A biological effect occurs when exposure to EMF causes some noticeable or detectable physiological change in a living system. Such an effect may sometimes, but not always, lead to an adverse health effect, which means a physiological change that exceeds normal range for a brief period of time. It occurs when the biological effect is outside the normal range for the body to compensate, and therefore leads to some detrimental health condition. Health effects are often the result of biological effects that accumulate over time and depend on exposure dose. Determining actual health risks from EMF exposure is complex. Not all investigators agree about the risk. In its EMF assessment, the National Institute of Environmental Health Sciences (NIEHS), based on the report of its expert Working Group [1,2], stated that biological effects are plausible at a tissue dose of 1 mV/m. According to Dawson et al. [3], contact current levels on the order of 10 µA or less, considerably below ICNIRP limits, can produce electric fi elds in some tissues that are well above the NIEHS’s 1 mV benchmark [4]. In addition, a growing number of studies in the literature suggest that there may be health risks at such EMF levels, possibly depending on many variables including duration of fi eld exposure, strength of the fi eld, person’s mass and age, general health, and probably genetic predisposition or vulnerability to cancer. Therefore, detailed knowledge of the biological effects is important to understand the generated health risks.