OFFICE OF CHEMICAL SAFETY

AND POLLUTION PREVENTION UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

RE : Meeting between Dow AgroScience s (DAS) and EPA to Discuss DAS’

Completed Physio logically Based Pharmacokinetic Model (PBPK)

, Recently

Conducted Chlorpyrifos Oxon Saturated Vapor Inhalation Study, and DAS’

Position Regarding the Toxicity Adjustment Factor for the Chlorpyrifos Oxon

List of Documents

1. Meeting Summary Page 1

2. Meeting Sign in Sheet Page 2

3. DAS PowerPoint Presentation s Page 4

Meeting Summary

On Tuesday, August 27 , 2013

, EPA’s Office of Pesticide Programs met with DAS to discuss

their completed PBPK model

. DAS had previously presented the model enhancements related to

dermal and oral exposure , which they have already submitted to EPA . This meeting focused on

the complete model, which now includes an inhalation component along with the completed

dermal and oral model components. DAS will submit the inhalation component of the PBPK

model to EPA in the coming weeks. They indicated that third party validation was currently

underway and would be submitted at the same time as the complete model

. EPA has begun

conducting its own validation of the model components already submitted

. DAS a lso discussed

the preliminary results of the chlorpyrifos oxon vapor inhalation study, which they expect to

submit to EPA by mid

- September. In addition, they presented their position regarding the

appropriate toxicity adjustment factor for the chlorpyrifos oxon.EPA and Registrant Meeting

– Phone Participants

Chlorpyrifos

August 2 7 , 201 3

Name Affiliation Phone Number E

- mail

Ken Racke DAS 317

- 337

- 4654 kracke@dow.com

Jon Hotchkiss Dow 989

- 636

- 6586 JAHotchkiss@dow.com

Joseph Velovitch DAS 317

- 337

- 4179 jjvelovitch@dow.com

Brian Bret DAS 916

- 780

- 7477 blbret@dow.com

Bruce Houtman DAS 317

- 337

- 3376 bahoutman@dow.com

Carol Burns Dow 989

- 636

- 2278 CJBurns@dow.com

Torka Poet PNNL 509

- 371

- 6984 Torka.Poet@pnnl.gov

James Nguyen EPA/HED 703

- 347

- 0377 nguyen.james@epa.gov

Stephanie Padilla EPA/NHEERL 919

- 541

- 3956 padilla.stephanie@epa.gov

Ginger Moser EPA/NHEERL 919

- 541

- 5075 moser.ginger@epa.gov

Cecilia Tan EPA/NERL 919

- 541

- 2542 tan.cecilia@epa.gov

Chuck Andrews CA DPR 919

- 445

- 3984 Chuck.Andrews@cd pr.ca.gov

Jay Schreider CA DPR 919

- 445

- 4241 Jay.Schreider@cdpr.ca.gov

Randy Segawa CA DPR 916

- 324

- 4137 rsegawa@cdpr.ca.gov

Lisa Ross CA DPR 916

- 324

- 4116 Lisa.Ross@cdpr.ca.gov

Sheryl Beauvais CA DPR 919

- 445

- 4268 sbeauvais@cdpr.ca.gov

David Duncan CA DPR 916

- 445

- 3870 dduncan@cdpr.ca.gov

David Rice CA DPR 916

- 324

- 3480 drice@cdpr.ca.gov

Xiaofei Zhang CA DPR 916

- 445

- 4267 xiaofeizhang@cdpr.ca.gov

### D ar i n L i ck f e l dt

A ugus t 27

, 2013 

# U pd a t e on C h l o r p y r i f o s I nh a l a t i on S t ud i es

a nd P B P K M od e l P r o j ec ts| 2 

## B ackg r ound I n f o rm a ti on

• DAS and o t he r CHP r eg i s tr an t s app r e c i a t e t he EPA’ s

e ff o rt s i n u s i ng t he be s t a v a il ab l e sc i en c e i n t he H u m an

H ea l t h Ri sk A ss e ss m ent

• CHP i s ahead o f m an y a c t i v e i ng r ed i en t s i n t he r eg r e v i e w

p r o c e ss and c ou l d po t en t i a ll y s e t p r e c eden t s b y w h i c h

o t he r a c t i v e i ng r ed i en t s will be a sk ed t o f o ll ow

• A g r i c u l t u r a l s t a k eho l de r s ha v e a l s o a sk ed f o r a sc i en c eba s ed app r oa c h be t a k en i n t he r e g r e v i e w o f CHP

• DAS aga i n o ff e r s a m ee t i ng s pe c i f i c a ll y wi t h CADPR t o

p r o v i de f u rt he r ba ck g r ound and c on t e x t on t he t op i cs

p r e s en t ed t oday| 3 

## A genda

• U pda t e on r e c en t C h l o r p y r i f o s O x on S a t u r a t ed V apo r

I nha l a t i on S t udy

• C h l o r p y r i f o s O x on : Bi o l og i c a l B a s i s f o r R e v i s ed To x i c i t y

A d j u s tm en t Fa c t or

• C he m i c a l S pe c i f i c ad j u s tm en t Fa c t o r s ( CSA F s ) f o r Or a l

E x po s u r e s t o C h l o r p y r i f o s and C h l o r p y r i f o s O x on

• U s i ng PBPK

/ PD M ode l s t o R e c on s tr u c t A gg r ega t e

E x po s u r e s o f t he C o l u m b i a U n i v e r s i t y C oho rt

- P r e li m i na r y

F i nd i ngs

## Jon H o t chk i ss 1



## , D a l and Jube rg 2



## , Mi chae l B a r t e ls 1



## , D a r i n L i ck f e l dt 2

1 

### The D ow C he mi

ca l C o m pany

, M i d l and MI

2 

### D ow A gro S c i

ences LL C

, I nd i anapo li s IN

A ugus t 27

, 2013 

# CH L OR PY R I F O S O X ON S A T URA TE D

V A P OR I NHA L A T I ON ST UDY| 5 

## O u tli ne

• St ud y O v e r v iew

• P ha s e 1 : D e t e r mina t ion o f S a t u r a t ed O x on V apo r C on c en t r a t ion

• P ha s e 2 : Limi t ed T K and Ti ss ue C h E I nhibi t ion K ine t i cs

> B lood O x on and T C P Le v els

> Lung

, R B C

, Br ain

, and P la sm a Choline s t e r a s e Ac t i v i ty



### • S umma r y and C on c lu s ions

• Que s t ions| 6 

## P u r pose

• D e t e r mine o x on s a t u r a t ed v apo r c on c en t r a t ion

> Con f li c t ing V p v alues



### • C ondu c t no s e

- onl y inhala t ion e x po s u r e t o s a t u r a t ed o x on v apo r

a t mo s phe re

• D e t e r mine t ime

- dependen t blood le v el s o f o x on and 3

, 5

, 6

- t r i c hlo r o

- 2-

p y r idinol ( T C P ) f o r in c lu s ion in PBPK/P D model

• D e t e r mine k ine t i cs o f o x on

- indu c ed inhibi t ion o f c holine s t e r a s e (C h E)

> Rou t e o f e x po s u r e = inhala t ion

> E x po s u r e

- and t i m e

- dependen t Ch E a c t i v i t y m ea s u r ed in Lung

, R B C

,

P la sm a and Br ain| 7 

## P hase 1 : D e t e rm i na ti on o f S a t u r a t ed O xon V apo r Level

• N e w lo t o f o x on s y n t he s i z ed

> P u r i t y = 100%

• Ident i f ic at i on b y p r oton and 13 C N M R, IR and MS



### • S olid o x on mel t ed (~ 45 ° C) and u s ed t o c oa t gla ss beads

• O x on c oa t ed bead s pla c ed in gla ss J- t ube t o gene r a t e v apo rs

• Op t imum f lo w r a t e o f c a rr ie r ga s ( f il t e r ed

, humidi f ied ai r) de t e r mined

• J- t ube ou t pu t deli v e r ed t o 42L f lo w- pa s t no s e

- onl y e x po s u r e c hamber

• C hambe r o x on c on c en t r a t ion de t e r mined b y H P L C /PESI

- M S/ M S

anal y s i s o f s o r ben t t ube elua t es

• C hambe r moni t o r ed f o r ae r o s ol f o r ma t ion u s ing a r eal

- t ime

ae r od y nami c pa r t i c le s i z ing ( APS ) s pe c t r ome t e r| 8 

## D e t e rm i na ti on o f S a t u r a t ed V apo r C oncen t r a ti on

• Te s t a t mo s phe r e gene r a t ed u s ing J- t ube f illed w i t h o x on -c oa t ed beads

> F lo w r a t e held c on s t an t ( 30 L / m in)

> T e m pe r a t u r e v a r ied t o adju s t v ola t ili z a t ion o f s olid o x on on beads

> APS u s ed t o m oni t o r pa r t i c le nu m be r

, s i z e and c on c en t r a t ion



### • S a t u r a t ed v apo r = in f le c t ion poin t w he r e ae r o s ol i s f o r med T e m p e r a t u r e ( ° C)ConcentrationOxon(mg/m3)ParticleConc. (mg/m3)

20 22 24 26 28 30 32 34 36 38 40 42 0 25 50 75 100 125 150 175 200

0

. 0 00 0

. 0 01 0

. 0 02 0

. 0 03 0

. 0 04 0

. 0 05 0

. 25 0

. 50 0

. 75 1

. 00 O

x o n C on c.

P a r t i c l e C on c. E ff ec t o f T e m p e r a t u r e on O x o n C o n ce n t r a t i on a nd

A e r o s o l P a r t i c l e C on ce n t r a t i on| 9 

## P hase 2 : L i m it ed T K and T i ssue C h E I nh i b iti on K i ne ti cs

• 6 h no s e

- onl y e x po s u r e t o s a t u r a t ed o x on v apo r a t mo s phe re

> O x on v apo r c on c en t r a t ion m ea s u r ed b y H P LC / PES I -MS / MS



### • R a t s ( n = 8 / g r o up ) s a cr i f i c ed 0

, 1

, 2

, 4

, 8 o r 24 h a ft e r e x po s u re

> n = 4 blood s a m ple s anal y z ed f o r o x on and T C P a t ea c h s a cr i f i c e t i me

> n = 8 lung

, R B C

, b r ain and pla sm a s a m ple s anal y z ed f o r Ch E a c t i v i t y a t

ea c h s a cr i f i c e t i me



### • Ex po s u r e s t a r t w a s s t agge r ed f o r c on t r ol and o x on g r oups

> G r oup s o f 6 r a t s w e r e pla c ed on c ha m be r a t 3 m in in t e rv als

> A ll c on t r ol r a t s pla c ed on c ha m be r (

~ 24 m in t o t al t i m e ) be f o r e f i rs t o x on

g r oup s t a r t ed

• M i n i m iz e potent i a l fo r o x on c onta m i nat i on of c ont r o l g r oups



### • A ll r a t s s a cr i f i c ed w

/ in 5 min o f sc heduled s a cr i f i c e t ime

• B lood s ample s f o r O x on and T C P anal y s e s w e r e d r a w n and e xt r a c t ed

w / in 5 min o f s a cr i f i c e t ime| 10 

## O xon V apo r C ha m be r C oncen t r a ti on

• 6 hr T im e W e i gh t ed A v erage ( T WA) C oncen t ra t i on = 35

. 3 μ g /m 3



### >

~ 14 % o f s a t u r a t ed C P F v apo r c on c en t r a t ion ( 254 μ g/m 3 ; M RID 49119501)



### >

~ 50

- f old highe r t han p r edi c t ed ( 0.837 μ g/m 3 ; V p = 4.65 x 10 -8 mm Hg) S a m p l e ID M e a s

u r e d A m oun t

(μ g O x on) V o l u m e C

h a m b e r

A t m o s ph e r e S a m p l ed O x

on C on c e n t r a ti on

(μ g / L) O x

on C on c e n t r a ti on

(μ g /m 3 ) O x

on C on c e n t r a ti on

( M e a n μ g /m 3 )

C o n t r o l 1A < LLQ 85L < LLQ < LLQ

C o n t r o l 1B < LLQ 85L < LLQ < LLQ

C o n t r o l 2A < LLQ 77

. 5L < LLQ < LLQ

C o n t r o l 2B < LLQ 77

. 5L < LLQ < LLQ

Ex p o s u r e A 0

. 1 10 7

. 5L 0

. 0 15 14

. 667

Ex p o s u r e B 0

. 0 27 7

. 5L 0

. 0 04 3

. 6 13

Ex p o s u r e C 0

. 2 73 7

. 5L 0

. 0 36 36

. 400

Ex p o s ur e D 0

. 3 27 7

. 5L 0

. 0 44 43

. 600

Ex p o s u r e E 0

. 3 44 7

. 5L 0

. 0 46 45

. 867

Ex p o s u r e F 0

. 3 08 7

. 5L 0

. 0 41 41

. 067

Ex p o s ur e G 0

. 2 75 7

. 5L 0

. 0 37 36

. 667

Ex p o s ur e H 0

. 2 82 7

. 5L 0

. 0 38 37

. 600

Ex p o s u r e I 0

. 4 22 7

. 5L 0

. 0 56 56

. 267

Ex p o s u r e J 0

. 3 20 7

. 5L 0

. 0 43 42

. 667

Ex p o s u r e K 0

. 0 01 7

. 5L 0

. 0 00 0

. 1 75

Ex p o s u r e L 0

. 4 60 7

. 5L 0

. 0 61 61

. 333

LL Q

= 0

. 000 5 9 μ g O x on 49

. 467

30

. 754 40

. 000

43

. 467

37

. 133 < LLQ

< LLQ

9

. 140 C ha m b e r Ox on

C o n c e n t r a t i on| 11 

## B l ood Leve l s o f O xon and 3

, 5 ,6 - T r i ch l o r op y r i d i no l ( T CP)

• N o oxon de t ec t ed i n b l ood a t an y sa m p l e t ime

> Ox on LL Q

= 3.53 x 10 -4 n m o l e/g b l ood ( 0.35 n M ; 0.118 ng/g b l ood)



### • B l ood T C P concen t ra t i on > LLQ t hrough 8 hr pos t- exposure

> T C P LL Q

= 1.23 x 10 -2 n m o l e/g b l ood ( 2.44 ng/g b l ood)



### O x o n a n d T C P i n Bl ood

T i m e A fte r Ex po s u r e ( hou r s) 0 1 2 4 8 24BloodConcentration(nmoles/gblood)

0

. 0001 0

. 001 0

. 01 0 .1 1

TC P L LQ T CP

O x o n LLQ T CP

O x on| 12 

## Lung

, RBC

, B r a i n

, and P l as m a C ho li nes t e r ase A c ti v ity

R BC

T i m e A fte r Ex po s u r e ( ho u r s)RBCChEActivity(%Control)

0 30 60 90 120 150 180

a

a = S i g n i f i c a n t l y d i ff er e n t t h a n c o n t r o l ( p < 0

. 05) 0 1 2 4 8 24 C on t r ol

O x on

P l as ma

T i m e A fte r Ex p o s u r e ( h ou r s)PlasmaChEActivity(%Control)

0 30 60 90 1 20 1 50 1 80

0 1 2 4 8 24

C on t r ol

O x on Br a in

T i m e A fte r Ex po s u r e ( hou r s)BrainChEActivity(%Control)

0 30 60 90 120 150 180

a

a = S i g n i f i c a n

t l y d i ff e r e n t t h a n c o n t r o l ( p < 0

. 05) 0 1 2 4 8 24 C o n t r ol

O x on L ung

T i m e A fte r Ex po s u r e ( hou r s)LungChEActivity(%Control)

0 30 60 90 120 150 180

0 1 2 4 8 24

C on t r ol

O x on| 13 

## Lung

, RBC

, B r a i n

, and P l as m a C ho li nes t e r ase A c ti v ity

L ung

T i m e A fte r Ex po s u r e ( hou r s)LungChEActivity(U/L)

0 10 00 20 00 30 00 40 00 50 00 60 00

0 1 2 4 8 24

C on t r ol

O x on RBC

T i m e A fte r Ex po s u r e ( hou r s)RBCChEActivity(U/L)

0 10 00 20 00 30 00 40 00 50 00 60 00

a

a = S i g n i f i c a n

t l y d i ff e r e n t t h a n c o n t r o l ( p < 0

. 05) 0 1 2 4 8 24 C on t r ol

O x on

P l as ma

T i m e A fte r Ex po s u r e ( hou r s)PlasmaChEActivity(U/L)

0 10 00 20 00 30 00 40 00 50 00 60 00

0 1 2 4 8 24

C on t r ol

O x on B r a in

T i m e A fte r Ex po s u r e ( h o u r s)BrainChEActivity(U/L)

0 10000 20000 30000 40000 50000 60000

a

a = S i g n i f i c a n t l y d i ff e r e n t t h a n c o n t ro l ( p < 0

. 05) 0 1 2 4 8 24 C on t r ol

O x on| 14 

## S u mm a ry

• The s a t u r a t ed v apo r c on c en t r a t ion f o r o x on i s

~ 35

. 3 μ g /m 3

>

~ 7

- f old le ss t han s a t u r a t ed C P F v apo r c on c en t r a t ion ( 254 μg /m 3 ; M R I D #

49119501)



### • I nhaled o x on v apo rs a r e ab s o r bed bu t r apidl y me t aboli z ed

> No o x on de t e c t ed in blood a t an y s a m ple t i me

• O x on LLQ

= 3

. 53 x 10 -4 n m ole / g blood (0

. 35 n M ; 0

. 118 ng / g blood)

> B lood T C P c on c en t r a t ion > LL Q t h r ough 8 h r po s t

- e x po s u re

• TC P LLQ

= 1

. 23 x 10 -2 n m ole / g blood (2

. 44 ng / g blood)



### • 6 h no s e

- onl y e x po s u r e t o s a t u r a t ed o x on v apo r r e s ul t s in

> No c lini c al s ign s o f O P t o x i c i ty

> No inhibi t ion o f Lung

, R B C

, Br ain o r P la sm a Choline s t e r a s e Ac t i v i ty| 15 

## C onc l us i ons

• I nhaled o x on v apo rs a r e ab s o r bed bu t r apidl y m e t aboli z ed

> B l ood l e v e ls < LL Q w i th i n 5 m i n of a 6 hou r i nha l at i on e x po s u r e

• T C P p r e s en t in blood o f o x on

- e x po s ed r a t s c on f i rms o x on ab s o r p t ion

• 6 h r N O E C f o r inhaled o x on v apo rs ≥ 35

. 3 μg o x on /m 3 air

> B a s ed on no Ch E i nh i b i t i on i n Lung, R B C, B r a i n o r P l a s ma

• Th e res ul t s o f t hi s s t ud y d em on s t ra t e t h a t t h ere i s no c holin es t erase

inhibi t ion a nd t h ere f o re no h a z ar d f r o m inh a l a t ion o f a sa t u ra t e d v a po r

c on ce n t ra t ion ( 35

. 3 μ g/m 3 ) o f C hlo r p y r i f o s O x on.

• Th ese d a t a s uppo r t a nd ex t e nd ou r p re v iou s C hlo r p y r i f o s v a po r s t ud y

(M R I D # 49119501 ) w h i c h re po r t e d t h a t t h ere w as no c holin es t erase

inhibi t ion a nd t h ere f o re no h a z ar d f r o m inh a l a t ion o f t h e p are n t m ol ec ul e

,

C hlo r p y r i f o s

, a t a sa t u ra t e d v a po r c on ce n t ra t ion o f 254 μ g/m 316 

# C hlo r p yr i f os S a t u ra t e d V a po r St udy

( M R I D # 49119501) 49119501)| 17 

## C ha m be r C oncen t r a ti on : CP F V apo r S t udy

6 h T WA

17.7 ppb

0.254 mg /m 3 Vo l u me

R e c o v e r y

- A

d j u s t e d a C h a m be r A ir C on c en tr a t i o n b

S a m p l e ID M e a su r e d A m o u nt A m o u nt Sa m p l ed C h l o r p y r if o s V a por

( μ g C h l o r p y r if o s) ( μ g C h l o r p y r if o s) ( L) ( p p b)

S a m p l e s t a k e n D u r

i n g E x p o s u re

C o n t r o l 1

- F c < L O D d

< L OD 2 6 .4 ( < L O D ; 0

. 1 0 ) e

C o n t r o l 2 -F < L OD < L OD 3 6 .0 ( < L O D ; 0

. 0 7)

C o n t r o l 3 -F < L OD < L OD 3 6 .0 ( < L O D ; 0

. 0 7)

C o n t r o l 4 -F < L OD < L OD 1 8 .0 ( < L O D ; 0

. 1 5)

E x p o s u r e 1 D -F 3

. 38 3

. 50 1 6 .5 1 4 .8

E x p o s u r e 2 D -F 3

. 96 4

. 10 1 6 .5 1 7 .3

E x p o s u r e 3 D -F 3

. 85 3

. 99 1 6 .5 1 6 .9

E x p o s u r e 4 D -F 4

. 37 4

. 52 1 6 .5 1 9 .1

E x p o s u r e 5 D -F 4

. 42 4

. 58 1 6 .5 1 9 .4

E x p o s u r e 6 D -F 6

. 47 6

. 70 2 5 .5 1 8 .3

C h a m b e r H

o m o g e n e it y f

S a m p l e P 1 -F 2

. 50 2

. 59 9

. 00 2 0 .1

S a m p l e P 2 -F 2

. 27 2

. 35 9

. 00 1 8 .2

S a m p l e P 3 -F 2

. 78 2

. 88 1 0 .5 1 9 .1

S a m p l e P 4 -F 2

. 80 2

. 90 1 0 .5 1 9 .3

a P e r c e n t R e c o v e r y ( E x t r a c t i on E f f i c i e n c y ) b a s e d on A n a l y s i s o f S p i k e d S o r b en t T u be s w as 9 6

. 6%

b V ap o r C o n c e n t r a t i o n ( p p b )

= [ ( μ g C F x 24 4 50 ) / ( M W o f C F x L i t e r s o f A i r C o l l e c t e d ) ] ; M W o f C F

= 35 0

. 6 g / m ol

c F r o n t a n d b a c k s e c t i o n s o f s o r b en t t u be s w e r e e x t r a c t ed a nd a n al y z e d s ep a r a t el y;

o n l y r e s u l t s f r o m a n a l y s i s o f fr o n t s e c t i o ns a r e r e p o r t e d ; e x t r a c t s fr o m b a c k s e c t i o n s w e r e a l l < L OD

d L i m i t o f D e t e c t i o n ( L O D ) = 0

. 0 3 7 5 μ g c h l o r p y r i f os

e V a l u es i n p a r e n t h es e s a r e L O D s e x p r e ss e d i n p p b b a s e d o n m a s s L O D ( 0

. 0 3 7 5 μ g C F ) a n d t h e v o l u m e o f c h a m b e r a i r s a m p l ed

f S a m p l e s t a k e n a t f o u r d i f f e r e n t e x p o s u r e p o r t s o n t h e n o se

- o n l y e x p os u r e c h a m b er C h l o r p y r i f os : V apo r I nha l a ti on E x p osu r e St u dy

St ud y 1 31 0 40| 18 T i m e A fte r E x p o s u r e ( h o u r s)BloodConcentration(nmoles/gblood)

0

. 0 001 0

. 001 0

. 01 0 .1 1 10

0

. 254 m g CP F /m 3

CP F LLQ 0

. 2 5 4 m g CP F

/m 3

T CP L LQ

0 2 4 6 12

T CP

C PF



### • N o o x on d e t ec t e d i n b l ood

• LLQ

= 0.00015 n m ole/g blood

• M easu r e m ent of C P F and T C P in blood confi rm s abso r ption and

syste m ic e x posu r e to C P F vapo rs 

# B l ood L eve l s: C PF

, O x on

, TCP| 19 P l as ma

T i m e a ft er ex po s u re 0 h our 2 h o ur 4 hour 6 h our 1 2 hour%ControlChEActivity(NormalizedtoMeanControlValues)

0 20 40 60 80 100 120 140 160

0 p p b ( c o n tr o l)

1 7

. 7 p p b CPF B r a in

T i m e a f t e r e x p o s u re 0 hour 2 hour 4 h our 6 h o ur 1 2 hour%ControlChEActivity(NormalizedtoMeanControlValues)

0 20 40 60 80 100 120 140 160

0 p p b ( c o n tr o l)

17

. 7 pp b C PF R BC

T i m e a f t e r e x p o s u re 0 hour 2 hour 4 h our 6 h o ur 1 2 hour%ControlChEActivity(NormalizedtoMeanControlValues)

0 20 40 60 80 100 120 140 160

0 p p b ( c o n tr o l)

17

. 7 pp b C PF L u ng

T i m e a ft er ex po s u re 0 h our 2 h o ur 4 hour 6 h our 1 2 hour%ControlChEActivity(NormalizedtoMeanControlValues)

0 20 40 60 80 100 120 140 160

0 p pb ( c on tr o l)

1 7

. 7p p b CPF 

# S at u rate d C PF V a po r S t u d y : % Con tr o l Ch E| 20 

# S at u rate d C PF V a po r S t u d y : Ch E A ct i v i t y ( U / L)

P l as ma

T i m e a ft e r ex p o s u re 0 h o ur 2 ho ur 4 ho ur 6 ho ur 12 hourCholinesteraseActivity(U/L)

0 1 0 00 2 0 00 3 0 00 4 0 00 5 0 00 6 0 00

0 p p b ( co n tr o l)

17

. 7 p pb CPF R BC

T i m e a ft e r ex p o s u re 0 h o ur 2 ho ur 4 ho ur 6 ho ur 12 hourCholinesteraseActivity(U/L)

0 1 0 00 2 0 00 3 0 00 4 0 00 5 0 00 6 0 00

0 p p b ( c on tr o l)

1 7

. 7 p p b CPF

B r a in

T i m e a f t e r e x po s u re 0 h our 2 hour 4 h o ur 6 hour 1 2 hourCholinesteraseActivity(U/L)

0 1 0 000 2 0 000 3 0 000 4 0 000 5 0 000 6 0 000 7 0 000

0 p p b ( c o n t r o l)

1 7

. 7 p p b CPF

a

a S i g n if i c an t l y d i ff e r en t t h an 0 pp b ( c o n t r o l ) a t t h e sa m e po s t

- e x po s u r e t i me L u ng

T i m e a ft e r ex p o s u re 0 h o ur 2 ho ur 4 ho ur 6 ho ur 12 hourCholinesteraseActivity(U/L)

0 1 0 00 2 0 00 3 0 00 4 0 00 5 0 00 6 0 00

0 p p b ( c on tr o l)

1 7

. 7 p p b CPF| 21 

# Su mm ar y : S at u rate d Ch l o r p y rif o s V a po r S t u dy

• Fe m a l e S p r ague D a wl e y r a t s w e r e e x po s ed 6 h t o 0 o r

17

. 7 ppb CP F v apo r ( 0 o r 0

. 254 m g /m 3 

## )

> O x on p r esen t i n e x posu r e a t m osphe r e @ 0

. 24 ppb ( 0

. 003 m g o x on /m 3 )

> A e r oso l p r esen t ( 0

. 0036 m g /m 3 ) w i t h MM A D 0

. 72 μ m ( G S D

= 2

. 1)



## • N o o x on de t e c t ed i n b l ood a t an y t i m e po i nt

• M a x i m u m b l ood CP F l e v e l s a t end o f e x po s u re

> < LL Q b y 6 hou r s pos t e x posu re



## • TCP b l ood l e v e l s s i m il a r a t 0 and 2 hou r s po s t e x po s u re

> > LL Q a t a ll pos t e x posu r e t i m e po i n ts



## • N o i nh i b i t i on o f C h E a c t i v i t y i n Lung

, RBC

, Pl a s m a o r

B r a i n w a s ob s e r v ed

– e v en i n t he p r e s en c e o f m ea s u r ed

sys t e m i c e x po s u r e t o CPF| 22 

## Q ues ti ons

### M i chae l B ar t e l s

, S ue Mar t y

, D a l and Juberg

A ugus t 27

, 2013 

# C h l o r p y r i f o s O x on : B i o l og i ca l B as i s f o r

R ev i se d To x i c i t y A d j u s tm e n t F ac t or| 24 

## O u tli ne

- B i o l og i ca l B as i s f o r R ev i sed Tox i c it y

A d j us t m en t Fac t or

• B a ck g r ound i n f o rm a t i on

• D a t a fr o m C o m pa r a t i v e C ho li ne s t e r a s e A ss a y s t ud y da t a

,

s ho wi ng:

> p r e f e r en t ial inhibi t ion o f RBC o v e r b r ain

> c o m ple t e f i r s t- pa ss m e t aboli s m o f C hlo r p y r i f o s Ox on



## • T i ss ue S en s i t i v i t y C o m pa r i s on- ne w i n v it r o IC

50 

## s t ud y da ta

• E ff e c t s i n po rt a l

- o f- en tr y GI t i ss ue o cc u r on l y a t h i gh do s e s ( ≥ 5 m g / k g ) and a r e no t c li n i c a l l y r e l e v ant

• P r opo s a l f o r b r a i n a s r e l e v an t endpo i n t f o r T A F f o r sys t e m i c

e x po s u r e s t o C h l o r p y r i f os| 25 

## B ackg r ound I n f o rm a ti on

• EPA i s in t e r e s t ed in i m p r o v ing T o x i c i t y A dju s t m en t F a c t o rs needed t o de r i v e

P O D v alue s f r o m o r al O x on e x po s u r es

• Chlo r p y r i f o s i s unique in t ha t m ul t iple s t udie s a r e a v ailable w hi c h p r o v ide da t a

on Ch E inhibi t ion ( Ch E I ) in s y s t e m i c t i ss ues

• I n t he 2010 D AS CC A s t ud y

, O x on w a s s ho w n t o eli c i t Ch EI in R B C

, bu t no t

b r ain t i ss ue a t do s e s ≤ 10 m g / kg

> Ox on

- ba s ed Ch E I i n R B C t iss ue w as m o r e p r onoun c ed f r o m Ox on than f r o m

Ch l o r p y r i fo s ( 76 % Ch E I at 1 m g/ k g Ox on v s 19 % Ch E I at 2 m g/ k g Ch l o r p y r i fo s )

> In c ont r a s t, no Ox on

- ba s ed Ch E I i n b r a i n t iss ue vs

. m ea s u r eab l e effe c t s f r o m

Ch l o r p y r i fo s ( 0 % Ch E I at 10 m g/ k g Ox on v s 48 % Ch E I at 10 m g/ k g Ch l o r p y r i fo s )

• T o in f o rm t he r ele v an c e o f O x on

- ba s ed Ch E I, i t i s i m po r t an t t o:

> a ss e ss the i m pa c t of 1 st pa ss m etabo lis m

> ut iliz e data f r o m non

- o r a l r oute i n viv o and a ls o i

n vi t r o Ch E s tud i e s that s ho w the

r e l at iv e s en si t ivi t y of Ox on

- ba s ed R B C and b r a i n Ch EI

> S u mm a r iz ed i n 2012 Do w A g r o S ci en c e s W h i te P ape r r epo r t ( M RID: 48913401)| 26

T es t m a t e r ial c omp a r

is on of C

h E i nh i b i t i on i n RBC/ p las m a vs. b r

ai n t iss u e of a du l t

f e m ale S D r

a t s ( M a r t y e t al. 2010

; 40 mg /k g O x on b r ai n d a t a f r om C o s t a 1990)

C P F O r a l

- G a v a ge

Do s e ( m g / k g)CholinesteraseActivity(%Control)

0

. 01 0.1 1 10 1 00 0 50 1 00 R BC

B r a in P l a s ma

O x o n O r a l

- G a v a ge

D o se ( m g / k g)CholinesteraseActivity(%Control)

0

. 01 0 .1 1 10 100 0 50 1 00 R BC

B r a in

P l a s ma S ub s tant

i a lly d i ffe r ent i nh i b i t i on

p r of il e s a ls o s een fo r C P F &

O x on:

• C P F sys te m ic a lly b i oa v a il ab l e,

wh il e no O

x on s een i

n b l ood

• O x on is si gn i f ic ant ly l e ss to xic

to sys te m ic

t iss ue s than C PF

• T h is is due to e

x t r e m e ly r ap i d,

and c o m p l ete p r e sys te m ic

h y d r o lysis of O

x on b y Ch E and

othe r e s te r

a s es| 27 G I

T r a ct 

### O x on

≤ 1 0 m g / kg S i t e s o f Pr e sy s t e m i c H y d r ol y s i s

o f C hlo r p y r i f o s O x on:

1) a q ueo u s p h as e o f G I co n t en ts

2) e n z y m e s i n G I

3) ca r b ox y l e s t e r a s e s i n G u t t i s s ue

4) P O N

- 1 e s t e r as e i n G u t ti s sue

5) E n z y m es / p r o t e i n s i n p o r t a l b l o od

6) L i v e r C Y P s a n d es t e r a s es

Ox on

- > T CP

S y s t e m i c c i r c ula t ion

- N o d e t ec t a b l e O x o n

( L O Q = 0

. 3 n M) Li v er T CP T CP

P o r t a l v ein 1

2

3

4 5 6

RBC

- > RBC

- i nh i b i t ed RBC

- i n h i b i t ed S i t es of Pr esys t e m ic Hy d r o lysis of O

x on



# ü ü T o f a c ili t a t e p r edi c t ion s o f

PK and P D

f r o m O x on , t he

e x i s t ing PBPK m odel f

o r C P F

ha s been m odi

f ied:

• in c o r po r a t e s O x on -s pe c i f i c

up t a k e r a t es

• u t il i z e s e x i s t ing r a t e s o f

p r e sys t e m i c m e t aboli s m o f

O x on

P r e sys te m ic

R B C/p l a s m a i nh i b i t i on a ls o r

e s u l t s i n O x on h y d r o lysis

- O x on b l ood l e v

e ls be l ow Ch E i

nh i b i to r y c on c ent

r at i ons| 28

• I n V i v o I nh i b i t i o n o f Ch E

i n Va ri ou s T

i ss u es o f R ats f o ll o w i ng I V

, I P

, D e r ma l o r O r

a l

a d m i n i st r a t ion o f C P F -Ox on (0

. 4

, 12

, 15 a nd 40 m g

/ k g

, r es p ect i ve l y; sam p l es c o ll ecte d 4 h r

po st- do s i

ng )

. Do se l

eve l s we r e se l ecte d t o i ndu ce r e l at i ve l y s i m il a r d e g r ees o f Ch E i nh i b i t i on

i n p l asma

, RBC

s

, b r a i n a nd d i a ph r a g m

, o r a l do s i ng r e qu ir e d t h e h i gh est do se l

eve l. ( d ata

f r o m Co sta et a l. 1990

).

D o se R ou teCholinesteraseActivity(%Control)

IV D e r m al IP O r al 0 20 40 60 80 100 P l a s ma

R BC

B r a in

D i aph r agm E qua l i nh i b i t i on i n the ab s en c e

of 1 st pa ss m etabo lism

M o r e i nh i b i t i on of R B C due to

p r e sys te m ic h

y d r o lysis of O

x on i n b l ood

B r a i n effe c t s m o r e c on s e r v

ed a c r o ss

r oute s

, due to sys te m ic

e x po s u re| 29

I n V iv o I nh i b i t i on of C h E i n V a r i ou s T iss u es of Ra t

s fo ll o w i ng I P a dm i n is t r a t i o n of

C P F-o x on ( 30 mg /k g)

. N ot e

- d a t a f r om Ca rr e t al. ( 2002 ).

S a m p li n g T i m e ( h r p o s t- do s i ng) 2 hr 24 hr 0 20 40 60 80 100 M e d u l l a

- Po ns

C o r p us S t r i a t um

C e r e b r a l C o r t ex

H i pp o c a m pus

S k e l e t a l M u s c le

Lu ng

H e a rt

Br ain r ep r e s en t a t i v e o f nu m e r

ou s sys t e m i c t i ss ue s| 30

I n V i t r o I nh i b i t i on of C h E i n V a r i ou s T iss u es of Ra t

s ( C h a mb e r s 2013 )

.

V al u es i n n M C h l o r p y r i fo s O x on c on ce nt

r a t i on

Br

ain r ep r e s en t a t i v e o f

nu m e r ou s sys t e m i c t i ss ues

GI t i ss ue s ha v

e

c o m pa r able s en s i t

i v i t y t o

sys t e m i c t i ss ues

R B C I C50 s i

m ila r t o all

t i ss ues

P la s m a I C50 highe s t

- due

t o p r e s en c e o f nu m e r

ou s

e s t e r a s e s ( in c luding

albu m in) A CHE A vg S t D ev

B r a in 3

. 77 0

. 10

R BC 4

. 19 0

. 69

R B C ( g h o s t s) 5

. 08 0

. 32

D u od e nu m ( f l u s h e d ) 3

. 72 0

. 21

D u od e nu m ( no t f l u s h e d ) 4

. 17 0

. 48

E s oph a gu s (

f l u s h e d ) 3

. 13 0

. 31

E s oph a gu s ( no t f l u s h e d ) 3

. 28 0

. 59

S t o m a ch 4

. 08 0

. 09

L u ng ( p e r

f u s e d) 7

. 21 1

. 32

L u ng ( n o t p e r

f u s e d) 8

. 57 0

. 85

H e a r t ( p e r f u s e d) 3

. 06 0

. 05

H e a r t ( n o t

- pe r

f u s ed) 3

. 91 0

. 05

D i a p h r a gm 6

. 64 0

. 28

P l a s m a 5 5

. 36 0

. 51| 31

I n vi t r o I nh i b i t i on of C h E i n V a r i ou s T iss u es of Ra t

s o r Rec omb i

n a nt H um a n E

n z y m e

( Da t a f r om M o r t e n se n 1998, C

h a mb e r s 2013, M

o se r 2011)BrainDuodenumEsophagusStomachLungHeartDiaphragmRBCHumanrAChEBrain-ImmunopptPlasma-ImmunopptLiver-ImmunoppptPlasma

S t ud y R e f e r e n ceIC50(nM)

M o rt ensen 1998 Ch a m be r s 2013 M ose r 2011 0 1 2 3 4 5 6 7 8 9 10 10 20 30 40 50 60

B r a i n a ls o r ep r e s entat iv e of nu m e r

ou s sys te m ic

t iss ue s i n vi t r o,

i n cl ud i ng G I t r a c t t iss ues

IC50 fo r hu m an A Ch E c o m pa r ab l e to pu r

i f i ed r at ChE N O E C

~ 0.3 nM| 32 

## P o r t a l- o f- E n t r y C h E e ff ec t s f o ll o w i n g o r a l i n t ake o f

C h l op y r if o s O xon

• P o ss ible P o r t al

- o f

- en t r y e ff e c t s t o G I ha v e been r epo r t ed a t 5 mg / k g f o r O x on

and 20 mg / k g f o r C hlo r p y r i f os

> S uppo r t s a n O x on To x i c i t y A dju s t me n t F ac t o r f o r po r t a l

- o f- e n t r y e ff ec t s o f 4

• No G I effe c t s at 1 m g/ k g Ox on ( o r 0.5 m g/ k g/da y w i th r epeated e x po s u r e)

> T hi s e ff e c t le v el o f 5 m g / k g f o r O x on i s 1500

- f old higher t han t he m a x i m u m

, m odelp r edi c t ed o x on c on c en t r a t ion s in d r in k ing w a t e r o f 112 ug /L

• N O AE L of 1 m g/ k g Ox on is 300

- fo l d h i gher than h i ghe s t p r ed ic ted d r i n ki ng w ate r

c on c ent r at i on

• Repeated do s e N O AE L of 0.5 m g/ k g is 150

- fo l d h i ghe r

> T he s e e ff e c t s a r e no t e x pe c t ed t o be c lini c all y r ele v an t:

• Ch E I i n G I t iss ue doe s not affe c t ne r v e s e x i t i ng the gut ( i .e., no effe c t s on othe r o r gan

s y s te m s)

• G I effe c t s b y othe r Ch E I agent s ( e.g., pha r m a c eut ic a ls ) a r e t r an si ent, not c on si de r ed to

ha v e l ong

- te r m cli n ic a l c on s equen c es

• O P to x ici t y on G I fun c t i on appea r s m i n i m a l

, and gene r a ll y on l y s een afte r i nge s t i on of

l a r ge bo l u s do s e s of Ox on ( ≥ 5 m g/ k g )| 33 

## S y s t e m i c C h E e ff ec t s f o ll o w i ng o r a l i n t ake o f

C h l op y r if o s O xon

• At e xt r emel y high o r al do s e s o f O x on ( 10 mg / k g ) t he r e i s no mea s u r ed

s y s t emi c bioa v ailabili ty o f t hi s c ompound ( LOQ

= 0

. 3 nM )

, due t o high

f i rs t

- me t a b oli s m in t he G I and li v e r

> no Ch E I i s s een in b r ain t i ss ue

, a t do s e s up t o 10 m g / kg

> 0

. 3 n M

= N O E C f o r Ch E I in M o r t en s on in v i t r o s t udy



### • N ume r ou s in v

i v o and in v

i t r o s t udie s ha v e s ho w n t ha t O x on

- indu c ed

C h E I in b r ain t i ss ue i s r ep r e s en t a t i v e and c on s e r v a t i v e o f C h E e ff e c t s

in man y o t he r t i ss ue s ( in c luding ne w in v i t r o da t a o f C hambe rs e t al .)

> I n c on t r a s t, Chlo r p y r i f o s c au s e s

~ 50% b r ain Ch E I a t 10 m g / kg

> Th ese d a t a s uppo r t a n O x on To x i c i t y A dju s t me n t F ac t o r f o r s y s t em i c

e ff ec t s o f 0 .5| 34 C omp a r is on of C

h E i nh i b i t i on i n RBC a nd b r

ai n t iss u e of a du l t f

e m ale S D r

a t s

a dm i n is t e r e d C P F o r C P F-o

x on via o r

al g ava g e ( M a r t y e t al. 2010)



### C PF C P F

- O x on

K e y E v e n t 1 K e y E v

e n t 2 K e y E v

e n t 3

D o se (m g / kg) C h o l i n e r i c

e f f e c t s i n G I

t i ss ue I nh i b i t i o n o f R BC

C h o l i n es t e r a se

A c t i v i ty I n h i b i t i o n o f B r a i n

C h o l i n e s t e r as e

A c t i v i ty

0

. 05

- - -

0 .1

- - -

0 .5

- - -

2

- +

-

5

- P i l ot

- ++

-

10

- +++ ++

1 0

- Pi l ot

- +++ ++

2 0

- Pi l ot + * + + ++ + ++

* G I e ff e c t s da t a i n a d u l t M a l e Lo n g

- E v a n r a t s

, f r o m M o s e r e t a l

. ( 19 9 5)

S c a l e f o r Ch E i nh i b i t i o n ( % o f c o n t r o l ) : ≥ 9 0 %

= "

- "

, 7 5

- 9 0 %

= " + "

, 4 0

- 7 5 %

= " ++ "

,

5

- 4 0 %

= " + ++ "

, < 5 %

= " +++ +" K e y E v e n t 1 K e y E v

e n t 2 K e y E v

e n t 3

D o se (m g / kg) C h o l i n e r i c

e f f e c t s i n G I

t i ss ue I nh i b i t i o n o f R BC

C h o l i n es t e r a se

A c t i v i ty I n h i b i t i o n o f B r a i n

C h o l i n e s t e r as e

A c t i v i ty

0

. 01

- - -

0

. 05

- - -

0 .1

- - -

0 .5

- ++

-

1

- +++

-

1

- P i l ot

- +++

-

5

- P i l ot + ^ + + ++

-

1 0

- Pi l ot + ^ + + ++

-

^ E f f e c t s e en ( m u c o i d f e c e s )

, i n o n l y 1 o f 3 s t u d y a n i m a l s a t t h i s d o s e l e v el

S c a l e f o r Ch E i nh i b i t i o n ( % o f c o n t r o l ) : ≥ 9 0 %

= "

- "

, 7 5

- 9 0 %

= " + "

, 4 0

- 7 5 %

= " ++ "

,

5

- 4 0 %

= " + ++ "

, < 5 %

= " +++ +"

M O A fo r sys te m ic t

iss ue effe c t

s dependent on sys te m ic b i oa v a il ab i li t y of C P F o r O

x on

E ffe c t s s een i n po r ta l

- of

- ent r y G I t iss ue o cc u r

on ly at h i gh do s es

R B C effe c t

s not r ep r e s entat iv e of e i the r K

e y E v ent 

## P o r t a l- o f- E n t r y vs

. S y s t e m i c C h E e ff ec t s f o ll o w i ng o r a l

i n t ake o f C h l o r p y r if os o r C h l op y r if o s O xon| 35 

## S u mm a ry

• C hlo r p y r i f o s and O x on ha v e unique pha r ma c o k ine t i c p r o f iles

> Chlo r p y r i f o s i s p r i m a r il y m e t aboli z ed in t he li v er

• but is s y s te m ic a ll y a v a il ab l e abo v e 0.1 m g/ kg

> O x on i s m o r e labile

, being r apidl y h y d r o l y z ed b y nu m e r ou s t i ss ue s

, in c luding I n t e s t inal lu m en

, po r t al v ein R B C & pla sm a e s t e r a s e s and li v er

• r e s u l t i ng i n no s y s te m ic a ll y a v a il ab l e Ox on at do s e l e v e ls up to 1 m g/ kg



### • A s a r e s ul t, R B C i s p r edi c t o r o f p r e s y s t emic e x po s u r e t o O x on

, v s

.

s y s t emic e x po s u r e t o C hlo r p y r i f os

• I n c on t r a s t, b r ain s en s i t i v i ty t o O x on e ff e c t s ha s been s ho w n t o be

c ompa r able t o nume r ou s o t he r s y s t emi c t i ss ues

> T he r e f o r e

, D AS p r opo s e s t ha t t he m o s t app r op r ia t e endpoin t f o r p r edi c t ion

o f ad v e rs e s y s t e m i c e ff e c t s f r o m o r al e x po s u r e t o O x on

, r ela t i v e t o

Chlo r p y r i f o s

, i s inhibi t ion o f b r ain Ch E a c t i v i ty| 36 

## R e f e r ences

• C a rr

, R

. L

., J

. R

. Ri c ha r d s on

, J .A. G ua ri sc o

, A. Ka c h r oo

, J .E. C ha m be r s

, T .A. C ou c h

, G. C

. D u r unna

, and E. C

. M ee k

.

( 2002 )

. E ff e c t s o f P C B e x po s u r e on t he t o x i c i m pa c t o f o r g anoph o s p ho r u s i n s e c t i c i de s

. T o x i c o l S c i

. 67 : 311

- 3 21.

• C ha m b e r s

, J .E. ( 2013 )

. I n v i t r o Sen s i t i v i t y o f C ho li ne s t e r a s e t o I nh i b i t i on b y C h l o r p y ri f o s

- o x on i n Se v e r a l T i ss ue s o f

t he R a t. C o ll e g e o f Vete ri na r y M ed i c i ne

, Mi ss i ss i pp i State U n i v e r s i t y.

• C o s t a

, L .G., B.E. M c D ona l d

, S. D

. M u r ph y , G.S. O m enn

, R

. J

. Ri c h t e r

, A.G. M o t u l sk y

, and C .E. F u rl on g ( 1990 )

. Se r u m

pa r ao x on a s e and i t s i n f l uen c e on pa r ao x o n and c h l o r p y ri f o s

- o x on t o x i c i t y i n r a t s

. T o x i c o l o g y and App li ed

Pha r m a c o l og y

, 103 : 66

- 7 6

.

• D o w A g r oS c i en c e s ( 2012 )

. W h i t e Pape r Di sc u ss i on o f T o x i c i t y Ad j u s t m en t F a c t o r s u s ed f o r t he Ri sk A ss e ss m en t o f

C h l o r p y ri f o s O x on i n Dri n k i n g W a t e r

. A S c i en c e I ss ue s Pape r f o r t he U S En v ir on m en t a l P r o t e c t i on A g en c y

,

s ub m i tt e d Au g u s t 17

, 2012 (MR I D : 489134 01 ).

• M a r t y

, M .S., and A.K. And r u s

. 2010

. C o m pa ri s on o f C ho li ne s t e r a s e ( A C hE ) I nh i b i t i on i n Y oun g Adu l t and P r e w ean li ng

CD R a t s a f t e r A c u t e and R epea t ed C h l o r p y ri f o s o r C h l o r p y ri f o s o r C h l o r p y ri f o s

- o x on E x po s u r e s

. An unpub li s h e d

r epo r t o f t he D o w C he m i c a l C o m pan y (D o w St ud y I D 09110 7 ) [ MR I D 48139 301 ]. T he D o w C he m i c a l C o m pan y

.

• M o r t en s en

, S. R

., M

. J

. H oope r

, and S. Pad ill a ( 1998 )

. R a t b r a i n a c e t y l c ho li ne s t e r a s e a c t i v i t y : de v e l op m en t a l p r o f il e

and m a t u r a t i on a l s en s i t i v i t y t o c a r ba m a t e and o r g anoph o s p ho r u s i nh i b i t o r s

. T o x i c o l o g y

. 125 : 13

- 1 9.

• M o s e r

, V. C

., and S. Pad ill a ( 2011 )

. E s t e r a s e m e t abo li s m o f c ho li ne s t e r a s e i nh i b i t o r s u s i n g r a t li v e r i n v i t r o

.

T o x i c o l o g y

. 281 : 56

- 6 2.| 37 

## Q ues ti ons38 

# BACKU P SL I D ES| 39 

## O u tli ne

– G aps i n C o l u m b i a E p i de m i o l og y S t ud y

• C o rr obo r a t i on / R ep l i c a t i o n

• E x po s u r e M ea s u r e m en ts

• R e l e v an t P ub li c a t i ons

• S e l e c t ed DAS and E x t e r na l P r e s en t a t i on s

- E p i de m i o l ogy| 40 

## C ha ll enges w it h E va l ua ti on o f C o l u m b i a D a t a / S t ud i es



## • Co rr obo r a ti o n / Re p li ca ti on

> N o r epli c a t ion o f C olu m bia c oho rt f indings

• Inconsistent findings a m ong 3 coho r ts ( Colu m bia, M t. S inai,

B e r keley/Cha m a c os)

• Independent r evie w s/ p ub l i c ati o ns have confi rm ed this lack of

confi rm ed association bet w een e x posu r e and effects ( E aton et al,

M ink et al, Li et al, P r ueitt, et al)



### > M RI s t ud y (C olu m bia onl y ) e v alua t ed b y 3 independen t

e x pe rt s w hi c h r e v eal si gni f ican t c on f ounding / de si gn

c hallenges

> U na v ailabili t y o f r a w da t a fr o m C olu m bia and o t he r c oho rts

> SAP ad v ise m en t t o no t u s e C olu m bia f o r quan t i t a t i v e r isk

assess m ent| 41 

## C ha ll enges w it h E va l ua ti on o f C o l u m b i a D a t a / S t ud i es



# • E x po s u re M eas u re m e n ts

> CDC c anno t c on f i rm ana l y t i c a l de t e c t i on m e t hod f o r

C h l o r p y r i f o s i n b l ood w h i c h unde rm i ne s t he c on f i den c e

i n t he r epo rt ed b l ood m ea s u r e m en t s o f m o s t s ub j e c ts

> D o s e -r e c on s tr u c t i on h i nde r ed b y s po t s a m p li ng and no

i n f o rm a t i on on app li c a t i on

> D o w e x po s u r e s t ud y de m on s tr a t e s c ha ll en g e wi t h s po t

s a m p li ng f o r po i n t e s t i m a t e s o f e x po s u r e

, u r i na r y T CPY

i s app r op r i a t e b i o l og i c a l m a r k e r and C h E I doe s no t

o cc u r be l o w do s e s p r ed i c t ed b y PBPK m ode li ng| 42 

# Pub li cat i ons

• E aton, D. L., Da r off, R. B

., A ut r up, H., B r i dge s

, J

., B uff l e r

, P

., Co s ta, L. G

., Co y l e, J

., M ck hann, G

., M ob l e y

, W

. C., Nade l , L., Neube r t, D., S c hu l te

- He r m ann, R. & S pen c e r

, P

. S . 2008. Re vi e w of the to x ic o l og y of c h l o r p y r i fo s w i th an e m pha sis on hu m an

e x po s u r e and neu r ode v e l op m ent. C r i t Re v T o xic o l, 38 S upp l 2: 1

- 125.

• L i

, A

. A

., Le vi ne, T

. E

., B u r n s

, C. J

. & K ent A nge r

, W

. 2012a. Integ r at i on of

ep i de m i o l og y and an i m a l neu r oto x ici t y data fo r r isk a ss e ss m ent.

Neu r oto xic o l ogy ,33:823

- 832

• L i

, A

. A

., Lo w e, K

. A

., M ci nto s h, L. J

. & M i n k

, P

. J . 2012b. E v a l uat i on of ep i de m i o l og y

and an i m a l data fo r r isk a ss e ss m ent: c h l o r p y r i fo s de v e l op m enta l neu r obeha vi o r a l

out c o m e s

. J T

o xic o l E n vi r on Hea l th B

C r i t Re v, 15: 109

- 184.

• M i n k

, P

. J

., K i mm e l , C. A

. & L i

, A

. A . 2012. P otent i a l effe c t s of c h l o r p y r i fo s on feta l

g r o w th out c o m e s : i m p lic at i on s fo r r isk a ss e ss m ent. J T o xic o l E n vi r on Hea l th B

C r i t Re v,

15: 281

- 316.

• P r ue i tt, R. L., G ood m an, J

. E

., B a il e y , L. A

. & Rho m be r g, L. R. 2011. H y pothe sis

- ba s ed

w e i ght

- of

- e vi den c e e v a l uat i on of the neu r ode v e l op m enta l effe c t s of c h l o r p y r i fo s

. C r it

Re v T o xic o l, 41: 822

- 903.| 43 

## S e l ec t ed DAS and E x t e r na l P r esen t a ti ons - E p i de m i o l ogy

• E va l ua t

i on o f B i oana l

y t i ca l M e t hods used

i n E p i de m i o l og i

ca l S t ud i es o f

C h l o r py r i f os E xposu r e

– M i chae l J

. B a r

t e l s

- S ep t e m be r 16

, 2008

– EPA SAP

• C h l o r py r i f os and E p i de m i o l ogy

– C a r

o l J

. B u r ns

– S ep t

e m be r 16

, 2008

– EPA SAP

• C h l o r py r i f os E xposu r e and N eu r

obehav i o r a l O u t co m es i n I n f an t s and P r e

- S choo l

C h il d r en

– E p i de m o l og i

c I n t e r p r e t a t i on and C o mm en t

s R ega r d i ng R au h e t a l 2006

– P a m e l a M i nk

– S ep t

e m be r 16

, 2008

– EPA SAP

• A W e i gh t

- o f

- E v i dence A ssess m en t o f

R ecen t E

p i de m i o l ogy S t ud

i es

– D oug l

as

W eed

– S ep t

e m be r 16

, 2008

– EPA SAP

• E p i de m i o l ogy R ega r

d i ng C h il d r en ’ s H ea l t h

– C a r o l J

. B u r ns

– A p r il 11

, 2012

– EPA

SAP

• H ypo t hes i s

- B ased W

e i gh t

- o f

- E v i dence E va l ua t

i on o f C h l o r py r i f o s and

N eu r odeve l op m en t

a l E ff ec t s

– Ju li e E

. G ood m an

– A p r

il 11

, 2012

– EPA SAP

• H u m an S t ud

i es

, A n i m a l S t ud i es

, M o A

, and W

e i gh t o f E v i dence

– Lo r

e n z R

. R ho m be r

g

– A p r il 11

, 2012

– EPA SAP

• E p i de m i o l ogy S u mm a r

y

– C a r o l J

. B u r ns

– A ugus t 21

, 2012

- EPA

## CH E M I CAL SPE C I F I C AD J U S TM E NT FACT O R S

( C S AF S) F O R O RAL EXPOS UR ES T O

CHL O R PY R I F OS AND CHL O R PY R I F OS OXON

P au l P r i ce

, M i chae l B ar t e l s

, and Torka P oet

A ugus t 27

, 2013| 45 

## H i s t o r y o f DAS e ff o r t s on t h i s i ssue

• 2007

- 2010 A CC L R I p r oje c t (H inde r li t e r e t al

., 2011 ;P r i c e e t al

., 2011)

• 2011 S c ien c e A d v i s o r y P anel p r e s en t a t ion on me t hodology

> Re c o mm enda t ion s on t he de v elop m en t o f v a r ia t ion m odel



### • S mi t h e t al

. ( 2011 ) publi c a t ion on v a r ia t ion in en z y me a c t i v i ty

• 2008

- 2011 N ume r ou s p r e s en t a t ion s a t S OT

, S R A, and ISES

• 2012

- 2013 D e v elopmen t o f:

> M o r e r igo r ou s app r oa c h f o r c on s t r u c t ion o f v a r ia t ion m odel

> 2D m odeling o f un c e r t ain t y

> Re v i s ed s t r a t eg y f o r de v eloping C SA F s ba s ed on SAP c o mm en ts

> De v elop m en t o f C SA F s f o r o x on| 46 

## C he m i ca l S pec ifi c A d j us t m en t Fac t o r s

• B a s ed on model o f human v a r ia t ion in s en s i t i v i ty t o C P F and o x on

• Fa c t o rs a r e s pe c i f i c t o t he s e tt ing o f a c u t e o r al s t anda r ds

> T he app r oa c h i s r ele v an t f o r o t he r r ou t e s o f e x po s u r e bu t s epa r a t e

anal y s e s a r e r equi r ed f o r ea c h r ou te

> A pp r oa c h c an be applied t o c h r oni c e ff e c t s a s w ell



### • R B C A C h E i s u s ed a s t he cr i t i c al e ff e c t f o r de f ining t he C SA Fs

> W hile w e belie v e t ha t R B C i s no t a biologi c al l y r ele v an t endpoin t f o r o x on

,

w e a r e u s ing R B C A Ch E I t o de r i v e t he C SA F s in t hi s e x a m ple.

> T he app r oa c h c an be applied t o b r ain A ChE



### • P r opo s ed app r oa c h add r e ss e s t he r e c ommenda t ion s f r om t he

Feb r ua r y 2011 S c ien c e A d v i s o r y P anel| 47 

## C ons t r uc ti on o f t he V a r i a ti on M odel

• B uild on t he Li f e S t age m odel o f o r al e x po s u r e s ( bi r t h t o adul t ) and add r e ss

bo t h C P F and o x on

• Pr o c e ss and r e s ul t s:

1

. P e r f o rm s en s i t i v i t y anal y s i s t o iden t i f y cr i t i c al pa r a m e t e rs ( 104 pa r a m e t e rs

→ 19 pa r a m e t e rs)

2

. I den t i f y pa r a m e t e rs t ha t v a r y a cr o ss indi v idual s ( 19 pa r a m e t e rs → 16

pa r a m e t e rs)

3

. De v elop di s t r ibu t ion s f o r t he 16 pa r a m e t e rs and build M on t e Ca r lo m odel

4

. A dd r e ss m ode r a t e t o s t r ong c o rr ela t ion s in inpu t s w h e n t he y w o u ld

in cr ea s e v a r ia t ion in r e s pon s e

– cr ea t e lin k ed pa r a m e t e rs ( 16 pa r a m e t e r

→ 15 pa r a m e t e rs)

5

. De t e rm ine m ini m u m s e t t ha t d r i v e s v a r ia t ion ( 15 pa r a m e t e rs → 3

pa r a m e t e rs) a t r ele v an t do s e s ( R B C A Ch E I > 10% f o r s en s i t i v e indi v idual s)| 48

1 10 100

0 0.2 0.4 0.6 0.8 1PercentofBackgroundActivity

F r ac t i on of th e popu la t i on Popu l a ti on v a r i a ti on i n RBC A C hE ac ti v it y a ft e r fi v e d a y s

o f o r a l do ses o f 0

. 3 a nd 0

. 1 m g / k g CP F f o r f u ll ( 15

p a r a m e t e r) a nd fi n a l ( 3 p a r a m e t e r) m od e l s

F u ll m ode l 0.3 m g/ kg

F u ll Mode l 0.1 m g/ kg

1 10 100

0 0.2 0.4 0.6 0.8 1

F r ac t i on of th e popu la t i on Popu l a ti on v a r i a ti on i n RBC A C hE ac ti v it y a ft e r

f i v e d a y s o f o r a l do ses o f 0

. 04 a nd 0

. 015 m g / k g

O x on f o r f u ll ( 15 p a r a m e t e r) a nd fi n a l ( 3 p a r a m e t e r)

m od e ls

F u ll m ode l 0.04 m g/ kg

F u ll m ode l 0.015 m g/ kg| 49

1 10 100

0 0.2 0.4 0.6 0.8 1PercentofBackgroundActivity

F r ac t i on of th e popu la t i on Popu l a ti on v a r i a ti on i n RBC A C hE ac ti v it y a ft e r fi v e d a y s

o f o r a l do ses o f 0

. 3 a nd 0

. 1 m g / k g CP F f o r f u ll ( 15

p a r a m e t e r) a nd fi n a l ( 3 p a r a m e t e r) m od e l s

F u ll m ode l 0.3 m g/ kg

F i na l Mode l 0.3 m g/ kg

F u ll Mode l 0.1 m g/ kg

F i na l Mode l 0.1 m g/ kg

1 10 100

0 0.2 0.4 0.6 0.8 1

F r ac t i on of th e popu la t i on Popu l a ti on v a r i a ti on i n RBC A C hE ac ti v it y a ft e r

f i v e d a y s o f o r a l do ses o f 0

. 04 a nd 0

. 015 m g / k g

O x on f o r f u ll ( 15 p a r a m e t e r) a nd fi n a l ( 3 p a r a m e t e r)

m od e ls

F u ll m ode l 0.04 m g/ kg

Redu c ed m ode l 0.04

m g/ kg

F u ll m ode l 0.015 m g/ kg

Redu c ed m ode l 0.015

m g/ kg| 50 

## S u mm a r y o f V a r i a ti on m ode l

• The v a r ia t ion model i s an age

- and gende r-s pe c i f i c model o f human

v a r ia t ion

• At do s e s 30 ug / k g v a r ia t ion r e s pon s e t o C P F c an be p r edi c t ed ba s ed

on v a r ia t ion in t h r ee pa r ame t e rs and v a r ia t ion in r e s pon s e in O x on t o

one pa r ame t er

> C PF

• P O N1 i n liv e r

/p l a s m a ( li n k ed)

• C Y P s c on v e r t i ng C P F to o x on

• C Y P s c on v e r t i ng C P F to T C Py

> O x on

• P O N1 i n liv e r

/p l a s m a ( li n k ed)



### • Global s en s i t i v i ty anal y s i s iden t i f ied t he s ame pa r ame t e r s f o r C PF| 51 

## M ode li ng fi nd i ngs on age

- r e l a t ed changes i n sens iti v it y

• Model p r edi c t s t ha t age -r ela t ed c hange s a r e s mall and do s e

dependent

> A t high do s e s ( > 200 ug / k g C P F and > 30 ug / k g o x on ) di ff e r en c e s in pla sm a

P O N1 m a k e c hild r en s ligh t l y m o r e s en s i t i v e ( 10

- 20% )

> A t lo w e r do s e s t he m odel s s ugge s t t ha t adul t s w ill be s ligh t l y m o r e

s en s i t i v e be c au s e o f di ff e r en c e s in ph y s iol og y t ha t lead t o di ff e r en t r e m o v al

r a t e s ( o x on pe rs i s t s s ligh t l y longe r in adul t s t han in f an t s)



### • Model p r edi c t s t ha t a t do s e s < 200 ug / k g o f C P F and > 30 ug / k g o f

o x on

, t he li v e r e ff e c t i v el y c lea rs o x on a s i t i s f o r med t hu s t he f e t u s i s

p r o t e c t ed f r om t he o x on

> T hi s e x plain s t he ob s e rv a t ion in r a t s t ha t t he f e t u s i s no t s en s i t i v e r ela t i v e

t o m a t e r nal t o x i c i ty| 52 

## U nce r t a i n t y

• The v a r ia t ion model i s e xt ended t o add r e ss un c e r t ain ty u s ing 2 -D

Mon t e C a r lo modeling

• The un c e r t ain ty anal y s i s f o c u s ed on t he t h r ee cr i t i c al model

pa r ame t e r s

.

• U n c e r t ain ty in t he v alue s o f t he s e o cc u rs a s a r e s ul t o f limi t a t ion s in

da t a on v a r ia t ion o f pa r ame t e rs

> M ean v alue and c oe ff i c ien t o f v a r ia t ion a r e un c e r t ain gi v en 30 s a m ples

> W e ha v e c ha r a c t e r i z ed t he un c e r t ain t y in en z y m e a c t i v i t ie s f r o m Sm i t h e t

al

. u s ing pa r a m e t r i c boo t s t r ap anal y s e s



### • O t he r s ou rc e s o f un c e r t ain ty ( modeling un c e r t ain ty, “s u r p r i s e ”

, e t c

. )

a r e add r e ss ed b y:

> Long hi s t o r y o f u s e o f t he m odel

, e x t en s i v e pa r a m e t e r i z a t ion

, and t he

e v alua t ion o f m odel u s ing m ul t iple da t a s e t s| 53 

## D esc r i p ti on o f M on t e C a r l o m ode li ng

• P opula t ion a ss e ss ed:

> S i x m on t h old indi v iduals

> I n f an t s a t bi r t h a r e p r edi c t ed t o be le ss s en s i t i v e t han s i x m on t h olds

> F inding s in in ea r lie r w o rk indi c a t e s t ha t adul t s a r e s i m ila r



### • St able e s t ima t e s w e r e ob t ained w i t h model r un s o f

> E a c h indi v idual’ s r e s pon s e i s s i m ula t ed o v e r f ou r da y s and f o r f ou r do s e s

> 1

, 000 indi v idual s in ea c h popula t ion

> 50 popula t ion s s i m ula t ed| 54



### 0 20 40 60 80 100

0

. 03 0

. 09 0

. 27 0

. 81 2

. 43PercentofBackgroundActivity



### Si ng l e Ora l D ose ( m g / kg) 

## M ax i m u m RBC AC h E A c ti v it y f o ll o w i ng a s i ng l e

o r a l dose| 55



### 0 20 40 60 80 100

0

. 03 0

. 09 0

. 27 0

. 81 2

. 43PercentofBackgroundActivity



### Si ng l e Ora l D ose ( m g / kg) 

## V a r i a ti on i n t he dose t ha t causes 10 %

i nh i b iti on o f RBC AC h E ac ti v it y

50 th

P e r c ent ile 5 th

P e r c ent ile 1 th

P e r c ent ile 10 % I nh i b i t i on| 56 0.00 20.00 40.00 60.00 80.00 100.00

0.03 0.30PercentofBackgroundActivity

S i ng le O r al D o se (mg /k g) 

## P l o tti ng an I nd i v i dua l s RBC AC h E D ose

R esponse t o D e t e rm i ne ED

10| 57 0.00 20.00 40.00 60.00 80.00 100.00

0.03 0.30PercentofBackgroundActivity

S i ng le O r al D o se (mg /k g) 

## V a l ues o f ED

10 

## f o r s i m u l a t ed i nd i v i dua ls| 58 0.00 20.00 40.00 60.00 80.00 100.00

0.03 0.09 0.27 0.81 2.43PercentofBackgroundActivity

S i ng le O r al D o se (mg /k g)



## V a r i a ti on i n ED

10 

## ac r oss a popu l a ti on

5 th

P e r c ent ile 1 st

P e r c ent ile 50 th

P e r c ent ile| 59 

## U nce r t a i n t y po r ti on o f M ode l c r ea t es equa ll y p r obab l e

desc r i p ti ons o f t he popu l a ti on va r i ab ility

0 20 40 60 80 100

0

. 03 0

. 09 0

. 27 0

. 81 2

. 43 0 20 40 60 80 100

0

. 03 0

. 09 0

. 27 0

. 81 2

. 43 0 20 40 60 80 100

0

. 03 0

. 09 0

. 27 0

. 81 2

. 43

0 20 40 60 80 100

0

. 03 0

. 09 0

. 27 0

. 81 2

. 43 0 20 40 60 80 100

0

. 03 0

. 09 0

. 27 0

. 81 2

. 43 0 20 40 60 80 100

0

. 03 0

. 09 0

. 27 0

. 81 2

. 43| 60 DO W A GRO S C I E NC ES R ES T R I C T ED 0.60 1.80 5.40

S i ng le O r al D o se (mg /k g) 

## Boo t s tr apped P opu l a t i ons

Lo w e r C on f i dence

L i m i t o f 50 th pe r cen t ile Lo w e r C on f i dence

L i m i t o f 5 th pe r cen t ile Lo w e r C on f i dence

L i m i t o f 1 th pe r cen t ile| 61 

# An i m a l a nd hu m a n m od e li ng res u l ts f o r C PF

D ose m g / kg

Bes t es t i ma t e o f t h e

do se ca u s ing 10 %

inhibi t ion L o w er 95 th p erce n t il e

c on f id e n ce li m i t o f t h e

do se ca u s ing 10 %

inhibi t ion



### H u m an 6 m on t hs

50 th 

### P ercen t ile 0

. 20 0

. 17

5 th 

### P ercen t ile 0

. 10 0

. 09

1 st 

### P ercen t ile 0

. 09 0

. 08| 62 

## C he m i ca l S pec ifi c A d j us t m en t Fac t o r s : I n t e r spec i es



# y n i m a l st ud P OD fr o m a hu m an s

ty p ic al icti on f or M od el p red ies I n ter-s p ec =| 63 

## P O D i n t he an i m a l s t ud y and it s equ i va l en t i n hu m ans

• EPA ’ s p r opo s ed P O D f o r C P F i s B M DL

10 

### in male neona t e s b y s ingle

o r al do s e mil k ( 0

. 36 mg / k g ) Ma r ty e t al

. ( 2010)

• The animal B M DL

10 

### i s t he e s t ima t e o f a do s e w he r e t he r e i s a 95 %

c on f iden c e t ha t t he do s e t ha t c au s e s 10 % pea k R B C inhibi t ion i s

highe r t han t he e s t ima te

• The animal B M DL

10 

### i s t r ea t ed a s being equi v alen t t o t he 95 % L C L o f

t he e s t ima t e o f do s e c au s ing 10 % inhibi t ion in t he 50 th 

### pe rc en t ile o f t he

popula t ion o f s i x mon t h old s

. The de f ini t ion i s:

> Con s i s t en t w i t h t he a ss u m p t ion o f m ini m al v a r ia t ion a cr o ss t e s t ani m als

> Con s i s t en t w i t h t he u s e o f pool s o f ani m al s in t he R B C A Ch E a ss ay

> Con s i s t en t w i t h t he c on c ep t o f a “ t y pi c al ” indi v idual| 64 

## C he m i ca l S pec ifi c A d j us t m en t Fac t o r s : I n t e r i nd i v i dua l

• Guidan c e on de v eloping c hemi c al s pe c i f i c adju s t men t f a c t o rs

s ugge s t s c al c ula t ing t he s i z e o f t he in t e r- indi v idual f a c t o r needed t o

p r o t e c t 90 %, 95 % and 99 % o f t he popula t ion ( Mee k e t al

. 2002

, WH O

, 2005

, EPA, 2011 (Dr a ft )).

• W e ha v e f o c u s ed on 95 th 

### and 99 th 

### pe rc en t iles

• N o t e ou r “ ty pi c al indi v idual ” i s an in f an t and in f an t s a r e belie v ed t o be

s ligh t l y mo r e s en s i t i v e t han adul t s a t high do s e s

, t hu s age -r ela t ed

v a r ia t ion i s al r ead y add r e ss ed in t he de t e r mina t ion o f t he p r edi c t ion o f

t he ty pi c al human and doe s no t need t o be in c luded in t he c al c ula t ion 

# hu m an se n sitive icti on f or M od el p red u m an

ty p ic a l h icti on f or M od el p red vi dual I n ter-i ndi

=| 65



## A n i m a l and hu m an m ode li ng r esu lt s f o r CPF

D o se m g/ kg

Bes t es t i m a t e of th e do se

ca u si ng 10 % i nh i b i t i on Lo w e r 95 th p e r ce nt ile

c onf i d e n ce li m i t of th e do se

ca u si ng 10 % i nh i b i t i on

Ra t pup d a ta

0

. 47 0

. 36

H u ma n 6 m on t hs

ME D I AN 0

. 20 0

. 17

5 th P erce n t ile 0

. 10 0

. 09

1 st P erce n t ile 0

. 09 0

. 08



# 1

. 2

17

. 0 36

. 0

= = ies I n ter-s p ec 8

. 1

09

. 0 17

. 0

= = vidual Inter-indi



# 1

. 2

08

. 0 17

. 0

= = vi dual I n ter-i ndi| 66 

## EPA ’ s p r oposed a PA D and i m pac t o f CSA Fs f o r CPF

E P A p r opo sal M od e l Bas ed V al ues

In t er

- s p ec i es 10 2 .1

In t er

- indi v idu al 10 1

. 8

- 2 .1

FQ PA 1 1

T o t a l 100 3

. 9

– 4

. 5



# F i na l a P A D i s 360 ug / kg d i v i ded by

3

. 9 t o 4

. 5

, or

90 t o 70 ug / kg| 67 

## EPA ’ s p r oposed a PA D and i m pac t o f CSA Fs f o r O xon

E P A p r opo sal M od e l Bas ed V al ues

In t er

- s p ec i es 10 1 .2

In t er

- indi v idu al 10 1

. 65

– 1

. 85

FQ PA 1 1

T o t a l 100 2

. 0

– 2

. 3



# F i na l a P A D i s 50 ug / kg d i v i ded by 2

. 0

– 2

. 3

, or

25 t o 22 ug / kg| 68 

## S u mm a ry

• D o w A g r o S c ien c e s belie v e s t ha t t he sc ien c e i s s u ff i c ien t t o w a rr an t a

r edu c t ion in t he adju s t men t f a c t o rs f o r C P F and o x on

> I n t e rs pe c ie s and in t e r indi v idual f a c t o rs c an be m u c h sm aller

> T he m odeling p r o v ide s e v iden c e t ha t in f an t s and t he de v eloping f e t u s a r e

no t a t ele v a t ed r i sk

f r o m C P F o r o x on



### • The s e r edu c t ion s u s e t he be s t sc ien c e and a r e c on s i s t en t w i t h

r egula t o r y guidan c e on de v eloping C SA F s and s hould be c on s ide r ed

in s e tt ing t he a c u t e o r al a PAD

• C on s ide r a t ion o f s u c h popula t ion modeling in f o r ming t he s t anda r d

s e tt ing p r o c e ss i s c on s i s t en t w i t h To x i c i ty in t he 21 st 

### C en t u r y| 69 

## Q ues ti ons

## U S I N G P B P K

/ P D M O D E L S T O R E C O N S TRUCT

A GG R EG AT E EXPOS UR ES O F TH E C O LUMB I A

UN I VE R S I T Y C O H O RT

- P R E L I M I NAR Y F I ND I N GS

P au l P r i c e and Torka P oet

A ugus t 27

, 2013| 71 

## C u rr en t m ode l o f PBPK / PBPD o f CP F f o r m u lti p l e r ou t es

o f exposu r e ( agg r ega t e exposu r e)

• Thi s model i s a w o rk in p r o c e ss and all f inding s a r e p r eli m ina ry

• Thi s model add r e ss e s all t h r ee r ou t e s f o r t he s ame indi v idual

• I ni t ial v e rs ion i s limi t ed t o:

> O ne da y o f do s ing and m ul t iple da y s o f f ollo w up

> I nhala t ion

, hand t o m ou t h

, and de rm al a ss u m e c on t inuou s 24 h rs e x po s u r e

and die t a r y do s e a r e a ss u m ed t o o cc u r a t one m eal



### • I nhala t ion e x po s u r e s a r e modeled a s c au s ing do s e s b y bo t h b y t he

lung and t he gut

• N o human v a r ia t ion bu t gende r

, age

, and bod y w eigh t o f indi v idual

c an be s pe c i f ied| 72 

## U se o f t he m ode l t o exp l o r e t he i m pac t o f r ou t e on CP F

i n b l ood and i nh i b iti on o f RBC AC h E

• Ex po s u r e pa r ame t e rs f o r ea c h r ou t e and s ou rc e w e r e adju s t ed t o

r e s ul t in ab s o r bed do s e s o f

~ 3 ug / k g ( do s e w a s s ele c t ed onl y f o r t he

pu r po s e o f c ompa r ing r ou t e s)

> I nhala t ion 24 hou rs a t 0

. 06 m g /m 3

> De rm al loading o f 1

. 5 m g o f C P F o v e r 60% o f a pe rs on’ s s u r f a c e a r ea f o r

24 h rs

> O r al do s e s o f 3 ug / k g f r o m die t o r hand

- t o -m ou t h e x po s u r es



### • I nhala t ion

, de r mal

, and hand

- t o

- mo u t h e x po s u r e s o cc u rr ed o v e r 24 h r

pe r iod

, bu t die t a r y do s e s a r e a ss umed t o o cc u r a t one meal

• 85 k g adul t f emale modeled

• I ndi v idual modeled f o r one da y o f e x po s u r e and 8 addi t ional da y s o f

f ollo w up| 73

0 .1 1 10 100 1000 10000

0 2 4 6 8ng/lCPF

D a ys 

# Ti m e co u r

s e o f C PF i n b loo d a f

t e r an

a b s o r b e d d o s

e o f 3 u g / k g b y v

a r io us

r o u t e s and s o u r c es

O r

al ( d i e t)

O r al (H a nd t o m o uth)

D e rmal

I nh al a t i on| 74

99

. 965 99

. 970 99

. 975 99

. 980 99

. 985 99

. 990 99

. 995 100

. 000

0 1 2 3 4 5 6 7 8 9RBCAChEActivityasapercentofbaseline

D a ys 

# Ti m e co u r

s e o f R B C A C

h E a c t ivi t y a f t e r a

d o s e o f 3 u g / k g b y v

a r io us r o u t es

O r al (d i e t)

O r al ( Ha nd t o m o u t h)

D e r m al

Inh al a t i on| 75 

## C onc l us i ons

• R ou t e o f e x po s u r e ha s a p r onoun c ed e ff e c t on t he le v el s o f C P F in t he

blood:

> E qui v alen t ab s o r bed do s e s b y t he de rm al and inhala t ion r e s ul t in 55 X and

14 X highe r a r ea unde r t he c u rv e (A UC ) , t hen b y t he o r al r ou t e ( die t)



### • I mpa c t o f r ou t e on R B C A C h E i s mu c h s malle r

> A UC o f de rm al i s 8% la r ge r

, hand

- t o -m ou t h o r al 12% lo w e r

, and inhala t ion

i s abou t 1⁄2 o f A UC f o r o r al ( die t)



### • Model s ugge s t s t ha t blood le v el s f r om all r ou t e s o f e x po s u r e a r e

bipha s ic

> C P F i s lipid s oluble and m a y be s lo w l y r elea s ed f r o m f at

> T hi s s lo w r elea s e r e s ul t s in a s e c ond pha s e in t he de c line in blood le v el s

t ha t i s m u c h s lo w e r t han t he ini t ial pha s e

> As a r e s ul t t he m odel p r edi c t s t ha t lo w le v el C F P blood c on c en t r a t ion s ( 30

t o 100 f old belo w t he pea k C P F le v el s) w i l l pe rs i s t f o r a w ee k o r m o re| 76 

## C ha ll enge o f t he C o l u m b i a coho rt

• P a r t i c ipan t s w e r e po t en t iall y e x po s ed f r om mul t iple s ou rc e s ( die t,

inhala t ion

, de r mal

, and hand

- t o

- mou t h)

• P a r t i c ipan t s w e r e adul t s

– t he r e i s limi t ed unde rs t anding o f ho w t o

model de r mal and hand

- t o

- mou t h e x po s u r e s f o r adul ts

• N o da t a a r e a v ailable on u s e o f pe s t i c ide s on t he da y s immedia t el y

p r io r t o en t e r ing ho s pi t al

• Onl y mea s u r eme n t s o f blood le v el s o f c hlo r p y r i f o s w e r e pe r f o r med in

t he ea r l y y ea rs o f t he s t udy

• R a w da t a a r e no t a v ailable

– onl y publi s hed s umma r ie s.| 77 

## D esc r i p ti on o f t he M odel

• Model add r e ss e s a s ingle da y o f e x po s u r e and mul t iple da y s o f f ollo w

up

• A dd r e ss all r ou t e s and s ou rc es

• D e t e r mine s blood le v el s o f C P F

, T C PY e x cr e t ion

, and pla s ma and

R B C c holine s t e r a s e a c t i v i ty

• N o v a r ia t ion in s en s i t i v i ty bu t age and bod y -w eigh t i s s pe c i f ied

> (A dul t f e m ale o f 75 k g and 12 k g w ei g h t in cr ea s e f o r la t e p r egnan c y )| 78 

## D a t a used i n t he ana l y s is

• D a t a f r om C olumbia U ni v e rs i ty s t ud y publi c a t ions

> A i r le v els

> S u mm a r y in f o rm a t ion on blood le v el s o f C P F f o r 1999



### • V a cc a r o s t ud y:

> S e v en indi v idual s w i t h a 4 hou r e x po s u r e s t o r e s idue s on c a r pe t s

– scr ip t ed

a c t i v i t ie s t o s i m ula t e high e x po s u r e in f an t beha v io rs



### • D a t a f r om V a cc a r o s t ud y w a s u s ed t o:

> De rm al loading on hand s u s ed a s a ben c h m a rk f o r all de rm al e x po s u re

> Es t i m a t ed K p v alue ba s ed on de rm al loading and T C PY e x cr e t ion t ha t

r e f le c t s pe s t i c ide f o rm ula t ion s

> No t e pe s t i c ide f o rm ula t ion in t he Colu m bia s t ud y i s no t s pe c i f ied in t he

publi c a t ions



### • O t he r s t udied a r e in t he li t e r a t u r e t ha t c ould r e f ine t hi s a ss e ss me nt| 79 

## R ange -fi nd i ng scena r io

• D e v elop a “ plau s ible ” e x po s u r e sc ena r io and de t e r mine ho w t he

p r edi c t ion s o f blood le v el s ma t c h up w i t h r epo r t ed mea s u r emen ts

• Fo c u s on t he la r ge s t 15 % o f t he mea s u r emen ts o f blood a s being t he

mo s t r eliable

> M a t e r nal blood le v el s 5

. 5

- 35 ng /l

> Co r d blood 6

. 6

– 65 ng /l



### • Ex po s u r e a ss ump t ions

> I nhala t ion

– u s e t he highe s t r epo r t ed ai r c on c en t r a t ion ( 0

. 345 ug /m 3 )

> Die t

– 90 th pe rc en t ile o f adul t die t a r y e x po s u r e f r o m m odeling ( 0

. 017 ug / k g)

> O r al do s e f r o m hand

- t o -m ou t h i s ba s ed on guidan c e in EPA 2012 S O Ps

• Fr a c t i on of hand and f r equen c y a r e s et at the l o w end of the r ange s fo r i nfant s

and hand l oad i ng s et at 1/10 of m ean hand l oad i ng i n V a cc a r o s tud y

.

> De rm al do s e

• B a s ed on 1/10 of the m ean hand l oad i ng i n V a cc a r o s tud y app li ed to 15 % of ski n

s u r fa c e| 80 

## R esu lts| 81

0.1 1 10 100 1000

-1 0 1 2 3 4 5 6 7 8CPFinbloodng/l

Da ys 

# T im e li n e for C o l u m b i a d a t a on

c h l orp y r i fo s i n b l ood| 82

0.1 1 10 100 1000

-1 0 1 2 3 4 5 6 7 8CPFinbloodng/l

Da ys 

# T i m i ng o f sa m p l es a nd ra ng e o f t op 1 5 %

o f re po rte d l eve l s i n c o r d b l ood

C o r d Bl ood| 83

0.1 1 10 100 1000

-1 0 1 2 3 4 5 6 7 8CPFinbloodng/l

Da ys 

# T imi ng a nd r a ng e of top 15% of

ma t e rn a l b l ood l eve ls

M a t e r na l Bl ood C o r d Bl ood| 84

0.1 1 10 100 1000

-1 0 1 2 3 4 5 6 7 8CPFinbloodng/l

Da ys 

# T im e c our se of c h l orp y r i fo s i n

b l ood fro m r a ng e -f i nd i ng sce n a r io| 85

0.1 1 10 100 1000

-1 0 1 2 3 4 5 6 7 8CPFinbloodng/l

Da ys 

# D er m a l d rives c h l o r p y rif o s l eve l s i n

b l ood

All Routes

D i et

Hand to Mouth

Inha l at i on

De r m al| 86 99.970 99.975 99.980 99.985 99.990 99.995 100.000

-1 0 1 2 3 4 5 6 7 8RBCAChEActivityasa%ofbaseline

D a ys 

### N o s i gn i f i can t im pac t on RBC AC h E ac t i v i t y i s pred i c t ed

t o occur e i t her a t ho m e or i n t he hosp i t al

All Routes

D i et

Hand to Mouth

Inha l at i on

De r m al



## N o s i gn ifi can t

change i n

ac ti v ity| 87 

## P r e li m i na r y conc l us i ons

• T he blood le v el s in t he t op 15% o f Colu m bia s t ud y f o r t he y ea r 1999 a r e

c on s i s t en t w i t h le v el s t ha t c ould plau s ibl y o cc u r f r o m r e s iden t ial u s e s i f:

> T he r e si den c e w a s t r eated s o m e t i m e i n the w ee k p r i o r to the i nd ivi dua l ente r i ng the

ho s p i ta l ; and the s ub j e c t had e x ten siv e de r m a l c onta c t to t r eated s u r fa c e s

• T he blood le v el s o f C P F c ould ha v e been a s m u c h a s 30

- f old highe r on t he

da y o f t he appli c a t ion t hen t he le v el s m ea s u r ed in t he s t udy

• T he s e highe r le v el s w ould no t ha v e c au s ed s igni f i c an t R B C A Ch E I a t an y t i m e

( w hile a t ho m e o r in t he ho s pi t al )

• T he c on c lu s ion i s t ha t t he da t a do no t indi c a t e an un s a f e e x po s u r e t o C P F

o cc u rr ed t o an y o f t he pa r t i c ipan t s

. No r do t he le v el s de m on s t r a t e t ha t

s igni f i c an t R B C A Ch E I o cc u rr ed a t an y t i m e.

• T hi s s uppo r t s Pr uei t t e t al

. ’ s f inding s t ha t t he a ss o c ia t ion s r epo r t ed b y

Colu m bia Uni v e rs i t y a r e no t due t o t he t o x i c i t y o f c hlo r p y r i f o s and a r e m o r e

li k el y a tt r ibu t ed t o al t e r na t i v e e x plana t ions| 88 

## Q ues ti ons