A joint research team in the College of Science, University of Al-Mustansiriyah conducted a study on the effect of rays’ exposure on various components of human blood. The study aimed at studying effect of ionizing rays, which may occur as a result of exposing to various sources of radiation in the various components of human blood. The study reviewed irradiation of human blood samples with several types of ionizing rays, the most important rays such as Alpha, Beta and Gamma during different periods of time, testing changes in the density of red and white blood platelets and biological effects of these sources on living cells. The study concluded that the effect of the Gamma ray is stronger than the rest of the other rays, which these rays are characterized by their high ability to penetrate tissues and cause a change in the levels of density of red and white blood platelets that lead to damage blood cells and severe atrophy of the entire lymphoid tissue.