Evaluation of Prenatal Pyrethroid Insecticide Exposure, Fetal Growth, and Neurodevelopmental Outcomes in a Thai Agricultural Birth Pilot Cohort Public
Adefris, Zelalem (2016)
Abstract
Recent research suggests that prenatal exposures to pyrethroid insecticides during critical periods of development may impair infant development both physically and neurologically. The present study aimed to assess the relationship between prenatal pyrethroid insecticide exposure, fetal growth outcomes, and neurologic integrity at birth. Neurobehavioral function was measured using seven clusters of the Brazelton Neonatal Behavioral Assessment Scale (BNBAS): Habituation, Orientation, Motor, Range of State, Regulation of State, Autonomic Stability, and Abnormal Reflex. Trimester-resolved concentrations of urinary 3-phenoxybenzoic acid (3-PBA) metabolites of pyrethroid insecticides were measured in order to assess exposures to the fetuses. Our study participants were part of the pilot birth cohort, the Study of Asian Women And their offSpring's Development and Environmental Exposures (SAWASDEE), which is comprised of tangerine farmworkers in Northern Thailand and their newborns. Maternal urinary pyrethoid concentrations in the SAWASDEE cohort are lower than concentrations in comparable birth cohorts. In addition, the pyrethroid levels are fairly homogenous with little variation across the samples suggestive of a continual or continuous exposure, most likely from widespread public health applications to control dengue. We observed no statistically significant associations for 3-PBA, fetal growth outcomes, and the BNBAS domains. Total pregnancy ΣDAP and second trimester mercury were significantly associated with orientation performance (ß=-0.007, p=0.002 and ß=-1.774, p=0.020, respectively). Third trimester ΣDAP was significantly associated with habituation performance (ß=-0.002, p=0.009) and second trimester mercury and cadmium were associated with motor performance (ß=-1.316, p=0.005 and ß=-3.137, p=0.004, respectively). These results suggest that SAWASDEE cohort participants likely have public health pyrethroid exposures that dominate any occupational exposures to pyrethroids. The lower 3-PBA levels combined with higher exposures to other neurotoxicants could have obscured any true associations between pyrethroid exposures and neurobehavioral or fetal growth effects. This study is the first to examine the impact of trimester-specific exposure to pyrethroid insecticides on neurodevelopment and fetal growth at birth.
Table of Contents
I. BACKGROUND & SIGNIFICANCE..........................................................1
Pyrethroid Insecticides...........................................................................1
Prenatal Exposure..................................................................................2
3-Phenoxybenzoic Acid..........................................................................4
Dialkyl Phosphate Metabolites & Heavy Metals........................................4
SAWASDEE Birth Cohort.........................................................................6
Brazelton Neonatal Behavioral Assessment Scale.....................................6
II. METHODS.........................................................................................7
Participants and Recruitment..................................................................7
Questionnaire and Medical Record Abstraction Data.................................8
Exposure Assessment.............................................................................8
Neurodevelopmental Outcomes Assessment...........................................10
Aims and Hypotheses............................................................................11
Data Analysis.......................................................................................12
III. RESULTS.........................................................................................13
Demographic Data................................................................................13
Exposure Distribution...........................................................................14
Outcome Distribution............................................................................15
Linear Regression Analysis.....................................................................15
Poisson Regression Analysis...................................................................18
IV. DISCUSSION....................................................................................18
Interpretation of Results........................................................................18
Limitations...........................................................................................22
V. CONCLUSION...................................................................................23
Summary..............................................................................................23
Recommendations for Future Research...................................................23
Policy Recommendations.......................................................................24
VI. REFERENCES...................................................................................26
VII. TABLES AND FIGURES....................................................................30
VIII. APPENDIX....................................................................................38
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