COHORT PROFILE Cohort Profile: The China Jintan Child Cohort Study

How did the study come about? Environmental toxicity, including lead exposure, is an important global health problem adversely affecting millions of children worldwide. In developing coun-tries, the prevalence of lead exposure is significantly worse.1–3 Children in China are exposed to diverse environmental pollutants.4 Although leaded gasoline was phased out in China, the prevalence of childhood lead exposure still remains very high at 20%.5 The toxic effects of lead on neurodevelopment are well known, impacting both cognitive and behavioural development.6–10 In addition, malnutrition caused by micronutrient deficiencies is still prevalent in develop-ing countries like China.11–12 Nutrition deficiency has been linked to children’s poor cognition and negative mental wellbeing.13–15 Furthermore, youth aggression and juvenile delinquency are being increasingly viewed as a public health problem.16–17 One recent large epidemiologic study reported considerable consistency across 24 countries in adolescents ’ self-reported problems.18 Like many other developing counties, China has been undergoing major social, economic and cultural changes in the last two dec-ades. These changes have had significant implications for children’s social and psychological function-ing.19,20 It has been reported from large-scale epide-miological surveys that 10–30 % of Chinese children and adolescents experience mental health problems,21 including negative behavioural outcomes. The Jintan Cohort Project was established in the summer of 2004 to help address these concerns on lead exposure and other environmental and health-related issues. This population-based pre-school cohort study was initiated in 2004 and reflects collaboration between American scientists from th