The relation between energy doses of ultra-violet radiation and actinic erythema produced

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Abstract
The purpose of the investigation was to ascertain what relation exists between the effect of radiation from a mercury vapour lamp on the skin as measured by the resulting erythema and the total amount of radiation energy or "dose" (intensity X time) received. The paper also gives the relation connecting dose and latent time. The question is of both theoretical and practical importance. It is a particular case of the general problem of how the extent of a biological reaction depends upon the quantity of any kind of radiation ([gamma]-, x- or ultra-violet rays) producing it. Particular attention was paid to the question of how the intensity of the radiation decreases with the distance from the source. The intensities were varied over wide limits (200:1) corresponding to distances varying from 40 cm. to 51/2 metres. The effect of a given "dose" of the weak intensity is aa great as that of the most powerful intensity used, and it is concluded that the production of erythema follows the Bunsen-Roscoe law for a photo-chemical action, i.e., the time factor is unity. If the latent time be plotted against the "dose" made on one part of a subject with the source of radiation constant, but the intensity of radiation varying, the observations lie on a single curve, i.e., if we take a separate series of curves connecting latent time and time exposure as obtained in the previous paper and plot "dose" instead of time of exposure, the separate curves become one. This curve gives the relation between the biological reaction of the skin as measured by the latent time for the production of erythema and the. quantity of radiation received.

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