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Background: Off-target drift of pesticides from farms increases the risk of pesticide exposure of people living nearby. Cholinesterase inhibitors (i.e. organophosphates and carbamates) are frequently used in agriculture and inhibit the enzymatic activity of acetylcholinesterase (AChE). Greenhouse agriculture is an important production method, but it is unknown how far pesticide drift from greenhouses can extend and expose people living nearby.
Methods: This study included 1145 observations from 3 exams (2008, Apr 2016 and Jul-Oct 2016) of 622 children aged 4-to-17 years living in agricultural communities in Ecuador. AChE and hemoglobin were measured from fingerstick blood samples. Geographic positioning of greenhouses and homes were obtained using GPS receivers and satellite imagery. Distances between homes and the nearest greenhouse edge, and areas of greenhouse crops within various buffer zones around homes were calculated. Repeated-measures regression adjusted for hemoglobin and other covariates estimated change in AChE relative to distance from greenhouses.
Results: The pooled mean (SD) of AChE activity was 3.58 U/mL (0.60). The median (25^th-75^th %tile) residential distance to crops was 334 m (123, 648) and crop area within 500 m of homes (non-zero values only) was 18,482 m² (7115, 61,841). Residential proximity to greenhouse crops was associated with lower AChE activity among children living within 275m of crops (AChE difference per 100m of proximity [95% CI]= -0.07 U/mL [-0.14, -0.002]). Lower AChE activity was associated with greater crop area within 500m of homes (AChE difference per 1000m² [95% CI]= -0.02 U/mL [-0.029, -0.010]) and especially within 150m (-0.026 U/mL [-0.046, -0.006]).
Conclusions: Residential proximity to floricultural greenhouses, especially within 275m, was associated with lower AChE activity among children, reflecting greater cholinesterase inhibitor exposure from pesticide drift. Analyses of residential proximity and crop areas near homes yielded complementary findings. Mitigation of off-target drift of pesticides from crops onto nearby homes is recommended.