The 1986 and 1988 UNSCEAR (United Nations Scientific Committee on the Effects of Atomic Radiation) reports: findings and implications.

The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) has published a substantive series of reports concerning sources, effects, and risks of ionizing radiation. This article summarizes the highlights and conclusions from the most recent 1986 and 1988 reports. The present annual per person effective dose equivalent for the world's population is about 3 mSv. The majority of this (2.4 mSv) comes from natural background, and 0.4 to 1 mSv is from medical exposures. Other sources contribute less than 0.02 mSv annually. The worldwide collective effective dose equivalent annually is between 13 and 16 million person-Sv. The Committee assessed the collective effective dose equivalent to the population of the northern hemisphere from the reactor accident at Chernobyl and concluded that this is about 600,000 person-Sv. The Committee also reviewed risk estimates for radiation carcinogenesis which included the new Japanese dosimetry at Hiroshima and Nagasaki. These data indicate that risk coefficient estimates for high doses and high dose rate low-LET radiation in the Japanese population are approximately 3-10% Sv-1, depending on the projection model utilized. The Committee also indicated that, in calculation of such risks at low doses and low dose rates, a risk-reduction factor in the range of 2-10 may be considered.

ICRU and ICRP activities are important to radiologists and allied scientists.

The ICRU and ICRP, two commissions of the International Society of Radiology, have provided Internationally accepted recommendations on radiation quantities, units, measurements, and protection for the past 50 years. A few salient points covered during recent meetings of these bodies are outlined. Radiologists and allied scientists are urged to make full use of such recommendations.

Report from the International Commission on Radiation Units and Measurements.

A summary of the activities of the International Commission on Radiation Units and Measurements since 1973 is presented.

Metal-filled resin composites. II.

Various particulate materials were combined with a BIS-GMA resin, and the resulting composites were evaluated. The fillers prevented, altered, had no apparent effect, or accelerated polymerization. Coupling agents also influenced polymerization. Physical properties varied widely with different fillers.

The new special names of SI units in the field of ionizing radiations.

New SI units for ionizing radiations have been recommended by the internation Commission on Radiation Units and Measurements (ICRU). These are the becquerel (symbol Bq), equal to the second to the power -1, and the gray (symbol Gy), equal to the joule per kilogram. It was recommended that the roentgen be replaced as the unit of exposure by the coulomb per kilogram (C/kg), for which no new name was proposed. The ICRU recommends that the units rad, roentgen, and curie be gradually abandoned over a period of ten years and that preparatory steps to this end be taken as soon as possible by various national and international bodies in order to facilitate a smooth, safe, and efficient transition.

The new special names of SI units in the field of ionizing radiations.

At its meeting in May-June 1975, the 15th Conference Generale des Poids et Mesures adopted two new special names of SI units; the becquerel, symbol Bq, equal to the second to the power minus one, s-1, for the quantity activity, and the gray, symbol Gy, equal to the joule per kilogram, J-kg-1, for absorbed dose and related quantities in the field of ionizing radiations. This action was preceded by a recommendation of the International Commission on Radiation Units and Measurements (ICRU) in 1974.