Background radiation is present on earth, water, air and soil. Examples include: Potassium 40 is in our body and Uranium is in the rock and/or soil.
Artificial radiation is other than background radiation. Examples include: X-ray machines used for basic research and medical diagnostic, Iodine 131 used for hyperthyroid treatment and Phosphorus 32 used for medical research.
Background radiation is the main source of exposure for most people. It accounts for about 80%, while 20% comes from artificial radiation.
Most atoms have a balance of positive and negative charge; therefore they carry a neutral charge and are stable.
Some unstable atoms will attempt to reach stability by releasing their radiation energies. This characteristic is called radioactivity and the change is called decay. Any atoms which release these radiation energies are called radioisotopes or nuclear substances.
Ionizing Radiation & Non-Ionizing Radiation
Non-ionizing radiation: Radiation that has sufficient amount of energy to vibrate or move the electrons around, but does not have enough energy to change them chemically. Examples include: laser, microwave, electric and magnetic fields.
Ionizing radiation: The removal of one or more electrons of an atom in the medium, resulting in a creation of a positively charged atom and a free electron with a negative charge. Nuclear radiation is ionizing radiation. Examples include: radioisotope or nuclear substance, X-ray, gamma ray.