Purpose

Mother's Day (May) is a holiday with substantial demand for flowers, associated with heightened flower production and escalated pesticide use. The effect of spray seasons on pesticide exposures of children living in agricultural communities but who do not work in agriculture is poorly understood. In this study, we estimated the association of time after Mother's Day harvest with children's acetylcholinesterase (AChE) activity. AChE is a physiological marker of organophosphate/carbamate pesticide exposures that may take up to 3 months to normalize after its inhibition.

Methods

We examined 308 children, aged 4-9 years, in Ecuadorian agricultural communities during a low flower-production season but within 63-100 days (mean: 81.5 days, SD: 10.9) after Mother's Day harvest. We quantified AChE activity (mean: 3.14 U/mL, SD: 0.49) from a single finger-stick sample.

Results

We observed positive linear associations between time after the harvest and AChE among participants living near plantations. The associations were strongest among participants living within 233 m [(0.15 U/mL (95% CI 0.02, 0.28)], slightly weaker among participants living within 234-532 m [0.11 U/mL (0.00, 0.23)], and not associated among participants at greater distances. Similar findings were observed across categories of areas of flower plantations within 500 m of homes.

Conclusions

These cross-sectional findings suggest that a peak pesticide-use period can decrease AChE activity of children living near plantations. These seasonal pesticide exposures could induce short- and long-term developmental alterations in children. Studies assessing exposures at multiple times in relation to pesticide spray seasons among children who do not work in agriculture are needed.

The healthy human brain is a mosaic of varied genomes. Long interspersed element-1 (LINE-1 or L1) retrotransposition is known to create mosaicism by inserting L1 sequences into new locations of somatic cell genomes. Using a machine learning-based, single-cell sequencing approach, we discovered that somatic L1-associated variants (SLAVs) are composed of two classes: L1 retrotransposition insertions and retrotransposition-independent L1-associated variants. We demonstrate that a subset of SLAVs comprises somatic deletions generated by L1 endonuclease cutting activity. Retrotransposition-independent rearrangements in inherited L1s resulted in the deletion of proximal genomic regions. These rearrangements were resolved by microhomology-mediated repair, which suggests that L1-associated genomic regions are hotspots for somatic copy number variants in the brain and therefore a heritable genetic contributor to somatic mosaicism. We demonstrate that SLAVs are present in crucial neural genes, such as DLG2 (also called PSD93), and affect 44-63% of cells of the cells in the healthy brain.