2005 年 53 巻 4 号 p. 422-424
We sought to investigate the early biological effects of chlorpyrifos among 53 Thai fruit farm workers by measuring the plasma cholinesterase (PChE) and red blood cell cholinesterase (AChE) activities, a biomarker of organophosphate (OPs) pesticide during one fruit crop. The ChE activity (Vm/Km) was spectrophotometrically analyzed before and after exposing to chlorpyrifos. The Vm/Km values of both non-spraying and spraying seasons are found as normal distribution pattern. The median PChE and AChE activities among farm workers in the non-spraying season were 2.3×10−3 s−1 and 7.26×10−5 s−1, respectively. The median PChE and AChE activities of the farm workers in the spraying season were 2.02×10−3 s−1 and 5.95×10−5 s−1, respectively. The mean Vm/Km values of PChE shifted left (t-test, p=0.013), indicating a decrease in PChE activity in the farm workers exposed to chlorpyrifos. However, the Vm/Km values of AChE in nonspraying season and in the spraying season were not different (t-test, p=0.246). We propose that PChE activity can be used as a biomarker for monitoring early toxicity induced by chlorpyrifos insecticide.