The case of Vatican Radio is but the latest episode in a half-century-long scientific controversy. Last December, a panel of the International Commission on Non-Ionizing Radiation Protection (ICNIRP), headquartered in Oberschleissheim, Germany, published a global review of epidemiological studies dealing with the impact on health of electromagnetic waves. The report covered a range of RF sources, including cellphones and communication towers, and one section reviewed eight epidemiological studies of residents living around radio and television transmitters, including Michelozzi's study.

The panel found the results inconclusive. "For these studies to be informative, there have to be better exposure assessments, and the numbers [of people in the samples] should be larger," says Anders Ahlbom of the Karolinska Institute in Stockholm, Sweden, who led the study. "Even taken together, they don't really suggest any health risks," he says.

RF radiation is nonionizing—that is, it cannot break the bonds in molecules—and no plausible biophysical mechanism has been proposed that would predict biological effects from low-level fields, except as related to heating. Therefore, many scientists in the field have viewed research on the biological effects of radio waves with some skepticism. Radio frequencies do, however, induce currents in parts of the human body, which can resonate as a half-wave antenna: there is a maximum in the fraction of incident energy that is absorbed in the whole body at 100 megahertz and at 800 MHz in the head—the latter is close to the 850 and 900 MHz frequencies used for mobile phones in the United States and Europe. Exposure limits, such as those recommended by the IEEE, take that effect into account.

In addition to epidemiological studies, researchers are looking at what happens to cultures of human cells (and also of other organisms) when they are exposed to radio waves of intensities that do not produce any significant heating in the material in which the radiation is absorbed. Most useful for risk assessment are standardized animal studies, which are being undertaken in a number of labs around the world. But some researchers are pursuing other areas of investigation, some of which are scientifically controversial.

At CNR-IREA, the Italian National Research Council's Institute for Electromagnetic Sensing of the Environment, in Naples, researchers place petri dishes with cell cultures in beams of radio waves and then compare the cells with control samples that have not been irradiated. DNA damage, cell division, oxidative stresses, and the induction of apoptosis (cell death) are some of the effects the small Naples group investigates.

So far, however, such studies "do not produce a coherent picture," says Maria Rosaria Scarfi, a researcher at CNR-IREA. Fundamentally, the absence of theoretical models explaining the interaction between electromagnetic fields and biological systems complicates the research, she says.

Despite the lack of compelling results, whether the focus is on cellular changes or statistical anomalies found in connection with radio transmitters, high-power lines, or mobile telephony, Ahlbom thinks that research should continue, because RF radiation is so ubiquitous. "So many people are exposed. I think it makes sense to try to investigate as much as possible whether there might be any risks, although the likelihood is against [there being any] risks."

In the meantime, the inhabitants of Cesano can, in principle, rest assured that they are in no great danger. "The exposure from the [Vatican] transmitters is much lower than what you receive from ordinary cellphones—several orders of magnitude lower," says Ahlbom. This does not mean, however, that Cesano residents actually are relaxing or giving up their struggle to close down the Vatican complex altogether.

Italy's stricter limits on RF energy exposure, ironically, seem to be have made the public more ill at ease rather than more confident. Though they were intended to provide an extra measure of safety, the limits "actually increased public fears and controversies," concludes Paolo Vecchia of Italy's National Institute of Health, in Rome, and Kenneth R. Foster, a professor of biophysical engineering at the University of Pennsylvania, in Philadelphia. Vecchia and Foster believe this is because the public took the stricter Italian limits to be an admission that RF fields really are dangerous in the long run.

For this very reason, Vecchia and Foster note in an article they wrote about the Vatican controversy for IEEE Technology and Society in winter 2002, the World Health Organization in Geneva has advised against adoption of overly cautious exposure limits. The organization warns that the credibility of exposure standards is undermined if limits are lowered to levels "that bear no relationship to the established hazards or have inappropriate arbitrary adjustments."

—Alexander Hellemans