7.9 CHAPTER SUMMARY
Chapter 6 followed RF energy from source emissions through external exposure to the internal fields and energy absorption determined by RF dosimetry. This chapter completed the progression by examining biological response and the circumstances in which a response may become an adverse health effect.
RF fields interact with the body through induced electric fields and currents and through the absorption of electromagnetic energy. At the lower end of the RF range, sufficiently strong induced fields may stimulate excitable tissues. Over most of the RF range, excessive absorption can cause whole-body or localized heating. The relative importance and spatial distribution of these mechanisms change gradually with frequency, exposure duration, body geometry, posture, grounding, and the characteristics of the incident field.
A measurable biological response is not necessarily harmful. Exposure guidelines are based on adverse effects supported by the weight of scientific evidence. Guideline developers identify adverse-health-effect thresholds where the evidence permits and otherwise may use conservative operational thresholds; reduction factors are then applied to derive the basic restrictions. Reported effects that are inconsistent, not independently reproducible, or not linked to impaired health continue to be studied but are not treated as established adverse effects.
Basic restrictions limit quantities within or at the surface of the body that are linked to the established interaction mechanisms. Reference levels provide conservative, more readily assessed quantities for routine compliance. Compliance with the appropriate reference level demonstrates compliance with the related basic restriction, while exceeding a reference level indicates the need for a more detailed assessment rather than proving that injury has occurred.
A suspected or confirmed overexposure requires prompt action, medical assessment where appropriate, preservation of reliable exposure information, and investigation of the incident. A compliance exceedance and a clinical injury are not the same: the presence or absence of nonspecific symptoms cannot determine either question by itself.