Biological Effects of Modulated Radiofrequency Fields

This report examines the literature on biological effects of exposure to modulated radiofrequency (RF) energy to determine whether present exposure standards and guidelines need to be modified further to take modulation into account. Modulation occurs in a wide variety of forms specialized for radar, wireless communications, broadcast communications, and industrial processes with the result that many waveforms, pulse widths, spectral properties, and temporal patterns need consideration. In pulse modulation the RF energy is rapidly switched on and off, whereas amplitude modulation produces a continually changing level of RF energy. Frequency-modulated RF energy has signal amplitudes that remain essentially constant, but vary in frequency within some narrowly prescribed range and more closely resembles nonmodulated RF energy than pulsed or amplitude modulated RF fields. For radar, pulses generally have durations measured in fractions of a microsecond to a few microseconds. Intervals between pulses (or pulse groups) are considerably longer resulting in low duty cycle, that is, RF energy is on for a small fraction of time during each period. But pulsed signals used for communications systems can have durations in the range of milliseconds, higher duty cycles, and additional modulation features. Specialized military systems constitute a subcategory with very intense, brief pulses.
Content:
• Front Matter
• Preface
• Table of Contents
• Executive Summary
1. Introduction
2. In vitro Studies
3. In vivo Studies
• 4. Human Studies
• 5. Epidemiological Studies
6. Biophysical Considerations
• 7. Discussion and Conclusions
• Acronyms
• References
• The NCRP
• NCRP Commentaries