The relationship between blood lead concentrations, intelligence and attainment in a school population: a pilot study

One-hundred-and-sixty-six children whose blood lead levels had previously been determined were assessed on a battery of psychometric tests. Blood lead levels ranged from 7 to 33 micrograms/100 ml, and the group performed within the average range on all tests of attainment and intelligence. There were significant associations between blood lead levels and attainment scores on tests of reading, spelling and intelligence, but not on mathematics. These differences in performances largely remained after social class was partialled out. Partial correlation and multiple regression analyses suggest that while only a small proportion of the variance in intelligence is explained by blood lead levels, this relationship is independent of social class. Caution is necessary in interpreting these findings, in view of the crude measure of social factors available.