Paper 252

Abstract Title:

VARIETY IN CONVENTIONS FOR SUB-DIVIDING THE BIOLOGICALLY ACTIVE ULTRAVIOLET REGION

Authors:

T.P. Coohill

Institutions:

Siena College, Loudonville, USA

Key Words:

Abstract:

Although the naming of the regions of the electromagnetic spectrum has a long and convoluted history, only one set of definitions is endorsed by an official scientific body for the biologically active region of ultraviolet radiation (UV). This was done at the Second International Congress on Light in Copenhagen in 1932. These regions were determined by Coblentz using the transmission properties of three common filters. A barium-flint filter (315-400nm) defined the UV-A; a barium-flint-pyrex filter (280-315nm)the UV-B; a pyrex filter (wavelengths shorter than 280nm) the UV-C. It was left to future meetings to correlate these physical measurements with biological reactions. That has not happened, although various effects are noted for each region. These are the official designations of the Commision Internationale De L'Eclairage. But widely noted authorities (e.g. Jagger) use different definitions such as - UV-A (320-400nm), UV-B (290-320nm) and UV-C (190-280nm). Other fractionations also exist especially in the photobiological literature (e.g. Photochem. Photobiol.). This presentation will discuss the reasoning behind these varying usages and the biological impetus for each fractionation. The hope is to limit the confusion resulting from different conventions and misinterpretations among authors. The latter is especially prevalent if manuscripts do not define which limits the author is using. Agreement on which limits to use does not appear to be forthcoming but some convergence of accepted usage may result from a discussion of the issue.