(NIOSH 2008-2010) This small project predicted expected ChE depression based on regulatory decision-making frameworks and compares those predictions with actual outcomes in Washington State’s ChE monitoring program. Scientists at PNASH and the Centers for Disease Control (CDC) are working to improve the current ChE laboratory test – increasing accuracy to ensure a ChE depression is due to pesticide exposure and identify the specific pesticide involved. Though some challenges exist, the oxime reactivation assay has been successfully applied to human and rat plasma samples providing kinetic information regarding ChE inhibition and reactivation. The second component of this project was the development of a process for tandem mass spectrometry of protein adducts in the blood of exposed workers. Once perfected, this would be the only effective tool for determining long term exposures as the protein adducts last much longer than the actual pesticides or urinary metabolites.