Lead Exposure and Children's Intellectual Performance

Abstract

The Institute of Child Health/Southampton study is the largest cross-sectional survey of lead exposure and children's intelligence. 402 six year olds in London with tooth lead concentration in three pre-defined ranges were selected for neuropsychological testing. This paper presents new findings on the relationship between child IQ and tooth lead levels which build on previous findings in four respects: Rather than simply classifying children into high, medium and low lead groups the actual concentrations of lead in each child's tooth have been used to provide a more powerful assessment of the association between IQ and body lead burden. The influence of parental and social factors on child IQ is explored in detail in order to see if any residual lead-IQ association exists after allowance for such confounders. The methods of multiple regression, including an 'optimal' statistical policy, are more fully described. The possibility of interactions between lead and confounders is explored. Findings are that parental IQ is the most important influence on child IQ, though several other factors (eg: family size, social class and quality of marital relationships) were also significantly related. There was no overall evidence that tooth lead concentrations were related to child IQ once these other factors were taken into account. However, a significant interaction between tooth lead and sex of child indicates that the lead-IQ association appears much more pronounced in boys. This unexpected finding needs cautious interpretation and further exploration in other studies.

The Health Effects of Low Level Exposure to Lead

“…With the adjustment for covariates, the effect size was diminished, although a consistent decrease in performance related to tooth lead was reported. Pocock et al (74) reanalyzed the Smith study. They used regression techniques and measured the interaction between lead and gender.…”

Characterizing Golden Eagle Risk to Lead and Anticoagulant Rodenticide Exposure: A Review

“…Other studies of lead dentin and intellectual functions support Needleman's findings in that deficits have not been found below lead dentin concentrations of approximately 10 ppm (Damm et al 1993;Pocock et al 1987). The association between bone lead and intellectual function also has been studied.…”

Chronic Lead Exposure in Children Living in Miskolc, Hungary, on the Basis of Teeth Lead Levels

“…It can be stated that the children living in Miskolc have been exposed with medium lead concentrations in the last 16 years. This exposure is the same as the exposure of children living in Boston (Rabinowitz et al 1991), in London (Pocock et al 1987), or in Ankara (Karakaya et al 1996).…”