| MadSci Network: Neuroscience |
Thank you for your question. I must admit that I don’t usually read the literature in radiology and the like, which is where cell phone literature would fall. However, since I use one, this gave me a good reason to look into what may or may not be occurring. From the literature that I read my judgement is that based on the current scientific literature we cannot say that there is a link between brain cancers and tumors and exposure to radio waves emitted by cellular phones. However, the study that would really shed some light on this issue has yet to be done (or is most likely occurring right now). Before I give details, allow me to give some insight into tumorigenesis (formation of tumors). A tumor is a population of cells that is growing out of control, along with “recruited” normal cells. Tumor formation is a complex process and is what we refer to as “multistep.” What multistep means is that several cellular events must take place in order for a cell to form a tumor mass. If the elements needed for each step aren’t present, a tumor will not form. Other forms of radiation (such as the radio waves emitted by a radar gun that police officers use to track a vehicle’s speed) can actually damage the DNA within a cell. In one experiment (1), scientists exposed cells in the lab to two kinds of cellular phone radio waves. They then performed an assay that assesses DNA damage. They found that the cellular phone radio waves did not induce DNA damage within the cells. A different study (2) found that stress hormones were not activated by exposure to cell-phone radiation, and furthermore that cell-phone radiation did not activate some typical oncogenes. Two of the oncogenes they looked at are also what we call immediate-early genes. Immediate- early genes are turned on, and their gene products are expressed in the cell, when something happens. For example, when you expose a male hamster to certain pheremones, cells coupled pheremone receptors show activation of these immediate-early genes (that’s one way we know that the cells have been activated). The problem with most of the studies conducted thus far is that the studies are what we call retrospective. In other words, most of these studies are looking at people who already have brain tumors, and then matching those cases with people who don’t, and are asking if there is a relationship between their cell-phone use, and brain cancer. The problem with this design is that one is not able to definitively pin-point the cause. The better design, although this may not be possible for ethical and legal reasons, would be find people who have not used a cell-phone before, give them a phone, make them use it for a period of so many years, for so long each day/month, and analyze the incidence of brain tumors. There are several problems with this design, but that is the only way we can definitively say, once and for all, that yes, cell-phones do or do not cause brain tumors (or cancers). If I were you, and I had this assignment I would either 1) create a poster on the current research that has been done, and what studies need to be done yet; 2) explore the mode or mechanism by which brain tumors/cancers might be formed from exposure to cell-phone radiation (a mechanism would be an exact step-by-step method of forming a tumor, from radiation entering the cell to formation of a tumor, whereas the mode would be a more generalized view). I don’t know if you used this service or not, but to look up some of the scientific literature, a good place to start is here: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed. That is a link to PubMed, a government database that queries a medical literature database known as Medline. References: 1. Malyapa RS, Ahern EW, Straube WL, Moros EG, Pickard WF, Roti R. Measurement of DNA damage after exposure to electromagnetic radiation in the celluar phone communication frequency band… Radiation Research. 1997 Dec; 148(6):618-27. 2. Byus CV. Effect of Immobilization and Concurrent Exposure to a Pulse-Modulated Microwave Field on Core Body Temperature, Plasma ACTH and Corticosteroid, and Brain Ornithine Decarboxylase, Fos and Jun mRNA. Radiat Res 2001 Apr;155(4):584-592. Aside: If you want to know what I think is going on…here goes…keep in mind, these are just my thoughts now, I don’t have any evidence to back any thing below this paragraph up. I think that the radiation we are exposed to from these cell phones are not in fact initiating carcinogenesis. Remember when I mentioned tumorigenesis (and carcinogenesis) are multi-step? There are two main steps: Initiation and Promotion. Initiation is some event that causes the cell to form a tumor if the conditions are right. Promotion is when the conditions are actually ripe for a tumor to grow. So there are some substances which initiate tumorigenesis (i.e., Phenobarbital can do this in the liver), but you need to have repeated exposure to some promoting agent as well (i.e., creosote on skin). If a chemical is strictly a promoter, and exposure to said promoter occurs prior to exposure to an initiator chemical, then no tumor will be formed. Only when the cell is initiated by exposure to an initiator, followed by repeated exposure to the promoter do we have tumor growth. Since a great deal of the literature is stating that this kind of radiation is not an initiator (it does not cause mutations of the DNA or something else that we call an epigenetic change – epigenetic changes are not mutations, but they cause a gene to be turned on or off), that means the radiation is probably either a promoter, or the early studies are merely a statistical anomaly, and there is no real correlation between cell-phones and cancer. Good luck with your project! I hope I was of some assistance! Lyle D. Burgoon Predoctoral Fellow – IET Department of Pharmacology and Toxicology College of Human Medicine National Food Safety and Toxicology Center Institute for Environmental Toxicology Michigan State University
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