm" within and across species and the increased chances of false positives due to the multiplicity of tests, the positive results seen are more likely due to random chance. The full results of the study were released in February 2018.