Last week the big science news was a new study saying cell phones don't increase cancer risk in kids. It was promptly called into question on The Huffington Post and elsewhere. Several reporters referenced the May 31 release by the World Health Organization about a "possible" link between brain cancer and cell phone use, which classed it in the same risk category as eating pickled vegetables and drinking coffee. In a related move, last week San Francisco passed a regulation requiring retailers to post radiation exposure warnings on every phone and hand every customer educational material counseling them on the possible risks to their health.
Am I a Bad Parent?
My step mom died of glioblastoma multiforme, but I just gave my son a dangerous cell phone to hold next to his developing brain. Am I a bad parent? Physics says no -- and suggests that San Francisco's 10-1 vote ignored basic science in favor of superstitious fear of the invisible.
Is San Francisco Choosing Superstition Over Science?
Cell phones run on microwaves. Light, microwaves and other parts of the electromagnetic spectrum are all forms of radiation. A single unit of radiation is called a photon. A photon can be thought of as a particle and as a wave. In 1905, Albert Einstein showed that the energy of a photon can be calculated as Planck's constant times the frequency of its wave form, or E=hv, one of the reasons he won the 1921 Nobel Prize.
The electromagnetic spectrum starts with radio photons, whose waves can be as long as a football field. They lumber past us with low frequency and low energy. Microwaves stroll about 100 times faster, followed by infrared at 100 times faster than microwaves, and then visible light waves at about a 100,000 times faster than microwaves. Waves at the high end of the spectrum fly past us at much faster frequencies still (and thus have much more energy).
This part of the spectrum includes ultraviolet light, x-rays and gamma rays, whose waves can be shorter than the nucleus of an atom and thus have very high frequency and high energy.
Some Radiation is Healthy For You
We need light radiation to stay healthy. Our own skin gives off infrared radiation, which is how we can be seen using night vision goggles. Microwaves have less energy than the infrared we give off, and far less than visible light. Microwaves, infrared and visible light can all be used to cook food and heat our coffee by concentrating them in an oven. The concentrated waves excite the molecules in a way that increases their vibration, and the friction that produces increases the temperature.
Some Radiation is Not
Like water, it's a matter of degree -- a stream nourishes; a tsunami destroys. It's not until you travel past the visible spectrum into ultraviolet light that you get photons that have enough energy to cause cancer. These photons have about 1 million times more energy than microwave photons, making them able to knock electrons out of atoms, ionizing the atoms and changing their chemical nature. Just imagine the force of a wave the length of a person being concentrated into a wave the length of a molecule and then slamming an atom over and over and over, and you can get a sense of the vast difference in power. That is what can break the bond between two carbon atoms, damaging DNA and causing cancer. But ultraviolet photons still don't have enough energy to penetrate us very deeply, so they only give us skin cancer.
X-rays are sometimes stopped by our skin, but if we are bombarded by enough of them they can penetrate through us, a few of them being absorbed by skin and muscle, many more by our bones, which are denser, which is why we can use them to make images of the inside of our bodies. X-rays can cause cancer, but our bodies can almost always stop it if the exposure is low enough. Gamma rays are so energetic that they can penetrate us, kill cells and cause cancer very easily, and in high exposures they cause radiation poisoning, which kills much more quickly by damaging our bone marrow and gastrointestinal tract.
Cell Phone Use Skyrockets, but Brain Cancer Rates Remain Stable
This all explains why broad epidemiological studies have shown no measurable links between cell phone use and brain cancer -- and the National Cancer Institute has shown no appreciable increase in brain cancer rates since 1987, despite a massive surge in cell phone use. The WHO study is, well, WHOoey, and they have hurt their own credibility by issuing a sensationalist, fear-mongering press release.
What We Cannot Say
It is true that the studies done to date cannot rule out a link, but that is because that's the way science works. We cannot observe the whole universe at once, so science involves making statements about the relative probability that something is true. That's why it uses statistics. And from all the studies done so far, statistically, the "link" is indistinguishable from chance -- which is what the footnote in the WHO press release admits. But none of this seems to matter to the San Francisco Board of Supervisors, whose ordinance is an example of governance based on opinion and fear over knowledge and measurement not unlike the Bush administration's false linking of breast cancer with abortion.
What to Worry About
So while it is possible that some mechanism we don't understand could be causing brain cancer at levels that are indistinguishable from chance, I gave my son a dangerous cell phone -- with one caveat: When he eventually gets his license, he promises not to text and drive. That's the real cell phone danger.
Pre-order Shawn Lawrence Otto's new book Fool Me Twice: Fighting the Assault on Science in America. Like him on Facebook.