Prenatal Chlorpyrifos Exposure and Head Circumference in the SAWASDEE Maternal Birth Cohort Open Access

Abstract

Background: Research suggests that prenatal exposure to Chlorpyrifos (CPF) is associated with adverse birth outcomes and may impair infant neurodevelopment. This thesis aimed to assess the relationship between average maternal urinary 3,5,6-trichloro-2-pyridinol (TCPy) concentrations, which are a specific metabolite of CPF, maternal paraoxonase 1 (PON1) phenotype, and infant head circumference at birth. This thesis supports ongoing research with the Study of Asian Women And their offSpring’s Development and Environmental Exposures (SAWASDEE), which is a maternal birth cohort comprised of 322 pregnant female farmworkers in Northern Thailand.

Methods: Multiple linear regression models were used to assess for associations between average TCPy concentrations throughout pregnancy, PON1 phenotype, and head circumference. Covariates were identified a priori using literature review and directed acyclic graphs. The final model covariates were PON phenotype, smoking status, location, gestational age, maternal age, maternal height, maternal BMI at enrollment, income, and infant sex.

Results: On average, head circumference at birth decreased by 0.22 cm for every 100 ng/mL change in maternal urinary TCPy, adjusting for covariates (CI95%: -4.7, 0.03; p=0.08). PON1 did not modify the association between prenatal CPF exposure and head circumference. Conclusions: These results suggest that prenatal CPF exposure is associated with head circumference at birth regardless of PON1 phenotype. This finding is of marginal significance given the limited sample size and power and warrants the need for additional research and appropriate intervention. 

Table of Contents

Table of Contents

I. Background 9

Chlorpyrifos 9

3,5,6-trichloro-2-pyridinol (TCPy) 11

PON1 12

Thailand Organophosphate Use 13

SAWASDEE Birth Cohort 14

Aims and Hypotheses 15

II. Method and Materials 16

Participants and Recruitment 16

Questionnaires and Medical Record Extraction 16

Biological Samples and Exposure Assessment 17

PON1 Enzyme Activity and Phenotyping 17

Statistical Analysis 18

Covariate Analysis 18

Aims 18

III. Results 19

Descriptive Characteristics 19

Linear Regression Analyses 20

Covariate Analysis 20

Aim 1 20

Aim 2 21

IV. Discussion 22

Interpretations 22

Strengths and Limitations 23

V. Conclusion 24

Summary 24

Future Directions 25

VI. References 27

About this Master's Thesis

Rights statement

• Permission granted by the author to include this thesis or dissertation in this repository. All rights reserved by the author. Please contact the author for information regarding the reproduction and use of this thesis or dissertation.

School	Rollins School of Public Health
Department	Environmental Health
Degree	M.P.H.
Submission	Master's Thesis
Language	English
Research Field	Biology, Molecular Health Sciences, Public Health Environmental Studies
Keyword	Head Circumference Prenatal Exposure PON1 Organophosphate Chlorpyrifos SAWASDEE Birth Outcomes
Committee Chair / Thesis Advisor	Dana Boyd Barr, PhD, Emory University

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