Objective Acetylcholinesterase (AChE) is an enzyme that metabolizes acetylcholine, an essential neurotransmitter, and is frequently used to monitor adult agricultural workers for exposure to cholinesterase inhibitor pesticides. Yet, there are no clear standards for AChE activity in children and adolescents, which prohibits evaluations of dangerous pesticide exposures in younger populations. Methods We measured AChE activity from a single finger stick blood sample data from 746 participants ages 4 to 26 years across 3,100 observations who resided in an agricultural county in Ecuador. We used generalized estimating equations to predict AChE activity levels in one year age increments from 5 to 25 years, accounting for nonlinear aging patterns and survey wave specific effects. We also decomposed variation in observed AChE activity levels into aging effects, differences in our recruited participants, and participant-specific aging patterns. Results Average AChE activity levels across all observations were 3.88 U/mL (standard deviation [sd] = 0.67). AChE activity levels increased nonlinearly as participants aged. We found that males had higher AChE activity levels than females and that those levels established themselves later in age than females. AChE activity levels increased essentially linearly from ages 5 to 12 or 18 years, depending on sex, at which point levels did not meaningfully change with age. Most variation observed in AChE activity levels were due to aging effects. Conclusion Our findings provide reference levels for AChE activity across childhood, adolescence, and into early adulthood that can be used by clinicians and researchers in the context of assessing neurodevelopment and potential exposure to neurotoxicants.

The authors have declared no competing interest.

The ESPINA study received funding from the National Institute of Environmental Health Sciences (R01ES030378, R01ES025792, R21ES026084, CHEAR project 2018-1599, U2CES026533, U2CES026560). Mr. Vashishtha was supported by NIH grant 1TL1TR001443.

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

. The institutional review boards at the University of California San Diego (USA), University of Minnesota (USA), Universidad San Francisco de Quito (Ecuador), UTE University (Ecuador) and the Ministry of Public Health of Ecuador approved this study. Additionally, the Commonwealth of Rural Parishes of Pedro Moncayo County endorsed this project and access to schools was approved by the Ministry of Education.

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