Weekend Reading:  A Scientist looks at the data.  Bob Berman Author, Zapped: From Infrared to X-rays, the Curious History of Invisible Light

Visualizing microwaves isn’t easy. Sizewise, picture each ray as a curled-up caterpillar, with its back raised and its front and back ends lower down. The largest microwaves look more like garter snakes, a foot in length, again with the midsection raised in a curve. Each curved caterpillar vanishes, then a new one appears in the same spot a trillion times a second. That’s a million million. It’s fourteen thousand times faster than individual frames appear in modern movies.

Should we be concerned? Some people certainly do worry. You can read the anxiety in local newspapers, where letters to the editor express fear about microwaves from cell towers, Wi-Fi, and even cell phones themselves and urge that Wi-Fi be banned in schools. Authorities sometimes respond to this pressure: in Woodstock, New York, in 2015, the school board placed a temporary restriction on school microwave Wi-Fi installations pending further investigation.

The issue of whether cell phone radiation is putting us in danger has generated much press, some thoughtful, some paranoid. An example of the latter is the widespread belief, expressed all over the Web, that corporations involved in the cell-phone industry (including manufacturers, electronics and software companies, and the carriers themselves), as well as government regulatory agencies and even large mainstream health organizations such as the American Cancer Society and the Mayo Clinic, are actively conspiring to suppress microwave hazards of which they are supposedly well aware.

Some of the fears are based on a report issued in 2011 by the World Health Organization’s International Agency for Research on Cancer (IARC). The agency had gathered in Lyon, France, to discuss scientific studies surrounding the question of whether there’s a relationship between radio-frequency-modulated electromagnetic fields (RF-EMF) and cancer. After intense deliberations, and to the great surprise of the world at large, experts decided to classify RF-EMF waves emitted by cell phones, cell towers, and Wi-Fi networks as category 2B, indicating a “possible human carcinogen.”

On the other hand, as a New York Times article pointed out in 2016, there have been many studies conducted on the issue, including the Million Women Study, in Britain, a Danish study of more than 350,000 cell-phone users, and studies examining the effects of radio waves in animals and cells growing in petri dishes. Those studies indicated that there is still “no convincing evidence of any link between cellphone use and cancer or any other disease. Also, the incidence of brain cancer in the United States has remained steady since 1992, despite the stark increase in cellphone use.”

Between the alarming conspiracy theories, the “possible human carcinogen” verdict, and reassuring reports like the one in the Times, it’s hard to know what to believe, and that in itself can cause anxiety, because we certainly need to know. More than a billion people use cell phones daily. Are our phones putting us in danger or not?

The short answer is probably not, but it’s still better to take certain precautions.

First of all, the microwave and radio bands consist entirely of nonionizing radiations. They simply don’t have the energy to knock electrons out of their orbits, which means they can’t cause changes on an atomic level. So even with prolonged exposure to microwaves or radio waves, there’s no danger of gene mutations or chromosome damage. And presumably there’s no possibility of such rays being carcinogenic.

Indeed, microwaves lie not merely outside the ionizing part of the electromagnetic spectrum but also far from it. Microwaves are less energetic than infrared radiation, which in turn is less energetic than visible light. And nobody can be harmed by, say, red mood lighting, even if it’s bright.

Is it okay to warm up your teenager’s brain? Regardless of whether microwaves can cause cancer (we’ll get to that in a second), we know that they do make atoms jiggle faster — another way of saying they heat tissue. One study showed a measurably increased blood flow on the side of the head where a cell phone was held. The effect was undeniable. But was it deleterious? Might it simply mean that a certain part of the brain had become actively engaged? One might point out that drinking a bowl of soup or enjoying a cup of tea will heat far more tissue, and to a much greater degree, than talking on a cell phone will, yet we don’t worry about the potential health risks of frequent tea drinking. Moreover, taking a single hot shower heats far more body tissue in one shot than using your cell phone non-stop for a month. So this “heating tissue” business is a good example of a real effect caused by radio-frequency radiation that sounds scary but in all probability is inconsequential.

Now to the cancer question: as of 2016, there are more than seven thousand major studies of RF “radiation” in the medical literature. As the Times reported, the very largest studies have failed to detect an association between cell-phone use and brain tumors or other cancers.

The largest investigation is the Interphone Study, which involved thirteen countries, including Canada, the United Kingdom, Denmark, and Japan. Researchers questioned more than seven thousand people who had been diagnosed with a brain tumor as well as a control group of fourteen thousand healthy people about their previous cell-phone use. The study found no association between cell-phone use and glioma (cancerous brain tumor) rates except in the group of participants who reported using their cell phone for at least 1,640 hours in their lifetimes without a headset. Those participants were 40 percent more likely than those who never used a cell phone to have a glioma. Since this finding contradicted other studies that uncovered no increased cancer risk, the Interphone Study authors speculated that people with brain tumors, looking for an explanation for the tragic disease that had befallen them, might be more likely than healthy people to exaggerate their cell-phone use.

Also reassuring are the results of studies involving workers whose occupations expose them to more than a thousand times more RF energy than the rest of us get. These lab technicians, cell-phone-tower maintenance workers, radar technicians, and others show no increased cancer rate whatsoever.

Still, some research leaves the door open to doubt. The results of ongoing studies, in progress since 2013, that expose animals to various microwave intensities have so far been generally reassuring, but in 2016, a study conducted on rats exposed to high levels of cell-phone-type rays for more than two years, starting before birth, found a 2 percent rate of brain cancer — but only in males, not in females. Oddly, none of the control-group rats developed tumors, though the usual rate would have been 2 percent. In other words, if it weren’t for an abnormally low cancer incidence in the control group, the cancer rate for the exposed rats and the unexposed rats would have been the same, and microwaves would have been given a clean bill of health. The whole thing was puzzling — so puzzling that most researchers do not accept the results, although some do.

One Danish study found that brain-tumor incidence increased among the segment of the population that used cell phones the most hours per day. It didn’t help when the giant British insurance company Lloyd’s, in 2014, announced that it would no longer sell insurance against health effects from microwaves. Many started wondering whether they were damaging themselves and their children by permitting unrestricted cell-phone usage.

These puzzling outlier studies need to be acknowledged, and we need to continue research into cell-phone radiation. But the fact remains that there has been no convincing evidence to date that cell-phone use increases the risk of cancer. So why the IARC 2B classification of microwaves as a “possible carcinogen”? Well, context is important. After all, the WHO classifies coffee in the 2B category, despite some investigative organizations such as Consumers Union saying that coffee is actually healthful. If after twenty years and seven thousand studies researchers had instead found evidence that microwaves are “probably” carcinogenic, that would have earned them a 2A classification, still lower than a class 1 “definite” cancer-causing rating. In other words, the 2B designation indicates that any effect must be very subtle. Indeed, the way things look now, the worst we might eventually find out about microwaves in terms of carcinogenesis is a tiny effect along the lines of one case per several million users — a hazard that would probably not inspire anyone to change his or her habits. Meanwhile, cell-phone-signal emissions have been steadily decreasing since 2005 as the technology has improved, rendering obsolete any findings from studies conducted before that.

As the American Cancer Society wisely points out, the fact that most studies so far have not found a link between cell-phone use and the development of tumors is unlikely to end the controversy and put us completely at ease — nor should it. These studies suffer from a number of limitations, which the ACS lays out: “First, studies have not yet been able to follow people for very long periods of time. When tumors form after a known cancer-causing exposure, it often takes decades for them to develop. Because cell phones have been in widespread use for only about twenty years in most countries, it is not possible to rule out future health effects that have not yet appeared. Second, cell phone usage is constantly changing. People are using their cell phones much more than they were even ten years ago, and the phones themselves are very different from what was used in the past. This makes it hard to know if the results of studies looking at cell phone use in years past would still apply today.”

Frequency, intensity, and duration of exposure can affect the response to radio-frequency radiation (RFR), and these factors can interact with one another and produce various effects. In addition, in order to understand the biological consequence of RFR exposure, one must know whether the effect is cumulative or whether compensatory responses result. In short, the issue of whether there is any adverse biological effect from the entire radio-frequency band (which includes TV and radio towers and not merely cell-phone microwaves) is complex. Major study results will be announced between 2017 and 2020, so the last word about microwave safety is still to come as of this writing.

While we wait for that last word, why not do what we can to minimize our exposure? Like all electromagnetic radiation, both visible and invisible, RFR intensity falls off inversely with the square of distance. This means that if you step twice as far away from a lightbulb as you were in the first place it will appear 2 to the second power, or four, times dimmer. Or if you spend your days wondering how bright the sun appears from Saturn, which is around ten times farther away from it than Earth is, simply calculate the square of ten. Thus from the ringed planet, the sun appears one hundred times dimmer than it does from Brooklyn. Quick and easy.

Similarly, if instead of holding your cell phone tightly against the side of your head, a mere inch from your brain, you put it on speakerphone or use a headset so that the phone and its antenna are now in a pocket twelve inches from your brain, you have reduced your brain’s incoming microwave intensity by 12 to the twelfth power, or a factor of 144. Or you could just join the under-twenty-five generation and switch to texting rather than talking. That way, you eliminate any hazard.

Excerpted from  Zapped: From Infrared to X-rays, the Curious History of Invisible Light Copyright © 2017 by Bob Berman. Used with permission of Little, Brown and Company, New York. All rights reserved.