Dentine Lead and Child Intelligence in Taiwan

Abstract

It is well known that lead is a developmental neurotoxin, but, because many factors influence a child's development, a safe level of lead for children is still not clear. In this study, personal lead exposure was assessed. A total of 940 deciduous teeth--mostly incisors--was collected from 764 children in grades 1-3 who attended 7 primary schools. Two of the primary schools were near smelters, 4 were in Taipei City, and 1 was located in a coastal village. Teachers were provided with a questionnaire about classroom performance, and 97% completed and returned the questionnaire to the laboratory. Parents were given a questionnaire about family background, pregnancy, and health history (92% returned). Dentine lead levels of shed incisors for children in Taipei City were higher than levels reported in Boston, i.e., mean (standard deviation) of 4.4 (3.5) versus 3.3 (2.5) micrograms/g, respectively (p less than .001). The lead values were significantly higher in children who attended school near a smelter than in children who attended school in Taipei City: 6.3 (3.3) (p less than .001). The mean lead levels in children who attended school in a coastal village was 5.1 (2.8). The ranges for all schools overlapped, which indicated that there were multiple lead sources. Intelligence scores from Raven's Colored Progressive Matrices Test were negatively correlated with lead levels, especially among girls and among children whose parents had less education. We adjusted for other risk factors--most notably parental education, which correlates inversely with lead levels--and found that the role of the lead term was lowered but not eliminated.