Method Development for Residential and Occupational Sampling of Organophosphorus Pesticides and Oxygen Analogs in Yakima Valley, WA

Abstract

PP-30-119 Background/Aims: A recent air monitoring study of organophosphorus (OP) pesticides in Washington State found substantial amounts of the oxygen analog of chlorpyrifos (CPF). Follow-up laboratory studies indicated that oxygen analog (CPF-O) could be produced artificially on the XAD-2 Resin OVS sampling tubes that are recommended by the US National Institute for Occupational Safety and Health (NIOSH Method 5600). Methods: The goals of this study were to measure the actual chlorpyrifos oxygen analog (CPF-O) levels during and following pesticide applications, and to develop optimal sampling procedures. Two air sampling media, OVS and polyurethane foam (PUF) tubes, were spiked in the laboratory with varying amounts of CPF (60, 200, 2000 ng) and air was drawn through the tubes at 2 L per minute for 24 hours. In addition, a side-by-side comparison of sampling methods was performed during orchard spraying of CPF. Samplers were located upwind and downwind, at distances ≥150 m and ≤10 m from the orchard perimeter. Results: The laboratory percentage CPF transformed to CPF-O on the OVS tubes ranged from 3% to 15%, and was inversely related to the spiking level. CPF-O was not detected on the PUF tubes for any of the spiking levels except the highest, where CPF-O represented 0.01% (SD: ±0.01%) of the total CPF. Conclusion: We concluded that (1) OP pesticide concentrations can be under-estimated using OVS sampling tubes if analysis for oxygen analogs is not conducted, (2) oxygen analogs measured on OVS sampling tubes do not represent the true concentration of these compounds in air, and (3) PUF sampling tubes appear to be a promising alternative sampling medium. The results will be used to document the presence or absence of CPF-O in air and on surfaces, to inform workers and nearby communities about potential exposures, and to develop recommendations on optimal air sampling procedures for both OP pesticides and oxygen analogs.