EPA's Records Disposition Schedule PEST 361 Scientific Data Reviews HED Records Center- File R180234- Page 1 of 73



### UNITED STATES ENVIRONMENTALPROTECTION AGENCY WASHINGTON, D.C. 20460

OFFICE OF PREVENTION, PESTICIDES OPP OFFICIAL RECOiiD AND TOXIC SUBSTANCES HEALTH EFFECTS DIVISiON SCIENTIFIC 0;\Ti\**I~EVIEWS** EPA SERIES 361 

### MEMORANDUM
Date: January7, 2010
SUBJECT: Chlorpyrifos: Reviews ofthe Coulston (1972), (Nolan (1982) and Kisicki (1999) studies with human volunteers includingcomments from the Human Studies Review Board (HSRB) meeting (June 2009).
PC Code: 059101 Decision No.: N/A Petition No.: N/A RiskAssessmentType: N/A TXRNo.: 0050308 DPBarcode: 0368390 Registration No.: N/A Regulatory Action: N/A Case No.: N/A CAS No.: 63-42-3 40CFR: N/A MRID No.: Coulston study: 00095175, Nolan Study: 00124144, Kisicki study: 44811002, 45144101, 47436401, 47436401, 47866701 and 47866703.

FROM:
And

THROUGH:

And

TO: John Doherty

# \.Q.\~ Risk

# Assessme~;~ Abdallah Khasawinah ./')'

# ~ Risk Assessment Branch IV Health Effects Division 7509P
JackArthur

# Au/~ Acting Branch chir""

. Risk Assessment**Bran~7 ~**  

### Ray Kent

# {---:J

# ·~**BranchCh~** Risk Assessment Branch IV Health Effects Division 7509P Veronique LaCapra Pesticide Re-evaluation Division 7507P

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### I. CONCLUSIONS
The updatedreviews ofthe Coulston (1972) and Nolan (1982) studies and original review of the Kisicki (1999) studies withchlorpyrifos inhumanvolunteers are attached. The Nolan and Kisicki studies were presentedto the Human Studies Review Board (HSRB) at a meeting held on June 24-25, 2009 (final report October 26, 2009). The HSRB comments onthe ethical aspects of these studies will be addressed separately by the Office ofPesticide Programshuman studies ethicsreviewteam. This memo addresses the scientific aspects ofthese studies.


### HED conclusions for each study are as follows:


### Coulston Study (1972). 

### (The HSRB didnotreview this study). No treatment-related effects were found on measured urinalysis, hematology, orclinical chemistryparameters except for depressed plasma cholinesterase (ChE) activity in subjects receiving the test material. Based on an-30% decrease in plasma cholinesterase activity byDay 16, the LOAEL for Dowco 179 was 0.03 mg/kg bw/day. The correspondingNOAEL was 0.014 mg/kg bw/day. Erythrocyte acetylcholinesterase activity was not affected at any ofthe doses. Althoughthis study is informative, it is deficientin many aspects (incomplete details ofthe methodology)that make its usefulness inhumanrisk assessments very limited. The study DERis attached.


### Nolan Study (1982). 

### The HSRB had no adverse comments onthe Nolan study. This study was a single dose (0.5 mg/kg) studythat demonstrated inhibition ofplasma ChE (up to 89%) following an oral dose. There was no consistent inhibition ofplasma ChE following a dermal dose of5 mg/kg. RBC AChE was determined not to be inhibited following eitherthe oral or dermal dosing. Analysis ofthe urine indicated that anestimated 72 ± 

### II% ofthe ingested dose and 0.95 ± 

### 0.559% ofthe dermal dose were absorbed. The study is consideredto be informative with respect to inhibition ofplasmaChE following oral administration and to have useful informationregarding pharmacokinetics following both oral and dermal administration.
Kisicki

### Study (1999). 

### The HSRB expressed concerns for the Kisicki study regarding the statistical procedures used for evaluatingthe intergroup RBC AChE data andthe method for determining the blood and urinary levels ofTCP (the principal metabolite ofchlorpyrifos). HealthEffects Division (HED) acknowledges the comments onthe statistical procedures and should the data for RBC AChE from the Kisicki studybe used for regulatory purposes, HED will reconsider conducting independent statisticalreanalysis. In its evaluation ofthe RBC AChE data, HED relied onthe individual response relative to the personspredosing background values. Only one personwas determined to demonstrate a pattern for meeting inhibition criteria with respect to time ofonset, duration and degree ofdifferences relative to theirpredosing value. Thus, HED has notrelied onthe group differences for determining the inhibition inthis study.
Inresponse to the HSRB's concernregarding the procedures used for preparationTCP for analysis, the DOW AgroSciences Company provided additional details related to the methodology inthe preparationthat clearly demonstrated that the appropriate acid hydrolysis step was includedto assure that total (free and conjugated) TCP was determined inboth the blood and the urine.

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The single dose Kisicki study demonstrated definite inhibition ononly one individual inthe high (2 mg/kg) dose group thus establishing a NOAEL of 1mg/kg. The study was determined to have a deficiency inthat plasma ChE assessment was not included. This confounded comparisonwiththe Nolan study.
The analysis ofthe blood andurine for TCP demonstrated only about 35% ofthe administered dose was absorbed by the gastro-intestinal tract. This is abouthalfofthe value of about 70% demonstrated in the Nolan study. The DOWAgroSciences Companyprovided (2009, MRID # 44811002) a rationale that supports the theory that this difference is due to the differences in the waythe chlorpyrifos was administered ineach study. In theNolan study, the chlorpyrifos was first dissolved in solvent, placed ontop ofa lactose pill which was swallowed bythe volunteers. In the Kisicki study, crystalline chlorpyrifos wasplaced in a capsule containing lactose andthe capsule swallowed. The difference incapsule vs. pill plus physical nature ofthe crystals due to dissolving in solvent inthe Nolan studymay bethe basis for the difference in absorptionrate. The lower rate ofabsorption inthe Kisicki study will be taken into consideration shouldthis study be used for pharmacokinetic modeling. Copies ofthe DERs for these studies are attached. Table I belowpresentsthe Executive Summaries for thesetwo studies.



### IV. RESULTSIDISCUSSION (orMRID SummaryTable, etc.)
MRIDSummary a e T bl E I 

### xample Study Type MRID Executive Summary Special Non-Guideline 00095175 In an oral multiple dose study (MRID 00095175), groups offour healthy adult male prisoners Study- human received 0.0, 0.0 14, 0.03, or 0.1 mg/kg bw/day Dowco 179 (purity, stability, and lot number not volunteers, Coulston et provided) for 48, 27, 20, and nine days, respectively. No treatment-related effects were found al, (1972). on measured urinalysis, hematology, or clinical chemistry parameters except for depressed plasma cholinesterase (ChE) activity in subjects receivingthe test material.
Plasma cholinesterase activity was reduced 46% by Day 6 in subjects treated with 0.10 mg Dowco 179/kgbw/day, which further decreased to 66% by Day 9. Dosing was stopped for the 0.1 mglkg bw/day group on Day 9 as plasma ChE activity was decreased >20% for all individuals in the dose group. In the 0.03 mg Dowco 179/kgbw/day group, plasma ChE activity was decreased 32%by Day 16 and remained decreased -30%through Day 20 when treatment was stopped. No significanttreatment-related effect on ChE activity was found in subjects ofthe 0.014 mg/kg bw/day group. Recovery ofplasma ChE activity in subjects treated with 0.1 mg/kg bw/day was observed by Day 25 and byDay 21 in subjects ofthe 0.03 mglkgbw/day group after cessation ofdosing. Erythrocyte acetylcholienesterase activity was not affected at any ofthe doses.
Based on an -30% decrease in plasma cholinesterase activity by Day 16, theLOAEL for Dowco 179 was 0.03 mg/kg bw/day. The correspondingNOAEL was 0.014 mg/kg bw/day. Classification. This study is classified as Unacceptable/Non-Guideline. Although the study contains some useful data that describes the potential for chlorpyrifos to inhibit plasmaChE in

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Study Type MRID

Special Non-Guideline 00124144 Study -human volunteers. Nolan et al, 1982)

Special Non-Guideline Study- human volunteers. Kisicki et al, 1999) 44811002 45144101, 47436401, 47436401, 47866701 and 47866703 Executive Summary humanvolunteers, there are several deficiencies 

### (incomplete details ofthe methodology) that preclude using the data for endpoint selection for risk assessment orfor informingthe uncertainty factors. The study has not been reviewed for either ethics or scientific considerations by the EPA Human Studies Review Board. In a single-dose human oral/dermal toxicity study with chlorpyrifos (1982, MRID 00124144), six male volunteers were given 0.5 mglkg chlorpyrifos (99.8% a.i., LotNo. AGR 166043) on a !acto tablet. Plasma and RBC cholinesterase activity were monitored at 2, 6, 12, 24 hours, and 2, 3, 4, 14, 22, 27, and 30 days post-dose. Approximately four weeks afterthe oral treatment, a single dermal dose (5 mg/kgto five subjects; 0.5 mglkgto one subject) was administered on the volar surface ofthe forearm. RBC and plasma cholinesterase activity were determined 2, 6, and 12 ho and on days I, 2, 3, 4, 6, 8, and 9 following dermal treatment. Blood and urine samples were analyzed for chlorpyrifos and 3,5,6-TCP (3,5,6-trichloro-2-pyridinol) concentrations.
No clinical signs oftoxicity and essentially no significant inhibition ofRBC cholinesterase activi were observed following eitherthe oral or dermal dose. Plasma cholinesterase activity was inhibited 83-89%relative to pre-dose activities following the oral dose (peak inhibition within 6-24 hours post dose) but was essentially unchanged following the dermal dose. Blood chlorpyrifos concentrations were low (<30 ng/mL; limit ofdetection 5 ng/mL), and chlorpyrifos was not found in the urine following either route ofexposure. 3,5,6-TCPblood concentrations peakedby six hours after oral exposure and 24 hours after dermal application. 3,5,6-TCP was cleared from the blood and eliminated in the urine with a half-life of27hours following both the oral and dermal doses. Using assumptions offirst-order absorption and elimination equations, it was estimated that 72 ±II% ofthe ingested dose and 0.95 ± 0.559% ofthe dermal dose were absorbed. Classification: This studied is classified asAcceptable/Non-Guideline and to contain useful information onthe potential for chlorpyrifos to inhibitplasma ChE in humans as well as pharmacokinetic data following oral and dermal administration. The pharmacokinetic data provide data useful for estimatingthe dermal absorption factor, The study, however, should not be used for

**en~:Ipoint** selection or for informingthe uncertainty factors for risk assessment. In a special acute oral study (1999, MR!Ds: 44811002,45144101,47436401,47436401, 47866701 and 47866703) performed to assess effects onhuman red blood cell (RBC) acetylcholinesterase (AChE), chlorpyrifos (99.8%; Lot#MM930503-17) in a gelatin capsule was administered to 6 human subjects/sex/dose group at dose levels ofO (lactose-filled capsule), 0.5 or 1.0 mg/kg (Phase !). When it was determinedthat there was no inhibition and no adverse reactions in these subjects, a secondphase of6 human subjects/sex/group were dosed similarly as control and 2.0 mglkg chlorpyrifos. The subjects vital signs (blood pressure, pulse, respiration and temperature were evaluated the morning priorto dosing and at 1, 2, 4, 8, 12, 24, 48 and 168 hours post dosing. In addition hematology, clinical chemistry and urinalysis assessments were performed one week post dose.
Blood was assessed at-10 hours, zero (pre-dose), and at 2, 4, 8, 12, 24, 36, 48, 72, 96, 144 and 168 hours post dose for RBC AChE activity. Plasma cholinesterase (ChE) was not assessed Blood and urine were collected at selected intervals and analyzed for chlorpyrifos, chlorpyrifos axon, and the principal metabolite 3,5,6-trichloro-2-pyridinol (TCP) to define the pharmacokinetics ofchlorpyrifos in humans. The paraoxonase (PONI) status was determined for each subject. Serum paraoxonase activity was measured against chlorpyrifos axon, paraoxon, and diazoxon, and called chlorpyrifos oxonase (CPOase), paraoxonase, or diazoxonase, respectively (MRID# 45144101). Additionally, the PONphenotype (i.e. QQ, OR and RR) was determined for each subject. SystemicEffects. There were no apparent clinical reactions or changes in clinical chemistry parametersrelatedto treatment.
PharmacokineticData. Chlorpyrifos was detected in the serum of4 ofthe 12 subjects (2-8

Page 4 of5

'IEPA's Records Disposition Schedule PEST 361 Scientific Data Reviews HED Records Center- File R180234- Page 5 of 73

Study Type MRID Executive Summary hours post dose) in thel.O mg/kg dose (range of 1.1-5.6 ng/g) and in 4 ofthe 12 subjects (2-12 hours postdose) in the 2.0 mg/kg dose (range 1.3-18 ng/g). TCP was detected in the blood of all subjects through 120 hours (0.5 and 1.0 mg/kg) and through 168 hours (2.0 mg/kg). The highest concentration ofTCP reached ranged from 110-380 ng/g (0.5 mg/kg), 140-610 ng/g (1.0 mg/kg), and 370-1600 ng/g (2.0 mglkg). Chlorpyrifos and chlorpyrifos oxon were not found in the urine at any dose level, and chlorpyrifos oxon was not found in the blood ofany subject. Subject#56 (QQ phenotype) the only subject demonstrating RBC AChE inhibition had a peakblood concentration of 18 ng/gm chlorpyrifos at 8hours following a 2 mg/kg dose, but withdrew from the study after 48 hours for a personal problem. This same subjecthad the highest levels ofserum (6671 ng/gm) and urinary (22.8 mg) TCP accumulated up to 48 hours. The serum chlorpyrifos and serum and urinary TCP data all suggested that this subject absorbed
more ofher dose than the other subjects on the study. CPOase for this subjectwas similarto the other subjects with the phenotype QQ.
RBCAChE. Zero time (predosing) baseline RBC AChE ranged from 8143±982 (±12%) to 9572±539 (±6%) UIL for males and 8576±556 (±6%) and 9165±709 (±8%) UIL for females indicating good precision for the baseline data. These RBC AChE values were withinthe expected range for humans. Only one individual had a decrease in RBC AChE that suggested inhibition by chlorpyrifos as indicated by being consistently decreasedat the critical hours post dosing. For this subject (#56, a female dosed with2 mglkg), inhibitionofRBC ACHE was observed at 8 (23% .J,), 12 (maximum 28% .J,), 24 (26%.J,), 36 (19%.J,) and 48 (21%.J,) hours post dose. There were no associated cholinergic symptoms reported, although atransient numbness in the upper arms in this subject was reported at about 2 hours post dosing or well before AChE inhibition and significant levels ofTCP in the serum were detected. The LOAEL is 2 mg/kg/day for RBC AChE based on 28% inhibition in one female subject. The NOAEL is 1 mg/kg. Classification: This study is classified asAcceptable/Non-Guideline and to contain useful information onthe pharmacokinetics oforally administered chlorpyrifos when administered in a capsule to human volunteers. The study, however, should notbeused for endpoint selection or for impacting the uncertainty factors for risk assessment. The RBC AChE inhibitory assessment aspects ofthis study depend upon only one subject showing clear evidence of inhibition. Another serious problem with this study with regard to comparing the results with other studies in human volunteers is that no assessments ofplasma cholinesterase were made. Differences in the method ofdose administration where a chlorpyrifos was administered in a capsule in this study and on top ofa lactose pill after dissolving in solvent in the Nolan study preclude direct comparison ofthe pharmacokinetic data.

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DATAEVALUATIONRECORD-IHJPI'LI:MENTAL CRLORPYRII'08 NONGlllDELDIE STUJW'IYP't>REPEATDOSEORALTOXIcrrY·HUMAN MRID1*195175**Ptlmaey~** BlallhEf&cts**Dl~** Oftlae afl'8lllc!dll!'ft.gi86lll U.S..Jim:hdl'"k:ntalProtecdo:n.AgeDcy Oncl'ommacYard 

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### c- No. Dli-AOOHI001122'12!5,EPA's Records Disposition Schedule PEST 361 Scientific Data Reviews HED Records Center- File R180234- Page 7 of 73

CHLORPYRIFOS Repeat Dose Oral Toxicity (Human) (1972) I Page 2 of11 Nonguideline 

### EPA Reviewer: Abdallah Khasawinah. Ph.D. RiskAssessment Branch IV, Health Effects Division (7509P) EPAWorkAssignment Manager: Myron Ottley, Ph.D. RiskAssessment Branch III, Health Effects Division (7509P)

TXR#: 0050308

## Signature:~·**(C~,L_** Date:

# Dm?--0

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### Signature: / ,F Date: 

# 1/7 

# /Jo Template version 02/06 

### ACC NO.: 092212 D

DATAEv ALUA noNREcoRD- suPPLEMENTAL 

# I1YR oooo\:::p::f

STUDY TYPE: Repeat Dose Oral Toxicity (Human) Nonguideline
PC CODE: 059101 DP BARCODE: D368390
TESTMATERIAL (PURITY):Dowco 179 (chlorpyrifos; purity not reported)
SYNONYMS: 0,0-diethyl-0-[3,5,6-trichloro-2-pyridyl] phosphorothioate
CITATION: Coulston, R., L. 

### Golberg, T. Griffin. (1972). Safety evaluation ofDOWCO 179 in human volunteers. Institute ofExperimental Pathology and Toxicology, Albany Medical College, Albany, NY 12208. ReportNumbernot provided. March 1972. MRID 00095175
SPONSOR: Notreported butpresumed: The Dow Chemical Company, Midland, MI
EXECUTIVE SUMMARY: In an oral multiple dose study (MRID 00095175), groups of'four healthy adult maleprisoners received 0.0, 0.014, 0.03, or 0.1 mglkg bw/day Dowco 179 (purity, stability, and lot number notprovided) for 48, 27, 20, and nine days, respectively. No treatmentrelated effects were found on measured urinalysis, hematology, orclinical chemistryparameters except for depressed plasmacholinesterase (ChE) activity in subjects receiving the test materiaL
Plasma cholinesterase activity was reduced 46% by Day 6 in subjects treated with 0.10 mg Dowco 179/kgbw/day, which further decreased to 66% by Day 9. Dosing was stopped for the 0.1 mg/kg bw/day group on Day 9 as plasma ChE activity was decreased>20% for all individuals in the dose group. In the 0.03 mg Dowco 179/kg bw/day group, plasma ChE activity was decreased 32%byDay 16 and remained decreased -30%through Day 20 when treatment was stopped. No significanttreatment-related effect on ChE activity was found in subjects ofthe 0.014 mg/kg bw/day group. Recovery ofplasmaChE activity in subjects treated with 0.1 mg/kg bw/day was observedby Day 25 and by Day 21 in subjects ofthe 0.03 mglkg

### bw/day group after cessation ofdosing. Erythrocyte acetylcholienesterase activity was not affected at any ofthe doses. Based on an -30% decrease in plasma cholinesterase activity by Day 16, the LOAEL for Dowco 179 was 0.03 mg/kgbw/day. The correspondingNOAELwas 0.014 mg/kg bw/day. Classification. This study is classified as Unacceptable/Non-Guideline. Although the study contains some useful datathat describes the potential for chlorpyrifos to inhibit plasma ChE in human volunteers, there are several deficiencies (incomplete details ofthe methodology) thatEPA's Records Disposition Schedule PEST 361 Scientific Data Reviews HED Records Center- File R180234- Page 8 of 73

CHLORPYRIFOS RepeatDose Oral Toxicity (Human) (1972) IPage 3 ofII Nonguideline 

### preclude using the data for endpoint selection for risk assessment orfor informing the uncertainty factors. The study has not beenreviewed for either ethics or scientific considerations bythe EPA Human Studies Review Board.
COMPLIANCE: Signed and dated GLP, Quality Assurance, and Data Confidentiality statements were not provided.EPA's Records Disposition Schedule PEST 361 Scientific Data Reviews HED Records Center- File R180234- Page 9 of 73

CHLORPYRIFOS Repeat Dose Oral Toxicity (Human) (1972) I Page4 ofII Nonguideline 

### I. MATERIALSAND METHODS:
A. MATERIALS:
I. 

### Testmaterial: Description: Lot/Batch #: Purity: Compound Stability: CAS # for TGAI: Structure:: 

### Dowco 179 Not reported Notreported Not reported Notreported 2921-88-2



### 2. Vehicle: Tablet (not further described) provided with the breakfast meal
3. Human Subjects: Number: Race: Sex: Age: Weight: Source: Physical Examination:

B. 

### STUDY DESIGN:
I. 

### Study date: Not reported Sixteen Notreported Male Not reported Not reported Volunteers from the Clinton Correctional Facility, Dannemora, NY Before the start ofthe study, each volunteer was given a thorough physical examination that included a chest X-ray, electrocardiogram, urinalysis, and hematology and clinical chemistry parameters.



### 2. Study subjects: Sixteen male volunteers from the Clinton Correctional Facility were divided into groups offour and assignedto the groups and duration oftreatment shown in Table I.

Table I. Studv desi2n Subiect# Dose lmo/ko bw/davl Duration ofexnosure 2, 4, 9, 16 0.0 7 weeks 7, 8, 14, 15 0.014 27 days 10,11,12,13 0.03 20 days

I, 3, 5, 6 0.10 9 days


### 3. Dose selection: A dose selectionrationale was not provided.
4. Dose preparation and analysis: Otherthan the doses being dispensed onto atablet at the concentrations shown in Table 1and provided with the breakfast meal, no other dosing information was provided.

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CHLORPYRIFOS 

### Results: Homogeneity analysis: Notreported Stability analysis: Notreported Concentration analysis: Not provided Repeat Dose Oral Toxicity (Human) (1972) I Page5 of 11 Nonguideline



### 5. Statistics: Statistical analyses for hematology, clinical chemistry, and urinalysis were not reported. Plasma and RBC cholinesterase activity were analyzed by three-way randomized factorial ANOVA.


### C. METHODS:
1. 

### Observations: It

### is assumed the test subjects were observed daily at the time oftreatment and/or blood collection; however no specific mention is made in the studyreport.
2. Bodyweight: Although the doses were administered on akg bw/day basis, body weight data
were not provided in the study report.
4. Hematology and clinical chemistry: Blood was collected for hematology and clinical chemistry analyses before treatment and ondays 7, 15, 22, 28, 35, 42, and 49 for control subjects; days 6, 13, 20, and 27 for subjects treated with 0.014 mg/kg bw/day; days 7, 15, and 22 and day 6post-treatment for subjects treated with 0.03 mglkg bw/day; and day 8 oftreatment and days 5, II, and 18 post-treatment for subjects treated with 0.1 mg/kg bw/day. The CHECKED (X) parameters were examined.

a. Hematology:

X Hematocrit (HCT) X Leukocyte differential count X Hemoglobin (HGB) Mean corpuscular HGB (MCH) X Leukocyte count (WBC) Mean corpusc. HGB conc.(MCHC) Erythrocyte count (RBC) Mean corpusc. volume (MCV) Platelet count Reticulocyte count Blood clotting measurements X Basophils

(Thromboplastin time) X Eosinophils (Clotting time) X Neutophils (Prothrombin time) X Lyrnohocytes X Monocytes

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CHLORPYRIFOS 

### b. Clinical chemistry

X ELECTROLYTES X Calcium Chloride Magnesium X Phosphorus Potassium Sodium X ENZYMES X Alkaline phosphatase (ALK) X Cholinesterase (ChE) Creatine phosphokinase X Lactic acid dehydrogenase (LDH) Alanine aminotransferase (ALT/ SGPT) X Aspartate aminotransferase (AST/ SGOT) Gamma glutamyl transferase (GGT) Sorbitol dehydrogenase Glutamate dehydrogenase Repeat Dose Oral Toxicity (Human) (1972) I Page 6 of11 Nonguideline

X OTHER X Albumin Creatinine X Urea nitrogen X Total Cholesterol Globulins X Glucose X Total bilirubin X Total protein (TP) Triglycerides X Uric Acid



### 5. Urinalysis: Urine was collected weekly during the study and analyzed for specific gravity, color, clarity, pH, and microscopic analysis. Samples ofthe urine were retained for determination ofDowco 179 and metabolic products.
6. Cholinesterase activity: Plasma and RBC cholinesterase (ChE) activity was measured by the method ofNabb and Whitfield (Arch. Environ. Health (1967) 15: 147) with acetylcholine perchlorate as the substrate followed by titration to pH 8.0 with sodium hydroxide. ChE activity was expressed as J.lmoles acetate/min/mL. Plasma and RBC ChE activity was monitored every 2-3 days during treatment (control: 1, 3, 6, 10, 13, 16, 18, 20, 23, 27, 30, 34, 37, 41, 44, 48 days; 0.014 mg/kg bw/day: 3, 6, 9, 13, 16, 20, 23, 27 days; 0.03 mg!kg bw/day: 1, 3, 6, 13, 16, 18,20 days; 0.10 mg/kg bw/day: 1, 3, 6, 9 days). After the treatmentperiod, plasma and RBC ChE activity were monitored onthe following until activities returned to pre-treatment levels: control: days 3 and 7; 0.10 mg/kg bw/day: days 2, 4, 7, 11, 14, 18, 21, 25, 28, 32, and 35; 0.03 mglkg bw/day: days 2, 6, 9, 13, 20, 23, 27, and 30; and 0.014 mg/kg bw/day: days 3 

### and 7.
II. 

### RESULTS:
A. OBSERVATIONS:
1. 

### Clinical signs oftoxicity: No treatment-related clinical signs oftoxicity were reported, except for one subjecttreated with 0.10 mg/kg bw/day Dowco 179 complained ofarunny nose, blurred vision, and faintness on the final day oftreatment. The subject was treated for a cold and was asymptomatic by the end ofthe day.
2. Mortality: All subjects survived the study.

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CHLORPYRJFOS 

### B. BLOODANALYSES: Repeat Dose Oral Toxicity (Human) (1972) IPage 7 ofII Nonguideline



### 1. Hematology: While individual data were provided, summary data ofmeasured hematological parameters were not provided. Review ofthe individual data indicatesthere were no treatment-related effects.
2. Clinical Chemistry: While individual data were provided, summary data ofmeasured clinical chemistryparameters were not provided. Review ofthe individual data indicates there were no treatment-related effects.
F. URINALYSIS: Urinalysis data were not provided. The study author stated that no treatment-related effects were found. Routine urinalysis which included specific gravity, color, turbidity, pH and determination ofcellular content were completelynegative of treatmentrelated effects for all individuals throughout the study. Urine samples were examined for the presence ofDowco 179, its oxygen analog and its metabolite 3,5,6- trichloro-2-pyridinol and were not detected in any ofthe samples. Details ofthe analysis and the limit ofdetection were not provided except for areference to the methodused (Final Report on SafetyEvaluation and Metabolic Studies. Institute ofExperimental Pathology and Toxicology, Albany Medical College, March 18, 1971).
G. CHOLINESTERASE ACTIVITY:
1. Plasma: As shownin Table 2a, plasmaChE activity was reduced 38% by Day 6 in the 0.10 mg/kg bw/day dose group, and further decreased to 60% ofpretreatment activity by Day 9. The study authors reported that dosing was stopped for the 0.1 mg/kg bw/day group on Day 9because plasma ChE was decreased>20% for all individuals in this dose group. In the 0.03 mg/kg bw/day group, plasma ChE activity was decreased 32% of pretreatment activity by Day 16 and remained decreased -30%through Day 20 when treatment was stopped. No significanttreatment-related effect was found in subjects of the 0.014 mg/kg bw/day group. Recovery ofplasmaChE activity in subjects treated with 0.1 mg/kg bw/day was observedbyDay 25 and by Day 21 in subjects ofthe 0.03 mg/kg bw/day group after cessation ofdosing. Summaryresults are also presented in Table 2b on the basis ofplasmacholinesterase activity in 1-1moles acetate/min/mL

Table 2a. Average percent change ofplasma cholinesterase relative to pre-treatment activity in subjects receivine; Dowco 179 daily Dose (mg/kg Da oftreatment

bw/day) I 3 6 10 13 16 19 20 27 Control 16 ± 33.7 9±21.1 11 ± 6.0 20 ± 10.8 12±11.0 2 ± 12.9 5 ± 15.1 7 ± 7.7 7 ± 11.0 0.014' 

### - 7± 8.9 7 ± 11.6 -9 ± 14.5**~19*±7.3** -18*± 17.4


### - -7± 13.2 -5 ± 17.9 0.03' -5 ± 6.8 -9 ± 11.4 -15' ± 17.9 -2 ± 29.3 -15* ± 18.9 -32* ± 15.4 -33* ± 15.1 -29* ± 15.6 

### - 0.10' 0 ± 39.6 2 ± 35.1 -38* ± 37.4 -60* ± 32.8 

### - - - - - Dose (mg/kg Da ofrecover

bw/day) 2 4 7 11 14 18 21 25 28 Controid -13 ± 19.7


### - 12±20.0


### - - - - - - 0.014' 14± 12.8


### - 18 ± 7.8


### - - - - - 

### - 0.03' -25 ± 15.0 

### - -20 ± 18.2 -26 ± 11.2 -30 ± 25.2 

### - -4 ± 3.9 -8±11.8 -6 ± 18.0 0.10 -53*±34.6 -47±31.0 -40* ± 34.4 -26 ± 34.6 -22 ± 39.2 -25±30.7 -31 ± 20.2 -3 ± 32.3 11±41.4EPA's Records Disposition Schedule PEST 361 Scientific Data Reviews HED Records Center- File R180234- Page 13 of 73

CHLORPYRIFOS Repeat Dose Oral Toxicity (Human) (1972) I Page 8 ofII Nonguideline

Results and statistics calculated by reviewer from data in Tables 33a and 33b on pages 39-40 ofMRID 00095175. Data from Tables 33aand 33b was entered into an Excel spreadsheet The activity for each individual on each study day was divided by the average activity measured prior to the start ofthe study. The average ofthe four subjects for each day was taken and placed that into the table and then the average and standard deviation for the group was computed. Balded results indicate >20%CHE inhibition

aActual days activity measured= 3, 6, 9, 13, 16, 20, 23, and 27 b Actual days activity measured= 1, 3, 6, 10, 13, 16, 18, and 20

c Actual days activity measured = I, 3, 6, and 9 dActual days activity measured = 3 and 7

e Actual days activity measured= 2, 6, 9, 13, 20, 23, and 27

**•~p<:O.OS**

Table2b. Plasma Cholinesterase

**(~-tmoles** acetate/min/mL) (Percent ChE inhibition) Day Control I 0.014 m2/kg 0.03 ml!ik2 I Plasma pretest 4.325±0.967 4.05±0.614 4.525±1.664 pretest 3.975±1.014 4.325±0.943 4.85±1.636 I 4.6±0.327


### - 4.45±1.62 3 4.475±1.25 4.45±1.01 4.3±1.766 6 4.625±1.04 4.475±1.053 3.95±1.377 (16) 9 4.9±1.25 3.775±1.037 (10)


### - 10 4.95±1.22


### - 4.675±2.36 13 4.94±0.46 3.45±0.52 3.25±0.91 (33) 16 4.3±0.70 3.45±1.14 3.25±1.53 (33) 18 4.28±0.66


### - 3.1±1.15 (36) 20 4.38±0.79 3.88±1.06 3.38±1.58 (30) 23 4.0±0.92 4.0±1.51

- 27 4.38±0.83 3.95±1.22


### - 30 3.93±0.90


### - - Recovery 2 

### - - 3.58±1.62 (26) 3 4.62±0.98 4.52±1.2


### - 4

- 

### - - 6
- 

### - 3.550.99 7 4.5±0.81 5.110.77 

### - 9 

### - - 3.62±1.88 II

- 

### - - 13 

### - - 3.4±2.06 (30) 14 

## - - - 18 

### - - - 20 

### - - 4.42±1.61 (9) 21 

### - - - 30

- 

### - 4.68±2.08 35 

### - - - 0.10 mg/kg
4.625±0.665 4.85±0.656 4.325±1.57

4.3±1.36 2.65±1.42 (44) 1.7±1.25 (64)



### -

-

-



### -

-

-



### -

-
2.0±1.30 (58)



### - 2.35±1.34 (50)

- 2.78±1.75 (41)



### - 3.48±1.42 (27)

- 3.15±1.14 (34) 2.9±0.88 (39)

- 3.55±1.32 (25)



### - 4.72±1.14 Results and statistics calculated by reviewer from data m Tables 33a and 33b on pages 39-40 ofMRID 00095175.

IUEPA's Records Disposition Schedule PEST 361 Scientific Data Reviews HED Records Center- File R180234- Page 14 of 73

CHLORPYRIFOS Repeat Dose Oral Toxicity (Human) (1972) I Page9 ofII Nonguideline 

### 2. RBC: As shown in SummaryTable 3a, Dowco 179 did not decrease the activity ofRBC ChE during the treatment period.

Table3a. Average percent change ofRBC cholinesterase activity relative to pre-treatment activity in subjects receiving Dowco 179 daily Dose (mg/kg Dav oftreatment

bw/day) I 3 6 10 13 16 19 Control -6 ± 5.8 4 ± 5.4 II± 3.7 14 ± 5.7 12 ± 4.1 5±4.5 5 ± 2.5 0.014'

- 0 ± 7.1 3± 11.3 -7 ± 9.9 -9 ± 9.1 I± 6.3 

### - O.Q3' -I± 3.6 6± 5.7 9 ± 5.3 9 ± 6.1 II ± 2.1 4± 2.7 5 ± 1.9 0.10' -I± 6.9 19 ± 4.7 12±7.0 6± 3.9


### - - - Results calculated by rev1ewer from data Tables 34aand 34b on pages 41-42 ofMRID 00095175

a Actual days activity measured= 3, 6, 9, 13, 16, 20, 23, and 27 bActual days activity measured= 1, 3, 6, 10, 13, 16, 18, and 20

c Actual days activity measured= 1, 3, 6, and 9 20 27 3 ± 2.8 20 ± 10.3 I± 6.9 2± 8.8 I±4.6


### -

- -

Summaryresults are also presented in Table 3b on the basis ofRBCcholinesterase activity in flmoles acetate/min/MI.

Table 3b. RBC Cholinesterase (umoles acetate/rnin/mL) Day Control 0.014**m~/k~** 0.03**m~/k~** I 0.10**mg/k~** RBC pretest 15.2±2.2 14.4±1.8 13.4±1.7 14.6±0.8 pretest 14.8±2.2 14.0±1.5 13.0±2.2 14.5±0.8 I 14.0±1.7 14.2±1.8 13.0±1.9 14.4±0.8 3 15.6±2.6 14.6±2.4 13.9±2.1 17.2±0.7 6 16.7±2.2 13.2±2.2 14.3±2.1 16.2±1.1 9 

### - 12.9±1.4 

### - 15.4±0.7 10 17.1±2.2


### - 14.4±1.8


### - 13 16.8±2.1 14.3±1.3 14.6±2.4


### - 16 15.6±2.1 14.3±1.4 13.7±2.1

- 18 15.8±2.1

- 13.8±2.4 

### - 20 15.5±2.6 14.3±1.4 13.4±2.0


### - 27 16.3±2.3 14.2±1.5


### - - 30 17.9±2.0 14.5±1.8


### - - Recovery 2 

### - - 14.0±1.9 14.5±0.8 3 16.8±2.2 14.1±1.4 

### - - 4

- 

### - - 15.2±0.6 6 

### - - 14.3±3.1


### - 7 17.0±2.1 14.4±1.8


### - 15.9±0.6 9 

### - - 14.2±1.6


### - II 

### - - 15.3±1.2 Tables 34aand 34b on pages 41-42 ofMRID 00095175


### III. DISCUSSION AND CONCLUSIONS:
A. INVESTIGATORS' CONCLUSIONS:
The Study investigator concludedthat ingestion ofDowco 179 at 0.03 mg/kg/day by humans for 21 days was athreshold level for measured changes in plasmaChE activity with no significanttoxicological effect. The plasma ChE activity in this group averaged 87% ofthe concurrent controls when compared on day to day basis and this was considered not statistically significantly different from the control. Ingestion of0.1 mg/kg/day ofDowco 179 resulted in marked plasmaChE depression whichresulted in termination ofthe dosing after 9

I'<C'"EPA's Records Disposition Schedule PEST 361 Scientific Data Reviews HED Records Center- File R180234- Page 15 of 73

CHLORPYRJFOS Repeat Dose Oral Toxicity (Human) (1972) IPage 10 of 11 Nonguideline 

### days. The RBC ChE activitywas not affected in any ofthe groups tested.


### B. REVIEWER COMMENTS: Groups offour male subjects were treated with 0.0, 0.014, 0.03, or 0.1 mg Dowco 179/kg bw/day up to 27 days. Notreatment-related effects were found onmeasured urinalysis, hematology, orclinical chemistryparameters in subjects receiving the test material. Data on the concentration ofDowco 179 and its metabolites in the urine were notprovided. Plasma ChE activity was reducedto 46% ofpre-treatment activity byDay 6 in subjects treated with 0.10 mg Dowco 179/kgbw/day, which further decreased to 66% ofpretreatment activity by Day 9. The study authors reported that dosing was stoppedfor the 0.1 mg/kg bw/day group on Day 9because plasma ChE was decreased >20% for all individuals in this dose group. In the 0.03 mgDowco 179/kgbw/day group, plasmaCHE activity was decreased to 32% of pretreatment activity byDay 16 and remained decreased -30%through Day 20 when treatment was stopped. No significanttreatment-related effect onChE activity was found in subjects ofthe 0.014 mg/kgbw/day group. Recovery ofplasmaChE activity in subjects treated with 0.1 mglkgbw/day was observedby Day 25 and byDay 21 in subjects ofthe 0.03 mg/kg bw/day group after cessation ofdosing.


### Based on an -30% decrease in plasma cholinesterase activity by Day 16, theLOAEL for the studywas 0.03 mg/kg bw/day. ThecorrespondingNOAEL was 0.014 mg/kg bw/day.
C. STUDY STRENGHTSAND WEAKNESSES: Strengths:
• Concurrent control (placebo)
• Three dose levels (provides quality dose-response information)
• Plasma and RBC ChE activity were monitored
• Blood sampling atmultiple time points. ChE activity was monitored on: 1, 3, 6, 10, 13, 16, 18, 20, 23, 27, 30, 34, 37, 41, 44,48 days (control); 3, 6, 9, 13, 16, 20, 23,27 days (0.014 mglkgbw/day); 1, 3, 6, 13, 16, 18,20 days (0.03 mg/kg bw/day); and 1, 3, 6, 9 days (0.10 mg/kg bw/day).
• Recovery phase
• Chlorpyrifos and metabolites (oxonand TCP) were monitored in urine. None ofthe compounds were detected in any sample (limit ofdetection was not provided)


### Weaknesses:

• Only one sex (males) used (age and weight ranges were notprovided).
• The purity, lot number, and stability ofthe test material were not provided.
• The study was conducted at a correctional facility.
• Each dose was given for a different duration without a clearrationale (i.e. Control for
seven weeks, 0.014 mg/kg bw/dayfor 27 days, 0.03 mg/kgbw/day for 20 days and 0.1 mg/kg bw/day for nine days).
• ChE activity measurements were not done every daypost dose.

H.

### ' EPA's Records Disposition Schedule PEST 361 Scientific Data Reviews HED Records Center- File R180234- Page 16 of 73

CHLORPYRIFOS RepeatDose Oral Toxicity (Human) (1972) I Page II ofII Nonguideline



### • The time after dose when samples were collected for ChE activity was notreported.
• The time ofurine collection relative to time ofdose was notprovided.
• Limit ofdetection ofchlorpyrifos and metabolites was notprovided.EPA's Records Disposition Schedule PEST 361 Scientific Data Reviews HED Records Center- File R180234- Page 17 of 73

DATAEVALUATION RECORD- SUPPLEMENTAL
CHLORPYRIFOS NONGUIDELINE STUDYTYPE: ORAL/DERMAL PHARMACOKINETIC- HUMAN MRID 00124144

Primary Reviewer: Prepared for
HealthEffects Division Office ofPesticidePrograms U.S. EnvironmentalProtectionAgency One Potomac Yard 2777 S. Crystal Drive Arlington, VA 22202 Preparedby Toxicology and Hazard Assessment Group Life Sciences Division OakRidge National Laboratory Oak Ridge, TN 37831 Task OrderNo. 207-2009

H. T. Borges. Ph.D

.. MT<ASCPl. D.A.B.T. Secondary Reviewers: R. A. Young. Ph.D

.. D.A.B.T.

Signature: 

## ------:=,...,.......,......,""- Date: 

## J) APR 0 8 2009 Signature:



# .J'(~ 

# ./J.

**~** Robert H. Ross. M.S

.. Group Leader QualityAssurance: K. Slusher M.S. Date: 

## APR 0

# a2DD9

Disclaimer
This review mayhave been altered subsequent to the contractor's signatures above.

Oak Ridge NationalLaboratory managed and operated by UT-Battelle, LLC., for the U.S. Department of Energy under ContractNo. DE-c_A_C_0.:._5-_0_00c___R2_2_7_2_5_._
--------------------



### /C{EPA's Records Disposition Schedule PEST 361 Scientific Data Reviews HED Records Center- File R180234- Page 18 of 73

CHLORPYRIFOS Oral and Dermal Pharmacokinetic Study (Human) (1982) IPage 2 of 13 Non2.uideline
EPAReviewer: John Doherty, Ph.D., DABT Reregistration Branch 1,Health Effects Division (7509P) EPAWorkAssignmentManager: Myron Ottley, Ph.D. Registration Action Branch 1, Health Effects Division (7509P)



### TXR#: 0050308 Signature:

# ·.\L.~ Date:\**'1"1~** Signature: 

## r 

# 'o Date: 

## ;hi /D T'em[late version 02/06 

### ACC NO. 249203
DATA EVALUATION RECORD- SUPPLEMENTAL 

## ilXR 0003<6'.22..

STUDYTYPE: Pharmacokinetic Study, Oral/Dermal; Human Nonguideline
PC CODE: 059101
TESTMATERIAL (PURITY): Chlorpyrifos (99.8% a.i.) DP BARCODE: D368390

SYNONYMS: 0,0-diethyl-0-[3,5,6-trichloro-2-pyridyl] phosphorothioate
CITATION: Nolan, R.J., D.L. Rick, N.L. Freshner, and J.H. Saunders (1982). Chlorpyrifos: Pharmacokinetics in human volunteers following single oral and dermal doses. The Dow Chemical Company, Biomedical Medical Research Lab, 607 Building, Toxicology Research Lab, 1803 Building, Midland, MI 48640. ReportNumbernotprovided, August 1982. MRID 00124144. Published in Toxicology and Applied Pharmacology 73:8-15, 1984. (MRID No.: 47918801).
SPONSOR: The Dow Chemical Company, Midland, MI
EXECUTIVE SUMMARY:
In a single-dose human oral/dermal toxicity study with chlorpyrifos (1982, MRID 00124144), six male volunteers were given 0.5 mg/kg chlorpyrifos (99.8% a.i., LotNo. AGR 166043) ona lactose tablet. Plasma and RBC cholinesterase activity were monitored at 2, 6, 12, 24 hours, and 2, 3, 4, 8, 14, 22, 27, and 30 days post-dose. Approximately four weeks after the oral treatment, a single dermal dose (5 mg/kg to five subjects; 0.5 mg/kg to one subject) was administered on the volar surface ofthe forearm. RBC and plasma cholinesterase activity were determined 2, 6, and 12 hours and on days I, 2, 3, 4, 6, 8, and 9 following dermal treatment. Blood and urine samples were analyzed for chlorpyrifos and 3,5,6-TCP (3,5,6-trichloro-2-pyridinol) concentrations.

No clinical signs oftoxicity and essentially no significant inhibition ofRBC cholinesterase activity
were observed following either the oral ordermal dose. Plasmacholinesterase activity was inhibited 83-89% relative to pre-dose activities following the oral dose (peak inhibition within 6-24 hours post dose) butwas essentially unchanged following the dermal dose. Blood chlorpyrifos concentrations were low (<30 ng/mL; limit ofdetection 5 ng/mL), and chlorpyrifos was not found in the urine following eitherroute ofexposure. 3,5,6-TCP blood concentrations peakedby six hours after oral exposure and 24 hours after dermal application. 3,5,6-TCP was cleared from the blood and eliminated in the urine with ahalf-life of27 hours following boththe oral and dermal doses.EPA's Records Disposition Schedule PEST 361 Scientific Data Reviews HED Records Center- File R180234- Page 19 of 73

CHLORPYRIFOS Oral and Dermal Pharmacokinetic Study (Human) (1982) IPage 3 of 13 Nonguideline 

### Using assumptions offirst-order absorption and eliminationequations, it was estimatedthat 72 ± 

### II% ofthe ingested dose and 0.95 ± 

### 0.559% ofthe dermal dose were absorbed.
Classification: 

### This studied is classified as Acceptable/Non-Guideline.
COMPLIANCE: 

### Signed and dated GLP, Quality Assurance, and Data Confidentiality statements were not provided.EPA's Records Disposition Schedule PEST 361 Scientific Data Reviews HED Records Center- File R180234- Page 20 of 73

CHLORPYRIFOS Oral and Dermal Pharmacokinetic Study (Human) (1982) IPage4 of 13 Nonguideline I. 

### MATERIALS AND METHODS:
A. MATERIALS:
1. 

### Test material: Description: Lot/batch #: Purity: Compound stability: CAS# Structure: 

### Chlorpyrifos Not described AGR 166043 99.8% a.i. (as stated) Notreported 2921-88-2



### 2. Vehicle: Methylene chloride for dissolving chlorpyrifos for placement on a 0.5 gm lactose tablet. DOWANOL DPM (dipropylene glycol methyl ether (DPGME)) was used as vehicle to apply the dermal dose.
3. Human Subjects: Number: Race: Sex: Age: Weight: Source: Instructions:



### B. STUDYDESIGN:
1. 

### Studydates: Notreported Six Caucasian Male 27-50 years 71.7-101.1 kg (mean 83.3 ± 10.3 kg) Volunteers Each volunteer was briefed on the study and asked to provide written consent. None were on oral medication and all were asked to refrain from any drugs including aspirin and alcohol 24 hours before and after each dose.



### 2. Study subjects: Six male volunteers, ages 27-50 years, were included in the study. Subject A served as a "pilot" and was given a single oral dose (0.5 chlorpyrifos mg/kg dissolved in food grade methylene chloride placed on alactose tablet) ofthe test material approximately one monthbefore the otherparticipants. Four weeks later, SubjectA also received a single (0.5 chlorpyrifos mg/kg) dermal dose (dissolved inmethylene chloride). Two weeks afterthe first dermal dose, SubjectA was given a second dermal dose (0.5 chlorpyrifos mg/kg dissolved in DPGME).
The main study consisted oftwo phases. Five subjects (B- 

### F) were dosed once orally (0.5 chlorpyrifos mglkg dissolved in food grade methylene chloride and placed on a lactose tablet) and once dermaliy (5 mg/kg chlorpyrifos in DPGME), thirty days after the oral dose.EPA's Records Disposition Schedule PEST 361 Scientific Data Reviews HED Records Center- File R180234- Page 21 of 73

CHLORPYRIFOS

Exoosure route Oral Dermal Dermal Dermal Oral and Dermal Pharmacokinetic Study (Human) (1982) IPage 5 of 13 Nonguideline

TABLE I. Study design

SubjectA (n-1) Subjects B-F (n-5) 0.5 mg/kg 0.5 mgfkg 0.5 mg/kg 

### - 0.5 mg/kg 

### -

- 5.0 mglkg



### 3. Dose selection rationale: The doses selected were based on a human tolerance study with chlorpyrifos (Coulston, F., Golberg, L., 

### Abraham, R., eta!., 1972, Final report on safety evaluation and metabolic studies on Dowco 179(IN151), Inst. Exp. Pathol Toxicol, Albany Medical College (as cited by WHO, 1973).
4. Dose preparation and administration: The oral doses for all subjects were preparedby mixing an appropriate amount ofchlorpyrifos in food grade methylene chloride. A sufficient volume ofthe chlorpyrifos/ methylene chloride mixture was applied to a 0.5 g lactose table, and the methylene chloride allowed to evaporate. Following 

### abreakfastmeal, the tablet was swallowed whole with -100mL water.
The dermal 5.0 mglkg doses for Subjects B- F were administered by spreading -10 ).LLikg chlorpyrifos dissolved in DPGME over -100cm2 

### surface ofthe volarforearm. The application site was not covered or occluded and no effort was made to influence evaporation. Following dermal application, the subjects were allowed to follow their normal bathing habits 12 to 20 hours later. The dermal doses administered to SubjectA were applied similarly, with the exception that the first dermal dose used methylene chloride as the solvent followed by application two weeks later where DPGME was the solvent for the 0.5 mg/kg dose.
Results: Homogeneity analysis: Notreported Stability analysis: Not reported Concentration analysis: Netincreases in tablet weight and chemical analysis ofduplicate tablets were used to verity the oral doses. Datawere not supplied. Thus, verification ofdermal doses was not reported.
5_ Statistics: Plasma and RBC cholinesterase activities were expressed as apercent ofthe mean oftwo to three pre-dose determinations. Other statistical methods were limited to the determination ofthe mean and standard deviation. Concentration-time and urinary excretion data for 3,5,6-trichloro2-pyridine (TCP) for each volunteer were fit simultaneouslyto the equation:
k xDosexF C = ' x exp (k, xtime-k, xtime)

b V, x(k,

- k,)
Urinary excretion rate=

### cb X k, 

### X v, X body weight



### The equations describe a one-compartment model with first-order absorption and elimination where Cb =theblood 3,5,6-TCP; F =thefraction ofdose absorbed; Vd 

### =thevolume of 

## 23EPA's Records Disposition Schedule PEST 361 Scientific Data Reviews HED Records Center- File R180234- Page 22 of 73

CHLORPYRIFOS Oral and Dermal Pharmacokinetic Study (Human) (1982) I Page 6 of 13 Nonguideline 

### distribution; and k,and k, 

### are the first order-absorption and elimination constants for 3,5,6- TCP. Optimal estimates for the model parameters were obtained using DACSL (DOW Advanced Continuous Stimulation Language, Agin and Blau, 1981).
C. METHODS:
1. Observations: Followingtreatment, the volunteers were observed for clinical signs of toxicity. Further details were notprovided.
2- SampleCollection: Blood -Heparinizedblood samples were collectedpriorto treatment and 2, 6, and 12 hours, and 1, 2, 3, 4, 8, 14, 22, 27, and 30 days post dose for analysis of plasma and RBC cholinesterase following oral treatment. RBC and plasmacholinesterase activity were determined 2, 6, and 12 hours and on Days I, 2, 3, 4, 6, 8, and 9 following dermal treatment. In addition, the blood samples were analyzed for the concentration of chlorpyrifos and 3,5,6-TCP.
Urine- Urine was collected 24-48 hours priorto dosing. Samples were pooled for the following intervals: 0, 6, 12, 24, 36, 48, 60, 72, and 96 hours post-dose. Two additional 12- hour urine collections were made starting at 156 hours and 180 hours after the 5.0 mglkg 

### dermal application. The urine volume and creatinine were determined for each sample, as well as the concentration ofchlorpyrifos and 3,5,6-TCP.
3. CholinesteraseActivity: RBC and plasmacholinesterase activity were determined using the micro-Michel method (Michel, O.H., 1961, Cholinesterase in human RBC and plasma. In Standard Methods ofClinical Chemistry, D. Seligson ed., Academic Press, NY, pp 93-98). Themethod was not further described. (The principle ofthe method relies on plasma orRBC acetylcholinesterase hydrolyzing the substrate acetylcholine in a standardbuffer solution (typically pH 8) to form acetate which causes a decrease in the pH ofthebuffer solution. The measured change in pH is proportional to acetylcholinesterase activity.
4. Chlorpyrifos and 3,5,6-TCP Concentration: Blood chlorpyrifos concentration was determined by extractingthe sample with acetone, evaporatingthe acetone and mixing the residual with hexane, and eluting the hexane through a 20% deactivated silica gel column. The hexane was collected and concentrated by evaporationbefore injection into an FID gas chromatograph equipped with a 3% OV-17 and 8% QF-1 column. Urine samples were analyzed similarly following direct extraction with hexane.
Blood 3,5,6-TCP was analyzed by mixing a sample with 0.!2N HCI and filtered through a C18 

### Sep-Pak column. The column was washed with two additionai!O mL volumes of0.12N HCl before being eluted withmethanol. The eluent-containingmethanol was mixed with l0 mL equal volumes ofsodiumbicarbonate and benzene. Following centrifugation, the benzene was discarded and sodium chloride, HCI and benzene were added. After mixing and centrifugation, the benzene was removed and the extract silylated. Aliquots ofthe silylated benzene extract were injected into an ECD gas chromatograph equipped with a 3%0V-I column. Urine 3,5,6-TCP was extracted and quantitated similarly following hydrolysis ofthe urine with concentrated H2

### S04 

### for one hour at 90°C.EPA's Records Disposition Schedule PEST 361 Scientific Data Reviews HED Records Center- File R180234- Page 23 of 73

CHLORPYRIFOS Oral and Dermal Pharmacokinetic Study (Human) (1982) I Page 7 of 13 Nonguideline 

### II. RESULTS:
A. CLINICAL SIGNS OFTOXICITY:
No clinical signs oftoxicity were observed during the study


### B. CHOLINESTERASEACTIVITY:
1. 

### Plasma: Following oral exposure, greater than 60% decreased activity was observed intwo of the five subjects two hours post-dose (first time point monitored), and four offive subjects displayed >70% lower activity at six hours post-dose (Table 2). Three ofthe six subjects displayed significant decreased plasma cholinesterase two hours post-dose (163%,**~**

### 70%,**~30%),** 

### and peak decreases occurred at 6 hours in one subject (187%), at 12 hours in two subjects (186%,**~89%),** 

### and at 24 hours inthree subjects (l71%,**~85%, ~86%).**  

### Recovery(< 20% decrease in activity) was observedby 22-30 days post dose.
As shownin Table 3, following dermalexposure,threeofthe five subjectsdisplayed apparently biologicallysignificant(>20%)plasmadecreased activityonorafter12hourspost-dose(Subject E**~** 

### 22%), on day 2 (SubjectE- 26%) or day 3 (Subject C**~** 

### 21%) that persisted at subsequent assessment times. Subject F (- 35% at Day3 3 only) was not considered to display actual inhibition since the lowerreading did not persist.

TABLE 2. Plasma cholinesterase percent decrease followine a sinele 0.5**~g/l_<.g_oral** dose Phase/interval Subject A (pilot) B 

### c D E F Pretest1 1.29 ± 0.13 1.13 ± 0.12' 0.87 ± 0.09 1.16 ± 0.12 1.26 ± 0.04 1.42 ± 0.17 2 hours

-2

- 63#



### - 70# 30# 6 hours 57 14# 87# 72# 84# 78# 12 hours 70 65# 85# 86 89 83 Day I 71 85 86 84 85 86 Day2 68 80 77 75 78 78 Day 3 37 73 74 71 71 76 Dav4 34 68 64 65 67 68 Day 8 ND3 58 48 49 56 54 Day 14 ND 28 17 30 36 27 Day 22


### - 12 22 30 37 28 Day 27 ND 9


### - 18 41 15 Day 30 ND 23 8 4 21 21 Chlorpyrifos* 

## x' 6-12 2-12 1-6 1-6 0-6 Percent mhibitiOn calculated by reviewer from data on pages 18 and 19 ofMRID 00124144 1Pre-test activity is the average oftwo (SubjectA) orthree (Subjects B-F) measurements and expressed as f<.. pHunits/hr 2

- value greater than pre-test 3 ND=Nodata 4 X not detected at detection limit of0.005 )..lg/mL Bolded numbers are peak inhibition # hours post oral dose chlorpyrifos was detected in blood

aDiffer from the study report which lists 1.09±0.09. The values are 1.23, 0.99 and 1.16 fro a mean of l.l3.EPA's Records Disposition Schedule PEST 361 Scientific Data Reviews HED Records Center- File R180234- Page 24 of 73

CHLORPYRIFOS Oral and Dermal Pharmacokinetic Study (Human) (1982) I Page 8 of 13 Nonguideline

TABLE3. Plasma cholinesterase oercent decrease followim! a sin2le 5 m2/k2 dermal dose
Phase/interval Subject B 

### c D E Pretest1 0.87 0.80 1.1 0.99 2 hours !3' +' 10 12 6 hours + 

### - 12 14 12 hours + 12 14 22 nav-1 + 15 18 19 nav-2 6 18 18 26 Dav 3 8 21 18 18 Day4 9 12 16 12 Day6 + 6 8 9 Dav8 + +
- 8 Dav9 + 15 9 14 Chlorovrifos' 0 6 6,24 0, 2, 10, 24 Percent mhtbttton calculated by rev1ewer from data onpages 18 and 19 ofMRID 00124144 1Cholinesterase activity (6. pH units/hr) on day 30 following acute oral dose 2 Bolded numbers are peak inhibition 3 No inhibition 

### *Sample interval when chlorpyrifos detected in blood F 1.12 + + + 19 + 35 + + + + 10



### 2- Whole blood: Following oral exposure, one subject (E) displayed RBC lower ((137%) cholinesterase two hours post-dose, but normal activity thereafter until day 14. Two other subjects (C and D) displayed RBC cholinesterase lower activity (153% and L46%) at 4 days post-dose. One ofthese subjects also displayed lowerRBC cholinesteraseonday 30post-dose (162%). These latter finding are considered spurious in light ofthe findings atprior and later assessment times which show comparable levels ofactivity among all subjects. Overall, no sustained decrease (i.e.> 30%) indicative oftrue enzyme inhibition was found in any ofthese subjects. Following dermal exposure (Table 5), none ofthe five subjects displayed RBC cholinesterase greaterthan 11% lower than the predosing mean at any time point.EPA's Records Disposition Schedule PEST 361 Scientific Data Reviews HED Records Center- File R180234- Page 25 of 73

CHLORPYRIFOS Oral and Dermal Pharmacokinetic Study (Human) (1982) IPage 9 of 13 Nonguideline

TABLE 4. RBC cholinesterase percent decrease following a sin1de 0.5 m2/k2 oral dose Phase/interval Sub'ect A (pilot) B 

### c D E Pretest1 0.92 ± 0.08 0.89±0.18 0.94 ± 0.08 0.91 ±0.15 0.90 ± 0.17 2 hours 10 + 2 + 6 hours 10 + + + 12 hours 182 + 2 + Day I 16 + 5 + Day2 8 + I + Day 3 I + + + Day 4 II 53 46 14 Day 8 NO + II 8 Day 14 NO 17 21 10 Day 22 16 X X X Day 27 NO 8 23 9 Day 30 NO 62 19 12 Percent mhJbJtiOn calculated by reviewer from data on pages 18 and 20 ofMRID 00124144 1Cholinesterase activity (,1, pH units/hr) 2 Balded numbers are peak inhibition NO= no data + value greater than pre-dose X result not included in**assessment~** no explanation provided 37 + + + + + II + 27 X + +

TABLE 5. RBC cholinesterase percent decrease following a sinele5 me/kg dermal dose Phase/interval Subject B 

### c D E Pretest1 0.342 0.76 0.80 0.93 2 hours 5 

### - + 3 6 hours + 3 + 3 12 hours + II + 10 Day I 

### s' + + + Day2 + + + + Day 3 + + + + Day4 + + 8 II Day6 + + + + Day 8 + + + I Day9 + + + + Percent mhibitiOn calculated by reviewer from data on pages 18 and 20 ofMRID 00124144 1 Cholinesterase activity (D. pH units/hr) on day 30 following acute oral dose F 0.96

2 2 + 6 4 I 9 4 3 +

2 Subject B activity was 0.82 on day 27 and 0.34 on day 30. Day 27 activity used for calculation 3 Bolded numbers are peak inhibition +No inhibition F 0.95 ± 0.18 5 + + + + + 13 + II X II

-



### 3. Chlorpyrifos and 3,5,6-TCPConcentration: Chlorpyrifos was detected sporadicallyin the blood ofall but one (subject A) at various times following oral (Table 6, from not detected to -0.005 up to 0.03 [.tg/mL) or dermal (Table 6, from not detected to -0.005 up to about 0.010 [.tg/mL) exposures. 3,5,6-TCP was detected in the blood ofall subjects at mosttime intervals following both oral ( up to 1.43 [.tg/mL) and dermal (up to 0.122 [.tg/mL in subject C) 

### exposures (Table 7). Following the oral dose, the highest level of3,5,6-TCP in the blood occurred at 2 (Subject C), 

### 4 (Subjects E, F), 6 (Subjects A and D), and 24 hours (Subject B) post dose. Peak TCP level following the dermal dose was at 24 hours for all five subjects. 3,5,6-TCP concentrations in urine were detected in each subject throughout the monitoringEPA's Records Disposition Schedule PEST 361 Scientific Data Reviews HED Records Center- File R180234- Page 26 of 73

CHLORPYRIFOS Oral and DermalPharmacokinetic Study (Human) (1982) I Page 10 of13 Nonguideline 

### interval (Table 8), with the highest concentrations ranging from 438 to 510f.!g/mL (oral dose) and 17.7 to 59.3 f.!g/mL (dermal dose). In all oral subjects, the highest 3,5,6-TCP concentration in urine was observed in 9 hours or less. Following dermal administration, the highest levels were generallyreached in about 24 hours or up to 42 hours (for one subject).
As shown in Table 9 (column 6), the apparent volume ofdistribution was 181 ± 

### 18 mL/kg (mean for the group), and the average halflife for 3,5,6-TCP eliminationfrom the blood was 26.9 hours (column 8) after oral treatment. No similarcalculationfor the halflife following dermal application waspresented in the reporttable butthe halflife was also estimatedto be similarto 27 hours. Based on the model parameters, 72 ± 

### 11% chlorpyrifos would be absorbed after oral treatment and 0.95 ± 

### 0.56% after dermal treatment. These results were in agreement with the concentration of3,5,6-TCP recovered in the urine following oral (70 ± 

### 11%) ordermal (1.02 ± 

### 0.57%).

TABLE 6. Blood chlorpvrifos concentration (u.2J'mL) Hours After Subject Dosing I A I B 

### c D 

### I E Oral Dose 0 ND ND ND ND ND 1 ND ND ND 0.006 0.005 2 ND ND 0.019 NA 0.011 4 ND ND 0.009 0.021 0.008 6 ND 0.012 0.012 0.021 0.008 8 ND 0.007 0.030 ND ND lO ND 0.008 0.006 ND ND 12 ND 0.028 0.015 ND ND Dermal Dose1 0 ND 0.007 ND ND 0.010 2 ND ND ND ND 0.008 6 ND ND 0.005 0.005 ND 10 ND ND ND ND 0.010 24 ND ND ND 0.006 0.007 48 ND ND ND NA NA Data from pages 21 and 22 ofMRID 00124144 1 Subject A received a single 0.5 rng/kg dermal dose while Subjects B-F received a single 5.0 mg/kg dermal dose ND =Belowdetection limit of0.005 )J.g/mL NA

**~Not** analyzed F

0.009 0.009 0.015 0.009 O.Ql8 ND ND ND

ND ND ND 0.005 ND NAEPA's Records Disposition Schedule PEST 361 Scientific Data Reviews HED Records Center- File R180234- Page 27 of 73

CHLORPYRIFOS Oral and Dermal Pharmacokinetic Study (Human) (1982) I Page 11 of 13 Nonguideline

TABLE 7. Blood 3,5,6-TCP concentration (JLI!imL) Hours After I Dosing I A (pilot) I B

1 ND ND 2 0.126 0.067 4 0.714 0.229 6 0.715 1 0.509 8 0.650 0.597 10 0.606 0.813 12 0.544 0.763 24 0.390 0.823 48 0.185 0.560 72 0.081 0.354 96 0.040 0.194

4 NA ND 6 NA ND 8 NA 0.028 10 NA 0.023 12 NA 0.043 24 NA 0.070 48 NA 0.068 72 NA 0.049 96 NA 0.032 144 

### I NA 

### I 0.019 Datafrom pages 23 and 24 ofMRID 00124144 1Bolded concentrations represent peak Subject I 

### c I D I Oral Dose

0.046 0.009 1.18 0.180 1.12 0.691 0.939 1.35 0.907 1.16 0.853 0.973 0.790 0.934 0.598 0.774 0.345 0.540 0.199 0.342 0.117 0.201 Dermal Dose2 0.019 0.018 0.067 O.DI8 0.079 0.020 0.107 0.037 0.102 0.035 0.122 0.057 0.106 0.056 0.080 0.046 0.060 0.031 I O.DI5 I 0.017 

### I 0.009 E I

0.012 1.09 1.19 1.07 0.994 0.810 0.818 0.624 0.268 0.081 0.060

ND 0.019 0.024 0.020 0.022 0.036 0.031 0.022 0.016 

### I

2 SubjectA received a single 0.5 mg/kg dermal dose while Subjects B-F received a single 5.0 mg!kg dermal dose ND =Below detection limit of0.005

**~-tg/mL** NA =Not analyzed

TABLE 8. Urine 3,5,6-TCP concentration (J..te/mL) followin2 oral dose Hours After I Dosing I A (pilot) I B

3 177 64 9 268 457 18 199 328 30 131 257 42 119 181 54 73 152 66 53 109 84 31 87 108 16 49

3 NA 1.4 9 NA 7.8 18 NA 21.1 30 NA 25.9 42 NA 24.8 54 NA 17.6 66 NA 20.6 84 NA 14.3 108 NA 9.5 162 NA 4.5 Data from pages 25 and 26 ofMRID 00124144 1Bolded concentrations represent peak ND

**~Below** detection limit of0.0025

**~Lg/mL** NA

**~Not** analyzed Subject I 

### c I D I E Oral Dose 231 167 438 510 492 409 269 212 368 229 177 229 140 134 208 121 116 178 96 95 57 65 73 67 38 34 30 Dermal Dose 2.2 3.3 ND 35.9 8.8 4.5 49.1 10.0 15.2 59.3 17.5 21.0 43.5 13.4 16.1 41.4 17.7 13.3 31.4 12.1 10.7 24.8 6.4 10.3 15.4 5.1 5.3 6.1 4.8 2.4 I F

0.216 0.996 1.43 1.29 1.16 1.04 1.05 NA 0.423 0.215 0.136

ND 0.013 0.028 0.014 0.019 0.029 0.028 0.019 0.018 ND

F

451 427 273 184 175 129 91 64 36

ND 10.8 13.2 7.9 55.5 24.2 8.7 16.4 9.9 3.88CHLORPYRIFOSOralandDermalPharmacokineticStudy(Human)(1982)IPage12of13Non2uidelineTABLE9.Modelparametersdescribingbloodconcentrationsandurinaryexcretionof3,5,6-TCPbyindividualvolunteersfollowingoralanddermaladministrationofchlo!]!Y!'ifosAbsorptionAbsorptionAbsorptionVolumeEliminationEliminationVolunteerWeightlagtimerateconstanthalf-life-distributionrateconstanthalf-life(kg)(hr)(hr')(hr)(mL/kg)(hr')(hr)Oral0.5melk2A77.11.91.70.41900.031821.8B80.71.60.16.91920.021931.7c83.71.03.00.22040.023229.9D71.71.00.32.11800.020533.9E101.8l.\2.70.3\600.032621.3F85.00.91.30.51600.024927.8Mean83.31.31.50.51810.025826.9'SD10.20.41.2180.0052Dermal5.0Ab77.1-0.022331.1---B80.7-0.027025.7---c83.7-0.049614.0---D71.7-0.033520.7---E95.0-0.024128.8---F85.0-0.028724.2--Mean83.20.032622.7SD8.40.0100Datafrompage12ofMRJD00124144aCalculatedasvolumedistributiontimeseliminationrateconstantbVolunteerAwasgivena0.5mg!kgdermaldoseandisnotincludedinmeanandstandarddeviationcalculationscHEDsecondaryreviewercalculatesthemeanandstandarddeviationas27.7±5.2.dBasedonthevaluesfromsubjectsB-FandnotincludingsubjectAAreaunderplasmatimecurve24.456.645.358.037.154.746.013.31.427.0611.176.163.263.186.173.29Renalclearance(mL/hr/kg)'6.04.24.73.75.24.04.60.9----Modelpredicted*lodoseabsorbed52847575697772II3.181.051.870.800.600.450.95'0.56.b.%Doserecoveredinurine49816773707970II2.601.001.980.700.500.901.020.57m"'"'"00a."'0iii".,0"'"'c;·:J"'0:J""c."".,m"'-i"'"'0;;;·3.:;;c;·0a""'"<J:m0"'"00a."'()":J:!!"000"'l;;!.,&l""'009.-..I"'EPA's Records Disposition Schedule PEST 361 Scientific Data Reviews HED Records Center- File R180234- Page 29 of 73

CHLORPYRIFOS Oral and Dermal Pharmacokinetic Study (Human) (1982) I Page 13 of13 Nonguideline


### III. DISCUSSIONAND CONCLUSIONS:
A- INVESTIGATORS' CONCLUSIONS: 

### Following oral or dermal treatment, no clinical signs oftoxicity were observed nor was RBC cholinesterase decreased. Plasma cholinesterase was decreased to 15% (i.e. 85% inhibition) ofpre-dose activities following oral treatment with 0.5 mg/kg chlorpyrifos but was essentially unchanged following dermal treatment with 5.0 mg/kg. Blood chlorpyrifos concentrations were low (<30 ppb), and no unchanged chlorpyrifos was found in the urine following eitherroute ofadministration. Average blood 3,5,6-TCP concentrations peaked at six hours after ingestion ofthe oral dose and at 27 hours after the 5.0 mg/kg dermal dose. 3,5,6-TCP was cleared from the blood and eliminated in the urine with a 

### TYz of24hours following both oral and dermal treatment. An average of70% ofthe oral dose, but <2% of the dermal dose was excreted in the urine as 3,5,6-TCP; indicating only a small fraction of the dermal chlorpyrifos dose was absorbed. The data also suggests that chlorpyrifos and its metabolite have a low potential to accumulate in man on repeated exposures.
B. REVIEWER COMMENTS:


### The objective ofthe study was to provide data onthe fate oforally and dermally administered chlorpyrifos inthe human. The kinetics ofchlorpyrifos and its principal metabolite 3, 5, 6-trichlor2-pyridinal (TCP) were investigated. No clinical signs oftoxicity or sustained inhibition ofRBC cholinesterase activity were observed following either the oral or dermal dose. In all five subjects, plasmacholinesterase was inhibited 83-89% relative to pre-dose activities following the oral dose (peak inhibition within 6-24 hours post dose) but was essentially unchanged following the dermal dose. Blood chlorpyrifos levels were extremely low (:S: 

### 30 ng/mL; limit ofdetection 5 ng/mL), and chlorpyrifos was not found in the urine following eitherroute ofexposure. 3,5,6-TCP blood concentrations peakedby six hours after oral exposure and 24 hours after dermal application. 3,5,6-TCP was cleared from the blood and eliminated in the urine with a mean half-life of-27hours following both the oral and dermal doses. Using assumptions offirst-order absorption and elimination, it was estimatedthat 72 ± 

### 11% ofthe ingested dose and 0.95 ± 

### 0.559% (based on the 5 subjects receiving 5 mg/kg dermal dose) and 3.18% (based on one subject receiving 0.5 mg/kg dermal dose) ofthe dermal dose were absorbed.
C. STUDYDEFICIENCIES:



### • not a double-blind study design and it is likelythat the subjects knewthey were actually given the test material.
• Same subjects administered oral and dermal doses ofchlorpyrifos
• only one sex (males)
• only one dose level- no dose-response information for either route ofexposure



### 3(EPA's Records Disposition Schedule PEST 361 Scientific Data Reviews HED Records Center- File R180234- Page 30 of 73

Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans 

# n**{)~** (non-guideline) 

### EPA Reviewer: John Doherty,

## Ph.D.e~ Reregistration Branch II, HealthEffe t, Divisihll

### ~J,. 

# ._./. / EPA SecondaryReviewer: LindaTay r,

## P~~<~C Reregistration BranchII, Health Effects Divtsion (7509P)


### TXR# 

### 0050308


### DataEvaluation Record
Study Type: Special

### Non-Guideline Assessment for RBC Cholinesterase in Humans.

DP Barcode: D368390 PC Code: 059101 SubmissionNo.: N/A Tox Chern. No.: 219AA

Test Material: DursbanR, 99.8% Chlorpyrifos (LotNo.: MM930503-17)
Citations: Kisicki, J.C., Seip, C.W. and Combs, M.L., 1999, "A Rising Dose Toxicology Studyto Determinethe No-Observable-Effect-Levels (NOEL) for Erythrocyte Acetylcholinesterase (AChE) Inhibition and Cholinergic Signs and Symptoms of Chlorpyrifos at Three Dose Levels", MDC Harris Laboratory, Lincoln Nebraska, StudyNo.: 21438 (for the Harris Project) and DRK-0044793-284 (for DOW AgroSciences), April 19, 1999, MRID No.: 44811002. Brzak, K.A. "A Rising Dose Toxicology Studyto Determinethe No-ObservableEffectLevels (NOEL) for Erythrocyte Acetylcholinesterase (AChE) Inhibition and Cholinergic Signs and Symptoms ofChlorpyrifos at Three Dose Levels

- Part B (Pharmacokineticparaoxonase data)". Toxicology and Environmental Research and Consulting, DOW, Study No.: 981176, June 5, 2000. MRID No.: 45144101. Juberg, D.R. and J.L. Mattsson "Updated DOW AgroSciences Response to EPA Query Regarding Two ToxicologyReports". DOWAgroSciences LLC, Indianapolis, IN, May 28, 2008, MRID No.: 47436401. Unpublished. Racke, K et a!, (2009) "Chlorpyrifos Response to EPA Query Regarding TCP Analytical Methods and Oral Absorption in Human Volunteers". ProjectNumber: KDR09232009, Unpublished study prepared by DowAgroSciences, LLC and CowChemical Company. MRID No.: 47866701. Unpublished.
McKellarL. (1979) "Determination ofChlorpyrifos and 3,5,6-trichloro-2- Pyridinal in Whole Blood and Urine by Gas Chromatography" ProjectNumber ACR/79/9. Unpublished study prepared by the Dow Chemical Company. MRID No.: 47866703. Unpublished.

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Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans (non-guideline)



### Sponsor: Some ofthe datafrom this study were published: Timchalk, C. etaa! (2002) A physiologicallybasedpharmacokinetic and pharmacodynamic (PBPK/PD) model for the organophosphate insecticide chlorpyrifos in rats and humans. Toxicological Sciences 66:34-53. MRID No.: 47918802.
DOW AgroSciences.
Executive Summary: In a special acute oral study (1999, MRID 44811002)performed to assess effects onhumanred blood cell (RBC) acetylcholinesterase (AChE), chlorpyrifos (99.8%; Lot#MM930503-17) in a gelatin capsule was administered to 6 human subjects/sex/dose group at dose levels ofO (lactose-filled capsule), 0.5 or 1.0 mg/kg (Phase 1). When it was determined that there was no inhibition andno adverse reactions in these subjects, a second phase of6 human subjects/sex/group were dosed similarly as control and 2.0 mg/kg chlorpyrifos. The subjects were valuated vital signs (bloodpressure, pulse, respiration and temperature the morningpriorto dosing and at 1, 2, 4, 8, 12, 24,48 and 168 hours postdosing. In addition hematology, clinical chemistry and urinalysis assessments were performed one weekpost dose. Bloodwas assessed at -10hours, zero (pre-dose), and at 2, 4, 8, 12, 24, 36, 48, 72, 96, 144 and 168 hours post dose for RBC AChE assessment. 

### Plasma cholinesterase (ChE) was not assessed. Blood and urine were collected at selected intervals and analyzed for chlorpyrifos, chlorpyrifos oxon and the principal metabolite 3,5,6-trichloro-2-pyridinol (TCP) to define the pharmacokinetics ofchlorpyrifos in humans. The paraoxonase (PONI) status was determined for each subject. Serum paraoxonase activity was measured against chlorpyrifos oxon, paraoxon, and diazoxon, and called chlorpyrifos oxonase (CPOase), paraoxonase, ordiazoxonase, respectively (MRID# 45144101). Additionally, the PON phenotype (i.e. QQ, ORand RR) was determined for each subject. 

### Systemic Effects. There were no apparent clinical reactions or changes in clinical chemistry parameters related to treatment. 

### Pharmacokinetic Data. Chlorpyrifos was detected inthe serum of4 ofthe 12 subjects (2-8 hours post dose) in thel.O mg/kg dose (range of 1.1-5.6 ng/g) and in4 ofthe 12 subjects (2- 12 hours postdose) inthe 2.0 mg/kg dose (range 1.3-18 ng/g). Subject (#56, QQ phenotype and the only subject demonstrating RBC AChE inhibition) but withdrewfrom the study after 48 hours had a peak concentrationof 18 ng/gm chlorpyrifos at 8 hours. This same subject also had the highest levels ofserum and urinary TCP accumulatedupto 48 hours. The serum chlorpyrifos and serum and urinary TCP data all suggestedthatthis subject absorbed more ofher dose than the other subjects on the study. CPOase for this subject was similarto the other subjects withthe phenotype QQ. TCP was detected inthe blood ofall subjects through 120 hours (0.5 and 1.0 mg/kg) and through 168 hours (2.0 mg/kg). Thehighest concentration ofTCP reached ranged from 110-380 ng/g (0.5 mg/kg), 140-610 ng/g (1.0 mg/kg), and 370-1600 ng/g (2.0 mg/kg). Chlorpyrifos and chlorpyrifos oxon were not found inthe urine at any dose level, and chlorpyrifos oxonwas not found in the blood ofany subject.

. 

### RBCAChE. Zero time (preclosing) baseline RBC AChE was from 8143±982 (±12%) to

2EPA's Records Disposition Schedule PEST 361 Scientific Data Reviews HED Records Center- File R180234- Page 32 of 73

Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Hwnans (non-guideline) 9572±539 (±6%) 

### U/L for males and 8576±556 (±6%) 

### and 9165±709 (±8%)

### U/L for females indicating good precisionfor the baseline data. These RBC AChE values were within the expectedrange for humans. Only one individual had a decrease in RBC AChE that suggested inhibition by chlorpyrifos as indicated by being 

### consistently decreasedat the critical hours post dosing. For this subject (#56, 

### a female dosed with 2mg/kg), inhibition ofRBCACHE was observed at 8 (23% -l-), 12 

### (maximum 28% -l-), 24 (26%-l-), 36 (19%-l-) 

### and 48 (21%-l-) 

### hours post dose. There were no associated cholinergic symptoms reported, although atransient numbness in the upper arms in this subject was reported at about 2hours post dosing or well before AChE inhibition and significant levels ofTCP in the serum were detected. TheLOAELis 2 mg/kg/day for RBC AChE based on 28% inhibition in one female subject. The NOAEL is 1 mg/kg.
Classification This study is classified asAcceptable/Non-Guideline and to contain useful information on the phannacokinetics oforally administered chlorpyrifos when administered in a capsule to human volunteers. The study, however, should not be used for endpoint selection or for impactingthe uncertainty factors for risk assessment. The RBC AChE inhibitory assessment aspects ofthis study depend upon only one subject showing clear evidence ofinhibition. Another serious problem with this study with regard to comparing the results with other studies in human volunteers is thatno assessments ofplasma cholinesterase were made. Differences inthe method ofdose administration where a chlorpyrifos was administered in a capsule inthis study and on top ofa lactose pill after dissolving in solvent in the Nolan study preclude direct comparison ofthe phannacokinetic data. 

### Compliance: No-Data Confidentiality Claims (No claim ofconfidentiality within the United States), GLP and Quality Assurance Statements were provided. The study was said to be conducted in accordance with all applicable U.S. guidelines as specified in Title 21 

### ofthe Code ofFederal Regulations parts 50, 556, 

### and 321 

### and the International Guidelines for HumanTesting as promulgated in the Declaration ofHelsinki (1964 

### and as amended 1996).


### Institutional Review BoardApproval. AdditionalComments on theEthics aspects of thisstudy wereprovidedbyMr. John Carley of the OPP. There were two letters (see pages 134 

### and 135 

### ofthe study report) from the Secretary (or acting secretary) ofthe MDS Harris Laboratory that indicated that the protocol was approved by the MDS Harris Institutional Review Board. These letters mentioned only minor changes to the protocol. There was no document in the study report that listed the membership or their professional status ofthe MDS Harris Institutional Review Board.
The study was conducted under the supervision ofJames C. Kisicki, M.D. who is the Medical Director, Clinical Research Division ofthe Harris Laboratories in Lincoln, Nebraska. Dr. Kisicki has Board Certification from the National Board ofMedical Examiners and American Board ofFamily Practice.

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Chlorpyrifos/P. C. Code 05910I Special RBC AChE Inhibition Study (1999) Humans (non-guideline) 

### PartA. Clinical aspects including AChE Assessments (MRID No.: 44811002).

A. TestMaterials:

Test Chemical: Chemical: Source: Lot: Purity: Appearance: CAS# Chemical

Name: 

### Experimental Constants

DursbanR

- technical name for chlorpyrifos DOW AgroSciences LLC MM930503-17 99.8% (scheduled for decertification in June 2003) White crystalline powder 2921-88-2 0,0-diethyl 0-(3,5,6-trichloro-2-pyridinyl) phosphorothioate Negative Control (placebo): Chemical: Lactose Source: Mallinckrodt N.F. Lot: 6279 KXHA Purity: CAS#
B. 

### Human Subjects: Not specifically stated but stated to "meets N.F. requirements" 63-42-3



### The subjects were recruited from the Lincoln, Nebraska area inresponse to a advertisement. The criteria for selection for inclusion and continuation in the study were described on pages I02 toI06 ofthe studyreport.
Some ofthe characteristics ofthe participants who were actually dosed with eitherthe control (lactose) orchlorpyrifos are as follows:

Number: Occupations: Age: Weight: Race: Medical History: 30 males and 30 females. Not stated for each individual. Males: 19 to 54 years; Females: 20 to 52 years. Males: 146 to 224 pounds; Females: 98 to 200. Males: 28 Caucasian, I black and I Asian; Females: all Caucasian. Table 4.4 (page 243) presented comments on the medical history of each subject. Inthe opinion ofthis reviewer, the medical history appeared to be typical ofa group of60 humans within this age bracket. There did not appearto be any medical conditions that would affectthe outcome ofthe study. The only entries for subject#56 were that she was a non-smoker and was hospitalizedtwice for childbirth (12/93 and I0/97).

Note: Additional tables presented the results ofurinary analysis for drugs (cocaine, ethanol and cannabinoids) taken from samples at screening and "interim". All entries were indicated as being negative. Datawere also presented for the results ofthe pregnancytest and all entries were negative.

4EPA's Records Disposition Schedule PEST 361 Scientific Data Reviews HED Records Center- File R180234- Page 34 of 73

Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans (non-guideline)


### C. Experimental Protocol. The experimental protocol is described in Table I below.
Table I. 

### Experimental Design.

Group Phrase Dose (mglkg) Subjects Comments

A I 0.5 6 o/6"' Blood sampled at -I0 and O, hrpretreatment and at 2, 4, 8, 12, 24, 36, 48, 72, 96, 120 144
6 o/6"' and 168 hours posttreatment and analyzed for B I 1.0 RBC AChE, chlorpyrifos and its metabolites.

D(J) I 0 6 o/6 "' Urine, blood pressure, pulse, ECG and body temperature and clinical laboratory (placebo) assessments were made at pretest and one 

## c II 2.0 6 o/6"' week after administration ofplacebo or chlorpyrifos. The subjects were released from the study D(2) II 0 6 o/6 

### 'f' after 7 days. (placebo)
Total**Subjects~** 30 oand 30 

### 'f'.

. . Phrase Iwas conducted first and when It was determmed that there was no InhibitiOn ofRBC AChE and there were no adverse effects, Phrase II was initiated. Phase I groups were dosed on I0/3/98 and Phase II groups were dosed on I0/17/98. 

### Note: In response to HED's questions concerningreassignment ofindividuals for inclusion in the study, the DOW Companyprovided a detailed response (D.R. Juberg and J.L. Mattsson, "Updated DowAgroSciences Response to EPA Query Regarding Two Toxicology Reports", May 28, 2008) that clarified the identity ofthe individuals on the study and their given dose. One question remains concerning the dose given to subject#47 and it cannotbe determined ifthis subject actually received the assigned dose of2 mg/kg or a slightly lower dose
C. Basis for Dose Level Selection:
The low dose of0.5 mg/kg was based on aprevious study (Nolan, 1984; MRJD 00124144) in which this dose level produced decreases in plasma ChE by 80% but had no effects
on RBC AChE and did notresult in clinical signs. This dose was included to provide aNOEL for RBC AChE. The nexthigher dose ofI mg/kg was thoughtto be a dose where noticeable RBC AChE might be expected without showing clinical signs in the subjects. The higher dose of 2 mglkg 

### was initiated when it was established that there was no inhibition ofRBC AChE at I mglkg 

### in order to reach a level where noticeable inhibition ofRBC AChE might be attained. It should be noted here that administration ofthe chlorpyrifos in this study was in a capsule but no capsule was used in the Nolan study.

D. Dosing Data Each subject was dosed based on his/her body weight and chlorpyrifos was weighed out to the 0.I mg and placed in white opaque number zero capsules the day priorto dosing. The


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Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans (non-guideline) 

### capsule was "filled withlactose" andthen closedpriorto dosing. Dataonthe actual mg of chlorpyrifos administered to each subject thatreceived the chlorpyrifos were presented inTable 4.27, page 545. This tablepresents the weight ofthe capsule, the weight ofthe capsule plus the chlorpyrifos as well as the weight plus lactose and the subject's weight to assure that each subject was administered the properdose in mg/kg. For example, subject#56 had abody weight of87.7 kg and was dosed with 173 mg ofchlorpyrifos (268 mgweight ofcapsule plus chlorpyrifos- 95 mgweight ofcapsule). The dose this person in the 2 mg/kg dose group received was 173 mg/87.7 kg= 1.97 mg/kg.
The subjects arrived at the clinic the day before scheduled dosing and at 8 PM were given a "snack" butfasted for the next 10 hours. The subjects were given abracelet with a unique bar codeto identifY specimens collected. Starting at approximately 7 AM, each subject was given his/her dose ofeither lactose only orchlorpyrifos containing capsule. Each subject was watched to assure the capsule was swallowed. Following swallowing, each subject was given 240 mL of water and it was assured by the study team that the capsule was swallowed. The subjects were given their lunch at approximately II:30 AM and dinner at4:30PM and then a snack at 8:30 PM. The subjects were kept atthe clinic for 48 hours and were required to return to the clinic at 72, 96, 120, 144 and 168 hours after initial dosing. Althoughthe subjects were asked about strenuous activity priorto coming to the clinic, there were no comments on the level ofphysical activitythe subjects were allowed following dose administration. There were restrictions on the consumption ofalcohol and tobacco as well as non-prescription and prescription drugs.
In response to several inquiries that HED made regarding why alternates were needed and the fate ofsome ofthe subjects, the DOW company responded in a supplemental report (2008, MRID 47436401). This report indicated that alternates were used because some ofthe originally assigned subjects either were late reporting or reported with various symptoms thatthe staff determined might affect the study. Ofthe alternates used there remains one subject (#47) where there is some confusion as to whether or not his dose was correctbased on conflictingbody weight and dose administered data. It

### cannotbe determined with certainty ifthis person was dosed at arate of 1.63 mg/kg orhis group dose of2 mg/kg.
C. Statistics (Reproduced from the study report page 23-25). Demographic variables: Descriptive statistics (mean, standard deviation. minimum, maximum, and sample size) were calculated for continuous demographic variables (age, height, and weight) andfrequency counts weretabulated for categorical demographic variables (gender, race, and frame size) by gender, by treatment group, and by phase.
Vital signs: Foreachphase, descriptive statistics were reported for all vital signs measurements (sitting systolic and diastolic blood pressure, pulse, respiration rate, and temperature) at each timepoint ofcollection. Ifa vital signs measurement was re-tested priorto dosing, the re-test value was used, instead ofthe original value, to calculate the descriptive statistics. However, ifa

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### re-test was required for apost-dose assessment, the original value was used to calculate the descriptive statistics. All collected data were included in the summarization ofvital signs assessments. Where individual datapoints were missing, datawere summarizedbased on reduced denominators. Signs and symptoms: Signs and symptoms were codedusing the 5th Edition ofthe COST ART Adverse Event dictionary. These data were tabulated by the number ofsubjects reporting at least
one symptom and as percent ofnumber ofsubjects dosed in each treatment group.
RBC AChE: RBC AChE concentrations were presented by subject and blood collection timepoint and were summarizedbytreatment group and gender using means and standard deviations. RBC AChEpercent ofbaseline concentration values were presented and summarized in the same way. Percent ofbaseline at timetwas calculated as follows:
Percent ofBaselineI = (AChE* I00)/baseline
where AChE represents the RBC AChE concentrations at timetand that individual's baseline is the average ofthe concentrations collected at time -I0 and time 0predose. All collected RBC AChE concentrations were included in the summarization by gender and treatment group. Where individual datapoints were missing, datawere summarizedbased on reduced denominators. These percent ofbaseline data were inspected and a depression of20% or more in any subject's RBC AChE activity, relative to the baseline and in the absence ofaconcomitant shift in the RBC AChE activity for the control group, was considered a significant depression. The RBC AChE activity was also normalized for both baseline and for RBC AChE activity for the concurrent control (placebo) group for gender atthe time interval. Percent ofbaseline normalized to concurrent control attime t was calculated as follows:
Normalized Percent ofBaseline,= (I00*AChEt/baseline)**~control,+** 

### I00
where AChE and baseline are defined as above and control is the meanpercent ofbaseline response for the control (placebo) group at time t by gender. These data were presentedby subject and timepoint and were summarizedby treatment group and gender for eachtimepoint using means and standard deviations.
For the statistical analysis, the normalized data were truncated after 96 hours for Phase I and after 48 hours for Phase 2 so that there would be a value for each subject at each time point. Then the truncated normalized data sets from Phase I and Phase 2 were analyzed, separately, using univariate repeated measures analysis ofvariance (ANOVA) methods and mixed effects modeling to investigate ifthere were statistical differences attributed to treatment. A univariate repeated measures ANOVA was performed as a split-plot analysis withthe gender by treatment combinations, denoted as group, as the whole plotfactor and time as the subplot factor. In this setting, the time and group bytime interactions are valid only ifthe data satisfied the sphericityproperty, which says measurements at all timepoints are equally correlated. Since this was not expected to betrue, statistical tests were adjusted for the violation ofthe sphericity

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### assumptionusing Greenhouse-Geisser and Huynh-Feldt adjustments.
Mixedeffects models were also used where gender and treatmentwere consideredto be fixed factors and time was consideredto be a random continuous covariate.
This approach allowedthe modeling ofthe effect ofgender and treatment overtime in a structured way, providingthe opportunity to identifY significant higher-order trends associated with AChE inhibition. Covariance structures andterms inthe mixed effects models weretested using likelihoodratio tests comparingnested models. Covariance structures failing to provide adequate fit and terms not statistically significant at the 0.10 level ofsignificance were excluded from the model. Differences among the treatmentby gender combinationpairs were tested using contrast statements withinthe final mixed effects model and were considered statistically significant at the 0.05 level ofsignificance.
All summarizationand analyses were conducted using SAS. Outputfrom all SAS programs are included in Appendix 3, Supporting Statistical Documents. 

### Specific Methods and Results
I. Comments onthe Subjects and TheirParticipation Duringthe Course ofthe Study.
There were sixty individuals (30 males and 30 females) enrolled in the study that were actually dosed withchlorpyrifos (36 subjects, 18 males and 18 females) or placebo (24 subjects, 12 males and 12 females). Ofthe 60 original subjects selected, about 14 were replaced by alternates priorto administration ofthe dose for various reasons. This is not consideredto affect the outcome.
Two subjects, one female placebo (#32) and one female dosed with 2 mg/kg (#56) did not completethe study. The former did not return for the day 6, 7 or 8post dosing assessments and was discontinued as perthe SOP. Sincethis subject was inthe placebo group, the dismissal of this subject is less consequential. The female (#56) dosed with 2 mg/kg chlorpyrifos was described as having a personal conflict and did notreturn on days 4, 5, 6, 7 or 8 for post dosing events. This subject will be discussed in the later sections ofthis review in more detail.
A third subject (#II), a male dosed with 1mg/kg did not provide a blood sample at 168 hours since he was outofthe area at the time. He returned to the clinic for subsequentfollow up investigations (physicals) and was not dismissed from the study. This is not considered consequential because 168 hours is well pastthe expectedtime ofeffect ofchlorpyrifos.
One subject (#6), a male inthe placebo group, consumed alcohol onposttreatment days 6 (equivalentto one Margarita). This is not considered consequential to the interpretation ofthe study.
Five subjects (#s 35, 43, 49, 50 and 60; mid-dose female, high-dose male, high-dose

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### female, control female, control female, respectively) either failed to provide urine samples for a given interval or did not collecttheir samples properly such as failure to collect ordid not collect in the proper container. This is not considered consequential to the assessment ofAChE but may be relevant to the pharmacokinetic studies.
2. Clinical Signs and Electrocardiogram
The subjects were instructed to inform the physicians and/or nurses ofany signs or symptoms that they experienced. They were also asked ifthey felt thatthey received the test material and ifthey did why. Vital signs includedblood pressure, pulse, respiration and body temperature and were assessed on the morning priorto dosing and at 1, 2, 4, 8, 12, 24, 48 and 168 hours post dosing. The observers that examinedthe subjects classified symptoms as possibly and/or probablyrelated to treatment ifa symptom was noted within 48 hours of treatment. Since the observers did not know ifa subject actually received chlorpyrifos, some of the subjects receiving the placebo were said to have symptoms possibly orprobablyrelated to the test material. Appendix Table I shows the signs that were indicated by the subjects in eitherthe placebo or groups dosed with 0.5, 1or 2 mg/kg ofchlorpyrifos. Electrocardiograms (ECG) were done on screening and one week after administration of the placebo orchlorpyrifos. Table 4.10 (pages 345 to 351) presented the data for these analyses. All result entries were reported as "normal". There were some subjects with "sinusbradycardia" noted at week one post dosing that was notpresent in the screenbutthese occurredin the placebos as often as in the treated subjects. There were no indications ofabnormal recordings to indicate that chlorpyrifos affected the heart. 

### The one week intervalbetween the time of test materialadministration andECGassessmentis consideredby this reviewertoo longto be meaningfulto detect for an acute response to an OP.
The study author asserted that "There were no differences noted during this study attributed to treatment withregard to signs or symptoms, vital signs orclinical laboratory results". HED reviewers concur withthis conclusion. There is no indicationthat a symptom in the treated groups was any greater than similar symptoms in the placebo groups. Other signs occurred at times that did not coincide with any indication ofinhibition ofRBC AChE.
3. Clinical Chemistry,Hematology and Urinalysis.
Clinical chemistry, hematology and urinalysis assessments were made at pretest screening and one week after dose administration. 

### The one week interval following dosing andclinical chemistry, hematologyandurinalysis is notconsideredby this reviewerto be themost appropriate time.
Serum chemistry included: ALT, AST, albumin, alkaline phosphatase, calcium, chloride, cholesterol, creatinine, GGT, glucose, inorganicphosphorous, LDH, potassium, sodium, total

9

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### bilirubin, total protein, urea nitrogen and uric acid. Special RBC AChE Inhibition Study (1999) Humans (non-guideline)



### Hematologyincluded: basophils, eosinophils, HCT, Hgb, lymphocytes, monocytes, neutrophils, plateletcount, RBC and WBC Urinalysis included: bacteria, bilirubin, blood, casts, glucose, ketones, leukocyte esterase, nitrite, protein, RBC, specific gravity, urobilinogen, WBC and pH. Inspection ofthe data tables (pages 413 to 454) did not indicate that these parameters were affected by chlorpyrifos treatment. It 

### shouldbe noted; however, that subject#56, the only subject showing inhibition ofAChE, withdrew from study after48 hours and did not provide blood orurine samples for clinical chemistry, hematology or urinalysis.


### 4. AChE Assessments. Analytical Methods for AChE assessment.
Bloodwas withdrawn via venipuncture onan arm vein and there were atotal of 14 blood specimens collectedper subject (ifthey completedthe study). Once drawn, the blood samples
were centrifuged for 12 minutes at 3000 rpm and the plasmadiscarded (except for the prescreening sampling). The erythrocytes were then washed with saline and centrifuged for an additional 12 minutes at 3000 rpm. The saline was discarded and the erythrocytes were washed twice by the sameprocedure. The resulting erythrocytes were stored frozen and shipped on dry ice from the clinical facility located in Lincoln, Nebraskato the MDS Clinical Laboratory located in Toronto, Ontario Canada. AChE was assessed by the Ellman method using acetylthiocholine
as the substrate. The analysis was made using a Hitachi 917 automated analyzer. Appendix 5 (pages 547 to 573) described in detail the methods for the preparation and assay and mean data for assessment ofthe RBC AChE by the Laboratory. It

### was noted that the standardprotocol for this assay called for initially centrifuging the whole blood for 30 minutes (see page 552) and not the 12 minutes as indicated for the subject's samples in this study. This difference is noted but it is not considered to impactthe interpretation ofthe data.
An overview ofthe results ofthe RBC AChE assessments is presented in Table 2. Comments on Table 2 are as follows. Additionalmean andindividualRBCAChEdata are in Appendix -11 

### in tablesA-J


### Precision of the data.
The mean results for all groups for RBC AChE data are presented in Appendix I. The
mean data for RBC AChE in U/L for the untreated male subjects when assessed at 0 hourranged from 8143 ± 982 (±12%) to 9572 ± 539 (±6%) for the five different groups. For females the range was 8576 ± 556 (±6%) to 9165 ± 709 (±8%). The highest mean for both males and females was found in Group B scheduled for dosing with 1.0 mg/kg with chlorpyrifos.

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### The mean values for males and females are within the expectedrange for human RBC AChE. In general, the analytical aspects ofthe measurement ofRBCAChE are considered appropriate.


### Indications of RBCAChEInhibition Basedon Comparison of theMeans.
Males. No treatment-related effect was observed in RBC AChE activity at any dose level. Columnthree ofTable 2 showsthatthe meanRBC AChE value for one ofthe two male placebogroups was 10.2% less than the preclosing mean and this difference was noted at 144 hours post dosing. The treatedmales based on mean datahad maximum decreases of-10.7%,

- 13.7% for the 0.5, 1.0 and 2.0 mg/kg dose groups respectively when comparedto the preclosing values. These maximum depressions ofthe means were at 96 hours postdose. Since chlorpyrifos is an organophosphate, it would be expected that inhibition would start to occur and remain from about 2 hours to over 24 hours. Thus, 96 hours is well pastthe critical hours for expected initiation ofinhibition.
Females. No treatment-related effect was observed in RBC AChE activity at the 0.5 and 1.0 mg/kg dose levels. At 2.0 mg/kg, one (Subject#56) ofthe six females displayed RBC AChE apparent inhibition (19%-28%) during the 8-48 hour time interval post dose. All otherfemales at this dose level showed no definite inhibition. Among females, the two control groups demonstrated that there was as much as a -9.6% decrease in RBC AChE and maximum difference was again at 96 hours. Thetreated groups demonstrated -6.8%, -8.7% and -10% (for all subjects but only -6.2% when one subjectthat did not complete the study is not included) for the 0.5, 1and 2 mg/kg dose groups, respectively. Thus, the decreases inthe means for all treated groups are near the maximum decrease that was noted in the placebo group but one subject in the high dose appears to show inhibition.
The data from several individual subjects are discussed below.

11



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Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans (non-guideline) Table 2. Overview ofthe results ofthe RBC AChE assessments.

Mean Lowest Highest Lowest% Preclosing Posttreatment Posttreatment for an Group (Hour0) U/L Mean (U/L) Mean (U/L) individual
D: Control! Males 8143±982 7316±598 8043±705 88.36%@ 144 hr (12%)1 -10.2%@ 144

## h? +2%@12hr (#10)3

Females 8619±861 7795±759 8817±884 83.26% @6 hr (10%) -9.6% @ 96hr +2.3%@ 8 hr (#34)
A: 0.5 rn/kg Males 8998±730 8036±738 9189±924 82.68% @ 96 hr (8%) -10.7%@ 96 hr +2.1%@ 8 hr (#9)

Females 8612±1160 8028±917 8938±917 88.62%@ 36 hr (13%) -6.8%@ 144 +3.8%@ 144 h (#19 

### 8: 1.0 mg/kg Males 9572±539 8263±399 9862±865 75.47%@ 96 hr (6%) -13.7%@ 96 hr +2.9% @4hr (#II)

Females 9165±709 8366±499 9396±517 88.99%@ 144 hr (8%) -8.7%@ 168 hr +2.5% @4hr (#33)
D: Control2 Males 9171±1112 8999±1020 9425±1041 89.71%@ 144 hr (12%) -2%@ 36 hr +2.8%@ 72 hr (#44)

Females 8576±556 8380±422 8941±442 88.40%@ 144 hr (6%) -2.2%@4 hr +4.3%@ 72hr (#50)
C: 2.0mglkg Males 8608±896 8584±806 9004±840 89.97%@ 36 hr (10%) (no difference) +4.6%@ 72 hr (#48)

Females 8623±855 7761±1239 8604±1064 71.77%@ 

### 12 hr (10%) -10%@ 12 hr. (no difference) (#56) 8089±1088 92.82%@ 12 hr -6.2%@ 12 hr4 (#58)4 Dataare from 5.1.1 and 5.1.2 for Groups A, B, and Control I and 9.1.1 and 9.1.2 for Group C and Control 2. 1The number in() is the standard deviation as percent ofthe mean. 2The percent is the difference

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Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans (non-guideline) between the highest or lowest mean vs. the control at the interval given. 3 The individual subject number for the person showing the lowestrelative reading for AChE and the interval thatthis reading was made. 4 Since subject 56 did not complete the study, the reading for the second lowest subject is also presented for this group or the mean for the reaming 5 subjects is presented.


### Indications of RBCAChEInhibition BasedonIndividualResponses, Note: Additional data on thephenotype association with RBCAChEarepresentedinAppendix 11 Tables. A-C.
Comment. There is an apparent decrease in the activity noted in Phase I for the males and/or females in the placebo, 0.5 and I 

### mg/kg dose groups since at hour 96 many ofthese (placebos included) suddenlyhave readings lower than theirprevious readings for RBC AChE. There was no explanation for this provided. See Table 5.1.2 on page 60 ofthe study report. Since hour 96 is well pastthe time when chlorpyrifos wouldbe expectedto startto cause inhibition, the impact ofthis sudden decrease in activity is not such as to seriously impactthe interpretation ofthe data. This sudden decrease in activity was not noted for Phase II

### ofthe study when bothplacebo and 2 mg/kg chlorpyrifos were tested (see Table 9.1.2 page 79 ofthe study report).
Males. Refer to Table H in Appendix. Column five ofTable 2 shows that for the control group males, one individual demonstrated 11.6% (subject# 1 0) and another demonstrated 10.3% (subject# 44) less thanhis preclosing value. Among the treated groups, there was a maximum of 17.4% (subject#9), 24.5% (subject#11) and 10% (subject# 48) apparent decrease in RBC AChE for the 0.5, 1.0 and 2.0 mg/kg dose groups, respectively. Since there are subjects inboth the 0.5 and 1.0 mg/kg dose groups that have apparent decreases in AChE it canbe implied that these individuals may be unusually sensitiveto inhibition ofAChE by chlorpyrifos. Thus, the following will discuss in more detail the overall response ofthese individuals throughout the study. Selected other subjects will also be discussed for the reasons givenbelow. Subject # 9. Group A. (0.5 mg/kg chlorpyrifos treatment). Subject#9 was a 19 year old Caucasianmale 75 inches tall and weighing 210 pounds and was a non-smoker. No clinical signs or abnormalities were noted in this persons clinical chemistry orECGassessments. This subject was reported as having intestinal cramps starting at 2 days, 22 hours and44 minutes post dosing that lasted 15 

### hours. This subjectreplied "no" when asked ifhehadreceived the test material and not the placebo.
This subjecthad RBC AChEreadings (in U/L) 

### of8294, 8602, 8437, 8646, 8844,8723, 8580,8261,8107,8250,6985 (-19%), 7535 (-12%), 7376 (-14%) and 7700 (-11%)forthe10, zero, 2, 4, 8, 12, 24, 36, 48, 72, 96, 120, 144 and 168 hour assessmenttimes respectively. Thus, indicating that the apparent decrease in RBC AChE did not beginuntil 96 hours after dosing. It

### is noted that the cramps didnotcoincide withthe lower AChE levels. It

### was noted above that there is aproblem withthe assays after hour 96 (see comment above).
At the onset ofthis subject's intestinal cramps (-72hours), his RBC AChE was atmost 3% less than the zero timereading. However, at 96 hours, his RBC AChE was lowest buthis cramps had already disappeared by 85-86 hours (see Appendix I).


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In conclusion, there is nojustificationto supportthatthis individual was unusually sensitiveto inhibitionofRBC AChE. Inhibitionwouldbeexpectedto appear within a few hours(- 4-8 hours) post dosing and not 96 hours later. There were also no symptomatic expressions indicative ofAChE inhibition (i.e. intestinal cramps are not a specificresponse to a AChE inhibitor and couldbe dueto manythings). 

### Subject #

### 11. Referto Table F in Appendix. Group B (1.0 mg/kg chlorpyrifostreatment). Subject# II was a 45 year oldblack male 71 inches tall and weighing 191 pounds and smoked
one and a halfpackages ofcigarettes a day. This subjectdid notreport for his day 

### 7 examinations or blood sampling. He did not submit urine for the 144to 156 houror 156 to 168 hourcollection intervals. He returned to the clinic "the following week" for a postphysical exam, ECG and laboratory workup. There was no record ofhowhe responded to whether or not he thoughthe had receivedthe test material ratherthanthe placebo. This subject's clinical laboratory work up for posttreatment indicatedhe was "moderately lipemic".
Ontwo occasions (referto page 468 and Appendix 4.2111) this subject was reported to have a headache. The first occasionbegan 3 hours and40 minutes post dosing andlasted for 19hours. Thismeans the headache started at II am on October 3 and lasteduntil 6 am on October4. The secondoccasionbegan22 hours and40 minutes (approximately 6 am onOctober4 postdosing and lasted I day and 9 hours. [There seems to be a reporting glitchhere becausethe first headache is reported to be resolved at 6:00 and the second headache starts at 6:00 both on October4, 1998. There may actuallybejust one headache.]

This subjecthadRBC AChEreadings (in UIL)of 10307, 10098,9097 (-10%), 10318, 9768 (- 3%), 9779 (-3%), 9977, 9768,9141 (-10%), 10153, 7700 (-24%), 9185 (-9%), 9218 (-9%) for the -I0, zero, 2, 4, 8, 12, 24, 36, 48, 72, 96, 120 and 144 hour assessmenttimes, respectively (not assessed at 168 hours). Thus, there was considerable variation inthis individual's readings for RBC AChEbutthey do not fit anexpectedpatternofinhibition by an organophosphate. Since maximum apparent decrease occurred at 96 hours post dosing (againthere is a problem with the hour 96 readings) andthe reading at 72 hours was 10153 or essentiallythe same as thepreclosing
zero hour, this subjectis not consideredto have chlorpyrifos related inhibition ofChE.
Itis noted thatthere was no consistentdepression ofRBC AChE during this interval whenthe subject experiencedhis headache. For example, the readings were -I0%, similar, -3%,- 3%. -3%, and -3% at 2, 4, 8, 12, 24 and 36 hoursrespectively.

In conclusion, there is nojustificationto supportthatthis individual was unusually sensitiveto RBC AChE inhibition bychlorpyrifos. The headachethatthis individual was reported as having did notcoincide withdecreased levels ofRBC AChE and itwas notpresent when AChE was lowest. 

### Subject #47. Group C (2 mg/kg chlorpyrifos treatment, butthis subjectmay have actually received a dose of 1.66 mg/kg). Subject#4

### 7 was a 24 year old Caucasianmale 69

14

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Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans (non-guideline) inches tall and 184 pounds. He responded "no" to the question about whether ornot he thought he received the testmaterial and did nothave any obvious symptoms ofAChE intoxication. This subjecthad highest "estimated dose received" (1.130 mg/kg compared withthe group mean of 0.59 mg/kg, see Table 16, page 47 ofthe Pharmacokinetics report) basedprimarily onplasma and urinary contentofTCP. This subjectdid nothave indications ofAChE inhibition since there was atbest a 5% decrease in activity at 24 hours butthepreceding and succeeding assessments were bothhigherthan the baseline.


### Subiect #48. Refer to TableD in Appendix. Group C (2.0 mg/kg chlorpyrifos treatment). Subject#48 was a 23 year old Caucasianmale 71 inches tall and weighing 162pounds and smoked I0-14 cigarettes a day. He responded no to the question about whether ornothe thought he received the test material. Accordingto the datatable onpage 471, this subject did not experience any symptoms during the post dosing phrase.

This subjecthad RBC AChE readings of8569, 8206, 8019, 8008,7887, 7689, 8206,7546 (-8%), 7832,8074,7766,7766,7942 and 8184 for the -10, zero, 2, 4, 8, 12, 24, 36, 48, 72, 96, 144 and 168 assessmenttimes respectively. Thus, this subject's maximum decrease at 36 hours
was immediatelyproceeded by a value actually the same as the zero time assessment and thus does not showa pattern consistent withinhibitionby anorganophosphate.


### Females. Refer to Tables I and J inAppendix. Column five ofTable 2 showsthat for the control group females, one individual demonstrated 16.7% (subject# 34) and another 11.6% (subject# 50) less thanherpreclosing value. Amongthe treated groups there was a maximum of 11.4% (subject #19), II% (subject#33) and 28.2% (subject# 56) apparent decrease inRBC AChE for the 0.5, 1.0 and 2.0 mg/kg dose groups, respectively. Since the subjects inboththe 0.5 and 1.0 mg/kg dose groups did not exceed the placebo group for apparent decreases inAChE, it is notimplied thatthere are individuals in these dose groups that may be unusually sensitive to inhibition ofAChEby chlorpyrifos. Subjects # 51 and 56 are discussed as follows. 

### Subject#51. Phase II Group C female, 2 mg/kg chlorpyrifos. Refer to Table 4 belowfor AChE data onthis subject. This subject

### sustaineda decrease of5 to 6% RBC AChE overthe critical hours of 12, 24, and 36. However, herpretest variation was also near 5%. This subject also had one ofthe highest levels ofTCP in herblood. Butthepeaklevel ofTCP did not correspond with the lowerreadings for AChE.
The placebo female group for Phase IIwas demonstratedto be very stable over the course ofthe seven days onthe study (see last column in Table 4) as indicatedbythe datafrom one individual who demonstratedthe most variation ofthe six females inthe placebo group. Overall, the 5-6% lowerreading in subject #51 is notedbut not consideredto be definite inhibition caused by chlorpyrifos.


### 5. Special considerations for subject#56

### who did not complete the study. Subject# 56. Group C, 2 mg/kg chlorpyrifos. As indicatedpreviously, subject# 56

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Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans (non-guideline) dropped out ofthe study after48 hours. It was originallyreported that "repeated attempts were made to contactthis individual wereunsuccessful and nopost study medical evaluationwas performed" (refer to page 28 ofthe studyreport). However, the supplementaryreport (2008, MRID 47436401) inresponseto HED's questions aboutthe fate ofthis individual asserts "In, 1999, RichardNolanPhD was a DAS toxicologistthat was the toxicology contact for the Kisicki study. Dr. Joel Mattssonwas in 1999 a DAS toxicologist working withDr. Nolan and was assured thatthe testing laboratoryhad contacted subject#56 personally and she reported no problems withthe studybuthadpersonal reasons for not returning for further evaluations. DAS is not aware ofany additional information on subject#56". There is still ambiguity with regard to statements aboutthis subjectregarding the comments inthe study report (page 28) where no contactwas made and inthe supplementaryreport (page 17) where contactwas saidto have been made. Overall, failure ofthis personto have data after48 hours does notprecludethat data on AChE assessment and pharmacokinetics obtainedpriorto 48 hours are notuseful and informative althoughthe lack ofdatafollowing 48 hours limitsthe assessment ofthe total PK picture. The possibilitythatthis subjectdeveloped clinical signs inresponse to treatment cannot beresolved onthe basis ofavailable information. Page 472 ofthe studyreport indicatesthatthis subjectreported experiencing "numbness ofthe upper arms" starting2 hours and 24 minutes after administration ofthe chlorpyrifos and lasting a total of42 minutes. Onpage 510, the table listingthe subject'sresponseto the question iftheythoughttheyreceivedthe test material does not include subject#56.

This subjectwasthe only subject onthe studythat demonstrated apparentRBC AChE inhibition. Table 3 belowprovides details about this subject and shows the extentofinhibition at the critical time interval. Itis apparentthatthis individual's RBC AChE is decreased starting at 8 hours andremaining so until 48 hours when she was lasttested.

Table 3 Summary ofSubject#56 Parameter Results Comments Description (a) A 34 year old Caucasian female 72 inches tall There is nothing obviously and weighing 193 pounds and was a non- different about this subjectto smoker. This individual did not report for the suggest an unusual susceptibility day 4, 5, 6, 7 or 8blood collection (see page to chlorpyrifos. The subjectwas 28) or assessment ofvital signs and did not genotype QQ but about halfthe provide urine samples after 48 hours. persons on the study had this genotype.

Symptoms (b) Subjecthad a transient "numbness in upper The numbness alone does not arms" that started to occur 42 minutes after seem to be a response to an dosing and lasted for 2 hours and 24 min (self AChE inhibitor and since this resolved without medication). occurred and was resolved by three hours, or before there was appreciable apparent inhibition ofAChE at 8hours post dosing,
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Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans (non-guideline) Parameter Results Comments the finding is notconsidered treatment-related.
RBCAChE 8426 at -10 hours Subject shows decrease in RBC lUlL 8910 at 0 hour AChEthat can be considered the (c) 8668 predosing mean critical times expected for an OP 8602 (no difference) at 2 hours, following an oral administration. 8525 (-2%) at 4 hours, 6688 (-23%) at 8 hours, 6221 (-28%) at 12 hours No other subject shows a similar 6424 (-26%) at 24 hours pattern ofdecrease in activity. 7051 (-19%) at 36hours 6882 (-21%) at 48 hours No additional assessments. Serum 18 ng/gm at 8 hours The serum chlorpyrifos data and chlorpyrifos 2.5 ng/gm at 12 hours the serum and urine TCP data all (d) All other times- not detected(< I ng/gm) indicate that subject# 56 absorbed chlorpyrifos to a The highest level in all other subjects was only greater extentthan the other 5.6 in a female (#21) dosed with I mg/kg. subjects in this study.
Serum TCP Subjecthas total of6671 ng/gm TCP in serum (0 to 48 hours) with values of71, 120, 1600, 1500, 1300, 1100 Since no assessments were made (e) and 980 ng/gm for the 2, 4, 8, 12, 24, 36 and 48 after 48 hours, the total TCP hour intervals, respectively. Note there was picture cannot be determined to little TCP in blood at 2 to 4 hours or at the time compare with the other subjects the numbness was noted. which seemedto have TCP present in the blood at the later This isthe highest (total ng/gm) for the times.
group dosed with 2 mg/kg sincethe range for all others (both sexes) was 1404 (#42) to 5860 (#47) ng/gm for up to 48 hours.
Urine TCP According to Table 14b for the 0-48 hour (corrected for interval, Subject 56 had atotal of22.8 mg or creatinine) was highest for the group dosed with 2 mg/kg. (0 to 48 hours) Since the range for the others in this group was 4.8 (#40) to 16.2 (#47) with a mean of8.4 ± 3 for all individuals excluding #56.
Estimated 0.640 mg/kg.

- from Table 16 The calculation ofthe total internal dose is limited since no internal dose of Compares favorably with the group mean of assessments for TCP or parent chlorpyrifos 0.59 ± 0.21 mg/kg (range 0.323 (#40) to 1.130 (g) (#47) mg/kg for the group dosed with 2 mg/kg. chlorpyrifos were made after 48 males 0.61±0.28; females: 0.568±0.12 mg/kg hours.
CPOase (h) Subjecthas reading of9278 Units/liter There is nothing unusual about

17

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Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans (non-guideline) Parameter Results Comments comparing favorably with the group mean of the serum activity ofCPOase, or 9523±1517 Units/liter. diazoxonase. Although her paraoxonase level was much Paraoxonase 367 UIL compared to group mean lower than the group mean this 737±430 U/L should not affect dosing with chlorpyrifos. Subjectwas described as phenotype "QQ low" which was a typical classification for many (about half) ofthe subjects in the study.
(a) Dataare from Appendix 4.3, page 242

.. (b) Dataare from Append1x 4.21.1, page 472. (c) Dataare from Table 4.13.2, page 407. (d) Data are from Table 5, page 34 ofthe Pharmacokinetics report. (e) Dataare from Table 7, page 36 ofthe Pharmacokinetics report. (f) Data are from Table 14b (corrected for creatinine), page 45 ofthe Pharmacokinetics report. (g) Dataare from Table 16, page 47 ofthe study report. (h) Dataare from Table 17, page 50 ofthe Pharmacokineticsreport.
Itis notedthatinthe screening studythis individual had a RBC AChE of7678 U/L. This
was listed as a clinical laboratory commentas "not significantin the context ofthis study". Whencompared to the mean for the -10 and zero hour samplings (mean= 8668 U/L), this would be 11% less. This value of 11% less is not asmuch as the approximately 28% decrease that was noted for this person following treatment with 2 mg/kg chlorpyrifos. Thus, the decrease in AChE after 8 hours is greaterthanthe spontaneous variation for this subject.
This subject has inhibitionratherthanrandom decrease inactivity since the decrease in activity starts at 8 hours andrises to a peak at 12 hours and then appears to startto decline at 24, 36 and48 hours. This wouldbe expected for an organophosphateAChE inhibitor. The pattern ofdecreased activity also correlates with the amount ofTCP in the serum as shown in Table 4.

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Hour

2
4
8
12
24
36
48
72
96
120
144
168
Net TCP Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans (non-guideline) 

### Table 4. Correlation between RBC AChE activity and blood level ofTCP in humans dosed with 2 mglkg chlorpyrifos.

Sub. #56(QQ'f')_ Sub. #47 (QQoL Sub. #5l(OR'f') sub. #48(0Ro) Placebo RBC TCP RBC TCP RBC TCP RBC TCP #44 (ORo) AChE Blood AChE Blood AChE Blood AChE Blood RBCAChE

= 71 +2% 580 -2% 420 -4% 180 -1%
-2% 120 +2% 640 -1% 580 -5% 250 = -23% 1600 = 790 -2% 1300 -6% 240 -3%
-28% 1500 = 910 -6% 690 -8% 260 -6%
-26% 1300 -5% 980 -5% 540 -2% 380 -6%
-19% 1100 = 960 -5% 750 -10% 460 -4%
-21% 980 -1% 1000 -3% 730 -7% 470 -5% Subject did not +4% 690 +1% 600 -4% 300 +1% return for additional +2% 460 +4% 420 -7% 210 -4% sampling. +7% 320 +6% 150 -7% 140 -4%
+2% 220 -2% 170 -6% 77 -10%
+7% 150 = 110 -2% 48 = 0 to 48 hrs 6671 0 to 48 hrs 5860 0 to 48 hrs 5010 0to 48 hrs 2240 N/A 0 to 168 hrs

- no 0 to 168 hrs 7700 0 to 168 hr s 6410 Otol68hrs 3015 data Definitely shows Highest levels of Sustains a slight Subject has lowest Shows that inhibition TCP do not decrease at critical level ofblood TCP activity correlating with correlate with times and is thus but seems to varies toblood level of .J.RBCAChE. possibly showing sustain a decrease 10%. TCP. inhibition. inRBC AChE Placebo #60 (QQ'f') RBCAChE
-3% -5% +1%
+2%
-1%

=

= -3% -3%

= -3% +1%
NIA

Shows that female RBC AChE is stable.

TCP data are from Table 7 page 36 mMRID No.: 45144101 and are ng/gm. Note: TCP data were notreported for the blood from the placebo group in Table 7 ofthe study report. RBC AChE data are from Table 9.1.2 page 78 from MRID No.: 44811002 and are the percent decrease(-) or increase(+) in RBC AChE relative to the baseline. The= sign indicates that the assessment was within ± 1% ofthe baseline.


### Table4 also presents data onthe variation ofRBC AChE activity in one other female and two males dosed with 2 mg/kg ofchlorpyrifos and the amount ofTCP in their blood. In addition, a male and a female from Phase II placebo group are includedto showthe spontaneous variation ofRBC AChE. It

### is noted thatthe female (#60) 

### is stablebut the male (#44) showed decreases. One otherplacebo male (Subject#41, data not shownhere because ifspace

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Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans (non-guideline) 

### limitations) also showed what appeared to be sustained decreased activity (4%-7% from 8hours to 36 hours post dose).
Table 4 indicates that female subject#51 sustains a slight decrease in RBC AChE and also has ahighblood level ofTCP but not at the critical times oflowerAChE readings. Therefore this subject is not considered to show definite evidence ofRBC AChE inhibition in response to 2 mg/kg ofchlorpyrifos since the level ofdecrease is too low and not coincident with serum TCP.



### PartB. Pharmacokinetic and ParaoxonaseData (Referto MRID No.: 45144101).

PartB 

### 1. Pharmacokinetic data.
Note: Additionaldata on thepharmacokinetics are inAppendixII TablesA-J
The sixty subjects on this study gave blood samples (5 mL) for the purpose of determination ofchlorpyrifos, chlorpyrifos oxon and 3,5,6-trichloro-2-pyridinyl (TCP) at -10 hours prior to dosing, at zero hour priorto dosing and at 2, 4, 8, 12, 24, 36, 48, 72, 96, 120, 144 and 168 hours postdosing. Urine samples from all urine voided (as perthe protocol) for the intervals -48 to -36 hours, -36 to -24 hours, -24 to -12 hours, -12 to 0 hours pretreatment and 0 to 6 hours, 6 to 12 hours, 12 to 24 hours, 24 to 36 hours, 36 to 48 hours, 48 to 60 hours, 60 to 72 hours, 72 to 84 hours, 84 to 96 hours, 96 to 108 hours, 108 to 120 hours, 120 to 132 hours, 132 to 144 hours, 144 to !56hours and !56to 168 hours post treatment. The blood and urine were analyzed by GC/MS for chlorpyrifos, its oxon analog and TCP and the method ofpreparation using internal standards was described. TCP was derivitized priorto analysis. In response to an inquiry form the Human Studies Review Board, additional details ofthe method ofanalysis were confirmed in two submissions (2009, MRID 47866701 and 47866703).
Datawere presentedthat demonstrated the recovery ofspiked samples for chlorpyrifos (98.0 to 99.8%), chlorpyrifos oxon (95.4 to 98.0%) andTCP (91.1 to 97.1%), andthe lower limit ofdetection was about I 

### ng/gm ofblood for chlorpyrifos and its ox on analog but was about 12.1. ng/gm for TCP. Similarly, recoveries offrom 96 to 104% for these chemicals from urine were demonstrated. Additional data demonstrated the stability ofthese chemicals in blood and urine stored -20 or -80 °C for 6 or 10 days.


### Blood and urine analysis for chlorpyrifos and chlorpyrifos oxon. Chlorpyrifos and chlorpyrifos oxonwere notfound in any ofthe urine samples from any ofthe subjects (refer to Table 10 ofthe study report page 39). Chlorpyrifos oxon was not found in the blood ofany subject (refer to Table 6 ofthe study report page 35). Chlorpyrifos was found only occasionallyin the blood (refer to Table 5 

### page 34 ofthe

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Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans (non-guideline) 

### studyreport). No subjects dosed with 0.5 mg/kg chlorpyrifos were found to have chlorpyrifos in theirblood. Subjects #II (1.0 ng/gm at 2hours), #14 (2.7 and 1.5 ng/gm at 4 and 8hours), #21 (5.6 and 2.9 ng/gm at 2 and 4hours) and #30 (1.1 ng/gm at 8 hours) dosed with I mg/kg were noted to have chlorpyrifos in theirblood atthe assessment times indicated. Subjects #47 (3.1, 1.3, 

### 3.4 and 1.8 ng/gm at 2, 4, 8 and 12 hours), #49 (3.1 and 1.7 ng/gm at 2 and 8hours), #56 (18.0 and 2.5 ng/gm at 8 and 12 hours) and #59 (2.2, 4.1, 4.1 and 1.5 ng/gm at 2, 4, 8 and 12 hours) dosed with 2 mg/kg were also shownto have chlorpyrifos in theirblood. These are very small amounts ofchlorpyrifos. The highest level (18 ng/gm) was found in subject#56 at 8 hours. These data suggest a short half-life for parent chlorpyrifos in bloodbutthere does not appear to be sufficient data to establish a firm number for the half-life ofchlorpyrifos in the blood.
Blood and urine analysis for theprincipalmetabolite TCP.
TCP was detected in the blood ofall 

### subjects dosed withchlorpyrifos. Referto Appendix Tables. D, E, F, G, and H.
"Thepercentrecovery corrected for dose as urinary TCP" was reported to be for both
sexes combined 34.7±19.6%. 30.8±9.9% and 29.5±10.4% for the 0.5, I 

### and 2 mglkg dose groups, respectively. (Referto Table 16 "Estimation ofdose Receivedby Volunteers", page 47.)
The extentofabsorption is less than the 70% earlierreport from Nolan (1984)1 and this may be attributed to the fact thatthe chlorpyrifos in this study was administered in a capsule and this would lead to slower absorption. In contrast, in the Nolan study, chlorpyrifos was dissolved in methylene chloride and placed ona 0.5-gram lactose tablet, which was swallowed with 100 mL ofwater.
The half-life ofTCP as indicatedbythe blood and urine data are shownin Table 5.
Table 5. Half-lives (in hours) based on TCP in the blood and urine.

Dose Blood" Urineb (mg/kg) Males Females Combined Males Females Combined 0.5 29.7±7.4 44.5±32.4 37.1±23.7 29.5±8.9 38.6±24.3 34.3±16.1 1.0 27.7±5.6 30.5±7.4 29.1±6.4 20.5±5.9 33.6±7.4 31.0±7.3 2.0 36.2±5.9 35.2±4.8 35.8±5.6 38.1±6.5 32.8±6.5 35.7±6.7
a. Table 9, page 38. b. Table 15, page 46.
(Note in MRID 4514410I)the printing is small and in some places difficult to distinguish 5, 6 and 8. The bestread ofthe number is in Table 5. Since there were only a few and mostly in the standard deviation, these questionable numbers should not impact the interpretation.)

I Nolan, R.J. et al, (1984) Chlorpyrifos: Pharmacokinetics in human volunteers. ToxicoL AppL PhannacoL 73:8-15.



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Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans (non-guideline) 

### Additional serum TCP data on selected subjects are presented in Table 4.


### PartB. 2. SerumParaoxonase and chlorpyrifos oxonase (CPOase) Assessment.
A 5 mL blood sample was taken priorto dosing and sentto the laboratory ofDr. Clement Furlong, DepartmentofMedicine and Genetics, University ofWashington, Seattle, Washington and assessed for paraoxonase activity using a spectrophotometric assay. Paraoxonase was tested with chlorpyrifos axon, paraoxon, ordiazoxonase. When the test substance was chlorpyrifos axon, the activity was called CPOase.
Table 17 ofthe studyreportpresented data for each subject and group means for the subjects dosed inbothphase I (October 3, 1998) and II (October 17, 1998). Table 5 summarizes the CPOase data in this study. Paraoxonase (range- -250 to -2502units/L, whenparaoxon was the substrate) and diazoxonase (range -6548 to 22452 units, when diazinon ox on was the substrate) data were also presented but not shownin this review since the subject ofthe review is chlorpyrifos.

Group CPOase Range Comment
Phase I 5 subjects were QQ (low), 5 were QR

Control 8418±1639 5430 to 10410 (medium). And 2 were "QQAow"

. Both the high and lowreadings were from OR individuals. Phase I % 

### were QQ and 7 were QR. The low

0.5 mglkg 

### 7965±1536 5412 to 13341 was from a QQ and the high was from a QR. Phase I 6 were QQ, 

### 5 were QRand I was RR.

I mg/kg 8463±1386 6599 to 11615 Thehigh value was from a QQ and the lowvalue was also from a QQ. Phase 2 6 were QQ and 5 were QR and one was

Control 11357±3097 6904 to 17333 RR. The high value was from the RR person and the low value was from a QQ person. Phase 2 6 were QQ, 5 were QRand I was RR.

2 mg/kg 9523±1517 7048 to 13018 The high value was from a QRperson and the lowvalue was also from a QR person.
Subject# 56 has a value of 9278 Units/liter and is very close to the group
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Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans (non-guideline) 

### Group CPOase Range Comment

mean and thus does not have an unusual abilityto metabolize chlorpyrifos oxon.



### Conclusions, Discussion, StudyDeficiencies and Classification.

I. Study author's conclusions.
The study author (page I0 ofthe studyreport) concluded "TheNOEL for signs and symptoms infasted human following a single oral dose was 2.0 mg chlorpyrifos/kg ofbody weight. The NOEL for RBC AChE inhibition in humans given a single oral dose ofchlorpyrifos
was 1.0 mg/kg ofbodyweight. The 2.0 mg chlorpyrifos/kg ofbodyweight dose level represented a threshold inthat it producedgreaterthan 17.3% depression in I of 12 volunteers."



### 2. Reviewer's conclusion and discussion, Signs andSymptoms. There was no indication that any ofthe signs and symptoms that
were noted in the subjects dosed with chlorpyrifos were different in eithertheirnature or degree ofseverity from the signs and symptoms that were noted in the placebo groups. Some reported symptoms inthe subjects that were dosed with chlorpyrifos occurred eitherwell before or after the time when chlorpyrifos absorption was maximal orwhen the blood orurine level ofTCP the principal metabolite ofchlorpyrifos was atits maximal level. Also, the only subject showing definite inhibition ofRBC AChE did not display any symptoms whenmaximum inhibition of AChE was attained and this subject's onlyreported sign ("upper armnumbness") occurred and resolved well before her RBC AChE was shownto be inhibited andbefore her serum level of TCP reached higher levels. Ifthe "upper arm numbness" was related to some other cause due to chlorpyrifos than inhibition ofRBC AChE it would still be expected for the numbness to persist while the absorption ofchlorpyrifos increased. Thus, the NOAEL for symptoms is> 2 mg/kg chlorpyrifos.


### PharmacokineticData. Based onthe pattern ofoccurrence ofTCPthe principal metabolite ofchlorpyrifos inthe blood and urine, chlorpyrifos is absorbedrather slowly from the gut and requiring about 8 to 12 hours for the TCP blood level to reach a maximum. Based on the blood level ofTCP, subject# 56 absorbed more chlorpyrifos inthe first 48 hours and this subject also had clearevidence ofRBC AChE inhibition.
The rate and extent ofabsorption ofchlorpyrifos in this study was slower and lower than reported in an earlier study (Nolan, 1984) and this was attributed bythe study author to be due to the differences in administration. In this study, chlorpyrifos was administered in a capsulebut in the earlier study it was administered ontop ofa lactose pill. The need for the capsule itselfto dissolve inthe g-I tract maybe a factor.

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Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans (non-guideline) 

### RBCAChEInhibition. Review ofthis study identified one subject (#56, a female dosed with 2 mg/kg, withgenotype QQ) as demonstrating inhibition ofRBCAChE. The decreases in RBC AChE were shownto correlate withhighlevels ofTCP inher serum. As muchas 28% inhibition was noted at 12 hours postdosing.

A second subject (#51, with genotype OR) was considered as possibly also showing inhibition and also had one ofthe highest levels ofserum TCP for the group dosed with 2 mglkg. Although this subjecthad decreases to only 5 to 6% ofher preclosing mean, this level of decrease was sustained overthe critical hours ofexpectedtime for an OP to inhibitblood AChE (i.e. 8to 24 hours). Inspection ofthe other four females in Phase 

### IIindicatedthat their RBC AChE activity was very stable overthe 168-hourpostdosing period. Overall, subject#51 is consideredto have only very minimum and indefinite inhibition.

None ofthe males were determined to be showing definite decreases in RBC AChE. It
was noted that one subject(#48,2 mg/kg group,OR) had decrease of8% at 12 hours and 10% at 36 hours buttwo placebo males indicatedthat variation inRBC AChE activity can also vary to a decrease of 10%. Also subject#48 had one ofthe lowestnet totals ofTCP in his blood for the group receiving 

### 2 mg/kg.
Thus, the NOAEL for RBC AChE inhibition is 1mg/kg and the LOAEL is 2 mg/kg. Only one female was concludedto have definite inhibition.

CPOase
This studyhas important data on each person's PON and CPOase. The single person showing inhibition had CPOase similarto other individuals inthe group dose with 2 mg/kg, but this person also hadthe highest absorption ofchlorpyrifos. Thus, the persons ability to absorb chlorpyrifos from the gastro-intestinal tract maybe more importantthatthe CPOase status ofthe individual. Study Classification.
This study is being classified as RESERVED since there are no current guidelines for classifying studies with human subjects.

4. Study deficiencies and compromisingissues.
-PlasmaChE was not assessed for. This is considered important since otherrecent studies withhumans and OPs include plasmaChE assessment. Also it was reported in the earlier (Nolan, 1984) withhumans that plasma ChE is inhibited at lower doses than RBC AChE by chlorpyrifos. This deficiency mayrender the studyunacceptablebasedon incompleteness of expected inclusions. This deficiency is considered a potentially serious omission.

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Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans (non-guideline)


### -The only subjectthat showed definite inhibition ofRBC AChE did not complete the study after the 48th hour assessments. This subject did notprovide blood samples for hematology or clinical chemistry at the scheduled one weekposttreatment time. The supplementaryreport (2008, MRlD 47436401) indicatedthatthis person was contacted via telephone and did not report adverse effects and that she had to leave the study for personal
reasons. This deficiency may be beyond the control ofthe laboratory and there is nojustification at this time to fault the laboratory for the subject not completingthe study.
-The hematology, clinical chemistry, urinalysis and ECG assessments were made one week following the administration ofchlorpyrifos. This is considered apoor design. These assessments shouldhave been done during the time ofpeakeffect ofchlorpyrifos on AChE. The assessments after one week are oflittle value since the chlorpyrifos has been cleared from the body and it would be expectedthat inhibition ofAChE would have beenpartiallyreversed by this time orthat the body adapted to the decreased AChE activity. -Although not a deficiency in itself, the analytical method used to detect chlorpyrifos, its
oxon and TCP has lower limits ofdetection in the order ofI ng/gm blood. Morerecent methodology that was used in the epidemiological studies has limits ofdetection about I

### 000 times more sensitive. Thus, the PKdata would have beenmore useful especially at the lower dose of0.5 mg/kg ifthe more sensitive method ofanalysis was used.

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Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans (non-guideline) Appendix I - Individual SubjectAnalysis for subjects showing symptoms orvariation inAChE
Subject# Symptoms or Events (a) RBC AChE Comments RED's Conclusion Placebo-Males
2 Increased appetite, headache Maximum decrease 12%@48 Since these subjects are (no) (moderate)- vomited. Starting 47 hrs. Other values are 89% to in the placebo group, hrs postdosing, lasting for 4 days, 6 I05%. ofpredose there symptoms or hrs. Possibly related to treatment. events cannot be due to "One can coca-colanext day''. chlorpyrifos treatment. 8 Headache (mild)- Starting I0 hrs Maximum decrease 9% @ 48 (yes) postdosing, lasting -13 hrs. hrs. Othervalues are 94% to Possibly related to treatment. 103%.
10 No symptoms or events. Maximum decrease 14%@ 96 (yes) hrs. Other values are 88% to 103%.
13 No symptoms or events. Maximum decrease 12% @ -I0 (yes) hrs. Other values are 97% to 112%. 37 Dizzy, feels weak, nausea, vomited, Maximum decrease 3%@ 96 (yes) body aches

- Starting 2 days, 18 hrs hrs. Other values 97% to I07% lasting (some symptoms) for up to 2 ofpredose. days II hrs. Possibly relatedto treatment. 41 Itching ofinsect bite. Starting 2 Maximum decrease 7% @ 24 (no) days 5 hrs, lasting II hrs. Unrelated hrs. Other values 95%ti I07% to treatment. ofpredose. 45 Nausea, vomited. Starting 2 days. No decreases. Values are I00 to (no) Lasting -20 min. Possibly related 110% ofthe predose. to treatment. 46 Headache (mild). Starting- 3 hrs. Maximum decrease 6% @ 2 hrs. (no) Lasting- 3hrs. Possibly relatedto Other values 98% to I08% of treatment. predose. 3112 subjects have headaches. 4112 thought they received the chlorpyrifos when it was not given. As much as a 14% decrease in RBC AChE can occur within the untreated group over the 7 day period. Placebo-Females
20 No symptoms orevents. Maximum decrease 7% at -I0 Since these subjects are (yes) hrs. Other values 94% to I07%. in the placebo group,



### 26 

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Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans 

### c ·d 

### r ) non-gm e me Subject# Symptoms or Events (a) RBC AChE Comments HED's Conclusion
23 No symptoms or events. Maximum decrease 7% at 144 there reactions cannot (yes) hrs. Other values 96 to II0%. be due to chlorpyrifos treatment. 29 "hiccough", heartburn. Starting II Maximum decrease 13% at 96 (no) hrs, lasting II hrs. Unrelated to hrs. Other values 95 to l07%. treatment. 32 No symptoms. Maximum decrease I7% and (no) sustains from 96 to 144 hrs. Other values 85 to l05%. Subject included to show variation in AChE.
50 Headache (mild)- Starting l day 21 Maximum decrease 12% atl44 (no) hrs. lasting 3 hrs. Unlikely related hrs. Other values 97 to I08% of to treatment. predose.
52 Headache (mild), loose stool, Maximum decrease 7% at 24 (yes) nausea, intestinal cramps, vomited. hrs. Other values 97 to l03% of Starting on days 3 and 4, lasting 6- predose. 10 hrs (some symptoms). Possibly related to treatment. 54 Headache (moderate and mild), Maximum decrease 4% at 36 (no) nausea. Starting 4-5 hrs, and again at hrs. Other values 97 to I07% of II hrs. Lasting 6-7 hrs and I 7 predose. hours. Possibly related to treatment. 60 lack ofappetite, headache (mild), Maximum decrease 5% at 4 hrs. (yes) nausea. Starting at 3-5 hrs or 13 Other values 97 to I02% of hours. Lasting 5 to 17 hrs. Possibly predose. relatedto treatment. 4112 (33%) females had headaches. 4112 thought they received the chlorpyrifos when it was not given. As much as 17% reduction in RBC AChE can be attained in the untreated female group. 0.5 mg/kg Chlorpyrifos-Males
3 Increased appetite. Starting I day Maximum decrease 15% at 48 Increasedappetite is (no) and 23 hrs. Lasting 4 days. hrs. Other values 94 to I02% of notan expected Unlikely relatedto treatment. predose. response to an OP. Not related to treatment Maximum decrease not supported by earlier or later decreases.



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Chlorpyrifos/P. C. Code 05910I Special RBC AChE Inhibition Study (1999) Humans (non-guideline) Subject# Symptoms or Events (a) RBC AChE Comments HED's Conclusion 5 Subject implied excessive salivation Maximum decrease 8% at 96 No support from either (yes) was why he thoughthe received the hours. Other values 90 to the symptoms or AChE test material but there were no 108%. datato for subjects indications ofexcessive salivation 11yes" response. listed in the events Table.
9 Intestinal cramps. Starting 2 days Maximum decrease 17% at 96 Not related to treatment (no) 22 hours. Lasting 15 hrs. Unlikely hrs followed by 11%, 13% and since onset did not relatedto treatment. 9% at 120, 144 and 168 hours. coincide with AChE,!,. Othervalues Othervalues were 87% to I05% ofpredose.
None have headaches. 

### 116 thoughtthey receivedthe chlorpyrifos. Note hour 96 had largest decrease in RBC AChE for all but one subject in this group suggesting some assay problem. Since it is hour 96, this should not confound the interpretation ofthe data. 0.5 mglkg Chlorpyrifos-Females
26 Nausea. Starting at I hr. Lasting 90 Maximum decrease 8% at 96, An initial localized (no) min. Probably relatedto treatment. 144 and 168 hrs. Othervalues nauseamay result from are 93% to I04%. an OP administration in
a capsule without concomitant 

### ,I,in AChE. Maximum ,l,in AChE does not coincide with symptoms. Not considered a definite response to chlorpyrifos. 31 Headache (moderate). Starting I Maximum decrease 14% at 96 Onset ofheadache does (no) day and 3 hrs. Lasting -2 hrs. hrs. Other values were 90% to not coincide with Unlikely related to treatment. I04% ofpredose. maximum 

### ,J, in AChE occurring much later. Notrelated to treatment. 36 Headache (mild), lightheaded, Maximum decrease 9% at 4 and Onset ofheadaches did (yes) headache (mild). Starting I hror 6 96 hrs. Othervalues were 92% not coincide with hrs. Lasting -2 hrs or -11 hrs. to 106%. maximum ,!,in AChE. Possibly related to treatment. 2/6 (33%) females had headaches. 

### 116 thought they received the chlorpyrifos. Maximum decrease in RBC AChE does not exceed the placebo group.



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Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans (non-guideline) Subject# Symptoms or Events (a) RBC AChE Comments HED's Conclusion 1.0 mglkg chlorpyrifos-Males
I Increased appetite. Starting I day Maximum decrease 7% @ 48 Symptom not expected (yes) and 23 hrs. Lasting 4 days six hrs. hrs. Other values are 95%to ofan OP exposure and Unlikely relatedto treatment. I I3% ofpredose. does not coincide with maximum ,!, AChE.
4 Loose stool. Starting 2 days and I5- Maximum decrease I5% @ 96 Symptoms do not (yes) 20 hrs and again on day 4 and I2 hrs followed hy deceases of8%, coincide with hrs. Lasting I min. Unlikely related 12% and 8% at 120, 144 and maximum ,!, in AChE. to treatment. I68 hrs. Other values 90% to 107%.
7 No symptoms or events. Maximum decrease 16% at 96 No support for subjects (yes) hours. Othervalues are 9I% to "yes" response. I 16%.
I I Headache (moderate and mild). Maximum decrease 25% @ 96 First headache may be not listed Starting -3 hrs and again at- 23 hrs. hrs. Othervalues were 89% (at associated with -II% Lasting

- I9 hrs and I day 9 hrs. 2hrs)to IOI%(at4hrs)of ,!, in AChE. Second Possibly related to treatment. predose. headache not associated with ,!, AChE or maximum decrease.
14 Queasy stomach. Starting 24 min. Maximum decrease 15%@ 144 An initial unsettled (yes) Lasting I0 min. hrs. Othervalues 88% to 99% (queasy) stomach may Possibly related to treatment. ofpredose. result from the capsule. Symptom does not coincide with ,!,AChE.
I/6 has a headache. This is less than the placebo group and there is no indication that this subjects headache
was more severe. 4/6 thoughtthey received the chlorpyrifos. The maximum decrease in this group was in an individual at 96 hrs postdosing.
1.0 mg/kg Chlorpyrifos-Females
24 Lost voice. Starting

- I8 hrs. Maximum decrease II% @ I68 Lostvoice not an (no) Lasting 8 hrs. hrs. Other values 95%to I05% expected response to an ofpredose. OP. Symptom does not coincide with,!, AChE. Notrelated to treatment.
25 Tired. Starting -4 hrs. Lasting I Maximum decrease 9% @ 96 Symptom does not (yes) hrs. Possibly related to treatment. and I20 hrs. Other values 92% coincide with to 102%. maximum ,!, ACHE. Not related to


### 29



## 4'1EPA's Records Disposition Schedule PEST 361 Scientific Data Reviews HED Records Center- File R180234- Page 59 of 73

Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans (non-guideline) Subject# Symptoms or Events (a) RBC AChE Comments HED's Conclusion
treatment. 30 Headache (mild), tired and repeated Maximum decrease 8% @ 96 Onset and duration of (no) headaches (mild). Starting 22 min, hrs. Other values 95% to I09% symptoms so not

- 2hrs,

- I0 hrs and

- 23 hrs. ofpredose/ coincide with J.AChE. lasting. Upto 8 days and 7 hrs. Possibly relatedto treatment. 33 Headache (mild). Staring

- 2hrs. Maximum decrease II% @ 144 Onset ofsymptom does (no) Lasting 4 hrs. Possibly related to hrs. Values from 96 hrs to 168 not coincide with treatment. hrs were 89% to 955. Other maximum ofany 

### J, in values were 97% to Ill%. AChE. 35 Back stiffness. Starting 22 min. Maximum decrease 6%@ 168 Symptom not an (no) Lasting -4hrs. hrs. Othervalues 94% to 115%. expected response to Unlikely related to treatment. OP treatment and does not coincide with maximum 

### J, AChE. Not related to treatment. 2/6 (33%) females had headaches. 1/6 thoughtthey received the chlorpyrifos. Maximum decrease does nor exceed placebo group for RBC AChE.
2.0 mg/kg Chlorpyrifos-Males
40 No symptoms or events. Maximum decrease 2% at 48 No support for subjects (yes) hrs. Othervalues 99% to I03%. t!yes" response.

47 Cut on chin. Starting 2 days. Maximum decrease 5% at 24 Notrelated to (no) Lasting 6 days. Unrelated to hrs. Other values 98% to I07% treatment. treatment. ofpredose.
None have headache. 116 thought they received the chlorpyrifos. Maximum decrease in group was to 10% for one subject (#48 at 36 hours) and dose not exceed the placebo. 2.0 mg/kg Chlorpyrifos-Females
51 Headache (mild- moderate). Maximum decease 6% at 12 hrs. Onset ofheadache does (yes) Starting at 4 7 min and again at 3 hrs Othervalues were 95 to I05% not coincide with 7 min and lasting 2-7 hrs. ofthe predose. AChEJ.. Not related to Possibly/probably related to treatment. treatment. One can coca-cola.
55 Headache (mild). Starting 3 hrs, Maximum decrease 5% at 120 Onset ofheadache does (no) lasting 19 hrs. Possibly relatedto hrs. Othervalues were 97 to not coincide with treatment. I07% ofpredose. AChEJ..

30EPA's Records Disposition Schedule PEST 361 Scientific Data Reviews HED Records Center- File R180234- Page 60 of 73

Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans (non-guideline) Subject# Symptoms orEvents (a) RBC AChE Comments HED's Conclusion
56 Numbness in upper arms. Starting Maximum decrease 28% at 12 See special discussion. not listed 42 min. Lasting 2 hrs and 24 min. hrs. ,J, starts at8 hours Numbness does not Possibly related to treatment. (23%-J,), coincide with AChE 

### ,J,
58 No symptoms orevents. Maximum decrease 7% at 12 No supportfor subjects (yes) hrs. Othervalues are 96% to uyes" response. 101%
59 Tired, headache (mild), chest Maximum decrease 7% at 12 Firstheadache does not (yes) tightness, shortness ofbreath, hrs. Othervalues were 95% to coincide with ,J, AChE, headache. Starting

- 2hrs, and I0 104% ofpredose. the onsetofthe second hrs. Lasting 3-13 hrs. Possibly headache is two hours relatedto treatment. before maximum,J, in AChE but ,J, is only 7%. HED does not conclude that the headache is treatment related.
3/6 (50%) females had headaches. Severity ofheadache not greaterthan placebo subjects and onsetdoes not coincide with AChE decrease. 3/6 thoughtthey received the chlorpyrifos. One subject has definite inhibition ofRBC AChE based on sustained decrease at critical times. 

### (a) Only those subjects havmgreports ofsymptoms, "events" orresponded "yes" (column I) to the question ifthey thought they received the test material are listed. Symptom data are from Appendix 4. Under symptoms, the entry in italics 

### refers to the study author's conclusionregarding whether ornot the symptom was related to treatment was made before the subjects were identified as to their dose group. AChE data are from Table 5.1.2 for phase I and Table 9.1.2 for PhaseII.

31EPA's Records Disposition Schedule PEST 361 Scientific Data Reviews HED Records Center- File R180234- Page 61 of 73

Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans (non-guideline) 

## Appendix II- List ofTables*

Table A. 

### Mean RBC CholinesteraseActivity (for all groups and all times).
Table B. 

### Serum Paraoxonase/CPOase and 0-hourRBC AChE Activity and Phenotype for dosed groups.
Table C. SerumParaoxonase/CPOase and 0-hour RBC AChE Activity and Phenotype for control groups.
Table D. Male RBC AChEActivity, Blood TCP Level and CP Level for the Group Dosed with 2 mg/kg.
Table E. Female RBC AChE Activity, Blood TCP Level and CP Level for the Group Dosed with 2 mg/kg.
Table F. Male RBC AChE Activity, Blood TCP Level and CP Level for the Group Dosed with I mg/kg.
Table G. Female RBC AChE Activity, BloodTCP Level and CP Level for the Group Dosed with 1mg/kg.
Table H. Male and FemaleRBC AChE Activity andBlood TCP Level for the Group Dosed with 0.5 mg/kg.
Table I. 

### Individual Male and Female RBC AChEActivity (Phase I Control).
Table J. 

### Individual Male and Female RBC AChE Activity (Phase 2 control)
*Tableswere preparedbyDr. L. 

### Taylor, HED.

32EPA's Records Disposition Schedule PEST 361 Scientific Data Reviews HED Records Center- File R180234- Page 62 of 73

Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans (non-guideline)

Table A. Mean RBC CholinesteraseActivity (U/L; mean± s.d.) Time/Dose (mg/kg) I oA o• I o.sA I LOA I 

### z.o• Males -10 7520±733 9292±1130 8758±706 9317±790 8802±753 0 8143±982 9171±1112 8998±730 9572±539 8608±896 2 8023±795 9282±1026 9145±714 9568±427 8675±844 4 7948±756 9145±1066 9046±623 9862±865 8642±924 8 8008±645 9189±1101 9189±924 9524±352 8613±872 12 8043±705 9198±1003 8848±663 9543±678 8584±806 24 8036±815 9051±852 9046±817 9599±637 8637±878 36 7674±556 8999±1020 8716±821 9295±626 8663±937 48 7505±845 9042±904 8246±896 8694±669 8567±881 72 7920±838 9425±1041 8974±810 9623±652 9004±840 96 7421±745 9209±849 8036±738 8263±399 8815±868 120 7536±694 9337±765 8571±691 8939±255 8807±904 144 7316±598 9302±800 8764±837 8714±418 8857±907 168 7770±734 9304±994 8527±764 8600±470 8793±562 Females -10 8488±829 8485±373 8804±1068 8833±597 8503±939 0 8619±861 8576±556 8612±1160 9165±709 8523±855 2 8611±915 8444±494 8666±1194 9095±366 8395±855 4 8762±902 8380±422 8412±1368 9396±517 8557±1181 8 8817±884 8716±535 8547±1010 9060±528 8230±1274 12 8404±696 8589±499 8334±917 8886±400 7761±1239 24 8503±900 8510±667 8434±857 9053±241 8092±1191 36 8089±829 8399±476 8244±1015 8617±379 8166±1100 48 8349±735 8545±496 8459±1068 8895±641 8057±1202 72 8551±583 8941±442 8938±1083 9181±477 8604±1064 96 7795±759 8620±537 8147±1213 8508±791 8551±812 120 8092±721 8712±507 8301±857 8466±612 8591±682 144 8144±872 8428±727 8028±917 8462±714 8526±1111 168 8036±876 8549±571 8!98±910 8366±499 8419±814 A B Datafrom Tables 5.1.1 (pages 55-57) and 9.1.1 (pages 76-77) ofMRID 44811002; Phase I; Phase 2



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Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans (non-guideline)

Table B. Serum Paraoxonase/CPOase and 0-hour RBCAChE Activitv and Phenotvoe #/phenotype I CPOase (U!L) I Paraoxonase(U/L) RBC AChE CU/L) 0.5 mg/kg ]range] 3M (OR) 6850 706 8613 5M (QQ) 8666 317 7942 9M (QQ) 10446 417 8602 12M (QOl 5412 250 9471 15M (OR) 6871 745 9889 18M (OR) 5412 562 9471 7276±1963 (male) 500±204 (male) 8998±730 (male) 19F (OR) 8073 595 7282 22F (OR) 6994 717 9218 26F (QQ) 8954 373 8602 28F (OR) 8091 895 9900 31F (QQ) 6671 261 9515 36F (OR) 13341 1346 7156 8687±2424 {female) 698±391 (female) 8612±1160 (female) mean±s.d. 7965±1536 {both) 599±315 {both) 1.0 mg/kg ]range] IM(QQ) 6599 317 9108 4M (RR) 8505 1479 9669 7M (OR) 9008 984 9713 llM(QQ) 7785 361 10098 14M (QQ) 8774 367 10087 16M (OR) 8325 834 8756 8166±874 (male) 724±464 (male) 9572±539 {male) 21F (QQ) 11615 467 9900 24F (QQ) 7534 295 9757 25F (QQ) 7426 339 9548 30F (OR) 10141 923 9130 33F (OR) 8019 1040 8140 35F (OR) 7821 756 8514 8754±1719 (female) 637±314 (female) 9165±709 {female) mean±s.d. 8463±1386 {both) 680±380 {both) 2.0 me/kg r range] 38M (OR) 13018 1234 8283 40M (QQ) 8918 345 10021 42M (OR) 7048 890 9372 43M (OR) 9134 801 8118 47M (QQ) 10213 456 7645 48M (OR) 8199 823 8206 9422±2051 (male) 758±320 (male) 8608±896 {male) 49F (QQ) 9997 367 7766 51F (OR) 10716 1234 7942 55F (RR) 9422 1590 10076 56F (QQ) 9278 367 8910 58F (QQ) 10!41 389 8195 59F (QQ) 8199 345 8250 9626±871 {female) 715±551 {female) 8523±855 (female) rnean±s.d. 9523±1517 (both) 737±430 (both)

pages 48-50, 55-57, and 76-77 (MRID 45144101), QQ (low); OR (m1d); RR (high)



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Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (!999) Humans (non-guideline)

Table C. Serum Paraoxonase/CPOase and 0-hour RBC AChE Activitv {control) and Phenotype Subject# CPOase (units/L) 

### I Paraoxonase (units/L) RBC AChE lUlL\ Control [ran•el 2M (RR) 9565 1668 9196 6M (OR) 5430 645 8921 8M (OR) 6329 728 6809 !OM (OR) 9350 882 7821 13M (QQ) 7678 317 8833 17M (QQ) 8001 311 7277 mean±s.d. 7726±1632 (male) 558±500 (male) 8143±982 (male) 20F (QQ) 10015 411A 8239 23FIQQl 6329 284 8723 27F (QQ) 8217 350 10208 29F (OR) 9871 834 7865 32F (QQ) 9817 434 8723 34F (OR) 10410 1207 7953 mean±s.d. 9110±1556 (female) 586±360 (female\ 8619±861 lfemale\ mean±s.d. 8418±1639 (both) 673±425 (both) Control [ran2e! 37M (OR) 9997 1001 9361 39M IQQ) 15894 567 8569 41M (QQ) 9206 378 9592 44M (OR) 9709 1045 10835 45M(OR) 11723 1112 7486 46M (OR) 11363 1134 9185 mean±s.d. 11315±2445 (male\ 872±319 Imale\ 9171±1112 Imale\ 50F (QQ) 10141 423 8492 52F (QQ) 10069 456 7744 53F (OR) !4096 1134 8261 54F (QQ) 6904 289 8602 57F (RR) 17333 2502 9086 60F (QQ) 9853 367 9273 rnean±s.d. 11400±3700 (female) 862±860 (female) 8576±556 (female) mean±s.d. 11357±3097 (both) 867±618 (both)

Pages 57 and 77 (MRID 44811002); QQ (low); OR (mid); RR (high)



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Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans (non-guideline)

Table D. Male RBC AChE Activitv, Blood TCP Level, and CP Level 12.0 m•ik•l Subject# 38 40 42 43 

### I 47 48

Hour AChE IU/Ll -10 9141 9680 9493 8041 7887 8569 0 8283 10021 9372 8118 7645 8206 2 8437 9922 9537 8206 7931 8019 4 8360 10109 9471 7964 7942 8008 8 9097 9856 9152 7942 7744 7887 12 8800 9768 9130 8327 7788 7689 24 8877 9790 9350 8228 7370 8206 36 8998 9889 9405 8437 7700 7546 48 8481 9636 9658 8129 7667 7832 72 9372 9966 9834 8668 8107 8074 96 8976 9966 9648 8690 7942 7766 120 9108 10021 9592 8052 8305 7766 144 8844 9955 9911 8569 7920 7942 168 8734 9691 9174 8668 8305 8184 Chlorpyrifos concentrations (112/2 in blood samples 0 ND ND ND ND ND ND 2 ND ND ND ND 3.1 ND 4 ND ND ND ND 1.3 ND 8 ND ND ND ND 3.4 ND 12 ND ND ND ND 1.8 ND 24 ND ND ND ND ND ND 36 ND ND ND ND ND ND 48 ND ND ND ND ND ND 72 ND ND ND ND ND ND 96 ND ND ND ND ND ND 120 ND ND ND ND ND ND 144 ND ND ND ND ND ND 168 ND ND ND ND ND ND TCP concentrations lmz/2) in blood samnles 0 ND ND ND ND ND ND 2 420 61 44 230 580 180 4 560 220 130 340 640 250 8 510 320 230 330 790 240 12 440 340 270 410 910 260 24 430 340 ns 520 980 380 36 500 360 360 610 960 460 48 530 410 370 610 1000 470 72 ++00 270 320 320 690 300 96 290 170 220 190 460 210 120 160 120 160 90 320 140 144 85 75 96 66 220 77 168 41 98 220 40 150 48 Data from Tables 5 and 7 (pages 34 and 36) ofMRID 45144101; ns no sample;
..alw RE!t t·umi



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Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans (non-guideline)

Table E. Female RBC AChE Activity, Blood TCP Level and CP Level (2 mg/kg) Subiect # 49 I 51 I 55 I 56 I 58 I 59

hours AChE U/L)

-10 7832 8283 10373 8426 8041 8063 0 7766 7942 10076 8910 8195 8250 2 7700 7931 10032 8602 8041 8063 4 7662 7997 10901 8525 8096 8162 8 8008 7986 10582 6688 (25) 7931 8184 12 7513 7640 10032 6221 (30) 7535 (8) 7623 (8) 24 8008 7722 10131 6424 (28) 8107 8162 36 8710 7700 10274 7051 (21) 8107 8052 48 7568 7876 10395 6892 (23) 7821 7788 72 7920 8195 10461 X 8503 7942 96 7986 8415 9933 X 7931 8492 120 8019 8569 9757 X 8228 8382 144 7931 7975 10472 X 7832 8415 168 8327 8074 9845 X 7876 7975 Chlorpyrifos concentrations (nell:! in blood samples 0 ND ND ND ND ND ND 2 3.1 ND ND ND ND 2.2 4 XX ND ND ND ND 4.1 8 1.7 ND ND 18.0 ND 4.1 12 ND ND ND 2.5 ND 1.5 24 ND ND ND ND ND ND 36 ND ND ND ND ND ND 48 ND ND ND ND ND ND 72 ND ND ND X ND ND 96 ND ND ND X ND ND 120 ND ND ND X ND ND 144 ND ND ND X ND ND 0168 ND ND ND X ND ND TCP concentrations (ng/g) in blood samples 0 ND ND ND ND ND ND 2 290 420 290 71 240 250 4 450 580 220 120 310 470 8 490 1300 520 1600 480 610 12 440 690 500 1500 340 610 24 470 540 600 1300 400 500 36 430 750 600 1100 430 480 48 360 730 530 980 360 390 72 200 600 340 X 190 220 96 130 420 210 X 110 110 120 84 150 120 X 65 58 144 52 170 73 X 37 32 168 35 110 45 X 24 23

0 Data from Tables 5 and 7 (pages 34 and 36) ofMRID 45144101, (Yo mhibitiOn from 0 hour), xx sample not analyzed, X subject leftstudy



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Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans (non-guideline)

Table F. Male RBC AChE Activity, Blood TCP Level and CP Level (1.0 ml!ik2l Subject# I 

### I 4 7 II I 14 I 16 AChE (U/ld_ -10 8272 9416 9603 10307 9823 8481 0 9108 9669 9713 10098 10087 8756 2 9625 9438 10230 9097 9845 9174 4 9823 9405 11198 10318 9801 8624 8 9284 9361 9834 9768 9878 9020 12 9042 10219 10109 9779 9658 8448 24 9306 10219 9966 9977 9658 8470 36 9119 9702 9746 9768 9295 8140 48 8074 8624 9196 9141 9174 7953 72 9295 10164 9801 10153 9867 8459 96 8283 8151 8096 

### noo U24) 8899 8448 120 9218 8723 8800 9185 9086 8624 144 8833 8426 9141 9218 8492 8173 168 8228 8734 9174


### - 8844 8019 Chlorpyrifos concentrations (ng/g in blood samples 0 ND ND ND Ns ND ND 2 ND ND ND 1.0 ND ND 4 ND ND ND 

# I ND 2.7 ND 8 ND ND ND ND !.5 ND 12 ND ND ND ND ND ND 24 ND ND ND ND ND ND 36 ND ND ND ND ND ND 48 ND ND ND ND ND ND 72 ND ND ND ND ND ND 96 ND ND ND ND ND ND 120 ND ND ND ND ND ND 144 ND ND ND ND ND ND 168 ND ND ND Ns ND ND TCP concentrations (ne/g) in blood samples 0 ND ND ND ND ND ND 2 140 49 370 260 170 !50 4 280 130 430 450 570 200 8 340 290 440 400 610 170 12 340 300 350 340 540 170 24 440 250 270 270 520 200 36 430 240 160 200 440 280 48 310 230 140 160 420 300 72 160 160 54 75 280 210 96 84 98 23 36 220 130 120 41 54 10 20 !50 84 144 18 34 ND ND 84 48 168 II 20 ND Ns 50 29 Datafrom page 56 of578 and Tables 5and 7(pages 34 and 36) ofMR!D 4514410I, ns no sample,



### 38EPA's Records Disposition Schedule PEST 361 Scientific Data Reviews HED Records Center- File R180234- Page 68 of 73

Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans (non-guideline)
II Table G. Female RBC AChE Activitv, Blood TCP Level and CP Level (l.O m2ik2l

Subiect # I 21 I 24 I 25 30 

### I 33 35 AChE (U/Ll -10 9416 9295 9031 9064 7942 8250 0 9900 9757 9548 9130 8140 8514 2 9460 9460 9240 8932 8965 8514 4 10087 9999 9152 9229 8866 9042 8 9394 9570 9427 9119 8624 8228 12 9361 9350 8855 8822 8470 8459 24 9317 9097 9339 8943 8877 8745 36 8789 9218 8624 8536 8074 8459 48 9361 9604 9174 8998 7766 8569 72 9064 9240 9460 9900 8503 8921 96 8637 8844 8437 8349 7178 9603 120 8954 9086 8426 8855 7601 7876 144 8932 9207 8580 8613 7156 8283 168 8624 8525 8855 8712 7678 7799 Chlorpyrifos concentrations**(ng/~** in blood samples 0 ND ND ND ND ND ND 2 5.6 ND ND ND ND ND 4 2.9 ND ND ND 2ND ND 8 ND ND ND 1.1 IND ND 12 ND ND NO NO NO ND 24 ND ND NO ND NO NO 36 NO ND NO ND NO NO 48 ND ND ND NO ND ND 72 NO ND ND NO NO NO 96 NO NO NO NO NO ND 120 NO ND ND ND NO NO 144 NO ND ND ND NO NO 168 NO ND ND ND ND NO TCP concentrations {nl!l!!) in blood samoles 0 NO ND ND NO ND NO 2 220 96 160 10 32 72 4 350 430 180 160 93 250 8 310 340 190 310 100 490 12 300 310 190 290 110 430 24 300 320 220 290 140 370 36 290 320 200 280 140 310 48 280 300 160 280 110 350 72 140 250 85 240 70 190 96 75 180 30 160 45 140 120 43 120 16 85 29 99 144 22 73 NO 45 17 75 168 13 47 NO 23 13 30 Datafrom page 56 of578 and Tables 5and 7 (pages 34 and 36) ofMRID 45144101; ns no sample;



### 39EPA's Records Disposition Schedule PEST 361 Scientific Data Reviews HED Records Center- File R180234- Page 69 of 73

Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans (non-guideline)

Table H. Male and Female RBC AChEActivity and Blood TCP Level (0.5 m2/k2) Subject# 

### I 3 5 9 

### I 12 

### I 15 18 MALES AChE (U/L) -10 8393 7865 8294 8877 9713 9405 0 8613 7942 8602 9471 9889 9471 2 8668 8547 8437 9218 10021 9977 4 8514 8481 8646 9031 9944 9658 8 8228 8217 8844 9482 9845 10516 12 8118 8030 8723 9229 9471 9515 24 8393 8074 8580 9394 9680 10153 36 7997 7810 8261 8910 9670 9746 48 7244 7128 8107 9053 9119 8822 72 8426 8074 8260 9504 9889 9702 96 8558 7282 6985(tl9) 8096 8525 8767 120 8679 7920 7535 Ul2) 8921 9207 9163 144 8283 8712 7376 (tl4) 9537 9548 9130 168 8107 7931 7700(Pll 8547 9295 9581 MALES TCP concentrations (ne:/ !) in blood samples 0 ND ND ND ND ND ND 2 23 49 24 29 160 51 4 95 53 140 83 250 100 8 97 51 130 96 240 130 12 96 130 240 97 210 130 24 130 98 130 100 190 120 36 140 100 130 110 190 llO 48 140 100 120 110 190 110 72 87 59 70 96 130 73 96 58 24 41 67 88 48 120 38 8 25 38 56 29 144 22 ND 14 19+ 33 IS 168 14 ND 10 ND 23 9 Subject# 19 22 26 28 31 36 FEMALES AChE ( /L) -10 9724 9086 8063 10010 8800 7139 0 7282 9218 8602 9900 9515 7156 2 7986 8932 8448 10252 9526 6853 4 7810 9141 8239 10593 8239 6501 8 8041 9097 8305 9966 8866 7007 12 7843 8349 8437 9779 8602 6996 24 7832 8866 8041 9746 8756 7365 36 7535 8987 7810 9834 8228 7068 48 7623 8921 8129 10109 8855 7117 72 7953 9394 8701 10516 9482 7579 96 7997 8646 7689 10153 7920 6474 120 7931 8437 7975 9581 8811 7073 144 7689 8195 7744 9218 8734 6589 168 7744 8657 7733 9130 9086 6837 FEMALES TCP concentrations (n

**~/g)** in blood sam les 0 ND ND ND ND ND ND 2 110 190 12 61 77 62 4 190 380 89 91 120 220 8 210 350 110 140 220 260 12 ND 310 110 130 230 230 24 189 220 130 140 210 220 36 179 ISO 190 110 200 230 48 180 140 180 91 190 230 72 110 59 160 46 130 150 96 88 31 140 25 64 83


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Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans (non-guideline) 120 58 17 120 14 41 49 144 35 ND 107 ND 22 27 168 23 ND 88 ND 14 19 Data from Tables 5 and 7 (pages 34 and 36) ofMRJD 4514410I



### 41EPA's Records Disposition Schedule PEST 361 Scientific Data Reviews HED Records Center- File R180234- Page 71 of 73

Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans (non-guideline)

Table I. Male and Female RBC AChEActivity (Phase I control) Subject# I 2 I 6 I 8 I 10 I 13 I 17 MALES AChE (U/L) -10 8294 7810 6562 8327 6985 7139 0 9196 8921 6809 7821 8833 7277 2 8910 8558 6782 8019 8448 7420 4 8382 8580 6622 8118 8481 7502 8 8239 8701 6886 7986 8481 7755 12 8360 8635 6886 7876 8789 7711 24 8734 8723 6655 8426 8173 7502 36 8448 7700 6864 8052 7689 7288 48 7711 7964 6083 7678 8536 7057 72 8569 8921 6672 7920 8195 7244 96 8151 7536 6336 6771 8206 7524 120 8404 7799 6457 7321 8041 7194 144 7810 7733 6281 7134 7799 7139 168 8206 8778 6677 7623 8019 7315 Subject# 20 23 27 29 32 34 FEMALES AChE (U/L) -10 7178 8481 9724 8382 8294 8866 0 8239 8723 10208 7865 8723 7953 2 7568 9053 10010 8382 8932 7722 4 7953 9504 10076 8426 8855 7755 8 8239 9174 10373 8701 8569 7843 12 7898 8657 9713 8118 8085 7953 24 7645 8844 10098 8195 8481 7755 36 7249 8712 9284 7843 8261 7183 48 7931 8800 9603 8184 8008 7568 72 7843 8789 9416 8437 8822 7997 96 7415 8272 8800 7073 8305 7002 120 7513 8360 9053 8283

- 7249 144 7722 7975 9570 8206



### - 7249 168 7689 8437 9317 7722



### - 7013 Datafrom Table 5.1.1 (pages 57) ofMRJD 44811002



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Chlorpyrifos/P. C. Code 059101 Special RBC AChE Inhibition Study (1999) Humans (non-guideline)

Table J. Male and Female RBC AChE Activity (Phase 2 control) Subject# 37 39 I 41 

### I 44 I 45 I 46 MALES AChE (U/L) -10 9878 8910 9240 10769 7387 9570 0 9361 8569 9592 10835 7486 9185 2 9394 8723 10197 10681 7898 8800 4 9757 8470 9240 10703 7590 9108 8 10318 8382 8998 10494 7645 9295 12 9999 8723 8998 10164 7613 9790 24 9680 8547 8789 10197 7810 9284 36 9669 8294 8910 10318 7453 9350 48 9713 8481 9119 10208 7645 9086 72 9482 8657 9394 10923 7975 10120 96 9306 8778 9460 10329 7810 9570 120 9427 8976 9504 10406 8096 9614 144 9416 8811 9174 9691 8184 10538 168 9823 8437 9548 10802 8041 9174 Sub.iect # 50 52 53 54 57 60 FEMALES AChE (UIL) -10 8107 7975 8712 8470 8734 8910 0 8492 7744 8261 8602 9086 9273 2 8327 7623 8547 8294 9020 8855 4 8239 7645 8349 8558 8866 8624 8 8415 7865 9031 8558 9218 9207 12 8404 7854 8723 8327 8987 9240 24 8415 7293 8756 8437 9174 8987 36 8063 7810 8470 8228 8668 9152 48 8184 7854 8844 8327 8954 9108 72 9108 8096 9273 9108 9229 8833 96 8426 7623 8811 9108 8899 8855 120 8965 7810 8569 8646 9229 9053 144 7337 7854 9339 8415 8778 8844 168 8382 7634 8591 8382 9086 9218 Data from Table 9.1.1 (pages 77) ofMRID 44811002



### 43EPA's Records Disposition Sctredute;>EST361 Scie"lilie Oala Reviews- HEO**Rooo•~• ~oolor**  l'ilo R1B0234 .9age

..Z3 .of

..73.--. 

# •**~** 13544



# • R180234

Chemical Name: Chlorpyrifos

PC Code: 059101 HED File Code: Memo Date: File ID: Accession #: 14000 Risk Reviews 1/7/2010 00000000 000-00-0134

HED Records Reference Center 1/13/2010 

# •

•