In 1994, there were 16 million cell phone users in the United States alone. By 2001, there were more than 118 million. The increase in cell phone usage has spurred concern as to whether cell phones can increase your risk for developing cancer.
To answer this question, we first need to discuss what type of radiation does cause cancer?
What are some of the most common sources of ionizing radiation?
UV radiation, medical x- rays and radon gas.
Radon is the leading source of natural radiation exposure and the second leading cause of lung cancer. Radon is a naturally occurring radioactive gas which is produced from the natural radioactive decay of uranium found in rocks and soil. Radon is a form of ionizing radiation and a proven carcinogen. Lung cancer is the only known effect on human health from exposure to radon in air. Radon gas comes from rocks and soils and becomes concentrated in enclosed sealed spaces, such as houses (especially basements), mines and other buildings. Exposure to radon in the home and workplace is one of the main risks of ionizing radiation. Ionizing radiation from radon causes tens of thousands of deaths from lung cancer each year globally. The Environmental Protection Agency (EPA) estimates that about 21,000 lung cancer deaths each year in the U.S. are radon-related.
(from EPA, major sources of ionizing radiation exposure)
What is ionizing radiation and how does it cause cancer?
Ionizing radiation is a form of high energy radiation, such as X-rays, γ-rays, and β particles (or electrons) which are powerful mutagens. Ionizing radiation can change the number of electrons on an atom, converting a compound to an ionized form, hence the name ionizing radiation. When exposed to ionizing radiation, your DNA can become damaged, chemically altered. These mutations, changes, may include: directly breaking the phosphodiester backbone of DNA, leading to DNA deletions; breaking open the imidazole ring of purines (these are your A & G bases – Adenine and Guanine). See the difference between a purine (A & G) and pyrimidine (C & T) bases in the image below. When damaged purine bases are removed from your DNA by a DNA repair protein glycosylase generates an apurinic site/AP site, also known as an abasic site.
Another common form of DNA damage occurs when cytosine is deaminated, thereby changing it to yield uracil (a nucleobase found in RNA nucleic acid, which Hydrogen-bonds with Adenine). Specialized enzymes, called DNA glycosylases, catalyses the excision or removal of uracil from the damage site, marking the first step of our base-excision repair (BER) pathway. After the damaged base is removed, important enzymes are recruited to perform the job of “cutting out” the remaining sugar fragments. Successful completion of base-excision repair involves insertion of a new Cytosine nucleotide.
What else can can cause DNA damage or DNA mutations?
Reactive oxygen species (ROS), such as hydrogen peroxide, superoxide and hydroxyl radicals, by-products of cellular respiration and components of inflammatory responses. ROS have been linked to cancer. One of the most common DNA lesions caused by ROS is 8-oxoG (8-Oxoguanine or 8-hydroxyguanine), the product of base oxidation. ROS can also be produced as a consequence of ionizing radiation, chemical oxidants, free radicals and transition metals (David SS, O’Shea VL et. al., Nature. 2007). Though cells have DNA repair processes which correct DNA changes cause from ROS, sometime aberrantly functioning cells under ‘oxidative stress’, can increase the likelihood of DNA damage. When 8-oxoG is not repaired and the cell replicates the genome this causes a G-to-T mutation. You can see an illustration of this mutation process in the figure below from my brilliant colleague and DNA repair expert, Dr. O’Shea.
(Figure from David SS, O’Shea VL, Kundu S. Nature. Base-excision repair of oxidative DNA damage. 2007 Jun 21;447(7147):941-50.)
So, what about those pesky cell phones? Do they emit ionizing radiation?
No. Cell phones emit radiofrequency energy, a form of non-ionizing electromagnetic radiation. Non-ionizing radiation is considered safe, though it can cause some heating effect. Though radiofrequency radiation can produce heat, it has not been shown to cause long-term damage to tissues.
To date, a link between cell phone use and cancers of the brain, nerves, or other tissues has NOT been found. This doesn’t mean we shouldn’t continue to perform studies on the possible risks of cell-phone usage. For example, we do know that cell phone usage, especially in the form of texting while driving, has been the cause of thousands of fatal car crashes.
So, what is the take home lesson for reducing your exposure to ionizing radiation?
Follow the same key principles that scientists like me, who work directly with radioactive isotopes and ionizing radiation (X-rays), distance, time and shielding.
Distance: Increase your distance from radiation sources. Identify ionizing sources (carcinogenic) which you are exposed. The farther away you are from a radiation source, the less your exposure.
Time: Reduce the amount of time you spend near the source of radiation. Don’t stay out in the sun too long, avoid excessive UV exposure.
Shielding: Wear sunblock to protect your skin for ionizing UV radiation.
Most important of all, ask questions. Find out what does emit ionizing radiation (radon in basements, UV in sunlight) and poses a cancer risk and what does not (cell-phones).
Don’t let the charming pseudoscience quacks, like the millionaire Food Babe and crew, mislead you into avoiding sources (which have not been shown to pose a risk), all the while misleading and distracting you from identifying real sources which have been unequivocally scientifically proven to pose a direct cancer risk (like ionizing radiation).