Biomonitoring of Exposure to Organophosphate Pesticides: McKelvey et al. Respond

Although urinary excretion levels of dialkyl­ phosphates (DAPs)—which are metabo­ lites and environmental degradates of OP insecticides—are useful as quantitative indi­ cators of exposure to OPs in agricultural workers, they are not as useful for the gen­ eral population. For agricultural workers, the source of the OP and time of exposure are typically known, and there is substan­ tial exposure above background, thus allow­ ing an unambiguous estimation of exposure levels (Chen et al. 2013). In contrast, urinary excretion levels of DAPs in the general popu­ lation represent an integrated measurement of intakes of both pesticide and pesticide metabo lites 1 or 2 days prior to sampling (Chen et al. 2012). Half­lives of OPs and their metabolites in the body range from a few hours to < 1 day (Chen et al. 2013; Timchalk et al. 2007). Evidence indicates that urinary DAPs in the general popula­ tion primarily result from exposures to non neurotoxic OP metabolites that are in food (Krieger et al. 2012). McKelvey et al. (2013) stated that