Electromagnetic fields (EMF) are invisible areas of energy, often referred to as radiation, associated with the use of electrical power and various forms of natural and man-made lighting. EMF can be categorized into non-ionizing (low-level radiation) and ionizing (high-level radiation). Non-ionizing radiation includes radiofrequency (RF) and extremely low frequency (ELF) fields, while ionizing radiation includes X-rays and gamma rays.