Prenatal serum thallium exposure and 36-month-old children's attention-deficit/hyperactivity disorder symptoms: Ma'anshan birth cohort study

Abstract Thallium (Tl) is a highly toxic heavy metal that has been suggested to be responsible for oxidative stress and mitochondrial dysfunction. However, few studies have focused on the relationship of prenatal Tl exposure with children's neurobehavioural development. The purpose of our study was to investigate the association between prenatal Tl exposure and attention-deficit/hyperactivity disorder (ADHD) symptoms in 36-month-old children. We used data from 2851 mother-newborn pairs from the Ma'anshan Birth Cohort Study (MABC); serum Tl concentration was assessed in the first, second and third trimesters of pregnancy as well as in the umbilical cord blood. We assessed ADHD symptoms in the children using the Chinese version of the Conners abbreviated symptom questionnaire (C-ASQ). The adjusted odds ratio (OR) for the risk of ADHD symptoms was 2.00 [95% confidence interval (CI): 1.20, 3.32] and 2.08 (95% CI: 1.26, 3.43) for the third (60.25–75.21 ng/L) and fourth quartiles of serum Tl (>75.21 ng/L), respectively, in the second trimester of pregnancy, in comparison with the first quartile of serum Tl (