Chlorpyrifos

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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
 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
Annual use, Lbs.
(% crop treated)
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
Stakeholders
 Dow Chemical Corp. and pesticide manufacturers
 Agribusiness, small farmers, and agricultural communities
 Consumers
 Government agencies
 The environment
Hazard Identification
What is it?
 White crystalline solid
 Synthesized from 3methylpyridine
 Hydrophobic; often applied
dry or in an oil/solvent
suspension
 Frequently marketed as
Dursban/Lorsban
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 consequences throughout nervous system
 Cognitive effects, among others
Acetylcholinesterase Inhibition
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!
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
Dose-Response Assessment
Child ingestion in an agricultural setting
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
IRED Human Health Assessment
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
Exposure Assessment
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
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
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 chlorpyrifos oxon
Little burden in water supply
 Indoor half-life
 Estimated around 30 days
 Accumulates on sorbant surfaces
Child vulnerability
 Children living in agricultural homes:
 Average of 0.52 ug chlorpyrifos/ 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!
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.
Precautionary Assessment
Community / Social Issues
Parameter
Score
Goal
2
Need
2
Future Generations
3
Democratic, community
based process
2
Alternatives
3
Total
12/15
Exposure Issues
Exposure Issues
Exposure
3
Multiple exposures
3
Children exposed
5
Consumer products
3
Occupational exposure
Food exposure
Total
3
3
20/20
Hazard/Toxicity
Hazard
9
Individual Sensitivity
3
Ecological hazard
3
Volume
5
Persistent
1
Bioaccumulation
2
Uncertainty
2
Total
25/30
Risk Management
Risk Perception
 “Pesticide Drift” and children
in California
 http://www.npr.org/templ
ates/story/story.php?story
Id=123817702
 Dow Chemical on Chlorpyrifos
and kids
 http://www.chlorpyrifos.c
om/myths-vs-facts.htm
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
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
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. 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 - Chlorpyrifos ToxFAQs: 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 - Chlorpyrifos Protects: 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 Questions?
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