Exploring the effect of organophosphate (OP) pesticide exposure on the development of the autonomic stress response in the children of agricultural workers
Date
2023-05
Authors
Barnett, Neil Patrick
Major Professor
Advisor
Greder, Kimberly A
Willette, Auriel A
Gilligan, Megan
Franke, Warren D
Martin, Peter
Committee Member
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Abstract
Background: Exposure to organophosphate (OP) pesticides has been shown to cause a variety of adverse developmental changes in children via changes in the production of the enzyme acetylcholinesterase (AChE), an enzyme that plays a major role in the functioning of the autonomic nervous system (ANS). The ANS is associated with a variety of health outcomes due to its role in stress reactivity, in which its component systems (the sympathetic and parasympathetic nervous systems) calibrate internal arousal states in response to stress.
Objective: To examine whether OP pesticide exposure among children and adolescents at different developmental stages affects the ANS response pattern, I investigated whether the effects of OP pesticide exposure affected autonomic reactivity to the Trier Social Stress Task (TSST) during different age ranges. This study used data from the CHAMACOS cohort, a longitudinal study of children of agricultural (farm) laborers who experience high levels of exposure to OP pesticides.
Methods: Autonomic reactivity was assessed through the administration of a modified version of the TSST at age 14. The TSST comprises: 1) a seated baseline, 2) a standing baseline, 3) a standing pre-stressor preparation period, 4) a standing speech task, 5) a standing math task, and 6) a seated debrief. Outcomes included heart rate (HR), respiratory sinus arrhythmia (RSA), and pre-ejection period (PEP). OP pesticide exposure was defined as the amount of pesticides being used within 1 km of the child’s residence (measured in kg/year) at prenatal, childhood (birth-5 years), and adolescence (12-14 years).
Results: Significant results were found for RSA during the preparation period for both the prenatal (β=-0.14, p=0.034) and adolescent (β=-0.17, p=0.039) period. Higher levels of exposure were associated with lower RSA (i.e., stronger parasympathetic withdrawal). A similar effect for PEP was found during the speech task (B=-1.05, p=0.053). Higher levels of exposure were associated with lower PEP (i.e., stronger sympathetic activation). No significant effects were found of OP pesticide exposure on HR.
Conclusion: OP pesticide exposure was shown to adversely impact the autonomic stress response. However, these impacts varied between branches in both the timing of the exposure as well as the segments of the TSST affected. Overall, these findings indicate that OP pesticide exposure had adverse developmental effects. Higher levels of prenatal and childhood OP pesticide exposure were associated with a more pronounced stress response to anticipatory stress and social evaluative threat.
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dissertation