The Alpha-ray Activity of Human Tissues

The radioactivity of the human environment has become a matter of increasing importance and concern in view of the hazards now known to be associated with the ingestion or inhalation of small quantities of radioactivity (cf. The Hazards to Man of Nuclear and Allied Radiations, 1956; The Measurement of Body Radioactivity, 1957). Interest has recently been largely concentrated on man-made activity, particularly the β emission of such substances as strontium 90, but our knowledge of the radioactivity of our environment is so scanty that it seems possible that a number of sources of irradiation of human beings may exist of which we are at the moment completely ignorant. It is well known that the human body normally contains small quantities of naturally occurring radioactive elements particularly concentrated in bone (Stehney and Lucas, 1955), but to what extent these materials are derived from foodstuffs, drinking water and other ingested substances, is largely unknown for any particular individual. Since many of the naturally occurring radioactive nuclides emit α particles it seemed worth while to look again for such α activities, both within the human body and its environment. In order to explore such a wide range of materials, mostly of very low activity and available often in small quantities, it is necessary to develop simple and sensitive methods of α-ray detection. This paper describes such a method and its preliminary application to human bone and teeth. Later reports will deal with substances forming part of the human environment.