## Presentation to the FIFRA SAP, April 19, 2016 

# Chlorpyrifos: Analysis of Biomonitoring Data

Internal, deliberative, not for distribution 1Dana Vogel, Director Health Effects Division Office of Pesticide Programs Environmental Protection Agency vogel.dana@epa.gov 703 - 305 - 0874 Presentation to the FIFRA SAP, April 19, 2016 

# Chlorpyrifos: Analysis of Biomonitoring Data Background and Overview

Internal, deliberative, not for distribution 23 

### • Organophosphate pesticide first registered in 1965 • In June 2000: • The technical registrants entered into an agreement with the Agency to eliminate and phase out nearly all uses that result in residential exposures • Some mitigation on food (apples & tomatoes) • Some mitigation for workers (PPE & engineering controls for some uses) • Registration Eligibility Decision (RED) in 2006 • September 2007 petition from NRDC & PANNA to revoke all tolerances & cancel registrations 

# Regulatory Context: Chlorpyrifos4 

### • FIFRA SAP 2008: New science on infants, children, & pregnant women from experimental laboratory toxicology & epidemiology studies since analysis for RED

• Evaluated both AChE & non - cholinergic modes of action
• FIFRA SAP 2009 : Approach for risk assessment of semi -volatile pesticides
• FIFRA SAP 2010 : Development of the draft “Framework for Incorporating Human Epidemiologic & Incident Data in Health Risk Assessment” 

# External Peer Reviews5 

### • FIFRA SAP 2011: Chlorpyrifos Physiologically- Based Pharmacokinetic/Pharmacodynamic (PBPK/PD) Modeling linked to the Cumulative and Aggregate Risk Evaluation System (CARES )
• Federal Peer Review 2012: MRI and neurobehavioral testing in children to further clarify results obtained by examination of the epidemiological cohorts
• FIFRA SAP 2012 : Further, more in - depth analysis on science on infants, children, & pregnant women from experimental laboratory toxicology & epidemiology studies. 

# External Peer Reviews6 

### • December, 2014 Revised Risk Assessment • RBC AChE inhibition as the critical effect for deriving the POD • PBPK/PD model used to derive human specific PODs for various age groups, routes, and durations • PBPK/PD model used to derive intra - species factor for some lifestages (not women of childbearing age) • Retained FQPA 10X Safety Factor: uncertainty in the human dose - response relationship for neurodevelopmental effects 

# Regulatory Context: Chlorpyrifos7 • EPA has been working to complete its human health risk assessment in registration review on a parallel track with its response to the 2007 PANNA & NRDC petition to revoke all chlorpyrifos tolerances and cancel all chlorpyrifos registrations.
• The timing of the petition response has been the subject of litigation. In 2015, the 9 th Circuit ordered EPA to respond to the petition by October 31, 2015 and to issue any final action by December 30, 2016.
• Accordingly, consistent with EPA’s revised human health risk assessment and in accordance with the 9 th Circuit’s order, in late 2015 EPA proposed to revoke all chlorpyrifos tolerances. EPA is now working to complete any final tolerance rule by the end of the year as ordered by the court. 

# Regulatory Context: Chlorpyrifos

### • From the 2012 SAP Report, pp. 49 - 50 (emphasis added): • The Panel acknowledged the limitations in the three longitudinal children’s cohort studies of estimating chlorpyrifos exposures ( i.e. , the Columbia study, the Mt. Sinai study, and the CHAMACOS study), based on the exposure measures collected, and was in general agreement that the data from these studies alone were not sufficient to derive a point of departure (POD) for purposes of quantitative risk assessment. • New information has emerged from the analysis that reduces some of the uncertainty in the biomonitoring data. 

# 2012 FIFRA SAP Report

89 

### • Per the 2012 SAP report, the agency was urged to find ways to use the epidemiology studies, in particular the CCCEH study, to inform the chlorpyrifos assessment (emphasis added):

• “...if one assumes that cord blood measurements reflect exposure levels during the critical prenatal period for induction of neurodevelopmental effects, then in theory, these would be the ideal data from which to derive the POD for chlorpyrifos in humans” 

### • In doing so, the agency was encouraged to make use of the PBPK model to further characterize CCCEH dose estimates • “... a [PBPK] model could be used to further characterize the dose estimates in the epidemiology studies, for additional dose response analyses. Such a PBPK model will become even more important in the event that the agency might, at some point in the future, decide to move from using AChE inhibition to another outcome.” 

# 2012 FIFRA SAP Report10 

### • Used PBPK model & EPA- OPP’s exposure assessment approaches to characterize exposure profile to women in the CCCEH cohort.

• Exposure approaches have been previously reviewed by SAP and have used extensively in risk assessments. • Results provide support for using cord blood data for POD. • Case studies developed to illustrate how the PBPK model would be used to predict internal doses from existing exposures to chlorpyrifos. 

# Risk Assessment of Pesticides11 

## • Background & Overview (Dana Vogel) • Overview of EPA Epidemiological Literature Review (Elizabeth Holman) • Interpreting Biomarker D ata in the CCCEH Cohort U sing a PBPK Model (Cecilia Tan) • Evaluation of CCCEH Blood D ata and Predicted E xposures (Wade Britton, Rochelle Bohaty, Danette Drew) • Point of Departure, Intra - Species E xtrapolation, the FQPA 10X Safety Factor, and Case Studies (Anna Lowit) 

# Outline of Presentations

## QUESTIONS?

12Elizabeth Holman, DrPH Health Effects Division Office of Pesticide Programs Environmental Protection Agency holman.elizabeth@epa.gov 703 - 603 - 8761 Presentation to the FIFRA SAP, April 19, 2016 

# Chlorpyrifos: Overview of EPA Epidemiological Literature Review

Internal, deliberative, not for distribution 13

## • Background and History of EPA review • Overview of U.S. Prospective Cohort Studies • Focus of Assessment • Synthesis of Epidemiological Literature • Columbia University Prospective Cohort Study • Additional Background • Highlights of Findings 

# Outline

Internal, deliberative, not for distribution 1415 • 2008 FIFRA SAP meeting - involved a preliminary review of the literature for chlorpyrifos, with a particular focus on women and children • “Chlorpyrifos likely played a role” but not “sole contributor” due to other co - exposures • Epidemiology studies "should not be considered ...basis for characterization of PoD”
• 2010 - OPP developed a draft “Framework for Incorporating Human Epidemiologic & Incident Data in Health Risk Assessment”

• Provides foundation for evaluating multiple lines of scientific evidence, including epidemiology, in the context of the understanding adverse outcome pathway (or mode of action) • Includes two key components: problem formulation and use of the modes of action/adverse outcome pathways (MOA/AOP) frameworks • Reviewed favorably by the SAP in 2010 • C onsistent with updates to the World Health Organization/International Programme on Chemical Safety mode of action/human relevance framework highlighting importance of problem formulation and need to integrate information at different levels of biological organization (Meek et al., 2014 ) 

# Background and History

Internal, deliberative, not for distribution16 

### • 2011 - agency released “Chlorpyrifos: Preliminary Human Health Risk Assessment for Registration Review”: • Focusing on the AChE inhibiting potential of chlorpyrifos • I ncluded assessment of exposures from dietary (food, water), occupational and residential pathways • Focus consistent with recommendation from 2008 SAP - AChE data provide most appropriate endpoint and dose - response data for deriving points of departure ( PODs ) for purposes of risk assessment • Also in 2011, the physiologically based pharmacokinetic- pharmacodynamic model (PBPK- PD) reviewed by FIFRA SAP 

# Background and History

Internal, deliberative, not for distribution17 • 2012 EPA updated and expanded targeted review of epidemiological data : • New etiologic papers (intelligence quotient) • New methodological papers (measurement error) • Socioeconomic status (SES) - Confounding Bias • Exposure characterization and validation • Supplemental analyses by authors • Draft Framework Analysis approach • 2012 SAP concurred with EPA ‘played a role ’ • December 2014 – HHRA, FQPA 10x • 2015 – EPA conducted updated epidemiological literature review • Expanded beyond chlorpyrifos to other OPs • Did not change 2014 conclusions 

# Background and History

Internal, deliberative, not for distributionInternal, deliberative, not for distribution 18 • Expanded beyond chlorpyrifos to other OPs • New results from 3 U.S. cohorts (Mt. Sinai, Columbia, CHAMACOS) • Non - U.S. cohorts (1 Mexico) • Other study designs: • Case - control (1 U.S .) • Cross - sectional (1 U.S., 2 China, 1 Canada) • EPA Document (09/15/2015): “Literature Review on Neurodevelopment Effects & FQPA Safety Factor Determination for the Organophosphate Pesticides”

2015 Epidemiological Data Review • Assessment focused on chlorpyrifos • 3 U.S. Cohorts (Mt. Sinai, Columbia, CHAMACOS) • 2012 SAP review – concurred with EPA conclusion that 3 U.S. cohorts is most robust available evidence • EPA Document (12/29/2014): “Chlorpyrifos : Revised Human Health Risk Assessment for Registration Review” 2012/2014 Epidemiological Data Review 

# Background and History19 

## • Based on 2012 SAP review and available studies assessed in 2015, EPA continues to conclude that data from the 3 U.S. cohorts are the most robust, relevant available epidemiological data 

# Background and History

Internal, deliberative, not for distribution20 

### • Three prospective birth cohorts to examine environmental exposures and adverse health outcomes

• Columbia cohort ( 1998 - 2004) – denoted as CCCEH • NYC, multi - ethnic, Cord Blood Chlorpyrifos 

### • Mt. Sinai cohort (1998 - 2001) • NYC, multi - ethnic, TCPy (fetal growth only), DAPs, PON1 

### • U of CA Berkeley Cohort (CHAMACOS) (1999 - 2002) • CA-Ag region, Mexican -American, ag worker, TCPy/DAPs, PON1 

### • Children’s Environmental Health and Disease Prevention Research Centers (funded by EPA and NIEHS) 

# Overview of U.S. Cohorts

Internal, deliberative, not for distributionInternal, deliberative, not for distribution 21 

### • Multi - ethnic populations: African -American, Dominican, Hispanic, Mexican -American, White • Younger mothers, ~25 years • Low prevalence risky health behaviors, co - morbidities (criteria) 

## Cohort Characteristics • Sought prenatal care (<20 - 26 weeks) • Residency requirement • Deliver participating hospitals • No diabetes, hypertension, HIV, history birth defects • No smoking, illegal drug use 

## General Eligibility 

# 3 Cohorts - Population Characteristics22 

### • “The Panel considers the Agency’s epidemiology review to be very clearly written, accurate , and to generally provide a very thorough review of the epidemiology literature .”
• “Overall , the Panel concurs with the 2008 SAP and the Agency in concluding that chlorpyrifos likely plays a role in impacting the neurodevelopmental outcomes examined in the three cohort studies.”
• “The strengths of the three studies support the Panel’s conclusion. There are nine strengths identified by the Panel which are discussed in the detailed response section of this report.” 

# 2012 SAP Review of Epidemiological Literature

Internal, deliberative, not for distribution23 

### “The conclusion is enhanced by the strengths of the three studies reviewed, specifically: • The longitudinal designs which permitted clear indications of the temporal relation of chlorpyrifos exposure to adverse neurodevelopmental outcomes; • T he inclusion of biomarkers of exposure as well as self reported exposure; • T he relative consistency of findings in different populations but using similar standardized exposure and outcome measures; • T he strength of the associations found ; 

# 2012 SAP Review – Strengths of 3 U.S. cohorts

Internal, deliberative, not for distribution24 

### • The use of objective measures of exposure and standardized, validated measures of outcomes; • The control of multiple confounding variables including other environmental exposures and other pesticides; • The suggestion of a dose - response effect; • Minimization in bias in assessing outcomes and exposures and the likelihood that biases and misclassification of exposures and outcomes resulted in a bias to the null, i.e. , under- estimation of effect; and • Attempts to investigate genetic and phenotypic effect modification and dose - response effects.” 

# 2012 SAP Review – Strengths of 3 U.S. cohorts (Cont.)

Internal, deliberative, not for distribution25 

### • Multiple outcomes assessed in these studies including • Fetal Growth • Neonatal Neurological Development • Infant Motor and Mental Development • Attention Disorders • Autism Spectrum Disorders • Intelligence Measures • Consistent with previous 2008 and 2012 SAP evaluations for chlorpyrifos, EPA is focusing this analysis on neurodevelopmental outcomes 

# Focus of Assessment

Internal, deliberative, not for distribution26 

### • Fetal Growth not the focus of this assessment: • Inconsistent evidence of organophosphate (OP) exposure and association with adverse birth outcomes/fetal growth outcomes • CCCEH observed evidence of an inverse association, i.e. : • I ncreasing cord blood chlorpyrifos associated with decreased measures of birth weight and length ( Whyatt et al., 2004) 

### • Mt. Sinai and CHAMACOS cohorts: • Reported either no association, or evidence of a positive relationship (Berkowitz et al., 2004; Eskenazi et al., 2004), respectively 

### • Given lack of consistency among cohorts for fetal growth metrics, proposed link between fetal growth and OP exposure is tenuous • EPA continues to monitor literature for chlorpyrifos exposure and fetal growth outcomes 

# Focus of Assessment

Internal, deliberative, not for distributionInternal, deliberative, not for distribution 27 

### Exposure Measurement, Confounding Adjustment, Statistical Analyses, Bias Considerations



# Methods and Analysis

# Exposure Assessment

28 

### • Cohorts differing exposure profiles, pathways, routes • Multiple biomarkers reflect different windows of exposure: • Self- report questionnaire (each cohort) • TCPy in urine (each cohort) • TCPy meconium (validation study) (Columbia) • Chlorpyrifos in cord blood (Columbia) at birth • Chlorpyrifos in air (validation study) (Columbia ) • AChE and BuChE in cord blood (CHAMACOS ) • DAPs in urine (CDC methods) (Mt. Sinai, CHAMACOS) • PON1 genotype and phenotype (Mt. Sinai, CHAMACOS)

# Methods to Control Confounding
• Statistical Adjustment (individual - level) • Race, education, income, housing quality • Tested for statistical interaction • Multilevel Model (Socioeconomic status, Columbia only) • Account group - level and individual - level variability • Restriction (design) • Through recruitment techniques, similar population characteristics 2930 

### • Biomonitoring data were collected from individuals within each cohort • The unexposed children in the epidemiology studies are those whose biomonitoring data are low and often below the limit of detection ( ie , so low as to not be measurable ) • The unexposed children are derived from the same populations and location in the same living and economic conditions as the exposed or highly exposed children • In this way, important issues such as socioeconomic status are similar across the entire group of exposure and unexposed 

# Restriction (Design) Methods to Control Confounding

Internal, deliberative, not for distributionInternal, deliberative, not for distribution 31 • 

### Other exposures including:

• 

### Polyaromatic hydrocarbons (PAH)

• 

### Environmental tobacco smoke (ETS)

• 

### DDT/DDE

• 

### Polychlorinated biphenyls (PCBs)

• 

### Organochlorines/ Hexachlorobenzene

• 

### Lead 

### • Demographic • Socio - economic status • Health - related • HOME/child stimulation • Postnatal environment • Other pesticides including: • Diazinon • Propoxur • Pyrethroid pesticides 

# Confounding Variables

# Statistical Analysis

32 

## • Statistical modeling decisions appropriate to the research question, characteristics of data etc.

• Missing data, <LOD • (imputed, sensitivity analyses) 

## • Sample size adequate main effects • Likely under- powered for effect modification • Sensitivity analyses to evaluate alternative modeling options

• Cessation of exposure, loss to follow upInternal, deliberative, not for distribution 33 

### • Errors in outcome and exposure measures occurred

• Design reduces differential bias • Validation study 

### • Confounding • Several control methods 

### Information Bias • Retention rate moderately high for birth cohorts ( 60 - 80% at 7 years) • Included and excluded comparable

• Measured variables 

### • Missing Data imputed Selection Bias 

# BIAS (Threats to Validity)34 CCCEH Mt. Sinai CHAMACOS Neonatal Neurodevelopment (2 - 5 days old) No Yes Yes Infant Neurodevelopment (6 - 36 months) Yes Yes Yes Attention Problems (3 - 5 years old) Yes No Yes Autism Spectrum Disorders Yes Yes Yes Intelligence Measures (6 - 9 years old) Yes Yes Yes 

# Outcomes Measured Across 3 U.S. Cohorts

Internal, deliberative, not for distribution

# Neonatal Neurodevelopment

35 

### • Brazelton Neonatal Behavioral Assessment Scale (BNBAS) • Goal: provide information parents/caregivers • 28 behavioral items - habituation, range of state, orientation • 18 primitive reflexes • Assessed 2 - 5 days post - partum • Trained neonatologists administered • Hospital setting • BNBAS only measured in CHAMACOS and Mt. Sinai cohorts

# Infant Neurodevelopment

36 

## • Bayley Scales of Infant Development II • Mental and Motor development index, 6 - 36 months • Reliable and valid as screening tool, early intervention • Measured in all 3 cohorts

# Attention Problems

37 

## • Measurement Tools • Combination Maternal report and direct observation • Child Behavior Checklist (maternal report) • Direct Assessment of child (K- CPT) • Hillside Psychometrician report 

## • DSM - IV ADHD symptoms • Assessed at 3, 3.5 and 5 years in CHAMACOS and CCCEH cohorts38 

## • Assessed in all 3 U.S. cohorts • The DSM -V defines ASD (autism spectrum disorder) which now encompasses several disorders that were different diagnoses in DSM - IV, including PDD (pervasive developmental disorder, a catch - all where the other categories didn’t fit )

• Depending on when the study was conducted, the authors may use the PDD or ASD criteria and terminology 

# Autism Spectrum Disorders

Internal, deliberative, not for distribution

# Intelligence Measures

39 • Wechsler Intelligence Scale for Children IV • Measured in all 3 U.S. cohorts • Verbal comprehension • Perceptual Reasoning • Working Memory (WM) • Processing Speed • Full Scale IQ (FSIQ) • Standardized US population, norms English and Spanish speaking populations • Age 6 - 9 years • Cultural Bias has been noted • Restricted sample populationInternal, deliberative, not for distribution 40 

## RESULTS41 

## • CHAMACOS and Mt. Sinai cohorts measured neurological effects 2 - 5 days after birth:

• Observed putative association with prenatal DAPs ( Engel et al., 2007; Young et al., 2005 ) • Cross - sectional Chinese study (Zhang et al., 2014) measured neonatal neurodevelopment assessed 3 days after birth:

• Statistically significant associations with prenatal DAPs from prenatal OP pesticide exposure 

# Neurological Effects Near Birth

Internal, deliberative, not for distribution42 

## • 3 US cohorts (CCCEH, Mt. Sinai, CHAMACOS) each reported evidence of prenatal chlorpyrifos or DAPs exposure and impaired mental and psychomotor development:

• Albeit not consistent by age at time of testing (ranging from 6 month to 36 months across the three cohorts)


## • Cross - sectional Chinese study ( Guodong et al. 2012) measured developmental quotient score for 23 - 25 month old children: • Observed no association with postnatal urinary DAPs 

## Mental/Psychomotor Problems

Internal, deliberative, not for distribution43 

### • Attentional problems and ADHD reported suggestive or positive associations in 3 prospective cohorts (2 U.S., 1 Mexican), and a U.S. cross - sectional study • Rauh et al., 2006; Eskenazi et al., 2007; Marks et al., 2010; Fortenberry et al., 2014; and Bouchard et al, 2010 • 3 cohorts – prenatal; Cross - sectional – postnatal
• Canadian cross - sectional study ( Oulhote and Bouchard 2013) did not observe association between postnatal DAPs and parentally reported attentional problems

• Outcome assessment may not have been sensitive enough 

# Attentional Problems

Internal, deliberative, not for distribution44 

### • 3 US cohorts and a U.S. case - control study reported suggestive or positive associations between OP exposure and autism spectrum disorders:

• Rauh et al., 2006; Shelton et al., 2014; Eskenazi et al., 2007; Furlong et al., 2014 • Studies vary in the magnitude of the overall strength of association, but consistently observe positive association between OP exposure and ASD. • For intelligence measures at age 7 years, CCCEH , Mt. Sinai, CHAMACOS reported an inverse relation between the respective prenatal measures of chlorpyrifos or DAPs • Rauh et al ., 2011 ; Engel et al., 2011; Bouchard et al., 2011. 

## Autism Spectrum Disorders (ASD) and Intelligence Measures

Internal, deliberative, not for distribution45 • Epidemiology, pre - natal : • Numerous epidemiological investigations observed a link between pre - natal exposure to chlorpyrifos or OPs (measured as chlorpyrifos, TCPy , or DAPs) and adverse effects on neurodevelopment through age 7 years, with additional more limited evidence up through approximately age 11
• Results across numerous studies show relatively consistent elevated risks associated with prenatal OP exposure:

• Autism spectrum disorders, intelligence decrements, attentional problems and ADHD, neurological effects near birth, and mental/psychomotor delays (6 months - 11 years ) • Results not always consistent with magnitude of association and ages where associations observed across studies 

# Prenatal vs. Postnatal Exposure

Internal, deliberative, not for distribution46 • Epidemiology, post- natal: • Smaller number of studies have assessed postnatal exposure to OPs (measured as DAPs) • Postnatal exposure assessed in the CHAMACOS cohort ( Eskenazi et al., 2007; Young et al., 2005; Bouchard et al., 2011) and 3 cross - sectional studies ( Guodong et al., 2012; Bouchard et al., 2010; Oulhote and Bouchard, 2013 ) • Postnatal exposures not assessed in the CCCEH and Mt. Sinai studies ( Rauh et al., 2011; Engel et al., 2011)

• Given that the major source of exposure (residential use) was cancelled partway through the CCCEH study, this limits the ability of this study to inform the impacts of long-term postnatal exposure to chlorpyrifos • Bouchard et al. (2010) looked at U.S. children age 8– 15 years in the 2000–2004 National Health and Nutrition Examination Survey (NHANES), and observed a positive association between attention and behavior problems and DAPs

• No other neurodevelopmental associations were found between postnatal biomarkers 

# Prenatal vs. Postnatal Exposure

Internal, deliberative, not for distribution

# Synthesis of Evidence

47 

## • Strength of observed associations high in some cases, but not all • Consistency in Brazelton (abnormal reflexes), ADHD - like behavior problems, Bayley (particularly MDI), and IQ (WM) • Alternative explanations investigated • Modeling, transformations, confounding variables

# Synthesis of Evidence

48 

## • Prospective studies (primary basis of conclusions) • Temporal relation • Issue of prenatal vs. postnatal exposure – datagap • Differential misclassification less likely • Biological plausibility • MOA unclear, several plausible hypotheses • Influence of cessation of residential exposure on association

• Limited evidence (low power), not designed to assessInternal, deliberative, not for distribution 49 

# Highlights of CCCEH Findings50 

### • Mothers and Newborn Study of North Manhattan and South Bronx conducted by Columbia University – referred to as CCCEH study • CCCEH study - measured parent chlorpyrifos in cord blood, and other indicators ( e.g ., air sampling, behavioral information )

• Other two birth cohorts generally measured non - specific urinary metabolites of chlorpyrifos and other OPs (TCPy , DAPs) • Therefore, EPA considers the CCCEH Mothers and Newborn Study research results as most relevant to the chlorpyrifos HHRA and is thus the focus of this analysis

• The other two cohorts and additional epidemiological literature provide important supporting information • 2008/2012 SAP concurred with this conclusion 

# Additional CCCEH Background

Internal, deliberative, not for distributionInternal, deliberative, not for distribution 51 

### • CCCEH study time period - spanned before and after when pesticide manufacturers voluntarily cancelled the use of chlorpyrifos in the home environment

• Researchers able to show change in exposure before (high use period) and after (low/no use period) the period of removal of chlorpyrifos products from the residential marketplace 

### From Whyatt et al (2004) 

# Additional CCCEH Background52 

# CCCEH Blood Levels

Internal, deliberative, not for distribution Year Percentile Cord Blood Chlorpyrifos (pg/g) Maternal Blood Chlorpyrifos (pg/g)
1998 - 1999 25 <LOD 2.60 50 3.78 6.70 75 8.80 9.55 90 12.1 16.0 95 15.1 19.4
2001 25 <LOD <LOD 50 <LOD <LOD 75 <LOD <LOD 90 2.45 2.44 95 2.58 2.61 Distribution of chlorpyrifos blood levels

<LOD = Less than limit of detection53 

### • D ata from CCCEH suggest maternal blood reasonable surrogate for cord blood • Levels of chlorpyrifos in maternal blood and umbilical cord blood were highly correlated: • Whyatt et al. (2003) r = 0.76, p<0.001, n=180 • Whyatt et al. (2009) r = 0.9, p<0.001, n = 64 • These together suggest that tracking the blood concentrations of the mother is a reasonable surrogate for the fetus

• Will hear more about this surrogacy issue in later presentations 

# Correlation Between Cord Blood and Maternal Blood

Internal, deliberative, not for distribution54 

### • Rauh et al. (2006) - 254 children followed through age 3 years and used a dichotomized statistical approach:

• ‘Low group’: ≤6.17 pg/g of CPF in cord blood • ‘High group’: >6.17 pg/g of CPF in cord blood • Statistically significant deficits of 6.5 points on the Bayley Psychomotor Development Index (PDI) at 3 years of age when comparing high to low exposure groups

• PDI decrements persist even after adjustment for group and individual level socioeconomic variables ( Lovasi et al. , 2011 ) 

# CCCEH Findings

Internal, deliberative, not for distribution55 

### • At age 3 years, when comparing high to low exposure groups ( Rauh et al, 2006) observed increased odds of: • Mental delay (OR=2.4; 95% CI: 1.1–5.1) • Psychomotor delay (OR=4.9; 95% CI: 1.8– 13.7) • Attention disorders ( OR=11.26; 95% CI: 1.79–70.99) • ADHD ( OR=6.50; 95% CI: 1.09–38.69) • PDD ( OR=5.39; 95% CI: 1.21–24.11) • In a follow- up study at age 11, increased odds of mild to moderate tremor when comparing high to low exposure groups ( Rauh et al. , 2015 ) 

# CCCEH Findings

Internal, deliberative, not for distribution56 • Rauh et al. (2011) evaluated relationship between prenatal chlorpyrifos exposure and neurodevelopment:

• 265 of the CCCEH cohort participants - 7 years old • Complete set of data including prenatal maternal interview data, prenatal chlorpyrifos marker levels from maternal and/or cord blood samples at delivery, postnatal covariates, and neurodevelopmental outcome data • D escribed the log of Working Memory Index (WMI) of children as linearly associated with concentration of chlorpyrifos (CPF) in cord blood:

• Slope = - 0.006 (95 % CI = - 0.01, - 0.002 ) • F or each standard deviation increase in exposure (4.61 pg/g ), observed a 1.4% reduction in Full - Scale IQ and a 2.8% reduction in Working Memory 

# CCCEH Findings

Internal, deliberative, not for distribution

# Conclusions

57 

### • Current database strengthens the 2008/2012 SAP conclusion that “chlorpyrifos likely plays a role” in observed adverse effects on child neurodevelopment
• Given study conduct, design, methods EPA believes more likely under- than over- estimate associations
• New Data (2012 and 2015) support and extend previous conclusion

• Retained FQPA 10x in HHRA (2014)Internal, deliberative, not for distribution 58 

# QuestionsCecilia Tan, Research Physical Scientist Health Effects Division Office of Pesticide Programs Environmental Protection Agency tan.cecilia@epa.gov 919 - 541 - 2542 Presentation to the FIFRA SAP, April 19, 2016 

# Chlorpyrifos: Interpreting Biomarker Data Use of a Physiologically Based Pharmacokinetic (PBPK) Model

59

## • Linking external exposures to internal doses • Background of PBPK modeling • PBPK model for chlorpyrifos • Addressing uncertainties in interpreting biomarker d ata • Likely exposure scenario • Time between exposure and sampling 

# Outline

60

## • Pharmacokinetics: Absorption, distribution, metabolism, and excretion (ADME) of chemicals in the body 

## • PBPK Models: A series of mathematical representations of biological tissues and physiological processes in the body that simulate the ADME of chemicals that enter the body * 

## • PBPK Modeling in Risk Assessment: PBPK modeling is a scientifically sound and robust approach to estimating the internal dose of a chemical at a target site and as a means to evaluate and describe the uncertainty in risk assessments * 

# Physiologically Based Pharmacokinetic (PBPK) Model

61 *Approaches for the Application of Physiologically Based Pharmacokinetic (PBPK) Models and Supporting Data in Risk Assessment (EPA, 2006)

## • PBPK models incorporate physiological and biochemical determinants of chemical disposition • PBPK models can be used to simulate the time course of internal dosimetry (e.g., blood concentrations) under various exposure scenarios (e.g., daily oral exposures) in different animal species. 

# PBPK Modeling

62

### Underlying assumption: equivalent biological response occur at equal tissue dose, not at equal external dose • Organize available mechanistic data • Identify data gaps and suggest new experiments • Predict chemical disposition under new/inaccessible conditions (e.g., high to low dose, inter- species, intra - species, route -to - route extrapolations) • Quantify uncertainty and variability in physiology and ADME • Can be linked to PD models to predict biological endpoints 

# Applications of PBPK Modeling in Risk Assessment

63

## • Linking biomarker data to exposure • Require knowledge of exposure scenarios and biomarker sampling procedures • Forward vs. reverse dosimetry • Linking biomarker data to health effects • Biomarkers measured in accessible media may not be a good surrogate for target tissue dose 

# Applications of PBPK Modeling in Biomarker Interpretation

6465 

## • Forward dosimetry: Compare observed biomarker data with predicted values from likely exposure scenarios and known temporal relationship between exposure and sampling • Reverse dosimetry: Estimate exposure concentrations from an assumed exposure scenario and temporal relationship between exposure and sampling 

# Forward vs. Reverse Dosimetry66 

## • What is the likely exposure scenario (e.g., which time course curve is reasonable)?

• Time between exposure and biomarker sample collection? 

# Two Major Sources of Uncertainty

### • December 2014 Human Health Risk Assessment • Using the PBPK- PD model to derive point - of- departure based on 10% RBC AChE inhibition by oxon • Food, water (oxon - only exposure), currently registered residential use (golf course, mosquitocide application), worker exposure (applicators, post - application) • April 2016 SAP • Using the PBPK model to simulate chlorpyrifos concentrations in blood ( NOT to derive PoD) • Food, water, worker exposure (applicators, post- application) 

# Using the Chlorpyrifos Model

67

# Chlorpyrifos PBPK- PD Model

68 Poet 2013 (MRID 49074901)

## • Originally developed in 2002, refined over the years as more data had become available. • The latest version includes multi - route exposures (Poet et al., 2014). • The model was reviewed by the FIFRA SAP in 2011. The Agency has continued to evaluate the refined model. 

# Chlorpyrifos PBPK- PD Model

69

# Model Calibration/Evaluation

70 Gray highlights: Data available for model calibration/evaluation Blue highlights: Chlorpyrifos concentrations measured in humans

### • A version of the PBPK model that describes physiological and biochemical changes during pregnancy is available • Not peer- reviewed • No time course data available for pregnant women • The model was built based on the best knowledge available • Preliminary results from the pregnancy model suggested that the combined effects from multiple physiological changes during pregnancy resulted in slightly lower chlorpyrifos concentrations in blood during the third trimester. 

# Using 75 kg Females as Surrogates for Pregnant Women

7172 

## EPA evaluated the exposures likely to have occurred in the CCCEH cohort, and whether these exposures could have resulted in the observed cord blood measures using the PBPK model • Food • Drinking water • Residential use: indoor application 

# Uncertainty: Exposure Scenarios?73 

# Likely Exposure Scenario: Residential Indoor Use, Post-Application Exposure74 

## • For CCCEH cohort, chlorpyrifos was measured in umbilical cord blood collected close to delivery. • Reported time for labor and delivery for the first pregnancy range from 8 to 20 hours (early labor phase 6 - 12 hours, active labor phase 4- 8 hours), and may become faster for subsequent pregnancies. • Time between last exposure and biomarker sampling can be bounded. 

# Uncertainty: Time Between Exposure and Sampling?75 

# Time Course of Blood Concentrations Biphasic Clearance Time Conc (pg/g) Peak on the 30th day 62.7 4 hours after the last peak 22.5 8 hours after the last peak 14.3 20 hours after the last peak 11.0 2 days after the last peak 9.6 Chlorpyrifos is removed from blood through (1) distribution to tissues, and (2) metabolism and excretion of chlorpyrifos. Rapid decrease immediately after exposure, half- life ~3 to 4 hours Gradual decrease several hours after exposure, half- life ~120 hours76 

### • The PBPK model for chlorpyrifos has been evaluated using human data, including chlorpyrifos concentrations in blood. • Two major uncertainties in linking biomarker data to exposures: • Exposure scenarios • Time between exposures and biomarker sampling • The PBPK model was used to simulate time course of chlorpyrifos concentrations in blood

• Likely exposure scenario: residential indoor use, post- application exposure • Time between exposures and biomarker sampling: ~4 hours to 2 days 

# SummaryInternal, deliberative, not for distribution 77 

# QuestionsWade Britton, MPH Health Effects Division Office of Pesticide Programs U.S. EPA britton.wade@epa.gov 703 - 308 - 0139



# Chlorpyrifos: Evaluation of CCCEH Blood Data and Predicted Exposures

78 Rochelle Bohaty, PhD Environmental Fate and Effects Division Office of Pesticide Programs U.S. EPA bohaty.rochelle@epa.gov 703 - 305 - 6381 Danette Drew Health Effects Division Office of Pesticide Programs U.S. EPA d rew.danette@epa.gov 703 - 305 - 6028 Presentation to the FIFRA SAP, April 19, 201679 

## • Introduction • Exposure Scenarios • Drinking Water • Food • Residential • Conclusions 

# Outline80 

### • The 2012 SAP report urged the agency to find ways to use the epidemiology studies to inform the chlorpyrifos assessment, in particular the CCCEH study • “...if one assumes that cord blood measurements reflect exposure levels during the critical prenatal period for induction of neurodevelopmental effects, then in theory, these would be the ideal data from which to derive the POD for chlorpyrifos in humans” 

### • In doing so, the agency was encouraged to make use of the PBPK model to further characterize CCCEH dose estimates • “...a [PBPK] model could be used to further characterize the dose estimates in the epidemiology studies, for additional dose response analyses. Such a PBPK model will become even more important in the event that the agency might, at some point in the future, decide to move from using AChE inhibition to another outcome.” 

# Introduction81 

### • Mothers and Newborn Study of North Manhattan and South Bronx conducted by Columbia University – referred to as CCCEH study • CCCEH study measured parent chlorpyrifos in cord blood, and other indicators ( e.g ., air sampling, behavioral information )

• Other two birth cohorts generally measured non - specific urinary metabolites of chlorpyrifos and other OPs (TCPy , DAPs) • Therefore, while the other two cohorts provide important supporting information, EPA considers the CCCEH Mothers and Newborn Study research results as most relevant to the chlorpyrifos HHRA, and is thus the focus of this analysis

• 2008/2012 SAP concurred with this conclusion 

# Introduction: CCCEH Study Background82 

# Introduction: Distribution of CCCEH Blood Concentrations Percentile Cord Blood Chlorpyrifos (pg/g) Maternal Blood Chlorpyrifos (pg/g) 1998- 1999 2001 1998- 1999 2001 25 < LOD < LOD 2.60 < LOD 50 3.78 < LOD 6.70 < LOD 75 8.80 < LOD 9.55 < LOD 90 12.1 2.45 16.0 2.44 95 15.1 2.58 19.4 2.61 < LOD = Less than Limit of Detection (0.5 and 1.0 pg/g)83 

## • Chlorpyrifos was one of the most widely used insecticides during the time of the CCCEH cohort and exposures were likely to have occurred • Used on a variety of food and feed crops • Results in dietary exposures from drinking water and food 

## • Until 2000, when nearly all residential uses were voluntarily cancelled , chlorpyrifos was one of the major insecticides in indoor residential settings 

# Introduction: Chlorpyrifos Regulatory History84 

## • EPA has evaluated likely exposures in the CCCEH cohort and whether they could have resulted in the observed blood measures using the PBPK model

1. Defined exposures (drinking water, food, and residential) to the women in the cohort 2. Quantified the magnitude of exposure/dose estimates from likely chlorpyrifos exposures 3. Compared PBPK model predicted blood levels resulting from these exposures to blood levels reported by CCCEH 

# Introduction: Evaluation85 

# Drinking Water Exposure86 • 99% is sourced from Croton and Catskill - Delaware systems
• Watershed protection contains objectives to prevent pollution from both agricultural (watershed overlap) and non - agricultural use sites
• Does not completely eliminate the potential for exposure to chlorpyrifos and chlorpyrifos - oxon 

# Drinking Water: New York City

New York City Surface Water Intakes 2001 National Land Cover Dataset New York City Surface Water Watershed87 

# Chlorpyrifos Transformation88 • Surface water monitoring data for Croton and Catskill - Delaware watersheds

• NYC Community Water System Reports – no detections • NYC Community Water System processing includes chlorination and source water mixing



### • Potential exposure to chlorpyrifos is virtually eliminated 

# Drinking Water: New York City
Year 1997 1998 1999 2000 2001 2002 2003 2004 Concentration (μg/L) 0.002 0.015 0.015 0.06 0.0423 0.0025 0.25 0.25 Bold font indicates measured concentrations. Other referenced concentrations are 1⁄2 the limit of detection.

Treatment Method Free Chlorine Percent Reduction Study 1 a 90.3 (pH 6.6) 85.7 (pH 8.6) Percent Reduction Study 2 b 100 pH 8.0 a. Chamberlain 2014 – Experimental time was representative of typical drinking water treatment condition b. Ormad 2008 – Experimental time not reported89 

# Food Exposure90 

## • 2014 Chlorpyrifos HHRA • Combined dietary exposure from all foods with a U.S. tolerance for chlorpyrifos • Chlorpyrifos is the residue of concern in food; the oxon metabolite is not expected to occur in food • Acute (one day) and Steady State (21 day) durations • Females of childbearing age, infants and children 

# Food Exposure: Background91 

## • Dietary methods have undergone multiple FIFRA SAP reviews • Dietary Exposure Evaluation Model TM 

## (DEEM) with the Food Commodity Intake Database (FCID), Version 3.16 • Calendex- FCIDTM 

## Model • Both models incorporate 2003 - 2008 consumption data from USDA’s National Health and Nutrition Examination Survey, What We Eat in America, (NHANES/WWEIA ) 

# Food Exposure: Methods92 

## • The food exposure results are reflective of those expected in the CCCEH study cohort • Food exposure results and the PBPK model have been used to : • Predict chlorpyrifos blood levels that may occur from food exposure • Evaluate the contribution of food as a source of chlorpyrifos exposure for women in the CCCEH cohort 

# Food Exposure : Application of Results93 

### • The PBPK model was used to predict chlorpyrifos blood concentrations from food exposure for the following scenario:

• Female, 72.9 kg • Following a single, repeated daily exposure to chlorpyrifos in food • Performed using the food exposure results for a range of percentiles of exposure • Predictions for the blood levels at 10 hours and 24 hours after peak exposure are compared to the blood levels measured in the CCCEH cohort 

# Food Exposure: PBPK Modeling94 Percentile of Exposure PBPK- Predicted 10 Hour Blood Chlorpyrifos

From Food (pg/g) PBPK- Predicted 24 Hour Blood Chlorpyrifos

From Food (pg/g) 2001 Maternal Blood Chlorpyrifos (pg/g) 10 < LOD < LOD -- 25 -- -- < LOD 50 < LOD < LOD < LOD 70 < LOD < LOD -- 75 -- -- < LOD 90 -- -- 2.44 95 < LOD < LOD 2.61 99.9 1.490 < LOD -- 

# Food Exposure Results95 

# Residential Exposure96 

### • “ Characterization of chlorpyrifos exposure experienced by women in the Columbia cohort, particularly during the pre cancellation period, remains an important uncertainty in using these data in quantitative risk assessment .” • “...the actual level of such exposure particularly during any critical window(s) of susceptibility is not known, and a better understanding of the range of possible exposures and the degree to which they may or may not have elicited inhibition of AChE, remains a key scientific question .” 

## SAP Recommendations for Residential Analysis97 

## • 2014 : Dose reconstruction analysis evaluated indoor exposures that were likely at the time of the CCCEH cohort and whether these could have elicited 10% RBC AChE inhibition, the regulatory endpoint for chlorpyrifos
• 2016: B iomarker analysis used the PBPK model under a variety of expanded exposure conditions to predict chlorpyrifos blood concentrations for comparison to blood levels reported in the CCCEH cohort 

## Residential Analyses Completed in 2014 and 201698 

### • In 1997, all chlorpyrifos residential indoor broadcast and total release aerosol/fogger uses were voluntarily cancelled

• Existing stocks could be phased out, or applied until depleted 

### • In 2000, the technical registrants agreed to phase out of nearly all remaining residential uses (including home lawn and indoor crack & crevice uses) • The phase out during the time of the CCCEH cohort implies indoor residential exposures could have occurred because chlorpyrifos products could have remained in the chain of trade and been legally used 

## Regulatory History of Residential Chlorpyrifos Use99 

### • Chlorpyrifos was one of the most widely used insecticides during the time of the CCCEH cohort and indoor residential exposures likely occurred • Insecticide usage information reported in the Columbia study publications is very limited • Whyatt et al. (2002) reported that pest control measures were used by 85% of respondents, treatment by themselves, or by housing superintendent, pest control operator (PCO) • Whyatt et al. (2009) reported that, of those who used pesticides, these were used once monthly 

# Residential Exposures in the CCCEH Cohort100 

## • EPA compared chlorpyrifos products and application types available during the time of the CCCEH cohort to reported pest control methods to determine which of these may have been used by the study participants • Whyatt et al. (2002): Broadcast and crack & crevice (perimeter) treatment by a pest control operator (PCO), 39%; aerosol can sprays, 26%; and total release foggers/bombs, 5% • Products registered as both 0.5% and 1.0% active ingredient (ai) formulations 

# Residential Exposures in the CCCEH Cohort101 

### • Screening- level analysis conducted using the 2012 Residential SOPs and available chlorpyrifos - specific exposure data to assess exposures from likely/reported uses • Handler (adult) and post- application (adults and children 1 to < 2 years old) exposures considered • Exposure parameters:

• Available exposure data includes registrant - submitted studies and open literature; primarily related to chlorpyrifos indoor crack & crevice and broadcast treatments 

# 2014 Dose Reconstruction Analysis

• M aximum, 1.0% ai formulation • Exposure duration (8 hours exposure on carpeted floors, 2 hours on hard flooring) • Amount handled (1 entire spray can for broadcast treatment, 1/2 can for crack and crevice)102 

### • PBPK model used to estimate RBC AChE inhibition from these estimated exposures

• Adult handler and post- application: dermal and inhalation exposures • Children 1 to < 2 years old post- application: dermal, incidental oral, and inhalation exposures 

### • Conservative PBPK model inputs:

• Less than 10% peak RBC AChE inhibition for all exposure assessed • Post- application exposures following broadcast and perimeter treatments, resulted in the highest exposure potential of all product types assessed 

# 2014 Dose Reconstruction Analysis

• 24 hour daily exposure • No adjustment for bathing/showering • Residence not left for 14 days • Daily residue dissipation (10%)103 

### • 2016 analysis is conceptually similar analysis to the 2014 dose reconstruction assessment

• Both use the 2012 Residential SOPs and chemical - specific exposure data 

### • Whereas the 2014 residential analysis used the PBPK/PD model to evaluate whether 10% RBC AChE inhibition could have occurred in the cohort, the 2016 analysis used the PBPK model to evaluate chlorpyrifos blood concentrations for comparison to CCCEH reported blood levels • 2016 analysis assesses only post - application exposures • PBPK model used under a variety of expanded exposure conditions



# 2016 Analysis104 • A total of 6 post- application exposure scenarios were developed to establish ranges of possible exposure levels to women in the CCCEH cohort and compare predicted internal dosimetry levels to those reported by the CCCEH investigators • Two post- application exposure scenarios mimic potential chlorpyrifos use patterns likely to have occurred and represent high - end indoor exposures

• Broadcast application of liquid chlorpyrifos to the entire hard floor surface • The highest of all assessed exposure scenarios • Perimeter application of liquid chlorpyrifos in a band or strip around a carpeted room • Likely the predominate treatment type during the CCCEH cohort given the 1997 broadcast cancellation 

# 2016 Analysis Exposure Scenarios105 

### • Four post - application exposure scenarios were assessed with use of the highest CCCEH blood value reported by Rauh et al. (2011), 63 pg/g • Establish an upper and lower exposure bound with use of this blood value 

### • Two post - application exposure scenarios (hard and carpeted flooring) that would have resulted in a peak concentration of ~ 60 pg/g on the final (30 th 

### ) day of PBPK simulation • Daily peak exposures back- calculated from the final day of exposure 

### • Two post - application exposure scenarios (hard and carpeted flooring) that would have resulted in a peak concentration of ~60 pg/g on day of application (1 st 

### day of PBPK simulation) • Simulates exposures following Day 1 peak exposure 

# 2016 Analysis Exposure Scenarios106 

### • Some of the 2014/2016 analysis PBPK exposure inputs differ in order to model more realistic exposure conditions • Daily shower following exposure • Once monthly (30 day) pesticide application • 8 and 2 hour daily exposure duration for contact with carpeted and hard flooring, respectively • 2014/2016 analysis PBPK model exposure inputs which are the same

• Daily post - application indoor exposures • Single pesticide application • 10 % daily residue dissipation 

# 2016 Analysis: PBPK Exposure Inputs107 • PBPK model simulations show a saw tooth pattern of daily, rapid increases in internal chlorpyrifos dose during exposure periods followed by a rapid decline after exposure • Peak internal dose for all simulations occurred during the final hour of daily exposure, just prior to the showering event • A rapid decline is seen following the showering event and continues to decline for 24 hours, just before initiation of the subsequent day’s exposure event • Internal dose increases once again immediately following initiation of the exposure event • Internal doses peak on the initial day of exposure and decline step -wise with each subsequent day modeled due to 10% daily dissipation input • Following the final day of exposure, internal dose continues to decline during terminal clearance phase 

# Results: 2016 Analysis PBPK Modeling108 

# Results: Perimeter and Broadcast PBPK Modeling

-1000 0 1000 2000 3000 4000 5000 6000 7000 8000

0 200 400 600 800 1000Blood Chlorpyrifos (pg/g)

Time (hours) Perimeter Application to Carpeted Flooring - 8 hours Broadcast Application to Hard Flooring – 2 hours

-200 0 200 400 600 800 1000 1200

0 500 1000 1500Blood Chlorpyrifos (pg/g)

Time (hours)109 

## Results: 60 pg/g C hlorpyrifos in Blood on the Day of Application ( Day 1) and on the Last (30th 

## ) Day; 2 Hour Daily Duration

-200 0 200 400 600 800 1000 1200

0 200 400 600 800 1000BloodChlorpyrifos (pg/g)

Time (hours) 60 pg/g

-10 0 10 20 30 40 50 60 70

0 200 400 600 800 1000BloodChlorpyrifos(pg/g)

Time (hours) 60 pg/g110 Model Run Highest Peak Blood Concn (pg/g) 24 Hour Blood Concn (pg/g) Blood Concn 10 Hours After the Peak on Day 30 (pg/g) Blood Concn 24 Hours After the Peak on Day 30 ( pg/g) Broadcast (Hard Floor; 2 hours) 7,179 41 42.6 31.7 Perimeter (Carpeted Floor; 8 hours) 1,053 13 12.9 10.7 60 pg/g Peak 30th Day (2 hours) ~ 1,030 4.3 6.44 4.79 60 pg/g Peak 30th Day (8 hours) 12.8 12.7 10.6 60 pg/g Peak on Day of Application (2 hours) 60 0.25 0.37 0.28 60 pg/g Peak on Day of Application (8 hours) 0.74 0.73 0.61



## Results: 2016 Analysis PBPK Modeling111 

## Results: Peak Chlorpyrifos Blood Concentrations on Day 1 0 1000 2000 3000 4000 5000 6000 7000 8000

Broadcast hard floor

(2h/day) Perimeter carpeted floor (8h/day) Peak at 60 pg/g on Day 30 (2h/day) Peak at 60 pg/g on Day 30 (8h/day) Peak at 60 pg/g on

Day 1 (2h/day) Peak at 60 pg/g on

Day 1 (8h/day) 7179

1053 1030 1030 60 60Blood Chlorpyrifos (pg/g) 

### Peak Concentration on Day 1 (pg/g )112 

## Results: Chlorpyrifos Blood Concentrations on Day 1 at Hour 24 0 5 10 15 20 25 30 35 40 45

Broadcast hard floor

(2h/day) Perimeter carpeted floor (8h/day) Peak at 60 pg/g on Day 30 (2h/day) Peak at 60 pg/g on Day 30 (8h/day) Peak at 60 pg/g on

Day 1 (2h/day) Peak at 60 pg/g on

Day 1 (8h/day) 41

13 4.3 13 0.25 0.74Blood Chlorpyrifos (pg/g) 

### Concentration at Hour 24 (pg/g)113 

## Results: Chlorpyrifos Blood Concentrations 10 Hours and 24 Hours After the Peak on Day 30 0 5 10 15 20 25 30 35 40 45

Broadcast hard floor

(2h/day) Perimeter carpeted floor (8h/day) Peak at 60 pg/g on Day 30 (2h/day) Peak at 60 pg/g on Day 30 (8h/day) Peak at 60 pg/g on

Day 1 (2h/day) Peak at 60 pg/g on

Day 1 (8h/day) 42.6

12.9 6.44 12.7
0.37 0.73 31.7

10.7 4.79 10.6 0.28 0.61Blood Chlorpyrifos (pg/g) 

### Blood Chlorpyrifos (pg/g)

10 hours After the Day 30 peak 24 hours After the Day 30 peak114 

# Distribution of CCCEH Blood Concentrations
Percentile Cord Blood Chlorpyrifos (pg/g) Maternal Blood Chlorpyrifos (pg/g) 1998- 1999 2001 1998- 1999 2001 25 < LOD < LOD 2.60 < LOD 50 3.78 < LOD 6.70 < LOD 75 8.80 < LOD 9.55 < LOD 90 12.1 2.45 16.0 2.44 95 15.1 2.58 19.4 2.61 < LOD = Less than Limit of Detection (0.5 and 1.0 pg/g)115 Last Day of 30 Day Simulation for Perimeter Carpet Exposure Scenario First Day of 30 Simulation for Perimeter Carpet Exposure Scenario 

## Residential Estimates Compared to CCCEH Blood Data

0 10 20 30 40 50 60 70

680 700 720 740 760 780Blood Chlorpyrifos (pg/g)

Time (hours) 63 pg/g 95 th -% ile, 19.4 pg/g 90th -% ile, 16.0 pg/g 7 5 th -% ile, 9.55 pg/g

0 200 400 600 800 1000 1200

0 10 20 30Blood Chlorpyrifos (pg/g)

Time (hours) 95 th -% ile, 19.4 pg/g 90th -% ile, 16.0 pg/g116 

## Residential Estimates Compared to CCCEH Blood Data

• The simulations, perimeter carpet exposure scenario and the 60 pg/g as the peak at Day 30, are very similar

• Maximum peak • Lowest peak (~60 pg/g) • 24 hour blood concentration following Day 1 peak • 10/24 hour blood levels after the final day peak exposure 0 200 400 600 800 1000 1200

0 200 400 600 800 1000Venous blood CPY (pg/g)

Time ( hr ) 60 pg/g Final Day Scenario Perimeter Use Scenario117 

## • The approaches used by EPA for estimation of drinking water, food, and residential exposures are supported by multiple SAPs • These exposure estimates make use of chemical - specific exposure and monitoring data, where available • The simulations of predicted chlorpyrifos blood concentrations for each exposure pathway were conducted using the robust, highly refined PBPK model • Integrating these approaches has allowed for predictions about the women in the CCCEH cohort 

# Summary118 

## • Chlorpyrifos blood concentrations predicted with the PBPK model are well within the range of levels reported in the CCCEH cohort

• The watershed protection plan and water processing virtually eliminates all chlorpyrifos drinking water exposure • Internal blood concentrations of chlorpyrifos from food exposures are consistent with the CCCEH blood levels post- cancellation • Higher levels of blood concentrations in 98 - 99 were likely from chlorpyrifos residential indoor usage 

# Conclusions119 

# QuestionsAnna Lowit, Ph.D. Senior Toxicologist, Health Effects Division Office of Pesticide Programs Environmental Protection Agency Lowit.anna@epa.gov 703 - 308 -4135 (work), 703 - 258 -4209 (cell) Presentation to the FIFRA SAP, April 19, 2016 

# Point of Departure, Intra -species Extrapolation, the FQPA 10X Safety Factor, and Case Studies

Internal, deliberative, not for distribution 120

# Point of Departure, Intra -species Extrapolation, & FQPA 10X Safety Factor

Internal, deliberative, not for distribution 121

### • From the 2012 SAP Report, pp. 49 - 50 (emphasis added ): • The Panel acknowledged the limitations in the three longitudinal children’s cohort studies of estimating chlorpyrifos exposures ( i.e. , the Columbia study, the Mt. Sinai study, and the CHAMACOS study), based on the exposure measures collected, and was in general agreement that the data from these studies alone were not sufficient to derive a point of departure (POD) for purposes of quantitative risk assessment. • New information has emerged from the analysis that reduces some of the uncertainty in the biomonitoring data. 

# Introduction

Internal, deliberative, not for distribution 122123 

### • Per the 2012 SAP report, the agency was urged to find ways to use the epidemiology studies, in particular the CCCEH study, to inform the chlorpyrifos assessment (emphasis added):

• “...if one assumes that cord blood measurements reflect exposure levels during the critical prenatal period for induction of neurodevelopmental effects, then in theory, these would be the ideal data from which to derive the POD for chlorpyrifos in humans” 

### • In doing so, the agency was encouraged to make use of the PBPK model to further characterize CCCEH dose estimates • “... a [PBPK] model could be used to further characterize the dose estimates in the epidemiology studies, for additional dose response analyses. Such a PBPK model will become even more important in the event that the agency might, at some point in the future, decide to move from using AChE inhibition to another outcome .” 

# Introduction

Internal, deliberative, not for distributionInternal, deliberative, not for distribution 124 • The dose - response point that marks the starting point for low- dose extrapolation. The POD may be a NOAEL/LOAEL, but ideally is established from BMD modeling of the experimental data, and generally corresponds to a selected estimated low- level of response. • Some form of extrapolation below the POD may be employed for estimating low- dose risk or the POD may be divided by a series of uncertainty factors to arrive at a reference dose (RfD). 

# Point of DepartureInternal, deliberative, not for distribution 125 

# Risk Metrics

MOE = Point of Departure Exposure Target MOE = Total Uncertainty Factors RfD = Point of Departure Uncertainty Factors126 • Dermal exposure to female worker to achieve 10% RBC AChE inhibition • External dose from exposure 8 hours/day, 5 day/week for 3 weeks • Blood concentration peaked at 120,000 pg/g • Blood concentration still above 100 pg/g at 32 days after the last exposure. • Food exposure for adult females: once daily exposure, steady state to achieve 10% RBC AChE inhibition

• Blood concentration approximately 7000 pg/g at the daily peaks . • Blood concentration never goes below 100 pg/g over the continuous 21 - day exposure simulation • Arnold et al. (2015 ) recently Concentrations of chlorpyrifos in blood associated with the predicted RBC AChE inhibition of less than or equal to 10% ranged from 6100 to 64000 pg/g (5 th to 95 th percentile). 

# PoDs from 2014 HHRA: 10% RBC AChE Inhibition

Internal, deliberative, not for distribution127 

### • Option 1: Lower limit of the top tertile (>6.17 pg/g cord blood) derived from Rauh et al. (2006).

• Includes 254 children followed through age 3 years and used a dichotomized statistical approach of ≤6.17 pg/g cord blood for the ‘low group’ and >6.17 pg/g cord blood as the ‘high’ group. • Statistically significant deficits of 6.5 points on the Bayley Psychomotor Development Index (PDI) at 3 years of age when comparing high to low exposure groups. • Increased odds of mental delay (OR=2.4; 95% CI: 1.1–5.1) and psychomotor delay (OR=4.9; 95% CI: 1.8– 13.7) at age 3 years when comparing high to low exposure groups. 

# Options for Point of Departure

Internal, deliberative, not for distribution128 

### • Option 1: Lower limit of the top tertile (>6.17 pg/g cord blood) derived from Rauh et al. (2006), cont’d.

• Large odds ratios for attention disorders (OR=11.26; 95% CI: 1.79–70.99), ADHD (OR=6.50; 95% CI: 1.09–38.69), and PDD (OR=5.39; 95% CI: 1.21–24.11) at age 3 years when comparing high to low chlorpyrifos exposure groups. • If the agency pursued this study for deriving a PoD, the appropriate value would be 6.17 pg/g cord blood. 

# Options for Point of Departure

Internal, deliberative, not for distribution129 • Option 2: Benchmark Dose estimates derived from linear regression reported in Rauh et al. (2011) for deficits in Working Memory.

• Evaluated the relationship between prenatal chlorpyrifos exposure and neurodevelopment among 265 of the CCCEH cohort participants who had reached the age of 7 years and had a complete set of data. • Described the log of Working Memory Index (WMI) of children as linearly associated with concentration of chlorpyrifos (CPF) in cord blood with a slope = - 0.006 (95% CI = - 0.01, - 0.002). • Each standard deviation increase in exposure (4.61 pg/g) there is a 1.4% reduction in Full - Scale IQ and a 2.8% reduction in Working Memory. • The concentration levels of chlorpyrifos in cord blood (and its 95% lower confidence limit, one - sided) can be estimated using the estimated slope and its 95% lower confidence limit (one - sided). 

# Options for Point of Departure

Internal, deliberative, not for distributionInternal, deliberative, not for distribution 130 Percent Reduction of WMI (%) Estimated concentration of CPF in cord blood c (pg/g): BMD BMDL 95 % lower limit (one - sided) of estimated concentration of CPF in cord blood (pg/g) 1 1.68 1.07 2 3.37 2.16 3 5.08 3.26 4 6.80 4.36 5 8.55 5.48 • At the 1 % change: BMDL values are close to the LODs of 0.5/1.0 pg/g for measuring chlorpyrifos residues in cord blood & thus have more uncertainty • At 3 - 5% change, concentrations are near or above the 6.17 pg/g which represents the lower limit of the top tertile where neurodevelopmental outcomes have been associated with chlorpyrifos exposure ( Rauh et al. , 2006, 2015 ) & thus may not be protective. • Therefore a 2% working memory reduction which corresponds to an internal dose measure of 2.16 pg/g chlorpyrifos in cord blood is proposed for use as POD.

• Quantitatively near the value reported by Rauh (2.8% reduction in working memory) • Within the range of levels measured in the blood samples collected by CCCEH. 

### Option 2: Benchmark Dose estimates derived from linear regression reported in Rauh et al. (2011) for deficits in Working Memory.131 • In typical risk assessments, PoDs are derived directly from laboratory animal studies and inter- and intra - species extrapolation is accomplished by the use of 10X factors. • The proposed PoDs are derived from human information obviating the need for the inter- species extrapolation. • The intra - species uncertainty factor (UF H ): • to account for variations in susceptibility within the human population (human variability) • and the possibility (given a lack of relevant data) that the database available is not representative of the dose/exposure response - relationship in the groups of the human population that are most sensitive to the health hazards of the chemical being assessed. • p harmacodynamics & pharmacokinetics can be considered separately. 

# Intra -Species Extrapolation

Internal, deliberative, not for distributionInternal, deliberative, not for distribution 132 

### • Some form of extrapolation below the POD may be employed for estimating lowdose risk or the POD may be divided by a series of uncertainty factors to arrive at a reference dose (RfD). 

# Intra -Species Extrapolation133 Pharmacodynamics (PD): • AOP(s) for neurodevelopmental outcomes related to chlorpyrifos exposure are not known, although there are many potential pathways suggested in the literature. By extension, the window(s) of susceptibility and associated duration(s) of exposure are not known. • CCCEH cohort: self- identified as African -American or Dominican, were 18–35 years of age, and who lived in specific urban areas (northern Manhattan (Central Harlem or Washington Heights/Inwood) or the South Bronx) for a year or more prior to pregnancy. This study population was of generally low socioeconomic status, with approximately 85% of the population having annual incomes of $30,000 or less. • Do not have adequate data to assess the relative sensitivity of CCCEH cohort compared with other groups. • Given the current state of knowledge, the PD variability cannot be quantified and is therefore unknown. The default 3X is retained. 

# Intra -Species Extrapolation

Internal, deliberative, not for distribution134 

### Pharmacokinetics (PK): • There is a robust PBPK model which accounts for population variability for infants, but a fully vetted, validated PBPK model is not available for pregnant women. • For PK variation, a data - derived factor cannot be derived and the default 3X is retained. Total Intra-species Factor: • Proposed to use a 10X intra - species extrapolation factor: 3X for PK variability and 3X for PD variability • Consistent with that used for methyl mercury. 

# Intra -Species Extrapolation

Internal, deliberative, not for distribution135 • The FQPA (1996) instructs EPA, in making its “reasonable certainty of no harm” finding, that in “the case of threshold effects, an additional tenfold margin of safety for the pesticide chemical residue and other sources of exposure shall be applied for infants and children to take into account potential pre - and postnatal toxicity and completeness of data with respect to exposure and toxicity to infants and children .” • Section 408 (b)(2)(C) further states that “the Administrator may use a different margin of safety for the pesticide chemical residue only if, on the basis of reliable data, such margin will be safe for infants and children.” • Note: The magnitude of the FQPA Safety Factor is a policy decision made by the agency. • The science underlying the policy decision is included in Charge Questions 6b & 6c. 

# FQPA 10X Safety Factor

Internal, deliberative, not for distribution

# Pre- and Post- Natal Toxicity Database

• Experimental Laboratory Animals : • There are numerous animal studies (rats and mice) in the literature that report changes in aspects of neurobehavioral function from adolescence to adulthood following developmental exposure.

• Adverse outcomes in several neurological domains including cognitive, anxiety and emotion, social interactions, and neuromotor function 

### • Extensive differences in study designs hinder comparability across studies

• Species; age, gender; exposure levels, timing, and route; test methods, equipment; procedures, endpoints; analyses, interpretations

# Pre- and Post- Natal Toxicity Database
• Studies involve early and/or late gestational and/or early and/or late postnatal dosing

• Timing of nervous system development not directly comparable across species. • Although, early postnatal periods in rodents generally correspond to last trimester in human development but later post- natal studies correspond more closely to early human infant. • No clear evidence of critical period of exposure: some neurobehavioral outcomes observed across all windows of exposure, others not. • Systematic comparisons across exposures, doses, and tests are lacking.138 

### • Epidemiology, pre - natal : • Numerous epidemiological investigations have observed a link between pre - natal exposure to chlorpyrifos or OPs (measured as chlorpyrifos, TCPy, or DAPs) and adverse effects on neurodevelopment through age 7 years, with additional more limited evidence up through approximately age 11. • Results across numerous studies show relatively consistent elevated risks associated with OP exposure:

• Autism spectrum disorders, intelligence decrements, attentional problems and ADHD, neurological effects near birth, and mental/ psychomotor delays (6 months - 11 years). • Results not always consistent with magnitude of association and ages where associations observed across studies. 

# Pre- and Post- Natal Toxicity Database

Internal, deliberative, not for distribution139 • Epidemiology, post- natal: • Smaller number of studies have assessed postnatal exposure to OPs (measured as DAPs ) • Postnatal exposure assessed in the CHAMACOS cohort ( Eskenazi et al., 2007; Young et al., 2005; Bouchard et al., 2011) and 3 cross - sectional studies ( Guodong et al., 2012; Bouchard et al., 2010; Oulhote and Bouchard, 2013 ) • Postnatal exposures not assessed in the CCCEH and Mt. Sinai studies ( Rauh et al., 2011; Engel et al., 2011)

• Given that the major source of exposure (residential use) was cancelled partway through the CCCEH study, this limits the ability of this study to inform the impacts of long -term postnatal exposure to chlorpyrifos • Bouchard et al. (2010) looked at U.S. children age 8– 15 years in the 2000–2004 National Health and Nutrition Examination Survey (NHANES), and observed a positive association between attention and behavior problems and DAPs

• No other neurodevelopmental associations were found between postnatal biomarkers 

# Prenatal vs. Postnatal Exposure140 

## • In sum, given that the extensive experimental laboratory animal database suggests that the post - natal period may be a potential susceptible time, the lack of postnatal exposure assessment in the CCCEH and Mt. Sinai studies is a source of uncertainty in the epidemiology database. 

# Pre- and Post- Natal Toxicity Database

Internal, deliberative, not for distribution141 • In the 2012 SAP report, the Panel noted the CCCEH studies had: • “Relatively modest sample sizes which limited the statistical power to classify some meaningful differences as statistically significant and to examine the effect of modification by race/ethnicity and other characteristics.” • “Relatively moderate to large exposure differences needed to see significant effects, likely due to the modest sample sizes used.” • The modest sample size in the CCCEH study makes it difficult to say that the dose - response relationship between chlorpyrifos and neurodevelopmental outcomes in the overall U.S. population has been fully characterized. • The magnitude of the PoD in the general U.S. population of infants and children may be higher or lower than that estimated using the CCCEH study results, and the shape of the dose - response curve may also be different. 

# Impact of Sample Size on CCCEH Findings

Internal, deliberative, not for distribution142 • There are remaining uncertainties surrounding • the lack of information on post- natal exposure and evaluation of such exposure to neurodevelopmental outcomes in the CCCEH and Mt. Sinai cohorts • the modest sample sizes which limited the statistical power and exposure differences required to see statistically significant results. • As such, there is sufficient uncertainty which prevents the agency from reducing or removing the statutory 10X FQPA Safety Factor. • EPA therefore intends to continue to retain the FQPA 10X Safety Factor for assessing risk from chlorpyrifos for infants, children, youths, and women of childbearing age for all exposure scenarios.

• Note: The magnitude of the FQPA Safety Factor is a policy decision made by the agency. 

# FQPA 10X Safety Factor

Internal, deliberative, not for distribution143 

### • Charge question 5a - c: Derivation of POD • 5a: Change from AChE inhibition based POD to neurodevelopmental outcomes • 5b: POD options • 5c: Calculation approach to deriving POD from Rauh et al (2011) • Charge question 6a - c • 6a: Proposal to retain 10X Intraspecies Extrapolation Factor • 6b - c: Science that underlies the policy to retain the FQPA 10X Safety Factor 

# Issues for Panel Discussion

Internal, deliberative, not for distribution

# Case Studies: Linking Exposure Assessment with PBPK Modeling to Derive Predicted Internal Doses

Internal, deliberative, not for distribution 144145 

## • EPA will need re - assess exposure from food, water, occupational scenarios along with other remaining uses with the new POD. • Case studies developed to illustrate how the PBPK model would be used to predict internal doses from existing exposures to chlorpyrifos.

• Exposure approaches have been previously reviewed by SAP and have used extensively in risk assessments. 

# Risk Assessment of Pesticides

Internal, deliberative, not for distribution146 

## • Proposed an internal concentration PoD of 2.16 pg/g adjusted by 10X based on the intra - species factor and 10X FQPA Safety Factor. • For assessing dietary (food & water): Internal concentration RfD is 0.022 pg/g. • For residential, occupational exposure assessment which uses MOE as the risk metric, the internal PoD of 2.16 pg/g will be used with a target MOE of 100. 

# Conducting a Risk Assessment Using Internal Dose as the POD

Internal, deliberative, not for distribution147 

### • PK profile for chlorpyrifos in blood is characterized by rapid increases and decreases during exposure periods and immediately after exposure, followed by slower decrease during the terminal clearance phase. • The CCCEH cord blood data are likely to represent data from the low points on the PK profile and likely in terminal clearance phase. • The agency will, to the extent possible, compare internal concentrations of chlorpyrifos at 10 and 24 hours after the last peak in each simulation, specifically for food exposure and occupational/residential exposure scenarios. 

# Conducting a Risk Assessment Using Internal Dose as the POD

Internal, deliberative, not for distributionInternal, deliberative, not for distribution 148 

# Time Course of Blood Concentrations Biphasic Clearance Time Conc (pg/g) Peak on the 30th day 62.7 4 hours after the last peak 22.5 8 hours after the last peak 14.3 20 hours after the last peak 11.0 2 days after the last peak 9.6 Rapid decrease immediately after exposure, half- life ~3 to 4 hours Gradual decrease several hours after exposure, half- life ~120 hours

Compare internal concentrations of chlorpyrifos at 10 and 24 hours after the last peak in each simulation, specifically for food exposure and occupational/residential exposure scenarios.• For CCCEH cohort, chlorpyrifos was measured in umbilical cord blood collected close to delivery & in mothers up to 2 days after delivery. • Reported time for labor and delivery for the first pregnancy range from 8 to 20 hours (early labor phase 6 - 12 hours, active labor phase 4- 8 hours), and may become faster for subsequent pregnancies. • Time between last exposure and biomarker sampling can be estimated. Internal, deliberative, not for distribution 149



## Biomarker Sampling Time – Considering Labor & Delivery150 Percentile of Exposure Food Exposure from Calendex Max Blood Levels of CPFOS (pg/g) 10 hour Blood Levels Post Exposure Values of CPFOS (pg/g) 24 hour Blood Levels Post Exposure Values of CPFOS (pg/g) 10 0.003 ug/kg/day 0.29 0.060 0.021 50 0.007 ug/kg/day 0.67 0.139 0.048 70 0.009 ug/kg/day 0.86 0.179 0.062 95 0.018 ug/kg/day 1.71 0.358 0.124 99 0.029 ug/kg/day 2.76 0.576 0.200 99.9 0.075 ug/kg/day 7.14 1.490 0.517 

# Food Exposure: Results PBPK ModelingInternal, deliberative, not for distribution 151 Last Day of Dietary Exposure to Adult Female at 99.9 th - ile for 40 consecutive days Dietary Exposure to Adult Female at 99.9 th ile for 40 consecutive days 

## Example Food Scenario: Adult Female at the 99.9th

## - ile

0 1 2 3 4 5 6 7 8

970 975 980 985 990 995 1000 1005 1010Blood (pg/g)

Time (hours) 10 hours post- peak 24 hours post- peak

0 1 2 3 4 5 6 7 80316293124155186217248279310341372403434465496527558589620651682713744775806837868899930961992Blood (pg/g)

Time (hours)-0.05 0 0.05

0.1 0.15

0.2 0.25

0.3 0.35

0 200 400 600 800 1000Blood (pg/g)

Time (hours) Internal, deliberative, not for distribution 152 Last Day of Dietary Exposure to Adult Female at 10th - ile for 40 consecutive days Dietary Exposure to Adult Female at 10th - ile for 40 consecutive days 

## Example Food Scenario: Adult Female at the 10th

## - ile

0 0.05

0.1 0.15

0.2 0.25

0.3 0.35

970 975 980 985 990 995 1000 1005 1010Blood (pg/g)

Time (hours) 10 hours postpeak 24 hours postpeak153 

## • The agency evaluated all potential occupational exposure scenarios as part of the 2014 HHRA. • ‘Low ’ occupational scenarios were provided in the issue paper for purpose of illustrating how occupational handler exposures and PBPK modeling can be integrated. 

# Example Worker Scenarios

Internal, deliberative, not for distributionInternal, deliberative, not for distribution 154 Last day of exposure resulting from the occupational handler exposure scenario, mixing/loading liquids (EC) for cole crops at 1 lb ai/A. Full profile resulting from the occupational handler exposure scenario, mixing/loading liquids (EC) for cole crops at 1 lb ai/A.

0 50 100 150 200 250 300 350

261 265 269 273 277 281 285 289 293 297 301 305 309 313 317 321 325 329 333 337 341 345 349Blood (pg/g)

Time (hours) 10 hours post- peak 24 hours post- peak

0 50 100 150 200 250 300 350013263952657891104117130143156169182195208221234247260273286299312325338Blood (pg/g)

Time (hours) 

# Example Worker Scenario: Cole Crop, Handler155 

### • Drinking water treatment methods have varying degree of chlorpyrifos removal. • Depending on the treatment method used by a given community water system exposure may be to chlorpyrifos or chlorpyrifos - oxon or a combination. 

# Drinking Water Exposure Potential

Internal, deliberative, not for distribution Treatment Method aChlorineChloraminesChlorinedioxidePotassiumpermanganateUltraviolet lightHydrogenPeroxideOzoneSoftening
pH 6.6 pH 8.6 pH 6.6 pH 8.6 pH 6.6 pH 8.6 pH 6.6 pH 8.6 pH 6.6 pH 8.6 pH 6.6 pH 8.6 pH 6.6 pH 8.6 pH 12 Percent Reduction b 90.3 85.7 8.7 9.2 34.3 27.5 15.3 5.2 14.5 1.9 7.6 3.1 60.9 30.3 100.0 a. Experimental time was representative of typical drinking water treatment conditionInternal, deliberative, not for distribution 156 

### Measured Concentrations ( Orestimba Creek, California) 

### Estimated Concentrations (lower bound scenario 1 lb a.i./ac./year)

• 120 day subset used for PBPK modeling 

# Drinking Water Exposure ScenariosInternal, deliberative, not for distribution 157 Input: Measured Concentrations Input: Estimated Concentrations 

# Females of Childbearing Age (13 -49 years old)

The PBPK model was used to predict the time course of chlorpyrifos concentrations in venous blood • Adult female weight 72.9 kg (160.7 lbs .); consumption 4x/d for total of 1.71062 L (57.8 oz )

During the maximum 4 month period: • [peak blood]: 6.24 pg/g During the maximum 4 month period: • [peak blood]: 1.97 pg/gInternal, deliberative, not for distribution 158 Input: Measured Concentrations Input: Estimated Concentrations 

# Infants: Formula Fed (with water)

The PBPK model was used to predict the time course of chlorpyrifos concentrations in venous blood • Infant fixed weight 4.8 kg (10.6 lbs .); consumption 6x/d for total of 0.688557 L (23.3 oz )

During the maximum 4 month period: • [peak blood]: 20.66 pg/g During the maximum 4 month period: • [peak blood]: 6.24 pg/g159 

## • Linking Exposure Assessment with PBPK Modeling to Derive Predicted Internal Doses: • Charge question 7. 

# Case Studies

Internal, deliberative, not for distribution

### • From the 2012 SAP Report, pp. 49 - 50 (emphasis added ): • The Panel acknowledged the limitations in the three longitudinal children’s cohort studies of estimating chlorpyrifos exposures ( i.e. , the Columbia study, the Mt. Sinai study, and the CHAMACOS study), based on the exposure measures collected, and was in general agreement that the data from these studies alone were not sufficient to derive a point of departure (POD) for purposes of quantitative risk assessment. • New information has emerged from the analysis that reduces some of the uncertainty in the biomonitoring data. 

# Summary

Internal, deliberative, not for distribution 160161 • Although in 2012, the SAP identified uncertainties precluding the use of the biomonitoring data for POD derivation, the SAP did recommend the agency find ways to use the epidemiology studies, in particular the CCCEH study, to inform the chlorpyrifos assessment (emphasis added):

• “...if one assumes that cord blood measurements reflect exposure levels during the critical prenatal period for induction of neurodevelopmental effects, then in theory, these would be the ideal data from which to derive the POD for chlorpyrifos in humans” • In doing so, the agency was encouraged to make use of the PBPK model to further characterize CCCEH dose estimates

• “... a [PBPK] model could be used to further characterize the dose estimates in the epidemiology studies, for additional dose response analyses. Such a PBPK model will become even more important in the event that the agency might, at some point in the future, decide to move from using AChE inhibition to another outcome.” 

# Summary

Internal, deliberative, not for distributionUncertainty Identified by the FIFRA SAP (2012, p. 48) Section Where Considered Comment Relatively modest sample sizes which limited the statistical power to classify some meaningful differences as statistically significant and to examine the effect of modification by race/ethnicity and other characteristics. 8.2. FQPA 10X Safety Factor for Infants & Children These points increase the uncertainty that the PoD based on the CCCEH cord blood data are not fully representative and have been used as support to retain the FQPA 10X Safety Factor. Relatively moderate to large exposure differences needed to see significant effects, likely due to the modest sample sizes used. Exposure at one point in prenatal time with no additional information regarding postnatal exposures. 162Uncertainty Identified by the FIFRA SAP (2012, p. 48) Section Where Considered Comment

Lack of clarity regarding a linear dose response instead of a potential threshold effect. 7.2 Options for PoD Based on the CCCEH Biomonitoring Data This remains an uncertainty since CCCEH investigators have not released the raw data publicly. However, given the modest sample size and that the voluntary cancellation occurred in 2000, the data may not support a different empirical model ( i.e , non - linear model). This point adds support to the selection of the 2% change in working memory as this value is within the measured data (albeit at the low end). 163164 Uncertainty Identified by the FIFRA SAP (2012, p. 48) Section Where Considered Comment Use of a single or average sample for exposure. Although Whyatt et al. (2009) noted moderate but significant correlations between meconium and cord and maternal blood and average urine TCPy, the representativeness of a single point exposure is still unclear. Time -varying exposures or the ability to define cumulative exposures would be preferable. 6.3 Residential Exposure to the CCCEH Cohort 7.1 Uncertainties with Using Biomarker for the PoD The agency notes similar uncertainties in Section 7.1. The agency has developed an analysis of the range of possible exposures to the CCCEH cohort. This analysis uses the best available information on pesticide use and chlorpyrifos applications from 1998 - 2004, including Whyatt et al (2003) which indicates that pesticide applications occurred approximately monthly. The agency’s predicted blood concentrations closely match those reported by CCCEH. Lack of specificity of a critical window of effect and the potential for misclassification of individual exposure measures. 164165 Uncertainty Identified by the FIFRA SAP (2012, p. 48) Section Where Considered Comment External generalizability of the cohorts given their unique racial/ethnic and socioeconomic characteristics. However, it should be noted that their exposures were within the range of those seen in NHANES. 8.1. Intra - species Extrapolation The agency concurs there are remaining uncertainties about the degree to which the CCCEH is more or less sensitive to other population groups. Thus, this issue is part of the rationale for retaining the 10X intra - species factor.

165166 Uncertainty Identified by the FIFRA SAP (2012, p. 48) Section Where Considered Comment Questions about biologic plausibility due to lack of clarity on mechanism of action, particularly at the low exposure levels seen in the cohorts and the limited and mixed results of animal studies showing neurodevelopmental effects. Appendix 3.0 (3.1.1, 3.1.2, 3.2) Background & Summary of Experimental and Epidemiology Studies on Neurodevelopmental Effects 6.3 Residential Exposure to the CCCEH Cohort The agency agrees that the AOP/MOA for neurodevelopmental outcomes are not known. The agency has conducted a systematic review of the laboratory animal literature. There is qualitative similarity with respect to the three major neurodevelopmental domains (specifically, cognition, motor control, and social behavior) between the laboratory animal studies and the epidemiology findings. The CCCEH exposure characterization analysis provides plausibility to the low blood levels. 166167 

## • Characterized predicted exposures to women in the CCCEH prior to giving birth. • Proposed approach for using the CCCEH cord blood data to derive a PoD for use in quantitative risk assessment. • Proposes an innovative approach to using the PBPK model to integrate external and internal dose from food, water, and occupational exposure assessment. 

# Summary

Internal, deliberative, not for distribution

## QUESTIONS?

168