Shamsul: We found that the blood lead collected from children at 5- or 6-years of age was more strongly associated with cognitive and behavioral development in children than was BPb measured in early childhood (Hornung, 2009). This was consistent with a brain imaging study we did in 23-year old participants who had been studied since birth (Brubaker, 2009). In another stiudy of younger children (i.e., 4 year olds), the 2 year blood lead levels were more strongly associated with cognitive outcomes. Cheers, Bruce

Shamsul: We found that the blood lead collected from children at 5- or 6-years of age was more strongly associated with cognitive and behavioral development in children than was BPb measured in early childhood (Hornung, 2009). This was consistent with a brain imaging study we did in 23-year old participants who had been studied since birth (Brubaker, 2009). In another stiudy of younger children (i.e., 4 year olds), the 2 year blood lead levels were more strongly associated with cognitive outcomes. Cheers, Bruce

 Dear Shamsul Bahari Shamsudin

        Most of literatures emphasized that there may be no threshold for developmental effects on children,  However, lack of overt symptoms does not mean “no lead poisoning, Lower levels of exposure have been shown to have many subtle health effects (Needleman 2002, Nevin 2000).

There may be no lower threshold for some of the adverse neurological effects of lead in children.

        Neurological effects of lead in children have been documented at exposure levels once thought to cause no harmful effects (

 I'd like to  refer you to my paper  on Lead abd Childhood  which presents some relevant data for answering your question (see the full text in the "contributions" of my RG profile)