The Presence of Dialkylphosphates in Fresh Fruit Juices: Implication For Organophosphorus Pesticide Exposure and Risk Assessments

Abstract

This study was designed to determine whether dialkylphosphates (DAPs) are present in fresh fruit juices, as a result of organophosphorus (OP) pesticides degradation. Fresh conventional and organic fruit (apple and orange) juices were purchased from local grocery stores. DAPs were found in both conventional and organic juices, and the original levels were higher, for both apple and orange juices, in conventional than in organic juices. Additional DAPs were found in OP pesticide fortified juices after 72 h of storage at 4 degrees C, suggesting a degradation of OP pesticides in juices. Overall, 12% and 36.2% of fortified azinphosmethyl, a dimethyl OP pesticide, and the combination of fortified diazinon and chlorpyrifos, both diethyl OP pesticides, were degraded to dimethyl and diethyl DAPs, respectively. Although the exact mechanism of the degradation is unknown, hydrolysis is likely the cause of OP pesticide degradation in juice. The presence of DAPs in fresh fruit juices clouds the validity of using urinary DAP measurements for estimating OP pesticide exposures in humans, particularly in children. The overestimated OP pesticide exposures based on urinary DAPs reported in other studies is likely due to the coexistence of preformed DAPs and DAPs resulting from OP pesticide exposures. Thus, before urinary DAP concentrations can be reliably used in exposure and risk assessment, the proportion of the concentration attributable to environmental DAP exposure, particularly through the diet, must be ascertained. In conclusion, urinary DAPs have many limitations when being used as biomarkers for OP pesticides in exposure and risk assessment, and caution should be exercised when interpreting DAPs results.

An Observational Study to Evaluate Associations Between Low-Level Gestational Exposure to Organophosphate Pesticides and Cognition During Early Childhood

“…However, it should be noted that the urinary concentrations of these metabolites are similar to those reported nationally and may thus increase our generalizability and relevance to a large percentage of the population. A final limitation is that we measured urinary DAP, and, particularly for dietary exposures (30), these may reflect exposure to nontoxic preformed metabolites as well as the parent organophosphate pesticides (which are toxic). Therefore, it is impossible to determine whether exposure was to the toxic organophosphate pesticides or to the nontoxic DAP environmental metabolites.…”

Acetylcholinesterase Activity and Neurodevelopment in Boys and Girls

“…In addition, urinary measurements may overestimate exposures to the parent compound because metabolite elevations also reflect exposure to less toxic ambient metabolites. 15 Quantification of AChE activity circumvents these problems. First, AChE levels can be interpreted without accounting for factors that affect organophosphate metabolism (eg, paraoxonase) because AChE inhibition is a physiologic response to exposure in relation to the individual' s sensitivity and ability to metabolize cholinesterase inhibitors.…”

Biomonitoring of Pesticides: Pharmacokinetics of Organophosphorus and Carbamate Insecticides

“…Although dialkylphosphate and trichloropyridinol have been routinely utilized as biomarkers for organophosphorus insecticide exposure, organophosphates can undergo environmental degradation to form these same chemicals, which have been detected in fruit products ( juice) or in solid foods (Lu et al, 2005;Morgan et al, 2005). Hence, due to the environmental stability of the dialkylphosphate and trichloropyridinol, recent research has questioned whether total urinary organophosphate metabolite levels may be reflective not only of an individual's contact with the parent organophosphorus pesticide but, in addition, exposure with intact metabolites present in the environment Bradman et al, 2005;Duggan et al, 2003;Lu et al, 2005).…”

“…Hence, due to the environmental stability of the dialkylphosphate and trichloropyridinol, recent research has questioned whether total urinary organophosphate metabolite levels may be reflective not only of an individual's contact with the parent organophosphorus pesticide but, in addition, exposure with intact metabolites present in the environment Bradman et al, 2005;Duggan et al, 2003;Lu et al, 2005). Thus, measured urinary metabolite levels may represent an exaggerated indicator of an individual's exposure to the parent compound (Duggan et al, 2003).…”

“…19.5 PK APPROACHES FOR ORGANOPHOSPHORUS AND CARBAMATE INSECTICIDES alkyl phosphate and trichloropyridinol levels prior to conducting a pesticide exposure study. A potentially more useful biomonitoring strategy could include an approach that measures the insecticides as well as their urinary metabolites not only in urine samples, but also in relevant environmental media and in a person's diet (Lu et al, 2005).…”