Friday May 25 10:00 AM EDT
"Cell Phones and Brain Tumors - A Neurosurgeon's Thoughts"
Cell Phones and Brain Tumors - A Neurosurgeon's Thoughts
By Theodore H. Schwartz, MD, NYPH - Weill Cornell Medical College
The number of cell phones in this country keeps rising, as does the number of brain tumors. But is there a relationship between the two?
A recent report from the General Accounting Office (news - web sites) found that federal agencies do not always provide the latest information and research on cell phone radiation to consumers, and often the information they do provide is too technical for the average consumer to fully understand.
Below, Dr. Ted Schwartz, a neurosurgeon from New York Presbyterian Hospital, speaks to the popular concern about the possible connection between cell phones and brain tumors.
How did the controversy arise?
There are currently over one hundred million cell phone users in this country. Along with the increase of cell phone usage, there has been an increase in the number of brain tumors diagnosed each year in the United States. Since cell phones emit electromagnetic energy, which in certain circumstances has been linked with causing tumors, and since the cell phones are held directly against the head, many people fear that the two statistics might be linked.
In the early 90s, public concern over the possible dangers of electromagnetic energy increased based on reports of a possible link between power lines and a type of blood cancer called leukemia. In the past few years, exhaustive scientific research has proven this association to be false, but at that time, the answer was still unclear, which heightened public suspicion. The possible link between cell phones and brain tumors then got a media boost when David Raynard appeared on Larry King Live to discuss his lawsuit against the cell phone industry for the death of his wife, a frequent cell phone user, from a brain tumor.
Despite public concern, most of the evidence against cell phones can be classified as either and quot;guilt by association and quot; or confusing and quot;correlation and quot; with and quot;causation and quot;. In other words, just because two events happen at the same time, it does not mean that one caused the other.
Cell phones are radio devices that operate at low power (less than 1 watt) by transmitting and receiving electromagnetic radiation in the radiofrequency (RF) zone of the spectrum. Since ionizing gamma rays and x-rays, which are known to cause cancer, are also part of the same electromagnetic spectrum, RF energy was mistakenly thought to similarly cause cancer. Ionizing gamma rays and x-rays can cause cancer when their energy is absorbed by the tissue and chemical bonds are broken, damaging DNA. RF energy, on the other hand, produces minimal heating of tissue. Although there is a small amount of experimental evidence that suggests RF energy can impact DNA in rats, this data has been contradicted by several other animal studies and is not well substantiated. Even if true, the doses administered in these animal studies were much larger than the exposure in humans and may have no relevance to cell phone use at all. So although the RF energy emitted by cell phones is in the electromagnetic spectrum, and other forms of electromagnetic radiation can cause cancer, RF energy is very different and has not been shown to cause cancer.
Increasing incidence of tumors
Several authors have speculated that the rise in brain tumors may be attributable to the rise in the use of cell phones. This is a classic case of a correlation between two events in which there is no causal relationship. The rise in the incidence of brain tumors has been shown to be in people over the age of seventy. This is primarily due to various technical improvements in diagnostic tests, such as MRIs, which identifies more people with small or minimally symptomatic brain tumors. Likewise, the increase in life expectancy and the aging of the baby boom generation has lead to a rise in the incidence of brain tumors. Recent studies on the demographics of cell phone users have shown that the elderly are the least likely to use cell phones, as the technology is new. The rise in brain tumors is therefore occurring precisely in the population that does not use cell phones.
Direct evidence against a link between cell phones and brain tumors
Even though theoretically we can't find a reasonable connection between cell phones and brain tumors, one might still wonder whether in fact people who use cell phones actually get more brain tumors. There are two ways to address the question. One can ask, and quot;Are people who use cell phones more likely to get brain tumors than people who don't use cell phones and quot; or, alternatively, and quot;Are people with brain tumors more likely to have used cell phones than people without brain tumors? and quot; Both questions have been explored in recent studies involving very large groups of cell phone users and brain tumor patients, and both studies agreed that there is no link between cell phone use and brain tumors.
Frequency of use
The evidence is even greater because these studies were very well designed and not only looked at the association directly but also indirectly. For example, if there were a subtle link between brain tumors and cell phone use than one could imagine that only people who used their cell phones very frequently would be at a higher risk. If the studies pooled everyone together, they might miss the link in frequent users. However, the data showed that people who used their cell phone for over an hour a day, or for over five years, were no more likely to have brain tumors than people who used their phones for less than five minutes a day, or for less than six months.
Brain tumor location
One of the most compelling arguments against the association between brain tumors and cell phone use is based on the location of the tumor. Most people tend to place the cell phone on the same side of the head when they speak. Since the RF energy falls off very quickly with increasing distance from the antenna, the dose of energy on the side of the brain where the phone is held is much larger than on the other side of the brain. Several studies in cell phone users with brain tumors have demonstrated that there is no significant correlation between the location of the tumor and the side of preference of the cell phone user. Likewise, tumors in cell phone users are not significantly more frequent in areas of the brain closest to the ear than in other areas of the brain. One study, which did find a tendency for more tumors to appear on the side where the cell phone was used, showed that these tumors were not located in the part of the brain closest to the antenna. The result therefore most likely represented an accidental association.
Although the evidence shows that there is no theoretical risk of brain tumors from cell phone use, and no actual significant increase in the incidence in brain tumors in cell phone users, a few outstanding questions remain which require further study. It is still possible that extreme use of cell phones - several hours a day over decades - may play a small role in promoting the growth of brain tumors. The number of people with such extreme usage is small and might not be evident in studies that do not sample a large enough population of users. Similarly, cell phone use might increase the risk of an extremely rare type of tumor very slightly, which would also require larger studies. These possibilities are extremely unlikely and should not raise fears in the general public. It is currently the recommendation of most experts in the field that cell phone use is safe and does not increase the risk of brain tumors.
Email this story - View most popular | Printer-friendly format
|Archived Stories by Date: