Organophosphates (OPPs),
pyrethroids (PYRs), and
neonicotinoids (NNIs) are three major classes of
insecticides used worldwide. They might compromise child neurodevelopment. However, few studies have explored the association between exposure to them and
dyslexia. The present study aimed to investigate the association between
dyslexia and exposure to the three classes of
insecticides, as well as explore the potential role of oxidative stress in the association. A total of 355 dyslexic children and 390 controls were included in this study. The exposure
biomarkers were determined by liquid chromatography-tandem mass spectrometry. Specifically, the exposure
biomarkers included three typical metabolites of OPPs, three of PYRs, and nine of NNIs. Additionally, three typical oxidative stress
biomarkers, namely,
8-hydroxy-2'-deoxyguanosine (8-OHdG) for DNA damage,
8-hydroxyguanosine (8-OHG) for
RNA damage, and 4-hydroxy-2-nonenal-mercapturic
acid (HNEMA) for lipid peroxidation were measured. The detection frequencies of the urinary
biomarkers ranged from 83.9% to 100%. Among the target metabolites of the
insecticides, a significant association was observed between urinary
3,5,6-trichloro-2-pyridinol (TCPy, the metabolite of
chlorpyrifos, an
OPP insecticide) and
dyslexia. After adjusting for potential confounding variables, children in the highest quartile of TCPy levels had an increased odds of
dyslexia (odds ratio [OR], 1.68; 95% confidence interval [CI]: 1.03, 2.75] in comparison to those in the lowest quartile. Among the three oxidative stress
biomarkers, urinary HNEMA concentration showed a significant relationship with
dyslexia. Children in the highest quartile of HNEMA levels demonstrated an increased dyslexic odds in comparison to those in the lowest quartile after multiple adjustments (OR, 1.64; 95% CI: 1.01, 2.65). Mediation analysis indicated a significant effect of HNEMA in the association between urinary TCPy and
dyslexia, with an estimate of 17.2% (P < 0.01). In conclusion, this study suggested the association between urinary TCPy and
dyslexia. The association could be attributed to lipid peroxidation partially.