Re: What was the first commercial use of ultraviolet radiation?

This is the best answer I can find on the Web (See below).  The other 
thought that comes to mind is the use of UV light to polymerize certain 
plastics.  I did a search using Yahoo with the following key words  - 
ultraviolet light history.  You might want to try the search yourself and 
use the additional key words - commercial plastics polymerize.

FLUORESCENT LAMP - (1937)
The fluorescent lamp was first introduced to the public at the New York 
World's Fair in the late thirties (1937). The lamps were introduced 
commercially in about 1938. The fluorescent lamp is a low pressure gas 
discharge source, in which the light is produced predominantly by 
fluorescent powders activated by ultraviolet energy generated by a mercury 
arc. Typically, a fluorescent lamp must efficiently generate 253.7 
millimicron ultraviolet radiation to excite the phosphors coating the 
inside of the tubular glass bulb. 
The lamp is usually in the form of a long tubular bulb with an electrode 
sealed at each end. The modern fluorescent lamp has an efficacy of 
approximately 65-80 lumens per watt. Today fluorescent lamps are also 
available in circular and 'folded' shapes. Lamps with various different 
color temperatures and color rendering properties are commonly available. 
The most common fluorescent lamp is the CW or cool white version, although 
new 'warmer' versions are now gaining popularity, worldwide. All 
fluorescent lamps require a ballast, for operation. 

Developed in the late 1980's the compact fluorescent lamp revolutionized 
the lighting industry. This lamp (also referred to as the PL lamp), is 
simply a folded fluorescent tube, sometimes no larger than a 
standard 'light bulb'. The ballast is usually mounted in the base pf the 
lamp. This new lamp allows most household incandescent lamps to be 
replaced with these new energy saving fluorescent lamps. In addition to 
retrofit applications, new 'pot light' fixtures have been developed 
specifically for the PL lamps, for residential, commercial and industrial 
lighting applications. PL lamps are available in various wattages from 
approximately 9 - 50 watts, and are available from all major lamp 
manufacturers.