Effects of children exposure to pyrethroid pesticides during infancy and toddlerhood on their ADHD symptoms at preschool age: A prospective study in Southwestern China.

Background: Wide exposure to pyrethroid pesticides (PYRs) during infancy and toddlerhood may be associated with ADHD symptoms at preschool age.

Methods: A total of 292 mother-child pairs participated in our study, we collected urine samples from children's aged 1, 2, and 3 and measured the concentrations of PYRs metabolites, including 3-phenoxybenzoic acid(3PBA), 4-fluro-3-phenoxybenzoic acid (4F3PBA), and 3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane carboxylic acid (DBCA). Children ADHD symptoms were assessed using the Conners Parents Symptom Questionnaire (PSQ) at preschool age. Poisson regression models with robust effort variance were used to estimate the effects of the single metabolite, the total amount of three PYRs metabolites (ΣPYRs) on ADHD symptoms.

Results: PYRs metabolites detection rate was >97 % at ages 1-3. ADHD symptoms prevalence was 15.14 %, with 20.55 % in boys and 10.27 % in girls (χ=5.911, P = 0.015). After adjustment for covariates, 4F3PBA concentrations at age 2 and ΣPYRs at age 1 was positively associated with preschool ADHD symptoms in all children (RR 1.06 [95 % CI=1.02-1.10]; 1.02 [1.01-1.03]) in multi-exposure models. In boys, 3PBA at age 1(1.07, [1.01-1.14]) and 4F3PBA at age 2(1.05, [1.00-1.09]) was positively linked to ADHD symptoms. While in girls, DBCA at age 1 (1.30, [1.05-1.59]), 4F3PBA at age 2 (1.10, [1.01-1.21]), and ΣPYRs at age 1 (1.02, [1.00-1.03]) were positively associated with ADHD symptoms.

Conclusions: Children are widely exposed to PYRs in rural areas of Yunnan, with exposure levels increasing with age. The prevalence of ADHD symptoms in preschool children is moderate, with a higher rate found in boys. As the concentrations of PYR metabolites increase, the risk of ADHD symptoms also rises. The effects of different types of PYRs on ADHD symptoms may vary by exposure duration and sex, with type II PYRs posing a greater risk than type I PYRs. Ages 1 and 2 may represent sensitive windows for PYR exposure influencing ADHD symptoms.