The evidence was convincing enough that the American Academy of Pediatrics has released a statement recommending that mobile phones be avoided by children. The International Agency for Research on Cancer (IARC) (part of the World Health Organization) has already classified mobile phones as a possible carcinogen (group 2B).
Of course, more research is needed to determine if these conclusions also apply to human beings and not just rats. These findings ARE preliminary and who knows what the final results and conclusions will be.
So, what do we know so far?
The group at greatest risk for development of brain tumors have the following characteristics:
1) Use of cell/wireless phone younger than age 20 (the younger the age with first use, the worse the risk)
2) Use of cell/wireless phone for more than 10 years
3) The more hours of cellular phone use over time, the higher the risk of developing brain tumors
4) Risk higher with analog cell/wireless phones (instead of digital)
5) Risk higher with increased overall total exposure
By some estimates, subjects who used cell phones for at least 10 years had a 2.4-fold greater risk of developing a brain tumor.
Though unclear how exposure to a phone's radiation leads to brain tumors, it is known that the radio-frequency radiation signal is absorbed up to 2 inches into the adult skull. Even more worrisome is that the depth of penetration is even deeper in children.
The risk is not just to the brain, but even the parotid gland which sits just in front of the ear. In one study published in 2008 revealed an increased risk of parotid gland tumors with cell phone use. Also, contact allergy is another not uncommon risk with cell phone use.
Symptoms that a patient may exhibit that may suggest a brain tumor are subtle and include hearing loss or ringing of the ear on the same side the phone is used on. [Blog article on cell phone use and tinnitus here.]
It is interesting to note that it is just possible that the cell phone industry is aware of these risks even as it denies any risk of health problems with phone use. If you read the small print that comes with your cell phone, cell phone makers state that mobile phones should not be in contact with your body or skin and should be kept a certain distance away when in use or when carrying around (i.e., do not carry around in your pocket, sock, etc).
For example, the iPhone 7 that just came out comes with a legal disclaimer stating that:
"To reduce exposure to RF energy, use a hands-free option, such as the built-in speakerphone, the supplied headphones, or other similar accessories. Carry iPhone at least 5mm away from your body to ensure exposure levels remain at or below the as-tested levels." [iPhone 7 legal disclaimer]Earlier phones emitted higher doses of radiation and came with a legal disclaimer to keep the phone at least 15mm away from the body (instead of 5mm for the iPhone 7). [iPhone 3 legal disclaimer]
In any case, to be on the safe side, it is recommended to talk on speakerphone or use a wired headset (not wireless), or avoid altogether if at all possible (use a regular desk / wall telephone).
When I carry my cell phone, I use a belt holder for both safety and convenience (which many consider unfashionable and ugly). For women, use a purse to carry the phone!
Report of Partial Findings from the National Toxicology Program Carcinogenesis Studies of Cell Phone Radiofrequency Radiation in Hsd: Sprague Dawley® SD rats (Whole Body Exposures). bioRxiv preprint first posted online May. 26, 2016; doi: http://dx.doi.org/10.1101/055699.
Risk of Brain Tumors From Wireless Phone Use. Journal of Computer Assisted Tomography, 2010; 34 (6): 799 DOI: 10.1097/RCT.0b013e3181ed9b54
Cell phones and brain tumors: a review including the long-term epidemiologic data. Surg Neurol. 2009 Sep;72(3):205-14; discussion 214-5. Epub 2009 Mar 27.
Mobile phones, cordless phones and the risk for brain tumours. Int J Oncol. 2009 Jul;35(1):5-17.
Cell phone use and acoustic neuroma: the need for standardized questionnaires and access to industry data. Surg Neurol. 2009 Sep;72(3):216-22; discussion 222. Epub 2009 Mar 27.
Cellular phone use and risk of benign and malignant parotid gland tumors--a nationwide case-control study. Am J Epidemiol. 2008 Feb 15;167(4):457-67. Epub 2007 Dec 6.