EARLY OBSERVATIONS OF RADIATION EFFECTS
Marie Curie's Professor proudly carried in his coat pocket a vial containing the first sample of radium (an emitter of high energy alpha particles and gamma rays) ever produced; shortly thereafter, the first radiation burn was documented. To verify association between radiation and tissue damage, early researchers taped pieces of the new metal to their skin to observe results and confirmed that the radioactive material was indeed causing the burns. The now-familiar story of a multi-decade epidemiological study of radium-watch dial painters revealed that these workers, who tipped the brushes with their lips and during their careers ultimately swallowed large amounts of radium, had an incidence of bone cancer significantly greater than expected for the general population. An increase in thyroid cancer has likewise been observed in adults who, during the 1940's, underwent neck irradiation during childhood. A relationship has also been established between childhood radiation and parathyroid adenomas.

BACKGROUND
Researchers have been unable to document a threshold level for causing radiation damage for long-term radiation effects. The assumption is made that the probability of radiation carcinogenesis and radiation-induced genetic abnormalities is never zero, regardless of how low the exposure dose The rates of carcinogenesis and radiation-induced abnormalities are too low to measure by most feasible techniques Time between exposure and manifestation of symptoms is inversely proportional to the absorbed dose At low exposure rates, biological repair corrects some of the damage Ionizing radiation includes charged particles, photons, and other products of natural and induced radiation. In the body, water is the most likely molecule most likely to be ionized by radiation. The water transfers its energy to another nearby molecule, inducing radiation damage in the second molecule. Depending upon dose rate, the tissue may or may not be able to repair itself. Effects recognized as being caused by ionizing radiation include acute burns, dermatitis and hair loss, and carcinogenesis, as well as genetic effects.

THE ALARA CONCEPT
In the mid- 1970s, the ALARA concept was proposed and in 1995 became a mandatory part of one’s Policy and Procedure Manual. It was designed to heighten the awareness of Nuclear Medicine Technologists to the risk of ionizing radiation and to minimize their absorbed dose. It was based upon maintaining the radiation dose As Low As Reasonably Achievable and has contributed to a significant overall reduction in dose to radiation workers.

MAXIMUM PERMISSIBLE DOSE
In accordance with current NRC Regulations, for Radiation workers, the Maximum Permissible Doses are listed below: whole body: 5 R in any given year = 50 mSv internal organ: 50 R in any given year = 500 mSv lens of the eye: 15 R in any given year = 150 mSv extremities: 50 R in any given year = 500 mSv (50 R is considered to be an acceptable level for the hands since there is essentially no bone marrow to be irradiated.) For members of the general public (our families and other non-radiation workers), the MPD is 0.1 R/yr.