The energy carried by a photon with an EMFs frequency f is given by E = hf , where h is Planck’s constant. The mode of interaction between a photon passing through a material and the material’s atoms or molecules is very much dependent on f . If f is greater than about 1015 Hz (which falls in the ultraviolet (UV) band of the EM spectrum), the photon’s energy is sufficient to free an electron and remove it completely, thereby ionizing the affected atom or molecule. Consequently,the energy carried by such EM waves is called ionizing radiation, in contrast with non-ionizing radiation(Fig. TF17-2) whose photons may be able to cause an electron to move to a higher energy level, but not eject it from its host atom or molecule.
Assessing health risks associated with exposure to EMFs is complicated by the number of variables involved, which
include: (1) the frequency f , (2) the intensities of the electric and magnetic fields, (3) the exposure duration, whether continuous or discontinuous, and whether pulsed or uniform, and (4) the specific part of the body that is getting exposed.
We know that intense laser illumination can cause corneal burn, high-level X-rays can damage living tissue and cause cancer and, in fact, any form of EM energy can be dangerous if the exposure level and/or duration exceed certainsafety limits. Governmental and professional safety boards are tasked with establishing maximum permissible exposure(MPE)levels that protect human beings against adverse health effects associated with EMFs. In the United States,the relevant standards are IEEE Std C95.6 (dated 2002), which addresses EM fields in the 1 Hz to 3 kHz range, and IEEE Std 95.1 (dated 2005), which deals with the frequency range from 3 kHz to 300 GHz. On the European side of the Atlantic, responsibility for establishing MPE levels resides with the Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR) of the European Commission.