Background. Lead is a major environmental pollutant for children which, event at low doses, may have a number of adverse effects, the most important of which are those that affect intellectual development. A study has been made of the intellectual impact of this element on school children in the Community of Madrid, where the lead levels detected are very low.

Methods. Five hundred fifteen children attending 23 schools randomly selected in Madrid and its metropolitan area were transported by class groups to a hospital for a general health exam including blood sampling. The parents completed a brief self administered questionnaire on environmental and sociodemographic factors. Teachers completed an 8-item questionnaire concerning the behavior and academic achievement of the children, based on the Abbreviated Version of the Boston Teacher Rating Scores. Blood lead levels were analyzed by atomic absorption spectrophotometry.

Results. The geometric mean blood lead was 38.5 μg/l (95% CI 17.7-83.6); 12 children were under the detection limits (15 μg/l), and 4 were ≥ 100 μg/l (max. 115 μg/l), the CDC limit. All the teachers' scores were inversely related to the lead levels, and significant relationships were observed with respect to remaining seated, reading comprehension, writing ability and math skills. The same findings are observed when factors such as the father's level of education are considered.

Conclusions. Children in the Community of Madrid have very low lead levels which, however, appear to have adverse effects on their intellectual development. These results suggest that the CDC limits may be too high, and that the safety threshold for lead may be the “zero” level.