The potential harm from microwave radiation (MWR) emitted by wireless devices, particularly for children and unborn babies, is the highlight of a new review.

Although the data are conflicting, associations between MWR and cancer have been observed.

The review, by L. Lloyd Morgan, senior science fellow at Environmental Health Trust, and colleagues, was published online July 15 in the Journal of Microscopy and Ultrastructure.

The authors reviewed the current literature showing that children face a higher health risk than adults. They evaluated peer-reviewed cell phone exposure epidemiology from 2009 to 2014, along with cell phone dosimetry data, government documents, manufacturers’ manuals, and similar publications.

Children and unborn babies face the highest risk for neurologic and biologic damage that results from MWR emitted by wireless devices, according to Morgan and colleagues.

The rate of absorption is higher in children than adults because their brain tissues are more absorbent, their skulls are thinner, and their relative size is smaller. The fetus is particularly vulnerable because MWR exposure can result in degeneration of the protective myelin sheath that surrounds brain neurons, they report.

Multiple studies have shown that children absorb more MWR than adults. One found that that the brain tissue of children absorbed about 2 times more MWR than that of adults (Phys Med Biol. 2008;53:3681-3695), and other studies have reported that the bone marrow of children absorbs 10 times more MWR than that of adults.

“Belgium, France, India, and other technologically sophisticated governments are passing laws and/or issuing warnings about children’s use of wireless device,” they write.

They note that MWR exposure limits have remained unchanged for 19 years, and that smartphone manufacturers specify the minimum distance from the body that their products must be kept so that legal limits for exposure to MWR are not exceeded. For laptop computers and tablets, the minimum distance from the body is 20 cm.

The authors explain that current exposure limits were established based on the erroneous assumption that tissue damage from overheating is the only potential danger of wireless devices.

However, extensive scientific reports have documented nonthermal biologic effects from chronic (long-term) exposure. Although government warnings have been issued worldwide, most of the public is unaware of such warnings, they write.

Raising “Appropriate Concerns”

The review authors “continue to raise appropriate concerns related to the ever-increasing role of technologies that emit nonionizing radiation, including cell phones and certain toys,” said L. Dade Lunsford, MD, Lars Leksell Professor of Neurological Surgery at the University of Pittsburgh, who was not involved in the study.

“They indicate that certain types of tumors, at least as reported, may have increased in incidence, including the most malignant brain tumors and perhaps hearing nerve tumors,” he told Medscape Medical News. However, he pointed out that there are issues with some of the data, and that many of the reports are anecdotal.

“Among the concerns with such public health data are the inability to determine if there is one or many environmental factors — cell phones are not the only concerns — that are related, or whether the perceived increase is simply better recognition at earlier stages based on the availability of MRI, as well as better reporting,” Dr. Lunsford explained.

“Perhaps it is enough to simply raise the alarm in the hope of liberating either government or industry-sponsored appropriately designed investigational research,” he noted.

“Regardless, it seems unlikely that the use of cell phones will diminish; cell phones have saved more lives than will ever be lost,” Dr. Lunsford said. However, “concerns related to the greatly expanded use of digital toys in childhood clearly warrant better science and, for the time being, appropriate vigilance.”

“Digital Dementia” Reported in Schoolchildren

The review points out the danger of childhood and fetal exposure to MWR, and the reasons the exposure is more pronounced in children than in adults, Morgan told Medscape Medical News.

“There are toys being sold to infants and toddlers that are dangerous,” Morgan said. “The risk from exposure to any carcinogen is higher in children, and the younger the child, the higher the risk. The risk to adults from exposure to any carcinogen, to a first approximation, does not vary with age.”

He explained that a problem known as “digital dementia” has been reported in school-aged children. The term was coined by German neuroscientist Manfred Spitzer in his 2012 book of the same name, and is used to describe how the overuse of digital technology is leading to a breakdown in cognitive abilities. It is sometimes also referred to as FOMO — fear of missing out — which is considered a form of social anxiety and is a compulsive concern about missing an opportunity for social interaction.

Take-Home Messages About Safe Use

As a take-home message for physicians and other healthcare practitioners, Morgan emphasized that wireless telecommunication devices need to be used in a safe manner. These devices are now part of everyday life, “but they can be used in a manner that is safe enough,” he said. “Cars are not safe, for example, but they are safe enough. The essential problem is the vast majority of the public has no knowledge of their hazards.”

Morgan and his colleagues have made some recommendations.

The first is that “distance is your friend.” The intensity of radiation decreases as the square of the distance from the source increases (the inverse-square law). He explained that holding a cell phone 15 cm from your ear “provides a 10,000-fold reduction in risk.”

Unless a cell phone is turned off, it is always radiating. When not in use, it should not be kept on the body. The best place for a cell phone is somewhere like a purse, bag, or backpack.

Devices should be kept away from a pregnant woman’s abdomen, and a mother should not use a cell phone while nursing, Morgan noted. “And baby monitors should not be placed in an infant’s crib.”

Children and adolescents need to know how to use these devices safely. Cell phones should not be allowed in a child’s bedroom at night, he continued. “The Pew Research Center has reported that 75% of preteens and early teens sleep all night with their cell phone under their pillow.”

Because the risk is cumulative, and more radiation is absorbed with more hours of use, children should be taught to minimize their wireless phone use, Morgan explained. Landlines, Skype, and computer phone services (when connected to the Internet with a cable) do not emit radiation and their use should be encouraged.

Finally, Wi-Fi routers in the home should be placed away from where people, particularly children, spend the most time. “Boys should not keep a cell phone in their front pants pockets,” he said. There is a potential harm to sperm, although no prepuberty studies of young boys have assessed whether early exposure to MWR has any effect on sperm after puberty, he acknowledged.

“And girls should not place their cell phone in their bras,” he added. This recommendation was based on a case study of 4 young women with a history of putting cell phones in their bras and who developed breast cancer — 2 at the age of 21 years (Case Rep Med. 2013;2013:354682).

The authors note that some studies have shown an increased risk for brain cancer with cell phone use, although some of these data have been disputed. In recent years, glioblastoma rates have increased in Denmark and the United States, and brain cancer incidence has increased in Australia, according to data drawn from cancer registries. The average time between exposure to a carcinogen and the diagnosis of a resultant solid tumor is 3 or more decades, so it will likely be several decades before tumors induced by childhood MWR exposure are diagnosed, they note.

Commenting to Medscape Medical News, Dr. Lunsford pointed out that much of the data are anecdotal and do not fit the hypothesis of a long latency interval between exposure and tumor development. For one of the 21-year-old women who developed breast cancer, cell phone exposure was only 6 years. “Unfortunately, we know neither the denominator nor the numerator of these index cases. Usage data are a closely guarded secret of phone service providers and a patient’s own recall of exposure may or may not be correct due to recall bias,” he noted.

In addition, the mechanism of oncogenesis is poorly understood and seems to conflict with the understanding that rapidly dividing cell lines, such as those in the skin, are the most susceptible to neoplastic transformation. However, there appear to be no reports of increased risk for local melanomas, basal cell cancers, or squamous cell cancers, which are the ones that would be expected to develop, Dr. Lunsford said.

Conflicting Data From Previous Studies

The potential health risks related to cell phone use, especially brain tumors, have remained a hot-button issue. Studies have been inconsistent and results have been conflicting. Currently, there is no consensus about the degree of cancer risk posed by cell phone use, if any at all.

A recent French study, for example, found that the heaviest users face a higher-than-average risk for gliomas and meningiomas (Occup Environ Med. 2014;71:514-522). There was no association between brain tumors and regular cell phone use, but the association was significant for those with heavy life-long cumulative use.

The first study to specifically assess the health impact of cell phone use on children and adolescents, conducted in Europe, found no association with risk for brain cancer, as reported by Medscape Medical News in 2011.

However, the debate was reignited the same year when the World Health Organization classified radiofrequency electromagnetic fields as possibly carcinogenic to humans (group 2B) on the basis of the increased risk for glioma that some studies have associated with the use of cell phones.

Also in 2011, a nationwide Danish extension study found no evidence of an overall increase in brain tumors or any cancers over an 18-year period. The original Danish study compared cancer risk for all 420,095 Danish cell phone subscribers with that for nonusers from 1982 to 1995, with follow-up to 1996. The update extended follow-up to 2007.

When analyzed by morphologic subtype of intracranial central nervous system tumor, there was a slight but nonsignificant increase in the incidence rate ratio for glioma in men (1.08; 95% confidence interval, 0.96 to 1.22). The ratio was highest in the shortest-term users (1 to 4 years).

However, the results of extension study were met with a fierce rebuttal from group of international experts, who joined together and posted their response on ElectromagneticHealth.org, a health education and advocacy group based in the United States.

J Microsc Ultrastruct. Published online July 15, 2014. Abstract