The Origin of UV-A, B and C
ASP Historian (emeritus) & Past-President (Deceased)
Modern phototherapy had
its beginning in Copenhagen in 1895 when Dr. Niels Finsen showed the Beneficial
Effects of light on tuberculosis of the skin. By 1929 the use of light for the
treatment of a variety of diseases had progressed to the point that a first
International Congress on "Actinology" was held in Paris. At that
time a committee on measurement and standardization of ultraviolet radiation
used in medicine was appointed. The second International Congress on Light (Congress
Internationale de la Lumiere) was held in Copenhagen in August 1932. The committee
reported as follows:
To recommend the standardization
of sources used in medicine, dividing the ultraviolet spectrum in three spectral
parts, defined provisionally by the following filters:
Noviol-A-Barium-flint (UV of long wavelength UV-A giving approximately the spectral band from 4000 to 3150 Å).
Barium Flint-Pyrex (UV of medium wavelength or UV-B giving approximately the spectral band from 3150 to 2800 Å ).
Pyrex (UV of short wavelength, or UV-C giving approximately the rays shorter than 2800 Å).
For each part of the spectrum, as defined by these filters, the measurement of radiation is to be made radiometrically
by means of a non-selective method (e.g., by a thermopile) and preferably (for
medical and meteorological measurements) expressed in milligram calories per
The lamp manufacturers are
advised to give energy data for these parts of the spectrum for all their lamp
types, stating all conditions of measurements.
The question whether the
specification of dosage should be on a physical or a correlated biological (erythemal)
basis was discussed at the first Congress in 1929, and again in the present meeting.
But the subject is so new that the physiologists and the phototherapists, who
use the erythemal test to gauge the initial dose, could not come to an agreement
Comment: The filters described
were apparently to be made by Corning Glass Works. At present, Corning does
not seem to have any records of these. The argument about whether to use physical
or biological units to describe effective dose certainly still continues, even
though the subject is hardly new. Lamp manufacturers apparently have not paid
attention to recommendations made as long ago as 1932.
Coblentz, W.W. (1932) Science