CP can react with oxidative reagents such as sodium hypochlorite and hydrogen peroxide producing their respective P@O oxygen analogue named Chlorpyrifos oxon (CPO), which is more toxic than CP (Pugliese et al., 2004).
Furthermore,both CP and CPO can be degraded to 3,5,6-trichloro-2-pyridinol (TCP) via hydrolysis (Duirk and Collette, 2006). Randhawaet al. (2007) reported that TCP was detectable in unprocessed field vegetables, and the amount of TCP after washing remained the same as that before washing. In this study, however, CPO and TCP were not detected in any of the samples.