*2.1. Study Design*

The present study was in compliance with ethical standards. The Office of the Human Research Ethics Committee of Walailak University approved the study protocol (approval number 58/099, approval date 24 December 2015). The study was a community-based cross-sectional design that was undertaken from January 2016 to December 2018. Children, aged 3 to 7 years, were randomly chosen from the communities in Pakpoon suburb, where traditional wooden boat repairs were commonly practiced. The Taro Yamane equation was used to calculate the sample size, with a 5% level of significance and with a confidence coefficient of 95% [18]. The parents or guardians of all children provided written informed consent. We used structured interview questionnaires for information concerning a child's age, gender, birth weight, body weight, and height, together with children's behaviors including duration of outdoor play, home and school environment, diet, and health status.

#### *2.2. Collection and Analysis of Blood Samples*

The collection of children's blood samples was performed by trained nurses. Approximately 3 ml of venous blood was collected from each child with ethylene diamine tetra-acetic acid as an anticoagulant. In preventing contamination during storage and transport, blood samples were stored at −20 ◦C in a sealed compartment. Blood samples were transported to Bangkok RIA Laboratory, Thailand for an assay for blood Pb levels with graphite furnace atomic absorption spectrophotometry. The limit of detection is 0.03 μg/dL.

#### *2.3. Assessment of Child Growth*

To assess growth of individual children, we used the standard weight for height curves for Thai children, prescribed by Thailand Ministry of Public Health [19]. Abnormal growth is defined as underweight or overweight using weight for height standards in accordance the Thai criteria; > +1.5 SD to > +3 SD (overweight), −1.5 SD to +1.5 SD (normal), < −1.5 SD to < −2 SD (underweight).
