Radio‐Frequency and Microwave Radiation

Abstract

Radio‐frequency radiation (RFR) is a type of nonionizing electromagnetic energy. Electromagnetic energy is the propagation of energy by time‐varying electric and magnetic fields. The fields are described by three vector quantities: electric‐field strength, magnetic‐field strength, and propagation vector. Typically, electric and magnetic fields are characterized at right angles to one another and to the direction of motion of the radiation, which is defined by the propagation vector. Radiation may be described by frequency, wavelength, and photon energy. RFR is nonionizing because the photon energy in this spectral region is not sufficient to ionize matter. However, by convention, RFR is described by frequency. Frequency is the number of wave cycles that pass a point in space in a second (s), and the unit is the hertz (Hz). Sometimes, the interaction of RF energy with matter is described by the wavelength, which is the length of one complete wave cycle. For the purposes of this chapter, the boundaries of the RF spectral region are 3 kilohertz (kHz) to 300 gigahertz (GHz). Usually, microwave radiation is considered a subset of RFR; however, an alternate convention treats radiowave and microwave radiation as two spectral regions. Sources of RFR are both natural and man‐made. Natural sources include terrestrial and extraterrestrial sources, and even the human body. Major man‐made sources are shown reviews are available. The source that has most consistently demonstrated the potential for overexposure during normal use is the unshielded dielectric heater (also called plastic sealers). Induction heaters have demonstrated the potential for overexposures to the magnetic field. Certain maintenance activities associated with broadcasting and radar have the potential for overexposure. This chapter surveys the effect of long‐term studies, ocular effects, behavioral effects, reproductive and developmental effects, and cancer. For the interested reader, reviews of biological effects are available.

Airborne disinfection using microwave-based technology: Energy efficient and distinct inactivation mechanism compared with waterborne disinfection

“…The distinct inactivation mechanisms should be attributed to the different characteristics of electromagnetic fields in air and water phases. The MW photons can be easily absorbed by water molecules to increase water temperature (Hitchcock, 2001;Jones, Lelyveld, Mavrofidis, Kingman, & Miles, 2002). Therefore, the thermal effect plays a major role in waterborne bacteria inactivation (Cara et al, 1999).…”

“…Therefore, the thermal effect plays a major role in waterborne bacteria inactivation (Cara et al, 1999). However, the MW photons are not easily eliminated by oxygen and nitrogen molecules in air (Hitchcock, 2001). Instead, most MW photons can directly react with the target microbial cells, and this process represents the non-thermal effects (Betti et al, 2004;Hong et al, 2004;Woo et al, 2000).…”