The 84 of blood samples comprise 57 children (68%) with age of 0-15years and 27 adults (32%) with age of >15 years. In children, the samples with Pbblood level <25 μg/dL make up 35.1% of all children samples while those >25 μg/L make up 44%. In adults, the blood samples with the Pb level <40 μg/L represents96.3% of all adult samples. Only 3.7% of the adult samples exhibit the blood Pb levelof >40 μg/dL. It is noted that the blood Pb level considered “normal” is <25 μg/L inchildren and <40 μg/L in adults. From these survey results, it could be concluded thathuman activities are important factors leading to Pb contamination in the upper MaeKlong watershed area. Therefore, if residential areas are located below the placewhere Pb ore layers exist, those living there are likely to take more risk in absorbingPb poisoning than those in the area without Pb ore. The results indicate that thehighest contamination is found in sediments, particularly in the mining areas. A highlevel of Pb is also identified in aquatic animals, namely mollusk, a kind of commonfood for people in the area of study. Taken from the area free from mining activities,the Pb level in the environmental samples is within the standard level. In theenvironmental samples collected in the vicinity of where mining activities exist, thePb level is always high.