Chemical bond dissociation induced by light occurs when a photon’s wavelength dependent quantum energy is equal to or greater than the energy of the molecular bond upon which it is incident. Photochemical damage to a life-critical biological structure can be induced by irradiation with photons having energy levels corresponding to the bond energies of biomolecular chemical bonds. Upon UV photon absorption, excited states and reactive species are created which react to form biologically non-functional reaction products. The history of photochemical microbial inactivation dates back to the discovery in 1877 by Downes and Blount (1) that ultraviolet light can damage microorganisms. In 1928 F.L. Gates (2) made the formal discovery that specific monochromatic wavelengths of UV light are bactericidal. The physical mechanism connecting specific wavelengths of light with specific molecular bonds was finally revealed by quantum mechanics, developed by Planck, Einstein, Bohr, Sommerfeld, de Broglie, Heisenberg, Dirac, Pauling and others during the first half of the 20th century. Biochemical research since then has shown that the most effective wavelengths, 250 nm to 280 nm, coincide with the peak absorption spectra of nucleic