A review of the reference dose for chlorpyrifos

Zhao, Qingyuan; Dourson, Michael; Gadagbui, Bernard

doi:10.1016/j.yrtph.2005.10.003

Cited by 33 publications

(20 citation statements)

References 36 publications

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“…Although these studies only provide data following a single dose, it is clear from these studies that a single dose of 0.5 mg/kg has measurable effects on plasma BuChE, but not erythrocyte (and thus presumably not brain) AChE. Coulston et al (1972), as reported in Zhao et al (2006), measured plasma (BuChE) and erythrocyte (AChE) cholinesterase in human subjects give repeated daily doses of chlorpyrifos at 0, 0.014, 0.03, or 0.1 mg/kg-day for 49, 28, 21, and 9 days, respectively. Erythrocyte AChE was not inhibited at any dose level.…”

Section: Vib Dose-response Analysis From Controlled Humanmentioning

confidence: 99%

“…However, in 2000 EPA proposed a reference dose of 0.3 µg/kgday, 10 times lower than the initial RfD established in 1986 (see note 1), and this value is now used for regulatory purposes. Zhao et al (2006) recently reviewed the current global regulatory values utilized for chlorpyrifos. The estimate of "safe" exposures to chlorpyrifos depends on the particular endpoint used, the specific study and species used, and the magnitude of the perceived uncertainty in the endpoint/study selected, which in turn dictates the uncertainty (or safety) factor used.…”

Section: Vic Is Inhibition Of Buche Appropriately Consideredmentioning

confidence: 99%

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Review of the Toxicology of Chlorpyrifos With an Emphasis on Human Exposure and Neurodevelopment

Eaton¹,

Daroff²,

Autrup³

et al. 2008

Critical Reviews in Toxicology

565

413

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Section: Vib Dose-response Analysis From Controlled Humanmentioning

confidence: 99%

Section: Vic Is Inhibition Of Buche Appropriately Consideredmentioning

confidence: 99%

Review of the Toxicology of Chlorpyrifos With an Emphasis on Human Exposure and Neurodevelopment

Eaton¹,

Daroff²,

Autrup³

et al. 2008

Critical Reviews in Toxicology

565

413

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“…Acute poisoning with OP in human is frequently seen in many countries and it is estimated to be the cause of more than 200,000 deaths around the world [1]. OP compounds used to fight pests include, parathion, chlorpyrifos (CPF) and malathion.…”

Section: Introductionmentioning

confidence: 99%

Adverse Effects of Organophosphorus Insecticides on Macrophage Activity in Persons at High Risk for Parasitic Infection

Ashour

Mohamed

Elsawy

2011

Macedonian Journal of Medical Sciences

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“…Chlorpyrifos (CPF) and related organophosphate insecticides can inhibit B-esterases, resulting in neurological effects at exposures sufficient to substantially inhibit brain acetylcholinesterase (AChE) activity (reviewed in Zhao et al, 2006). Inhibition of red blood cell (RBC) AChE activity is recognized as an early biological marker of this critical effect in numerous current risk assessments of CPF, with substantial inhibition of RBC AChE activity occurring at exposures below those resulting in inhibition of brain AChE activity (ATSDR, 1997;USEPA, 2000;van Gemert et al, 2001;Health Canada, 2003;UK ACP, 2003;WHO, 2004;Zhao et al, 2005Zhao et al, , 2006.…”

Section: Introductionmentioning

confidence: 99%

“…Inhibition of red blood cell (RBC) AChE activity is recognized as an early biological marker of this critical effect in numerous current risk assessments of CPF, with substantial inhibition of RBC AChE activity occurring at exposures below those resulting in inhibition of brain AChE activity (ATSDR, 1997;USEPA, 2000;van Gemert et al, 2001;Health Canada, 2003;UK ACP, 2003;WHO, 2004;Zhao et al, 2005Zhao et al, , 2006. Plasma butyrylcholinesterase (BuChE) activity, which constitutes 99% of human plasma B-esterase activity (van Gemert et al, 2001), can be inhibited at exposures below those required to inhibit RBC AChE, but no adverse biological effects are causally associated with the inhibition of plasma BuChE (Nolan et al, 1984;Lotti, 1995;Albers et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Cholinesterase inhibition in chlorpyrifos workers: Characterization of biomarkers of exposure and response in relation to urinary TCPy

Garabrant

Aylward

Berent

et al. 2008

J Expo Sci Environ Epidemiol

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The objective of this study was to evaluate the quantitative relation between measured red blood cell acetylcholinesterase (RBC AChE) and plasma butyrylcholinesterase (BuChE) activities with exposure to chlorpyrifos (CPF) as assessed by measurement of urinary 3,5,6-trichloro-2-pyridinol (TCPy) in a study group of workers occupationally exposed in the manufacture of CPF and a referent group of chemical manufacturing workers. Measures of plasma BuChE and RBC AChE activity and urinary TCPy concentration collected over a year-long study (1999)(2000) in CPF-exposed workers (n ¼ 53) and referents (n ¼ 60) were analyzed using linear mixed models to characterize exposure-response relationships. Intraindividual variability in cholinesterase measures was compared between CPF-exposed workers and referents. Urinary TCPy concentrations in CPF workers were substantially elevated compared to referents, with median and 95th percentile concentrations during typical employment conditions 10-fold and more than 30-fold higher, respectively, than corresponding measures in the referents. Intraindividual variability in cholinesterase activities was substantial, with 17% of unexposed referents experiencing one or more plasma BuChE measures more than 20% below baseline over a year of repeated, periodic measurements. RBC AChE activity, an early biomarker of effect, was unrelated to urinary TCPy concentration over the entire range of exposure, up to 1000 mg TCPy/g creatinine (Cr). Plasma BuChE activity, a non-adverse biomarker of exposure, was negatively related to urinary TCPy concentrations above approximately 110 mg TCPy/g Cr. No-effect levels for inhibition of plasma BuChE and RBC AChE corresponding to absorbed doses of CPF of approximately 5 and greater than 50 mg/kg/day, respectively, were identified. These findings are consistent with previous no-effect level determinations for ChE inhibition in humans and suggest that general population CPF exposure levels are substantially below the identified no-effect levels. The doseresponse relationships observed in this study are consistent with predictions from the previously published physiologically based pharmacokinetic/ pharmacodynamic model for CPF. Intraindividual variability in measured cholinesterase activities in referents was substantial, suggesting that ongoing monitoring programs may have a substantial rate of false positives.

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A review of the reference dose for chlorpyrifos

Cited by 33 publications

References 36 publications

Review of the Toxicology of Chlorpyrifos With an Emphasis on Human Exposure and Neurodevelopment

Review of the Toxicology of Chlorpyrifos With an Emphasis on Human Exposure and Neurodevelopment

Adverse Effects of Organophosphorus Insecticides on Macrophage Activity in Persons at High Risk for Parasitic Infection

Cholinesterase inhibition in chlorpyrifos workers: Characterization of biomarkers of exposure and response in relation to urinary TCPy

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