Prenatal Organochlorine Exposure and Neurobehavioral Performance ina Thai Agricultural Birth Cohort Open Access

Horne, Ashley Anna (2017)

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Background: DDE is a metabolite of DDT, an organochlorine pesticide associated with acute and long term health effects which is restricted in some countries and still in use in others. DDE can persist in the environment decades after use has stopped, and can travel via wind and water. As a result, use in one geographical area can affect a population and environment in other places with restricted or prohibited use. Exposure of pregnant women to organochlorine pesticides is of particular concern, since the developing fetus is known to be more susceptible to harmful effects of toxic chemicals than the general population. Our study aims to fill the current gap in literature which examines prenatal exposure to DDT and its metabolites using repeated measures of exposure with respect to the effects on newborn neurobehavioral development. Methods: We conducted a data analysis of de-identified pilot cohort data using multiple linear regression to evaluate the effect of DDE exposure during individual trimesters of pregnancy and overall on newborn neurological development using the Neonatal Behavioral Assessment Scale (NBAS) among 52 Thai agriculture workers. Results: In our study of an agricultural based cohort of Thai women recruited during the first trimester, we determined prenatal exposure to DDE has an effect on NBAS performance in the motor and regulation of state assessment clusters. Using multiple linear regression, we observed a significant association between decreased regulation of state average score and increased DDE exposure at all collection points during the study, where the most significant exposure was during the first trimester (p= 0.003, r2=0.295). These results agree with current research which suggests a key period of susceptibility to pesticide toxicity in the first trimester of pregnancy. No associations between the models with the motor cluster average score as the outcome were significant. Conclusions: There is evidence that prenatal exposure to DDE negatively affects neurobehavioral activity in neonates. Additional research is needed on a larger sample size in order to accommodate some of the limitations of the current study, and provide more power for adding additional covariates of interest to the initial full model.

Table of Contents

1 Introduction 1

1.1 Organochlorine (OC) Pesticide Use: Background and Toxicity 1

1.2 Prenatal DDE Exposure and Neurobehavioral Development 3

1.2. a DDE and NBAS 4

1.2. b DDE and other behavioral measures during infancy 5

1.2. c DDE in later childhood development 6

1.3 Neonatal Behavioral Assessment Scale (NBAS) 6

1.4 SAWASDEE Pilot Birth Cohort 8

2 Materials and Methods 10

2.1 Research Goals and Hypotheses 10

2.2 Study Participants: SAWASDEE Pilot Cohort, Thailand 10

2.3 Demographic Data Collection 12

2.4 Exposure Assessment: DDE in Maternal and Cord Blood 12

2.5 Outcome Assessment: NBAS Performance 13

2.6 Statistical Analysis 14

3 Results 15 3.1 Demographic Characteristics 16

3.2 Exposure Distribution 16

3.3 Outcome Distribution 17

3.4 Linear Regression Models 18

4 Discussion and Study Limitations 19

5 Conclusions and Future Directions 22

6 References 24 Tables and Figures 34

Table 1: Pilot Birth Cohort Characteristics (n=52) 34

Table 2 : Summary Statistics for Organochloride Concentration in Blood (Crude), Plasma ng/mL 36

Table 3: Summary Statistics for Organochloride Concentration in Blood (Log 10 Transformed), Plasma ng/mL 33

Table 4: Summary Statistics for NBAS Outcomes 36

Table 5: Linear Regression Results: Final Model 37

Table 6: Motor Cluster Models with Partial Correlation Coefficients 38

Table 7: Regulation of State Models with Partial Correlation Coefficients 39

Figures 40 Figure 1: Breakdown of DDT to DDE and DDD metabolites (59) 41

Figure 2: 12 Initial Persistent Organic Pollutants include in the Stockholm Convention (2004) (60) 42

Figure 3 Brazleton Scoring Clusters (39) 43

Figure 4 inclusion criteria for analysis 44

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