Cell phone, microwave oven or any electronic devices which are capable of radiation, do they harm human body? In order to answer that question, it is important to understand the nature of radiation. The radiation which are not ionizing do not harm human body. Radio wave, microwave or electromagnetic radiation which are not x-ray or gamma ray do not pose threat to human health. As the energy level of this waves are not good enough to cause harm. Although rumors were around that cell phone causes cancer, till now there had been no scientific papers suggesting so but a lot there to prove on the contrary. Same goes for microwave or any non-ionizing radiation. They can be harmful to human body if subjected to prolonged exposure and main causative agent would be heat.
Below is excerpt from the article about the nature of radiation:
Based on nature of radiation, it can be classified into two types. The criteria are Ionizing radiation and non-ionizing radiation.
Ionizing radiation: In the simplest word radiation which consist of particles which are energized enough to knock electron from atom or in other words capable of forming ions by changing the electronic configuration of a stable atom is known as ionizing radiation. These are the type of radiation which is capable of damage at cellular level, with other adverse effect. There are main four types of ionizing radiation: Alpha particles, Beta particles, Gamma rays and X-rays. Both Gamma rays and X-rays belong to the electromagnetic spectrum. Where else ultra violet (UV) radiation can be considered both ionizing and non-ionizing, depending on the energy content of the wave. Compared to the non-ionizing radiation ionizing radiation pose much more severe health risk for human.
Non-ionizing radiation: The particles or the wave for radiation is not energized enough to alter the electronic configuration of the atoms involved. As it is not highly energized, it pose none or whatsoever threat to human health. Types of non-ionizing radiation include radio waves, microwaves and radiation within the visible spectrum of the electromagnetic spectrum. Ultra Violet radiation is also considered non-ionizing radiation.