dal Salmonella spp. (28%), T. gondii (24%), Listeria monocytogenes (19%), and norovirus (11%). These estimates cannot be compared with prior (1999) estimates to assess trends because different methods were used. Additional data and more refined methods can improve future estimates.20:T4d0,The decomposition of aqueous ozone is generally due to a chain reaction involving ·OH radicals. Many organic solutes (impurities) can react with ·OH to yield ·O₂^- upon addition of O₂. ·O₂^-transfers its electron to a further ozone molecule in a rather selective reaction. The ozonide anion (·O₃^-) formed immediately decomposes into a further ·OH radical. Compounds that convert ·OH radicals into ozone-selective ·O₂^-, therefore, act as promoters of the chain reaction. The efficiencies of different ·OH to ·O₂^- converters (e.g., formic acid, primary and secondary alcohols (including sugars), glyoxylic acid, and humic acids) are tested in the presence of other ·OH radical scavengers that do not primarily produce ·O₂^- (carbonate, aliphatic alkyl compounds, and tert-butyl alcohol). The derived reaction kinetics allows one to qualitatively interpret the variation of the lifetime of O₃ found in model solutions and even in natural waters and during drinking water treatment.21:T6bd,

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