Occurrence and the exposure potential of selected pesticide residues in strawberries, particularly preformed human malathion biomarkers in leaves and berries

A series of studies clarified pesticide issues related to potential pesticide exposures of strawberry harvesters and consumers resulting from residual field and produce residues.;Strawberry harvester exposure is primarily due to hand contact. The determination of dislodgeable foliar residues (DFR) utilizes a weak detergent solution to wash residues from the leaf surface. This contrasts with physical contact-transfer that occurs in the field. Two physical sampling procedures to measure transferable foliar residue (TFR) were developed, Benchtop Surface Roller (BSR) and Automated Surface Wipe (ASW). DFR and TFR using BSR and ASW measurements were evaluated in 3 field studies following malathion applications at DB Specialty Farms, Santa Maria, CA in 2006-2008. DFR (0.025 to 0.16 mug/cm2) and BSR (0.007 to 0.021 mug/cm2) were the highest at PHI. DFR was higher and decayed more rapidly than BSR.;Hand exposure of harvesters predominates (60 to 88% of total dermal exposure). Since hands are points of contact with foliage and latex gloves are discarded after each work period, they may be a useful dosimeter. Residues were highest at the PHI (1670 +/- 497 to 481 +/- 145 mug/pair, 2-2.5 h). Malathion residue was <10 mug/pair after a month. In the early morning residues were higher than in the afternoon due to morning dew. Glove residues may be a good indicator of potential pesticide exposure since long-term, low-level transferable residue can be measured.;Time-concentration studies of malathion and preformed biomarkers in strawberries and leaves were conducted (2007 and 2008). Malathion decayed quickly and was not detected in berries after 3 weeks and in leaves after 1.5 months. Dimethylphosphates (DMPs) and malathion acids (MAs) were measured in leaves and berries. DMPs in berries (nmol/g) were higher than malathion in berries. The nmol ratio of DMPs to malathion ranged 2 to 13 at the PHI and 22 to 76 after 3 weeks. When malathion was not detected in berries and leaves, DMPs were detected. Malathion and biomarkers were higher in leaves than in berries. Preformed DAPs in food must not be used to represent OP exposure. DMPs in leaves may be the source of DMPs in berries.