The concept of a maximum permissible exposure.

Abstract

Mr. President, members of the Radiological Society of North America, and guests, it is a great honor and a great responsibility to be selected to give the Carman Lecture. The choice of the Carman lecturer is one of the privileges and duties of your president. When Doctor Bouslog asked me to accept this responsibility, he asked that I report to you on some aspect of the radiological work of the Metallurgical Project—the project that was concerned with chain-reacting piles and producing plutonium. Reports of many specific research activities have already been made, notably those ineluded in the plutonium symposium before this society in 1946. Instead of reporting specific experiments, I decided to discuss one of the biggest problems we had to face in the Health Division of the Plutonium Project and one which you must face every day; namely, to what amount of ionizing radiation may a person be exposed day after day without detectable damage to himself or future generations. Radiologists as a group have been content to accept the decisions of the national and international committees and commissions with regard to the maximum permissible exposure. In this lecture I will present to you some clinical and experimental data that will help you to form your own concept of a maximum permissible exposure. The word “concept” applies to the idea of a thing which the mind conceives after knowing many related facts. The facts needed are the results of chronic exposures of men and animals to ionizing radiations. The expression “maximum permissible exposure” means the largest exposure in any selected time period, such as a day or week, to which you are willing to permit yourself or anyone else to be exposed repeatedly. This was formerly called the “tolerance dose.” This annual lecture is to honor the memory of Russell D. Carman. It was suggested to me that it would be an original approach to give a memorial lecture without in any way connecting the subject with the person being memorialized. That approach cannot be used tonight because Doctor Carman was a man of broad interests in the field of radiology. In this city, in 1924, he read a paper (13) before this society on the occupational hazards of the radiologist. While he did not talk about tolerance dose or maximum permissible exposure, he did discuss the effects which make it necessary for us to establish what is tolerable. It is fitting, therefore, that this topic be the subject of a memorial lecture to that great radiologist. Shortly after x-rays were discovered, some of those who worked with them were injured. The need for means of protection was obvious. It was recognized that to get complete protection while still using these rays, and the gamma rays from radium, was almost impossible. Scientists have tried, therefore, to find a rate of exposure which could be tolerated.