Blood—brain barrier[ edit ] A review stated that "The balance of experimental evidence does not support an effect of 'non-thermal' radiofrequency fields" on the permeability of the blood-brain barrier , but noted that research on low frequency effects and effects in humans was sparse. Non-ionizing radiation There is no strong or consistent evidence that mobile phone use increases the risk of getting brain cancer or other head tumors. Its only consistently observed biological effect in humans is tissue heating.
In animal studies, it has not been found to cause cancer or to enhance the cancer-causing effects of known chemical carcinogens. In a World Health Organization working group classified cell phone use as "possibly carcinogenic to humans". The CDC states that no scientific evidence definitively answers whether cell phone use causes cancer.
Electromagnetic hypersensitivity Some users of mobile phones and similar devices have reported feeling various non-specific symptoms during and after use. Studies have failed to link any of these symptoms to electromagnetic exposure. In addition, EHS is not a recognised medical diagnosis. There are many proposed national and international standards, but that of the International Commission on Non-Ionizing Radiation Protection ICNIRP is the most respected one, and has been adopted so far by more than 80 countries.
Currently there are efforts underway to harmonise the different standards in existence. Many governmental bodies also require that competing telecommunication companies try to achieve sharing of towers so as to decrease environmental and cosmetic impact.
This issue is an influential factor of rejection of installation of new antennas and towers in communities. 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 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.
Precautionary principle[ edit ] In , the World Health Organization WHO recommended that the precautionary principle could be voluntarily adopted in this case. According to the WHO, the "precautionary principle" is "a risk management policy applied in circumstances with a high degree of scientific uncertainty, reflecting the need to take action for a potentially serious risk without awaiting the results of scientific research.
Although all of these are problematic in application, due to the widespread use and economic importance of wireless telecommunication systems in modern civilization, there is an increased popularity of such measures in the general public, though also evidence that such approaches may increase concern. Some national radiation advisory authorities, including those of Austria,  France,  Germany ,  and Sweden,  have recommended measures to minimize exposure to their citizens.
Examples of the recommendations are: Use hands-free to decrease the radiation to the head. Keep the mobile phone away from the body. Do not use telephone in a car without an external antenna. The use of "hands-free" was not recommended by the British Consumers' Association in a statement in November , as they believed that exposure was increased. In , Professor Lawrie Challis and others said clipping a ferrite bead onto hands-free kits stops the radio waves travelling up the wire and into the head.
Also, with the permittivity of the brain decreasing as one gets older and the higher relative volume of the exposed growing brain in children, radiation penetrates far beyond the mid-brain. According to the FTC, there is no scientific proof that so-called shields significantly reduce exposure from electromagnetic emissions. Such shields "may interfere with the phone's signal, cause it to draw even more power to communicate with the base station, and possibly emit more radiation.