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By Greg Lapin, N9GL, Chairman
ARRL RF Safety Committee
February 10, 2000
Understanding the scientific basis of RF Safety can be a lifetime's work. Here's the first in a series of columns by Greg Lapin, N9GL, the chairman of the ARRL RF Safety Committee, that's aimed at clearing away the confusion and misconception.
An amazingly complicated topic, the interactions of electromagnetic energy with biological tissue is a mystery to most. Add to this the general lack of understanding of how RF energy behaves in the presence of tissue. Very few people understand near-field antenna behavior. Compound that with resonance and polarization effects of RF with respect to tissue size and orientation and you have an engineering problem that is very difficult to define. Along with the engineering uncertainties in the field come the biological uncertainties. It is very unusual to find a research laboratory with expertise in both of these complicated topic areas, and it is not uncommon to find basic mistakes in research studies that can invalidate the conclusions. Despite this, most of the electromagnetic bioeffects scientific community has been able to agree on a standard of safe exposure levels, which is what the FCC regulations have been based on. A combination of RF bioeffects studies on laboratory animals and a compilation of the health histories of people who have been exposed over their lifetimes to RF energy make up the data input to a determination of safe levels of RF exposure. These are all topics that will be covered in future articles. It is my hope that the brief overviews of these topics will provide hams with the basis to understand and critique things that they see and hear about the topic. In particular, when biased and inflammatory news items appear on TV and in the papers, the person armed with this understanding will be able to recognize them for what they are, and dismiss them.
In the many years that I have been speaking about RF Bioeffects at scientific conferences, ham club meetings, and hamfests I have found that most people are concerned about the "C" word, Cancer. While there is much more to RF Safety than this family of diseases, it is understandable that it is something that might strike fear into even the most diehard of ham radio operators.
In this, the first of my monthly columns covering aspects of RF Safety, I'll discuss scientific investigation with an emphasis on cancer. In future columns I'll expand on many of the topics raised here, but let's start off with an overview.
I grew up in the 1960s and 1970s, when scientific advances were coming hard and fast. Cancer was targeted as one of the two diseases that science would conquer in these decades (the other being heart disease), and even though this has not come to pass, enormous strides have been made. A diagnosis of cancer is no longer the automatic death sentence that it once was. Back in the early days of this fight, there was a trend in scientific investigation in which different chemical substances were tested for their cancer causing potential (or, in scientific lingo, carcinogeneity).
One problem with investigations of this kind is that it takes a lifetime of exposure to most carcinogenic things for the disease to occur. To speed up the process, scientists exposed laboratory animals (usually mice and rats) to massive doses of a given chemical. Amazingly, it appears that just about everything caused cancer, and it seemed like every other week in the news we were being warned that things we used every day caused cancer: insecticides, the oil used in our transformers, cyclamates, saccharin and even coffee.
It was fortunate that many of these adverse reactions were discovered, and the public health has benefited by removal of these chemicals from our society. It turned out that other apparent cancer-causing agents were not, however. The study that targeted coffee was later disproved. Although cyclamates are no longer sold, the other artificial sweetener, saccharin, is still available in stores, with a warning on the package: "Use of this product may be hazardous to your health. This product contains saccharin which has been determined to cause cancer in laboratory animals."
Although the original study was not disproved, it was shown that normal use of this chemical had such a low probability of causing cancer that it was not considered to be a public health hazard. It was later realized that there is a chance of cancer occurring whenever the body is subjected to an insult that can damage cells. One study that concerned me at the time said that people who repeatedly bit their cheeks could form cancer in that spot. In my pre-braces days, that was happening to me. You can bet that I was happy to get that fixed!
A prevalent theory of how cancer occurs says that whenever cells are injured or die, the process that repairs or replaces them can make mistakes. A very small percentage of those mistakes can cause a cancerous cell to occur. Let's backtrack a bit and introduce some definitions. Cancer is a family of diseases that is characterized by cells that replicate too rapidly. It is called a family of diseases because there are many different types of cancer and most of them have different characteristics. The cells of our body normally replicate but usually, in adults, new cells are produced only in order to replace others that have died (in children there is more normal cell replication in order to produce more tissue as they grow). The cancerous cells often form a structure that is called a tumor, though some cancers don't, such as leukemia, which produces too many white blood cells that are then released into the bloodstream.
The unrestrained growth of cancerous cells is caused by a defect in their DNA. DNA is made up of genes, which contain the blueprint of every part of our bodies, including plans for how cells grow. Every time normal cells reproduce, they replicate their DNA and this becomes the basis of the new cells. There is a chance that DNA replication will not happen correctly, and this is called a mutation.
There are billions of possible errors that can occur when DNA replicates. Most of these mutations simply cause the new cell to die. Very few of the possible errors can create a new cell that is cancerous. Don't forget that mutation is the basis of Darwin's theory of evolution; it is not necessarily a bad thing and has been happening since the beginning of time. A very interesting type of cell to study with regard to cancer is the brain cell. Cells in the adult brain do not normally replicate at all. This removes one of the ways that those cells can become cancerous.
Yet, brain tumors still occur. Another mechanism for the formation of cancerous cells is when the DNA of a cell is damaged. The body has the ability to repair damaged DNA and if the repair process is faulty it is possible that a few of the billions of possible mutations can result in a cancerous cell. So, we have two occasions in which normal DNA can be modified to make a cell cancerous. Forcing the need for cell replication, usually by killing other cells, and directly damaging cell DNA, which requires a DNA repair process, both can lead to this result. Yet still, the statistical probability of this happening is miniscule.
The more times that DNA replication or repair happens, the more chance of the bad mutation occurring. Much like a roulette wheel, the more times you spin it, the more likely one of the spins will result in a 00. Even if a cell's DNA is modified to become cancerous, the disease hasn't taken over yet. The human body's immune system is constantly on the lookout for cells that it does not recognize. If it is able to determine that a mutation has occurred, it will often kill the mutated cell. This further lessens the probability that a mutation will successfully lead to cancer.
Considering that mutations occur every day, the probability of forming a viable cancer is so low that it may take more than 100 years for this to occur. Anything that increases that probability can statistically lessen this amount of time. Take smoking for example. Smoking has been shown to cause cancer in the population (more on this in future columns), yet there are people who have smoked for more than 50 years and have never developed the disease. Some influences do not directly cause DNA replication or repair to occur, but merely the presence of such a factor during DNA changes can lead to mutations. These influences are considered to be most dangerous for children, who have a much higher percentage of their cells replicating than adults do.
The key question that most hams should ask is, "Is RF one of these influences?" Actually, this is not exactly true. The main question that I have been asked by most hams is more like, "Can I still use my linear to break through pileups to get that new one?" However, I take that to mean the same thing. Since the answer is not a simple one, I'll have to address it in my next column. Until then, follow the FCC RF Safety Regulations--and keep trying for that new one.
Editor's note: First licensed in 1969 at age 13 as WN1NUK in Connecticut, Greg Lapin, N9GL, went on to earn a PhD in electrical engineering from Northwestern University. He started working in the RF Safety world after spending many years first studying cardiac function imaging and then brain tumor kinetics. He is currently chairman of the ARRL RF Safety Committee and a member of the IEEE Committee on Man and Radiation. A former professor of Biomedical Engineering and Neurology at Northwestern, he now works as a consulting professional engineer in the electronics industry. Lapin professes to still be fascinated by virtually all aspects of Amateur Radio. One of his many interests is electronic design, and he is the author of Chapter 8, "Analog Signal Theory and Components" in The ARRL Handbook for Radio Amateurs. His non-ham interests include making things grow in his garden and serving as commissioner of the local children's softball league. At other times when he is not working or doing his kids' homework, you might find him with the local emergency services agency, climbing his tower, building a new QRP rig, playing with his APRS setup, responding to QSL cards, going off on a DXPedition, or trying to get that new one. Readers may contact Greg Lapin at g.lapin@ieee.org.
