Research objects - Children aged of 3 to 14 years old, living in Tan Long commune, Đong Hy district, Thai Nguyen province and Ban Thi commune, Cho Don district, Bac Kan province Inclusion criteria: Do not suffer from serious diseases such as cerebral palsy, disability... Parents or caregivers directly agree to participate in the study (sign consent form) - Parents or caregivers directly Inclusion criteria: Having children aged of 3 to 14 years old chosen into study Be caregivers directly the children everyday Agree participate to study - Environment samples: soil, drinking water and air samples where the children live in to evaluate the lead contamination risk 6 2.1.2.