Biomarkers of Chlorpyrifos Exposure and Effect in Egyptian Cotton Field Workers

Abstract

BackgroundChlorpyrifos (CPF), a widely used organophosphorus pesticide (OP), is metabolized to CPF-oxon, a potent cholinesterase (ChE) inhibitor, and trichloro-2-pyridinol (TCPy). Urinary TCPy is often used as a biomarker for CPF exposure, whereas blood ChE activity is considered an indicator of CPF toxicity. However, whether these biomarkers are dose related has not been studied extensively in populations with repeated daily OP exposures.ObjectiveWe sought to determine the relationship between blood ChE and urinary TCPy during repeated occupational exposures to CPF.MethodsDaily urine samples and weekly blood samples were collected from pesticide workers (n = 38) in Menoufia Governorate, Egypt, before, during, and after 9–17 consecutive days of CPF application to cotton fields. We compared blood butyrylcholinesterase (BuChE) and acetylcholinesterase (AChE) activities with the respective urinary TCPy concentrations in each worker.ResultsAverage TCPy levels during the middle of a 1- to 2-week CPF application period were significantly higher in pesticide applicators (6,437 μg/g creatinine) than in technicians (184 μg/g) and engineers (157 μg/g), both of whom are involved in supervising the application process. We observed a statistically significant inverse correlation between urinary TCPy and blood BuChE and AChE activities. The no-effect level (or inflection point) of the exposure–effect relationships has an average urinary TCPy level of 114 μg/g creatinine for BuChE and 3,161 μg/g creatinine for AChE.ConclusionsOur findings demonstrate a dose–effect relationship between urinary TCPy and both plasma BuChE and red blood cell AChE in humans exposed occupationally to CPF. These findings will contribute to future risk assessment efforts for CPF exposure.

Biochemical Changes Associated with Long Term Exposure to Pesticide among Farmers in the Gaza Strip

“…This suggestion is supported by the toxicology symptoms ( Table 5) such as loosing appetite and by numerous studies [43] [46]- [47] that reported disturbance of lipid and protein metabolism in animals exposing to organophosphourus insecticides.…”

Probabilistic assessment of chlorpyrifos exposure to rice farmers in Viet Nam

“…With Sri-Lankan and USA farmers, this decline to baseline occurred in approximately 96 h 6,25,26 ). The recent study conducted by Farahat et al 24 indicated that urinary TCP concentration returned to the baseline level in excess of 168 h post application among Egyptian cotton farmers. All of these findings are to be expected, based on the 26.9-h half-life urinary TCP elimination reported by Nolan et al 27 If we assume first order kinetics, then four half-life periods will reduce the maximum value to approximately 6% and 3% of the maximum value, respectively.…”

“…The possible explanation for this elevated urinary TCP level on day 1 could be the farmers' use of pesticides outside of their main crops. 24 Also, some of farmers were exposed to chlorpyrifos through purchase and preparation of chlorpyrifos for the spraying missions on the next day.…”

Butyrylcholinesterase as Biomarker of Occupational Exposure Among Female Cotton Workers

“…BChE in normal group was higher than in exposed group population. Farahat et al (17) organized the studies to seek out the effect of chlorpyrifos -a widely used organophosphates pesticide -on BChE activity, among agriculture worker. It was established that BChE activity decreased gradually by end of the spraying season.…”