Figure 1.

The electromagnetic spectrum with its characteristic frequencies, wavelengths, and electromagnetic energy. The electromagnetic spectrum ranges from extremely long wavelengths with small frequencies (e.g., ELFs (extremely low frequency) and VLFs (very low frequency)) to extremely short wavelengths with high frequencies (e.g., UV (ultraviolet), x-rays or gamma-rays). Depending on the wavelength and frequency, it comprises both nonionizing and ionizing radiation. * In case for pulsed electromagnetic fields (PEMFs), “frequency” and “repetition rate” are often used synonymously, knowing that lower-frequency electromagnetic pulses are super-positioned by higher frequencies, yielding a wider frequency spectrum. The range of extremely low frequency pulsed electromagnetic fields (ELF-PEMFs) considered in this review is marked in red.