Photolytic. When sulprofos was exposed to sunlight as deposits on cotton foliage, glass surfaces and in aqueous solution, the insecticide degraded rapidly (half-life <2 days). Irradiation of sulprofos in aqueous solution using UV light (l >290 nm) was also very rapid (half-life <2 hours). The major degradative pathway involved oxidation of the methylthio sulfur to the corresponding sulfoxide and sulfones, hydrolysis of the O-phenyl ester and oxidative desulfuration of the P=S group. Products included the corresponding sulfone and sulfoxide from the parent compound, an O-analog sulfone, a phenol, a phenol sulfone and a phenol sulfoxide and four unidentified compounds (Ivie and Bull, 1976).