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Chlorpyrifos

Chlorpyrifos. ENV H 572 Hilary Zetlen. Chlorpyrifos. Organophosphate pesticide Marketed by Dow Chemical since 1965 Domestic and agricultural uses. Prevalent Use. Broad spectrum of applications Treatment of crops, lawns, building materials. 10 million lbs. applied each year

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Chlorpyrifos

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  1. Chlorpyrifos ENV H 572 Hilary Zetlen

  2. Chlorpyrifos • Organophosphatepesticide • Marketed by Dow Chemical since 1965 • Domestic and agricultural uses

  3. Prevalent Use • Broad spectrum of applications • Treatment of crops, lawns, building materials. • 10 million lbs. applied each year • Majority applied to corn (approx. 5.5 millions lbs. annually) • Commonly used for vegetables, tree fruit in Washington state • Home use canceled in 2000 • Previously most commonly used residential pesticide • Limited to tightly controlled childproof mechanisms

  4. Annual use, Lbs. (% crop treated)

  5. Regulatory Standing • CERCLA • Reportable quantity of release = 1 lb. • Clean Water Act • Allowable level = 20 ug/ L • FDA • 0.05-15 ppm on food • FIFRA / EPA • Currently undergoing registration review • NRDC / PAN requesting revocation of registration • Final decision in 2015

  6. Stakeholders • Dow Chemical Corp. and pesticide manufacturers • Agribusiness, small farmers, and agricultural communities • Consumers • Government agencies • The environment

  7. Hazard Identification

  8. What is it? • White crystalline solid • Synthesized from 3-methylpyridine • Hydrophobic; often applied dry or in an oil/solvent suspension • Frequently marketed as Dursban/Lorsban

  9. Organophosphate Pesticides • “Nerve agents” • Somewhat chemically similar to sarin, VX • Compounds of special concern to the EPA • Priority for review under Food Quality Protection Act • Cholinesterase inhibitors • Inhibits breakdown of acetylcholine • Major consequencesthroughout nervous system • Cognitive effects, among others

  10. Acetylcholinesterase Inhibition

  11. Chlorpyrifos Toxicity • Acute exposure • Numbness, headache, dizziness, nausea, difficulty breathing, loss of consciousness, convulsions, paralysis • Chronic exposure • Cognitive impairment, disorientation, depression, lack of coordination, speech difficulties • Other effects • Lack of evidence for carcinogenic effect • Possible endocrine disruptor!

  12. Developmental Effects • Prenatal exposure • Significant growth deficits in length and birthweight, increase in birth defects • Neurotoxicity • Disruption of brain development at sub-acetylcholinesterase inhibiting levels • Early childhood effects • Measured umbilical cord blood concentrations at delivery • >6.17 pg/g “high exposure” group • Associated with significant psychomotor and cognitive delays at 36 months

  13. Dose-Response Assessment Child ingestion in an agricultural setting

  14. EPA Reference Dose • RfD = 0.003 mg/kg/day • Dow Chemical Company: • Sixteen human male volunteers ingested 0, 0.014, 0.03, or 0.10 mg/kg/day of chlorpyrifos • 20 days at the low and mid dose; treatment of the high-dose group (0.1 mg/kg/day) discontinued after 9 days due to a runny nose and blurred vision in one individual • Mean plasma ChE in this group was inhibited by about 65% • UF = 10 for human variability • FQPA, 1996: additional UF of 10 for children and females <50 years old • “Low-to-mid confidence” in estimated RfD

  15. IRED Human Health Assessment

  16. Prenatal chlorpyrifos exposure • Average birthweight in “high exposure” cohort = 3.24 kg • Lowest observed umbilical plasma concentration = 6.17 pg/g • Average adult plasma volume = 3.0 L • 3.0 L * (1.025 kg/L) / 70 kg = 42 g plasma/ kg body weight • 42 g/kg * 3.24 kg = 136.22 g plasma/infant • (6.17 pg chlorpyrifos/ g plasma) * 136.22 g plasma = 840.48 pg/infant • So how many mg/kg? • 840.48 pg/infant * (1 mg/1,000,000,000 pg) * (1 infant/3.24 kg) = • 2.59 * 10-7 mg/kg at birth!! – about 100 times smaller than EPA RfD • significant psychomotor and cognitive delays at 36 months

  17. Exposure Assessment

  18. Exposure Routes • Ingestion • Considered primary risk for Chlorpyrifos exposure for general population • Metabolites present in urine in 82% of US adults • Inhalation • Requires presence of aerosolized pesticides • Particular risk for applicators, mixer-loaders • Dermal • Occupational exposures • “Take-home” exposures

  19. Agricultural workers and their families • Much higher concentrations of chlorpyrifos in home • Correlates with proximity to orchards/application zones • Accumulates on household surfaces, dust, dirt • Lingers after application

  20. Chemical fate • Biological half-life • Approx. 10-30 hours • Metabolites excreted in urine • Soil half-life • 60-120 days • Sensitive to sunlight, microbial digestion • Oxidation to chlorpyrifosoxon • Little burden in water supply • Indoor half-life • Estimated around 30 days • Accumulates on sorbant surfaces

  21. Child vulnerability • Children living in agricultural homes: • Average of 0.52 ugchlorpyrifos/ pair of hands • Dermal dose • 3% absorption / 3.24 kg newborn = 4.8 * 10-8 mg/kg • Oral dose • Hand-to-mouth behavior • 100% absorption / 3.24 kg newborn = 1.6 * 10-4 mg/kg • Inhalation dose • 30 ug/m3 24 hours after pesticide application • 60 times higher than EPA limit!

  22. Risk Summary • EPA RfD: 0.0003 mg/kg/day for children • Prenatal exposure with significant developmental effects: • Approx. 2.59 * 10-7 mg/kg at birth • Significant exposures arising from: • Agricultural communities • Drinking water • U.S. allowable lifetime dose = 20 ug/L • Current standards are woefully inadequate to prevent long-term developmental consequences.

  23. Precautionary Assessment

  24. Community / Social Issues

  25. Exposure Issues

  26. Hazard/Toxicity

  27. Risk Management

  28. Risk Perception • “Pesticide Drift” and children in California • http://www.npr.org/templates/story/story.php?storyId=123817702 • Dow Chemical on Chlorpyrifos and kids • http://www.chlorpyrifos.com/myths-vs-facts.htm

  29. Registration review • Docket opened May 2009 • Human health assessment • Public comment period July-September of this year • Scoping: lack of emphasis on developmental toxicology data! • Environmental/endangered species impact assessment • Public comment October-December 2013 • Final registration decision in 2015

  30. Recent regulatory action • New limitations to protect salmon, steelhead under Endangered Species Act announced in September 2009 • Created in conjunction with the National Marine Fisheries Service • New labeling guidelines • Limitations on application: buffer zones, increased environmental monitoring, fish mortality data

  31. References • Eskenazi, et al. Exposures of children to organophosphate pesticides and their potential adverse health effects.  • Fenske, et al. Children's exposure to chlorpyrifos and parathion in an agricultural community in central Washington State.  • Fenske, et al. Biologically based pesticide dose estimates for children in an agricultural community.  • Fenske, et al. Potential exposure and health risks of infants following indoor residential pesticide applications.  • Gore. Environmental Toxicant Effects on Neuroendocrine Function.  • Griffin, et al. Oral and dermal absorption of chlorpyrifos: a human volunteer study.  • Gurunathan, et al. Accumulation of chlorpyrifos on residential surfaces and toys accessible to children.  • Rauh, et al. Impact of Prenatal Chlorpyrifos Exposure on Neurodevelopment in the First 3 Years of Life Among Inner-City Children.  • Simcox, et al. Pesticides in household dust and soil: exposure pathways for children of agricultural families.  • Slotkin and Seidler. The alterations in CNS serotonergic mechanisms caused by neonatal chlorpyrifos exposure are permanent. 

  32. Resources • EPA - Chlorpyrifos Fact Sheet:http://www.epa.gov/pesticides/reregistration/REDs/factsheets/chlorpyrifos_fs.htm • EPA - Chlorpyrifos Risk Information:http://www.epa.gov/iris/subst/0026.htm • EPA - Chlorpyrifos Interim Risk Management Decision:http://www.epa.gov/oppsrrd1/reregistration/chlorpyrifos/ • ATSDR - ChlorpyrifosToxFAQs:http://www.atsdr.cdc.gov/tfacts84.html • Pesticide Action Network – Chlorpyrifos:http://www.pesticideinfo.org/Detail_Chemical.jsp?Rec_Id=PC33392 • National Agricultural Statistics Service - Agricultural Chemical Use Database:http://www.pestmanagement.info/nass/app_usage.cfm • National Resources Defense Council - Our Children At Risk: http://www.nrdc.org/health/kids/ocar/chap5b.asp • Dow Chemical - ChlorpyrifosProtects:http://www.chlorpyrifos.com/ • NPR - "Pesticide drift eluding efforts to combat it", 2/28/10:http://www.npr.org/templates/story/story.php?storyId=123817702 

  33. Questions?

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