The production of erythema of the skin by exposure to x-ray radiation.

ElINE manifestation of overexposure of the skin to x-ray radiation employed diagnostically is the appearance of an erythema similar to sunburn. This paper presents the experimental results of a study which was completed to determine the amount of radiation from a dental x-ray machine that is required to produce an erythema of the skin on the flexor surface of the forearm. There are many references in dental literature which state that an exposure of 1,200 milliampere seconds* at a target-skin distance of 8 inches will cause an erythema of the skin; therefore, no single area of skin should be exposed to more than one-half of the erythema dose, or 600 Ma.S., in any two-week period. To test the validity of these statements, circular areas of skin, 11/8 inches in diameter, were exposed on the flexor surface of the forearms of 20 male volunteers of college age. In the beginning phase of this investigation, exposures were initially of short duration and then were gradually lengthened to approach the exposure time necessary to produce a clearly defined pink area on the forearm. The smallest exposure found to produce an erythema was 425 Ma.S., although many subjects did not experience an erythema until they had received 550 to 600 Ma.S. of exposure to x-ray radiation. After the approximate magnitude of the exposure required to produce erythema had been determined, a second series of tests was performed on nineteen additional male volunteers of college age in an effort to determine more exactly the amount of radiation from a dental x-ray machine that is required to produce an erythema of the skin on the flexor surface of the forearm. Each subject was given 600 Ma.S. of x-ray exposure, which was administered to a circular area on the flexor surface of one forearm. This area was observed again in twenty-four hours. If an erythema had appeared, a similar area on the flexor surface of the other arm was given 10 per cent less exposure, or 540 Ma.S. If no erythema had appeared, the other arm was given 10 per cent more exposure, or 660 Ma.S. The initial appearance of the erythema was determined by the subject. The results of the experiments with these nineteen individuals are listed in Table I. Six of the nineteen subjects did not cooperate to the extent of permitting the second arm to be exposed. However, even the exposure of one arm provided