What a confusing world we live in! First, we hear that RF is harmful, then we hear that it's not.

These days, we hear about people blaming their cell phones for causing their brain tumors, and then we hear that a study of cell phone users showed that they don't get any more brain tumors than non-cell phone users. We hear of rats exposed to dosages of RF that are more than 100 times higher than what a cellular telephone produces and end up living longer than their unexposed counterparts. We hear that hams get some forms of blood cancer more than other people do, then we realize that the data were massaged to indicate this, and no such statement could be correctly made. This is the world of electromagnetic bioeffects.

The pendulum of opinion about the safety of RF swings back and forth. For people in the scientific end of the RF safety business, it presents quite a quandary when dealing with the public. A recent editor's comment about a paper that I was writing for the scientific press warned me not to talk about "safe limits" of RF exposure. The editor went on, "scientists are usually very uncomfortable certifying anything as 'safe'." That's a problem that science has. We work in probabilities and there is hardly ever a 100% chance of anything. Even if a level of RF exposure has a very low probability of being associated with disease, scientists don't want to call it "safe" because some people will still get sick. We can't completely rule out RF as the cause of the sickness. We can only say that it probably isn't.

The scientific world has a hard time talking to the rest of the world about RF safety. We understand that all the evidence shows there is little chance that RF from devices such as a cellular telephone or a ham's antenna tower will harm anyone. People don't want a probability; they want a sure thing, particularly when it comes to their health. This doesn't explain how the same people manage to get into their cars and drive in traffic every day, but that's a topic for another article.

The pendulum can also swing too far in the other direction. The other extreme is not celebrated in the press and we don't hear so much about it. There are people who are convinced that RF cannot hurt them, and find it ridiculous that anyone would think otherwise. Many of these people have been working around RF signals for many years and, because they are healthy, they are sure that there can be no ill effects from any RF exposure. The same people are convinced that there is another motivation behind the FCC RF safety regulations, other than protection of the public. It is to these people that I point out the example of cigarette smoking. I don't know anyone who does not believe that smoking is bad for human health. However, we all know, or have heard of, people in their 90s who have smoked every day since they were in their 20s and are still in perfect health. No one disputes that these people exist, but no one disputes that there is a direct correlation between smoking and lung cancer, as well as very strong associations to many other diseases. Biological variation is one of the great mysteries of humanity.

RF safety standards are based on the best scientific information available. Laboratory studies with animals and epidemiological studies with humans have identified RF exposure levels that have clear ill effects. The more extreme forms include death of cells due to excessive heating. Lesser exposures have been identified as causing behavioral changes. The safety standards take all of this into account and set exposure limits that are intended to prevent any of these effects from occurring in the population.

Safety standards are developed without relying on known or presumed biophysical mechanisms for the various effects that they are trying to prevent. For instance, a number of studies on animal behavior have shown that animals change their behavior when exposed to certain levels of RF. The behavioral changes have been manifest as changes in the ability to perform tasks. Some examples include monkeys trained to hit a feeder bar to get rewarded with a food pellet. When the RF exposure reaches a given level, they do this less often. Rats who have been trained to negotiate a maze lose the ability to do so when the RF exposure is high enough. The standards bodies have recognized these as undesirable effects and have set exposure limits to prevent them. Whether heating in the brain changes its function, or tissue heating disturbs the animals to the extent that they no longer want to perform their tasks, or if some other undefined mechanism has been responsible is not the issue. The primary goal of the standard limit is to prevent the effect regardless of its cause.

Some people ask about athermal effects. That is a whole subject unto itself and is something that I will write about in more detail in future articles. However, don't forget that the standards were developed to prevent detectable changes in scientific test subjects. Mechanisms causing the changes are not considered in setting the limit, so if some of the observed changes were found to be caused by an athermal effect, they are also covered by the safety standards.

RF bioeffects are real. Don't let any of your experiences convince you otherwise. Many effects are undetectable. You don't feel an internal cell that has absorbed too much heat; most of your body's temperature sensors are at the skin. You often can't detect that your behavior has changed due to RF exposure. Some damage takes years of exposure to be noticed.

To protect us from influences that cannot be seen, heard, smelled or felt we have developed RF safety standards. The FCC has codified these standards in its regulations to make sure that we 1) know that they exist, and 2) follow them to keep ourselves, our families, and the general public around us from being harmed.

We owe it to ourselves, the people around us, and Amateur Radio to deal with RF safely and reasonably. We can do so by staying informed about the realities of RF safety, and not letting the unfounded extreme views that reside at either end of the pendulum affect what we know to be right.

Editor's note: Greg Lapin, N9GL, started working in the RF safety world after spending many years first studying cardiac function imaging and then brain tumor kinetics. He serves as chairman of the ARRL RF safety Committee and as a member of the IEEE Committee on Man and Radiation. A former professor of Biomedical Engineering and Neurology at Northwestern University, Lapin now works as a consulting professional engineer in the electronics industry. He was first licensed while a teenager in 1969 and continues to 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 helping his kids with their 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." You can reach him by email at g.lapin@ieee.org.