Project title: Passive and Active Air Sampling for Residential Exposures to Airborne Organophosphorus Pesticides and Oxygen Analogs ("Oxons") in Central Washington State
Completed in: 2012
Organophosphorus (OP) pesticides are some of the most widely used insecticides in the United States, and spray applications are a concern for public health due to potential human exposures from distant transport via off target volatilization and particulate drift. Initial tests on active air sampling methods found the NIOSH recommended sampling matrix (OVS XAD-2 Resin Tubes) to artificially transform substantial amounts of chlorpyrifos (CPF) to its oxygen analog (CPF-O) in the laboratory (up to 32%) and in the field, leading to inaccuracies in reported levels CPF and CPF-O in past field studies. A series of side-by-side tests identified the PUF matrix as a superior sampling medium for OP pesticides and their oxygen analogs. Passive air sampling methods were developed and tested in a laboratory exposure chamber and in the field to measure airborne exposures to OP pesticides and oxygen analogs in an agricultural community. Results show that the new PUF-PAS method combined with sensitive analysis (LC/MS-MS) may be used to improve our understanding of the continued fate and transport at low levels typical of residential communities down to method limits of quantification of 0.01to 0.05 ng/m3. PUF-PAS air sampling rates were similar to other semi-volatile organic compounds (SVOCs), ranging from 1.6-8.4 m3/day. The PUF-PAS devices were deployed in the Yakima Valley region of Washington State and measured cumulative monthly air concentrations during pre-thinning, thinning, and non-application seasons. Results demonstrated that air concentrations of CPF during pre-thinning season were 5-10x higher than AZM during thinning season. Households proximal to tree fruit fields (≤250m) reported significantly higher outdoor air concentrations CPF and AZM than non-proximal households. Indoor air concentrations were significantly reduced compared to outdoors, and farmworker households reported higher mean air concentrations of CPF than non-farmworker households. Very few samples detected oxygen analogs indoors. Indoor surface deposition (ng/m2) and air concentration (ng/m3) measurements were correlated. Higher proportions of oxygen analogs (2-35%) were identified in air, particularly in samples further from potential sources of application and during times of increased cumulative solar radiation (mJ/m2). This research highlights the ability of oxygen analogs ability to persist in air, resulting from atmospheric transport, photolysis, or reaction with oxidizing agents. Opportunity for exposure to oxygen analogs outdoors is a greater concern than indoor exposures. When considering cumulative and aggregate effects of exposure to OP pesticides in order to protect the unique health needs of children, the inclusion of oxygen analogs in risk assessments is necessary.