title: Biomarkers of chlorpyrifos exposure and effect in Egyptian cotton field workers.
abstract: BACKGROUND
  Chlorpyrifos (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.
  
  
  OBJECTIVE
  We sought to determine the relationship between blood ChE and urinary TCPy during repeated occupational exposures to CPF.
  
  
  METHODS
  Daily 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.
  
  
  RESULTS
  Average 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.
  
  
  CONCLUSIONS
  Our 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.
authors.affiliation: Department of Community Medicine and Public Health, Faculty of Medicine, Menoufia University, Shebin El-Kom, Egypt.
authors.forename: Fayssal M
authors.initials: FM
authors.lastname: Farahat
authors.forename: Corie A
authors.initials: CA
authors.lastname: Ellison
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Bonner
authors.forename: Barbara P
authors.initials: BP
authors.lastname: McGarrigle
authors.forename: Alice L
authors.initials: AL
authors.lastname: Crane
authors.forename: Richard A
authors.initials: RA
authors.lastname: Fenske
authors.forename: Michael R
authors.initials: MR
authors.lastname: Lasarev
authors.forename: Diane S
authors.initials: DS
authors.lastname: Rohlman
authors.forename: W Kent
authors.initials: WK
authors.lastname: Anger
authors.forename: Pamela J
authors.initials: PJ
authors.lastname: Lein
authors.forename: James R
authors.initials: JR
authors.lastname: Olson
mesh_terms: D000110:Acetylcholinesterase / Q000097:blood; D000328:Adult; D000383:Agriculture; D015415:Biomarkers / Q000097:blood* / Q000652:urine*; D002091:Butyrylcholinesterase / Q000097:blood; D004390:Chlorpyrifos / Q000031:analogs & derivatives / Q000378:metabolism / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D004534:Egypt; D003368:Gossypium; D006801:Humans; D007306:Insecticides / Q000378:metabolism / Q000633:toxicity*; D016273:Occupational Exposure; D011728:Pyridones / Q000378:metabolism / Q000652:urine; D018570:Risk Assessment; D055815:Young Adult
chemical_list: D015415:Biomarkers; D007306:Insecticides; D011728:Pyridones; C009618:O,O-diethyl O-3,5,6-trichloro-2-pyridyl phosphate; C012587:3,5,6-trichloro-2-pyridinol; D000110:Acetylcholinesterase; D002091:Butyrylcholinesterase; D004390:Chlorpyrifos