Acetylcholinesterase Activity and Pesticide Exposure

Much of our work is focused on the role of acetylcholinesterase (AChE) activity in children.  AChE activity is a stable marker of cholinesterase inhibitor pesticide exposure. Our findings first showed that children living with a floricultural worker had statistically significant lower AChE activity compared to children who did not live with agricultural workers. Comparing the AChE activity of children in the lowest 15th percentile with that of children in the upper 33rd percentile we found an OR of 3.39 (95% CI: 1.19, 9.64) (Suarez-Lopez, 2012). This suggests that floricultural workers may introduce into their homes sufficient amounts of cholinesterase inhibitor pesticides to affect AChE activity. We also considered the relationship of AChE activity to both the temporal proximity to the flower harvest and physical proximity to flower plantations. There was a linear association with each of these factors and a significant interaction between time after harvest and proximity to flower plantations with the strongest association among children who lived within 233 m of flower plantations (Beta=0.15; CI [0.02, 0.28]), slightly attenuated for those who lived between 234-532 m from a plantation (Beta=0.11; CI [0.00, 0.23]), and not significantly related for children living more than 532 m from a plantation (Beta=-0.04; CI (-0.09, 0.01]). (Suarez-Lopez et al. 2017b) Thus cohabitation with a flower plantation worker, living closer to flower plantations, and temporal proximity to high pesticide spray seasons all result in lower AChE activity, indicating greater exposure to pesticides.

Physiological Impacts of Pesticide Exposure

We have shown that pesticide exposure has physiological impacts on children in the cohort. We have found that a 1-U/mL decrease in AChE activity was associated with a 2.86-mmHg decrease in systolic blood pressure (95% CI: –5.20, –0.53) and a 2.89-mmHg decrease in diastolic blood pressure (95% CI: –5.00, –0.78), after adjustment for potential confounders (Suarez-Lopez et al., 2013b). However, we also found that both physical proximity of a child’s residence to flower plantations (0.24 SD per 1000 m; CI [0.01,0.47]), and greater area of flower plantations within 150 m of a child’s residence (0.03 SD per 1000 m2; CI [0.00,0.06]) were associated with an increase in SBP after multivariate adjustment. (Suarez-Lopez 2018) And that children examined closer to the heightened pesticide spray period had higher blood pressure such that for every 10.9 days closer to the harvest the OR of hypertension or elevated blood pressure doubled (OR=2.0, CI [1.3,3.1]). (Suarez-Lopes 2019a) There are clear physiologic changes in children who have experienced greater exposure to pesticides than those with lesser exposure.

Neurobehavior and Pesticide Exposure

In addition, we have shown impacts of pesticide exposure on neurobehavior. AChE activity was associated with lower neurobehavioral development in the domains of attention, inhibitory control, and memory among boys but not girls in fully adjusted multi-variate models (Suarez-Lopez et al., 2013a). This suggests that non-occupational pesticide exposures may affect critical cognitive skills, which may negatively impact learning and academic performance among boys. However, both boys and girls examined soon after the flower harvest had lower neurobehavioral performance (in the domains of Attention/Inhibitory Control, Visuospatial Processing and Sensorimotor) compared to the children examined later (Suarez-Lopez et al., 2017b). This suggests that a peak pesticide use period may temporarily affect neurobehavioral performance of children. In addition, our findings indicate an inverse relationship between residential proximity to flower plantations and neurobehavioral measures in the domains of Memory/Learning and Language. For every 100 m that a residence was closer to flower plantations there was an increased likelihood of lower scores in Memory/Learning of OR=1.24, CI (1.05, 1.46), and Language OR=1.09, CI (1.00, 1.19). Suarez-Lopez 2019c

Mental Health and Pesticide Exposure

More recently we have been focusing on the relationship between pesticide exposures and mental health among children. In children aged 11-17 we found that lower AChE activity was associated with increased symptoms of depression and that the association was stronger for girls than boys (Betas=1.61, and 0.69, respectively), and for children below the median age of 14.38 years than those above the median (Betas 1.61, and 0.57, respectively). These factors were synergistic such that the associations of younger girls were Beta=3.30, OR [0.54,6.05] and the OR for elevated symptoms per SD decrease in AChE for these children was 2.58 [1.26, 5.27]. (Suarez-Lopez 2019b) We also compared the relationship between the change in AChE activity between two timepoints in 2016 with hormonal markers and depression and anxiety scales at the second timepoint. We found that for every 10% decrease in AChE activity there was a corresponding increase of 0.96 units for depression symptoms (CI 0.1, 1.9) and an OR of 1.67 (CI 1.04, 2.66) for depression score. Again, these associations were stronger for girls than boys (OR 2.72 [1.23, 6.00], 1.18, [0.59, 2.37]) respectively.