## REVIEW OF CHILDREN’S HEALTH

EPIDEMIOL OGY COHORT STUDIES CAROL H. CHRISTENSEN, PH. D ., MPH

EPIDEMIOL OGIST USEP A, OFFICE OF PESTICIDE PROGRAMS April 10, 2012 FIFRA SAP

# Bac kground and History

 

### September 2008 EP

A presented targ eted revie w of three ch ildren ’shealth cohor t studies  

### FIFRA SAP R epor t:  

### “Chlorp yrif os lik ely pla ye d a role” Cannot conclude “c hlorp yrif os is the sole contributor” due to **2**

 Cannot conclude “c hlorp yrif os is the sole contributor” due to

other co - ex posures  

### Howe ve r,e pidemiolog y studies "should not be considered ...basis f or c har acterization of Po D ”  Lac k biologically plausible MOA, e xposure uncer tainties  

### Supplemental analyses recommended

# Bac kground and History

 

### April 2012 EP

A updates and e xpands its targ eted revie w of these data:  Ne w etiologic papers  Intellig ence Quotient (IQ)  Ne w methodological papers  Socioeconomic status (SES) **3**

 Exposure ch aracterization and v alidation

 Supplemental analyses (unpublished) (Appendix 4)  Draft Fra me wo rkAnalysis approac h  Wo rk ing towa rd WO E Ev aluation
 

### Pa nel guidance reg arding qualitative and/or quantitative use these studies in risk assessment

# Ov er vie w of Cohor ts

**4**  Columbia cohor t (1998 - 2002)

 NYC, Dominican and African - American Mothers - Infant pairs  Cord Blood Chlorp yrif os  Va lidation studies (air

, mater nal blood, urine, meconium )  Mt. Sinai cohor t (1998 - 2001)  NYC, mu lti - ethnic (African American, Hispanic, White)

(African American, Hispanic,  Measured TPCy (fetal gr ow th only) and DAPs  PON1 ge notype and phenotype  U of CA Ber ke ley Cohor t (CHAMACOS) (1999 - 2002)  Me xican - American, agricultural wo rk er population  Measured TPCy and DAPs  PON1 ge notype and phenotype

# Ov er vie w of Cohor ts

**5**  

### Three prospective bir th cohor ts to e xamine environmental ex posures and adverse health outcomes  Chlorp yrif os/OP studies f ocus of this revie w  Bir th outcomes Neur odevelopment   

### Enr olled wo men during pregnanc y,f ollow c hildren thr ough time, m ultiple measures  

### Children ’sE nvir onmental Health and Disease Prev ention Re searc h Centers (funded by EP A and NIEHS)

# Po pulation Char acteristics

 Sought prenatal care (<20 - 26 w eeks) Re sidency requirement  Multi - ethnic populations: African - American, Dominican, Hispanic, **6 General Eligibility**  **Cohor t Char**  **acteristics**

 Re sidency requirement  Deliv er par ticipating hospitals  No diabetes, h yper tension, HIV , history bir th defects  No smoking , illeg al dr ug use Dominican, Hispanic, Me xican - American, White  Yo ung er mothers, ~25 ye ars  Low prev alence risky health behaviors, co - morbidities (criteria)

### Exposure Measurement, Conf ounding Adjustment,

Statistical Analyses 

# Methods and Analysis **7**

# Exposure Assessment

**8**  

### Cohor ts differing e xposure pr ofiles, pathw ay s,r outes  Inner - city

, agricultural and both residential, occupational  

### Multiple biomar ke rs reflect different windows of e xposure:  Chlorp yrif os in cord blood (Columbia) TC Py in urine (eac h cohor t)  in urine (eac h cohor  DA Ps in urine (CDC methods) (Mt. Sinai, CHAMACOS)  TC Py meconium (v alidation stud y) (Columbia)  AC hE and BuChE in cord blood (CHAMACOS)  PON1 g enotype and phenotype  Chlorp yrif os in air (v alidation stud y) (Columbia)  Self - repor t questionnaire (eac h cohor t)

# Exposure Assessment

**9**  

### Ideal Measures

 Estimates e xposure during critical window of susceptibility  Re peat samples  periodicity

, v ariability of e xposure  Re flectiv e of tr ue rank of actual e xposure flectiv ue rank of actual e xposure  Timing of sample collection with application  

### Actual Measures  One - time, or av erag e of tw o samples  Third trimester (unknown window of effect)  Specific and non - specific biomar ke rs of c hlorp yrif os Adapted D . Savitz 2002

# Exposure Measurement Error

**10**  

### Exter nal e xposure v ersus measured inter nal dose

 Re flects total e xposure (all r outes)  

### Single measure, third trimester  Te mporal - spatial patter ns of e xposure unclear 

### Exposure during critical window of dev elopment  

### Exposure during critical windo elopment  Lik ely third trimester impor tant  

### Missing e xposure data  Imputation methods, data  

### Labor atory err ors  Extensiv e QA/QC measures, CDC laboratories

# Exposure Va lidation Stud y

**11**  

### Questionnaire Data:  

### 85% repor t use pesticide, most repor t at least monthly use  Evidence consistent use prior to 2000

 

### Exter nal Data  

### NY C Housing Authority repor ted use  To tal usag e in NYC housing greater than NY state Ag uses prior to voluntary cancellation

# Exposure Va lidation Stud y

 

### Air monitoring  

### Last 8 - wks, stationary air  

### Pe rsonal (48 - hr) and  

### Biomar ke r Collection:  

### Mater nal Urine  

### Last trimester  

### At deliv ery  

### Mater nal blood **12**

 

### Pe rsonal (48 - hr) and

 

### Intr a<inter v ariability  

### Mater nal blood  

### Meconium  

### Neonate urine

 

### Compare Cord blood  Etiologic measure 

### Pe riod of R apid Decline of Use Wh ya tt et al. 2007, 2009

# Exposure Va lidation Stud y
**13** Meconium we ek 14 thru deliv ery

We ek 14 We ek 24 Conception We ek 20 Cord Blood

First trimester Second Trimester Thir d Trimester We ek 32 thru deliv ery: bi
we ekly air monitor and ma te rnal urine sample We ek 32 (pilot): 48 hr

. air We ek 14 We ek 24 Conception We ek 20 

## Cord blood, meconium, mater nal urine Cord Blood

# Exposure Va lidation Stud y

**14 Cord Blood Measur**  **es Cor re**  **la te**  **with Meconium (e xposur**  **e period)**

Wh ya tt et al. 2009

# Exposure Assessment

**15**  

### Uncer tainties Re main  

### Limited window of e xposure measured  One - time measure (Columbia, Mt. Sinai)  CHAMACOS averag es tw o e xposures  Va lidation studies sugg est some degree of correlation  

### Unknown periodicity of e xposure  Pe aks, constant  

### Prev alence of pesticide ex posure high  Median concentration TC Py within rang e of g eneral population (NHANES)  Ma y indicate difference actual and measured

# Methods to Control Confounding

 

### Re **striction (design)**   

### Through recr uitment tec hniques, similar population ch ar acteristics  

### Sta **tistical Adjustment (individual**  **- le** **ve l)**  **16**

 

### Sta **tistical Adjustment (individual**  **- le** **ve l)**   

### Ra ce, education, income, housing quality  

### Te sted fo r statistical inter action  

### Multile**ve l Model**  **(SES , Columbia**  **only)**  

### Account group - lev el and individual - lev el va riability

# Methods to Select P otentially Conf ounding V

ariables
 

### Methods  Searc hing literature, other studies in area  Te sted univ ariable and m ultiv ariable models  Included if obser ve d +/
- 10% c hang e in estimate  Evidence of statistical conf ounding **17**

 Evidence of statistical conf ounding

 Forw ard/Bac kw ard step - wise selection pr ocedures  Include if known risk factor  Evidence of biological conf ounding  

### Man y known or suspected conf ounding va riables measured and modeled  Emphasis on P arsimon y

# Conf ounding Va riables

 

### Demogr aphic  

### Health - related  

### Other environmental ch emicals: Lead, Mercury

, Diazinon , Propo xur **18 General Factors**  **Major P otential (r**  **esidual) Conf**  **ounding V ariables** 

 

### Environmental ex posures PA H, ETS, DDT/DDE, PCB, OC/HCB  

### Po stnatal environment Diazinon , Propo xur

 

### Socio - economic status  In g eneral, c hallenging to measure

# When Conf ounding Bias?

Conf ounder CPF Exposure **19 Lead, Mercur**  **y*** **cor re**  **la tion**  **<0.10**

*P ersonal Communication R. Wh ya tt ρ <0.20 – lik ely no effect 0.20< ρ <0.40 – little c hance 0.40< ρ <0.60 - some effect 0.60< ρ <0.80 – strong effect ρ >0.80 – collinearity ND Outcomes

# Conf ounding: Other OPs

**20 Ef**  **fects of**  **Chlorp yrif**  **os on**  **the odds**  **of Mental De** **velopment Delay**  **on the**  **Bayle y**  **Scales of Infant**  **De velopment**  **at a**  **ge 36 months**  **. (**  **β coef**  **ficient, 95%**  **CI, p -** **value)**

**Model 1 Model 2**  **Model 3 Model 4**  **Chlorp yrifos**  **2** 2.3 (1.1, 5.2) 3.8 (1.5, 9.4) 2.0 (0.9, 4.5) 3.2 (1.3, 8.2 ) **Chlorp yrifos**  2.3 (1.1, 5.2)

p=0.03 3.8 (1.5, 9.4)

p=0.004 2.0 (0.9, 4.5)

p=0.11 3.2 (1.3, 8.2 )

p=0.02 **(ln)Diazinon** 0.57 (0.35, 0.95) p = 0.03 0.6 (0.3, 0.9) p =0.03 **( ln**  **) 2**  **- isopropo** **xyphenol (propo** **xur)** 1.5 (0.9, 2.5) p=0.12 1.5 (0.9, 2.6)

p=0.11 Appendix 4: Wh ya tt and Ra uh , 2011 (unpublished)

# SES: Multilev el Analysis

 

### The stud y of the effects of collective or group ch ar acteristics (as we ll as individual ones) on individual - level outcomes  

### Not all associations ex plained by individual lev el **21**



### Not all associations ex plained by individual lev el ch ar acteristics  

### Group - lev el va riables ma y affect individuals directly and also constr ain the ch oices that individuals mak e  

### Improv e accur acy and precision of statistical models include Group and Individual lev el

# SES: Multilev el Analysis (cont.)

Group lev el CPF estimates **22**

Group lev el va riables

Individual lev el v ariables Lov asi et al. 2010

# Statistical Analysis

**23**  

### Statistical modeling decisions appropriate to the researc h question, c haracteristics of data etc.  

### Missing data, <L OD  (imputed, sensitivity analyses)  

### Sample size adequate main effects  

### Lik ely under - powe red fo r effect modification  

### Sensitivity analyses to ev aluate alter native modeling options

### Fetal Grow th, Neonatal Neurological

Development, Infant Motor and Mental 

# Re sults **24**



### Development, Attention Disorders, Intellig ence Measures

# Fe tal Grow th and Char acteristics

**25**  

### Authors hy pothesized link betw een pesticide and effects on fetal grow th  

### Hypothesized link to neurodevelopment  

### Medical record linkag e Bir th we ight, length, ponder al inde x  

### length,  

### Gestational ag e,preter m bir ths  

### Head circumference  

### Effect modification ev aluated  

### PON1 ge notype and phenotype

# Fe tal Grow th and Char acteristics

**26 Columbia**  **Cohort Mount**  **Sinai**

**Cohort U of CA**  **Berk eley**  **Cohort** Markers of Exposur e: Chlorpyrifos TC Py (fetal gr owth) TC Py DA PS **Birth Length** In verse Null Po sitive ( n.s .) Po sitive **Birth Length** In verse

(Null post 2000) Null Po sitive ( n.s .) Po sitive **Birth W eight**  In verse

(Null post 2000) Null Po sitive ( n.s .) Null **Head Cir** **cumf er** **ence at Birth**  -- Null (Inverse (NS))* Null Po sitive (Inverse*) **Ges tational**  **Ag e**  -- Null Null Null (Inverse*) * PON1 g enotype or phenotype

# Neonatal Neurodev elopment

**27**  

### Brazelton Neonatal Behavioral Assessment Scale (BNB AS)  

### Goal: provide inf or mation parents/caregivers  

### 28 behavior al items - habituation, ra ng e of state, behavior habituation, orientation  

### 18 primitiv e refle xe s  

### Assessed 2 - 5 da ys post - par tum  

### Tr ained neonatologists administered  

### Hospital setting

# Neonatal Neurodev elopment

**28**

Consistent, refle xe s **Columbia Cohort**  **Mount Sinai** 

**Cohort U of CA** 

**Berk eley**  **Cohort** Exposur e Measur e CPF DA PS DA PS refle xe s Outcome measure good quality DA Ps only , limitation Measur e

**BNBAS (Abnormal**  **reflex es)**  -- Po sitive* Po sitive **BNBAS (Other Beha**  **vior al)**  -- Null Null * PON1 g enotype or phenotype

# Infant Neurodev elopment

**29**  Ba yley Scales of I nfant Dev elopment II

 Mental dev elopment inde x (MDI)  Psych omotor dev elopment inde x (PDI)  Measured 6 - 36 months  High reliability and v alidity as screening tool f or ear ly inter ve ntion  Child Behavior Chec klist  Designed to assess "social competence" and "behavior problems" in c hildren (Mater nal repor t)  Ra ce/ethnicity small propor tion of score v ariance  99 - item questionnaire to ascer tain behavior and/or attentional  Home Obser vation Measurement of the Envir onment (HOME)  Stim ulating environment f or c hild dev elopment  Effect modification ev aluated  PON1 g enotype and phenotype

# Infant Neurodev elopment

**30 Columbia Cohort**  **Mount Sinai Cohort**  **U of CA Berk** **eley Cohort** Marker s of Exposur e: Chlorpyrifos DAPS TC Py DAPS **Ba yley**  **Scores 6 months**  **(MDI/PDI)** -- -- Null/Null In verse (NS )/Null **(MDI/PDI) Ba**  **yley Scores 12 months**  **(MDI/PDI)** Null / Null In verse(*/**) / null (NS) Null/Null Null / Null **Ba yley Scores**  **24 months (MDI/PDI)**  Null / Null In verse( n.s .)/Null Null/ Null In verse / Null **Ba yley Scores**  **36 months (MDI/PDI)**  In verse/ Inverse
-- -- *PON1 ge notype or phenotype; ** A mong blacks and Hispanics

# Attention Problems

**31**  

### Measurement To ols  

### Combination Mater nal repor t and direct obser va tion  Child Behavior Chec klist (mater nal repor t)  Direct Assessment of c hild (K - CPT)  Hillside Psych ometrician repor t  

### DSVM - IV ADHD symptoms

 

### Assessed at 3, 3.5 and 5 y ears in tw o cohor ts

# Attention Problems

**32** Sensitivity of test at 3 yrs limited Consistent results , tw o **Columbia Cohort**  **Mount**

**Sinai Cohort**  **U of CA**

**Berk ele**  **y Cohort**  Exposur e : CPF DA PS DA PS results , tw o different ex posures Prenatal lead, lac k postnatal **( PDD)**  Po sitiv e (36 mo.) -- Po sitiv e (24 mo.) **Odds of ADHD/**  **atte ntion**  **pr oblems**  Po sitiv e

(36 mo.) -- Po sitiv e (NS 3 year s) Po sitiv e (5 year s)

# Intellig ence Measures

**33**  

### We ch slar Intellig ence Scale f or Children IV  

### Ve rbal comprehension  

### Pe rceptual Re asoning  

### Wo rk ing Memory (WM) Processing Speed   

### Full Scale IQ (FSIQ)  

### Standardized US population, nor ms English and Spanish speaking populations  

### Cultural Bias has been noted  

### Re stricted sample population

# Intellig ence Measures

**34**

Consistent results across studies (WM) **Columbia Cohort**  **Mount Sinai** 

**Cohort U of CA** 

**Berk ele**  **y Cohort**  Exposur e CPF DA PS DA PS (WM) Larg e number missing tests, include/e xc lude comparable **Mental**

**Development (**  **WISC -**  **IV)** In ve rs e

( FSIQ , WM) In ve rs e (NS)

( FSIQ , per ceptual re asoning , WM) In ve rs e (FSIQ ,

WM, pr ocessing speed, v erbal, per ceptual re asoning)

### Draft Fra me wo rkAnalysis 

# Ev aluation and Synthesis **35**

# Strengths and Limitations

 Measurement outcome and ex posure ex tensiv e,va lidated, reliable  Impor tant conf ounding va riables  Unknown factor ma y correlate with CPF  Howe ve r,a mong known or hy pothesized factors with **36 Str**  **engths Limita**  **tions**

 Impor tant conf ounding va riables measured and modeled  Design and analysis decisions aid comparability betw een gr oups  Re duce man y sources of bias  Pe er - revie we d publications hy pothesized factors with potential positiv e conf ounding bias, lac k evidence e xplain obser ve d associations  In ge neral, difficult to tease out SES in an y epidemiolog y stud y  Re striction, individual and group lev el m ulti - va riable analysis (R 2 moderately high)  Ro le of postnatal envir onment  Limited instances in whic h measured, not conf ounder

# Stud y Design Issues

 

### A priori hy potheses

 

### Statistical modeling appropriate  Discussed v arying degrees  

### Selection Criteria ex tensive  Enhance inter nal va lidity  Re duce e xter nal v alidity (g ener alizability) **37**

 Discussed v arying degrees

across studies  Missing data imputed when possible  

### High prev alence e xposure, outcome enhanced stud y powe r  Limited ev aluation of inter action with other ch emicals, OPs

# Statistical Analysis and Grouping

 

### Several Methods Used across studies:  

### Motiv ated by sample size, stud y hy pothesis  

### Grouping str aight - fo rw ard, fully ex plained  

### Analysis issues not alw ay s discussed in full **38**

 

### Analysis issues not alw ay s discussed in full
 

### Several sensitivity analyses perf or med  

### QA/QC measures  

### Alter nativ e hy potheses ex plored  

### Model fitting exe rcises, shape of data

# Exposure Measurement

**39**  

### Chlorp yrif os (parent), non - specific ( TC Py , DAP)  Lac k specificity

, direct comparability  Ma y e xplain heter og eneity  

### Unknown temporal, spatial patter n of e xposure Constant, inter mittent, and/or sporadic   One - time measure correlated with long er - ter m mar ke r  Meconium=mater nal urine ( av e .)=cord blood  

### Cohor ts’ e xposures greater than, but compar able to population median  Generalizable to US population

# Outcome Ascer tainment

**40**  

### Outcome Measures

 Similar , aids comparison  Clinical, researc h settings  Spanish/English  Quality Assurance and Control adequate  Stated obser ve rs blinded in some, not all studies  

### Limitations  Neur odev elopmental assessments subjective  Cultural bias –We ch slar tool  

### Non - differential err or lik ely  Multiple e xposure ameliorates potential differential bias

# Conf ounding Bias

**41**  

### Multiple methods of control  

### Re striction, individual - and group - lev el (SES)  

### Cannot e xc lude possibility positive conf ounding bias of unknown factor Lead, mercury

, other OP , OC, PCB, PA H  

### mercury , OC, PCB  

### SES  Multi - dimensional, both +/
- conf ounding biases  Hierarc hal regression analysis utilized to assess  

### Lac k ex amination of heterog eneity by other envir onmental e xposures

# Threats to V

alidity

 

### Re tention rate moder ately high f or bir th cohor ts (60 - 80%  

### Err ors in outcome and ex posure measures occurred **42 Selection Bias**  **Inf or**  **ma tion Bias** 


### bir th cohor ts (60 - 80% at 7 y ears)  

### Included and e xc luded compar able  Measured v ariables  

### Missing Data imputed occurred  Design reduces differential bias  Man y e xposures  

### Non - differential ma y hav e reduced effect sizes

# Synthesis of Evidence

**43**  

### Strength of obser ve d associations high in some cases, but not all  Non - differential ex posure measurement err or could reduce magnitude 

### Some evidence of e xposure - response in studies  

### evidence xposure response in studies  

### Consistenc y in Br azelton (abnor mal refle xe s), ADHD - lik e behavior pr oblems, Ba yley (par ticular ly MDI), and IQ (WM)  

### Alter nativ e e xplanations inv estig ated  Modeling , transf or mations, conf ounding va riables

# Synthesis of Evidence

**44**  

### Prospective studies  

### Te mpor al relation  

### Differential misclassification less lik ely  

### Biological plausibility  

### See other sections, ge ner ally plausible, lac k specific details MOA  

### Influence of cessation of residential ex posure on association  

### Limited evidence (low powe r), not designed to assess

# Conclusions

**45**  

### Current database strengthens conclusion 2008 “c hlorp yrif os lik ely pla ys a role” in obser ve d adverse effects on c hild neurodevelopment Given stud y conduct, design, methods EP A believes  

### en stud conduct, design, methods EP A believ more lik ely under - than over - estimate associations
 

### Integration across streams of inf or mation will continue

### Section 4.0

Appendices 4 - 6 

# Questions **46**

# Appendix 4: Supplementary Analyses Columbia U . Cohor t
 

### Bounding  

### See Hattis PBPK  

### How man y “LBW?”  

### Not designed to address  

### Loss to f ollow - up  

### Non - differential by ex posure group (4)  

### Pre - cancellation clarification **47**



### address  

### Ba yley Scores  

### Expanded tw o to fo ur categories, highest category greatest risk 

### clarification  

### Exposure lev el decline  

### Conf ounding analysis  

### Diazinon , propo xur