The fast reaction of gaseous ozone, O-3(g), with aqueous iodide, I-(aq), was found to be affected by environmentally relevant cosolutes in experiments using cavity ring-down spectroscopy (CRDS) and electrospray ionization mass spectrometry (ESIMS) for the detection of gaseous and interfacial products, respectively. Iodine, I-2(g), and iodine monoxide radical, IO(g), product yields were suppressed in the presence of a few millimolar phenol (pK(a) = 10.0), p-methoxyphenol (10.2), or p-cresol (10.3) at pH >= 3 but unaffected by salicylic acid (pK(a2) = 13.6), tert-butanol, n-butanol, or malonic acid. We infer that reactive anionic phenolates inhibit I-2(g) and IO(g) emissions by competing with I-(aq) for O-3(g) at the air/water interface. ESIMS product analysis supports this mechanism. Atmospheric implications are discussed.