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Lead Levels and Educational Achievement

There have been continued debates about the extent to which lead exposures at subclinical levels may have small but detectable effects on longer term cognitive ability and educational achievement. A Christchurch study has now produced evidence of a a direct association between the two.

The issue was examined in a 10-year longitudinal study of the relationships between dentine lead levels at age eight and educational outcomes at age 18. This study was based on a cohort of over 1,000 Christchurch-born children studied as part of the Christchurch Health and Development Study.

Children with mildly elevated (12 ppm) dentine lead levels at age 8 showed signs of educational delays at age 18. These children more often had reading delays as young adults, left school without educational qualifications and had lower rates of success in School Certificate examinations. These relationships between early dentine lead levels and later academic achievement persisted when the relationships between early lead levels and later academic outcomes were corrected for a series of social and childhood factors that were related to elevated dentine lead values.

"These results are clearly consistent with the view that there may be a cause and effect association between early lead levels and later educational success," the study concluded.

It was also noted that these findings showed close parallels with recent US research that has suggested that, at relatively low levels, lead may have small but detectable effects on levels of educational achievement. In general, the study provides empirical support for recent moves to reduce childhood lead exposures, including the introduction of lead-free petrol.

"Whilst the effects of lead on cognitive development appear to be relatively small, it can nonetheless be argued that, to the extent that lead appears to make a unique contribution to cognitive variability, it is important that all reasonable steps are taken to minimise this source of risk to children. The significance of the present study is that it shows that the harmful effects of early lead exposure are not short-lived and extend into young adulthood, having impacts on later educational achievement and life opportunities".

Professor David Fergusson, Christchurch Medical School