Detectable organophosphorus pesticide exposure in the blood of Nebraska and Iowa residents measured by mass spectrometry of butyrylcholinesterase adducts

► Butyrylcholinesterase is a biomarker of OP exposure. ► Purified BChE pooled from 2000 donors was tested by mass spectrometry. ► Low levels of methoxyphosphorylated BChE were identified.