Association of Prenatal Chlorpyrifos Exposure and Birth Weight in a Thai Birth Cohort Study Public

Abstract

Intro: Organophosphate (OP) pesticides are among the most commonly used insecticides worldwide. Though exposure is ubiquitous, developing fetuses and young children are known to be particularly vulnerable to toxic environmental exposures, with the potential for lifelong health consequences. Previous studies have identified agricultural regions in northern Thailand as particularly high risk for OP exposure. Accordingly, the Study of Asian Women and their Offspring’s Development and Environmental Exposures (SAWASDEE) was established in 2017 in the Chiang Mai province of northern Thailand, with the aim to evaluate prenatal insecticide exposures in relation to both birth outcomes and neurodevelopment in children. Using this dataset, this study specifically focuses on the association between maternal levels of TCPy (a urinary metabolite specific for the OP pesticide chlorpyriphos) and the primary outcome of birth weight, while evaluating the role of paroxonase 1 (PON1) phenotype as an effect modifier.

 

Methods: Participants were recruited between July 2017 and June 2019 in the Fang and Chom Thong districts of Chiang Mai province, Thailand. Women who met inclusion criteria were identified during routine antenatal care visits at hospitals or local health clinics, and 394 participants were ultimately enrolled (334 completed the study). Data collected included maternal questionnaire data, trimester-specific serum/urine analysis, and birth outcome measurements. Data analysis was conducted using SAS studio, using linear regression techniques to create trimester-specific and summary models describing the exposure-outcome relationship. Variable selection for the final model was determined using directed acyclic graphs (DAGs).

 

Results: Based on our DAG, several factors were identified as potential confounders between the exposure and outcome and were therefore controlled for in our linear regression models. Overall, we did not observe a statistically significant linear relationship between TCPy and birth weight.

 

Discussion: The strategy for variable selection used in this study avoids pitfalls associated with selecting variables based on statistical significance alone. While our study does not suggest a linear relationship, a non-linear relationship between TCPy and PON1 may be plausible. Further studies - perhaps evaluating a different DAG, and accounting for different covariate interactions - are needed to clarify the potential risks of chlorpyriphos exposure in this population.

 

 

 

Table of Contents

Table of Contents

 

Introduction ...............................................................................................................................1

Methods......................................................................................................................................4

Results .......................................................................................................................................8

Discussion .................................................................................................................................10

Conclusion.................................................................................................................................11

Acknowledgements.....................................................................................................................11

References.................................................................................................................................13

Appendix...................................................................................................................................19

 

About this Master's Thesis

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School	Rollins School of Public Health
Department	Environmental Health
Degree	M.P.H.
Submission	Master's Thesis
Language	English
Research Field	Environmental Health
Mot-clé	birth weight chlorpyrifos Thailand TCPy organophosphate pesticide
Committee Chair / Thesis Advisor	Dr. Dana Barr, PhD, Emory University

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