Aggregate Exposures under the Food Quality Protection Act: An Approach Using Chlorpyrifos

Shurdut, Bradley A.; Barraj, Leila M.; Francis, Marcie

doi:10.1006/rtph.1998.1250

Cited by 57 publications

(22 citation statements)

References 26 publications

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“…That is, DAP levels in children's urine rose during the spray months, and because of the relatively short biological half-lives of most OP pesticides, the levels subsequently decreased as agricultural applications ended. This pattern is also consistent with the general theory that children are exposed continuously to a low level of these pesticides through their diet and that this chronic exposure is punctuated by episodes of relatively higher exposure from additional sources and pathways, such as residential pesticide use (20). In this agricultural community, pesticide applications on crops appear to serve as multiple-point sources for those residing in the region, and exposures rise and fall accordingly.…”

Section: Discussionsupporting

confidence: 85%

Temporal association of children's pesticide exposure and agricultural spraying: report of a longitudinal biological monitoring study.

Fisker-Andersen

et al. 2002

Environ Health Perspect

139

112

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We measured organophosphorus (OP) pesticide exposures of young children living in an agricultural community over an entire year and evaluated the impact of agricultural spraying on exposure. We also examined the roles of age, sex, parental occupation, and residential proximity to fields. We recruited 44 children (2-5 years old) through a Women, Infants, and Children clinic. We collected urine samples on a biweekly basis over a 21-month period. Each child provided at least 16 urine samples, and most provided 26. We analyzed samples for the dialkylphosphate (DAP) metabolites common to the OP pesticides. DAP concentrations were elevated in months when OP pesticides were sprayed in the region's orchards. The geometric means of dimethyl and diethyl DAPs during spray months were higher than those during nonspray months (p = 0.009 for dimethyl; p = 0.018 for diethyl). Dimethyl DAP geometric means were 0.1 and 0.07 micro mol/L for spray months and nonspray months, respectively (57% difference); diethyl DAP geometric means were 0.49 and 0.35, respectively (40% difference). We also observed differences for sex of the child, with male levels higher than female levels (p = 0.005 for dimethyl; p = 0.046 for diethyl). We observed no differences due to age, parental occupation, or residential proximity to fields. This study reports for the first time the temporal pattern of pesticide exposures over the course of a full year and indicates that pesticide spraying in an agricultural region can increase children's exposure in the absence of parental work contact with pesticides or residential proximity to pesticide-treated farmland.

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Section: Discussionsupporting

confidence: 85%

Temporal association of children's pesticide exposure and agricultural spraying: report of a longitudinal biological monitoring study.

Fisker-Andersen

et al. 2002

Environ Health Perspect

139

112

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“…It has been suggested that in vitro concentrations of OPTs Յ10 M are the most appropriate to mimic in vivo conditions (Buratti et al, 2002, based on chlorpyrifos plasma concentrations (90 nM) measured in human volunteers (Nolan et al, 1984) and on the estimation of environmental exposure in U.S. adults and children (about 1.4 -1.61 g/kg/day) (Schurdut et al, 1998;Rigas et al, 2001), obtained by applying pharmacokinetic models to biomonitoring data. On the same line, starting from urinary alkylphosphate levels, a body burden of 208 g/kg azinphos-methyl (corresponding to 6.5 M in plasma) was estimated in orchard workers at the steady state (Carrier and Brunet, 1999).…”

Section: Discussionmentioning

confidence: 99%

Malathion Bioactivation in the Human Liver: The Contribution of Different Cytochrome P450 Isoforms

Buratti

D'Aniello²,

Volpe³

et al. 2004

Drug Metab Dispos

104

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ABSTRACT:Among organophosphorothioate (OPT) pesticides, malathion is considered relatively safe for use in mammals. Its rapid degradation by carboxylesterases competes with the cytochrome P450 (P450)-catalyzed formation of malaoxon, the toxic metabolite. However, impurities in commercial formulations are potent inhibitors of carboxylesterase, allowing a dramatic increase in malaoxon formation. Malathion desulfuration has been characterized in human liver microsomes (HLMs) with a method based on acetylcholinesterase inhibition that is able to detect nanomolar levels of oxon. The active P450 isoforms have been identified by means of a multifaceted strategy, including the use of cDNA-expressed human P450s and correlation, immunoinhibition, and chemical inhibition studies in a panel of phenotyped HLMs. HLMs catalyzed malaoxon formation with a high level of variability (>200-fold). One or two components (K mapp1 ‫؍‬ 53-67 M; K mapp2 ‫؍‬ 427-1721 M) were evidenced, depending on the relative specific P450 content. Results from different approaches indicated that, at low malathion concentration, malaoxon formation is catalyzed by CYP1A2 and, to a lesser extent, 2B6, whereas the role of 3A4 is relevant only at high malathion levels. These results are in line with those found with chlorpyrifos, diazinon, azynphos-methyl, and parathion, characterized by the presence of an aromatic ring in the molecule. Since malathion has linear chains as substituents at the thioether sulfur, it can be hypothesized that, independently from the chemical structure, OPTs are bioactivated by the same P450s. These results also suggest that CYP1A2 and 2B6 can be considered as possible metabolic biomarkers of susceptibility to OPT-induced toxic effects at actual human exposure levels.

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“…Studies that relied solely on urinary TCPy as an index of chlorpyrifos exposure have typically yielded estimates of daily chlorpyrifos exposure of approximately 0.1-2 µg/kg-day for urinary concentration of TCPy between 2 and 20 µg/L (Hill et al, 1995;Gibson et al, 1998;Shurdut et al, 1998;Quackenboss et al, 2000;Timchalk et al, 2002b). For example, in the Farm Family Study, Curwin et al (2007b) estimated the "absorbed daily dose" of chlorpyrifos of 0.27-1.96 and 0.24-1.36 µg/kgday in 25 farm and 25 nonfarm children, respectively.…”

Section: Vib Dose-response Analysis From Controlled Humanmentioning

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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Aggregate Exposures under the Food Quality Protection Act: An Approach Using Chlorpyrifos

Cited by 57 publications

References 26 publications

Temporal association of children's pesticide exposure and agricultural spraying: report of a longitudinal biological monitoring study.

Temporal association of children's pesticide exposure and agricultural spraying: report of a longitudinal biological monitoring study.

Malathion Bioactivation in the Human Liver: The Contribution of Different Cytochrome P450 Isoforms

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

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