Low-level environmental lead exposure and intellectual impairment in children--the current concepts of risk assessment.

Lead is an environmental contaminant. The majority of epidemiological research on the health effects of lead has been focused on children, because they are more vulnerable to lead than adults. In children, an elevated blood lead (B-Pb) is associated with reduced Intelligence Quotient (IQ) score. This paper summarizes the current opinions on the assessment of the health risk connected with the children's environmental exposure to lead. The B-Pb level of concern of 100 μg/l proposed by the US Centers of Disease Control in 1991 was for a long time accepted as the guideline value. In the meantime there has been a significant worldwide decrease of B-Pb levels in children and present geometric mean values in the European countries range from 20 to 30 μg/l. The recent analyses of the association of intelligence test scores and B-Pb levels have revealed that the steepest declines in IQ occur at blood levels < 100 μg/l and that no threshold below which lead does not cause neurodevelopmental toxicity can be defended. European Food Safety Authority (EFSA) concluded in 2010, on the basis of results of Benchmark Dose (BMD) analysis, that an increase in B-Pb of 12 μg/l (BMDL₀₁) could decrease the IQ score by one point. It seems that this value can be used as a "unit risk" to calculate the possible decrease of IQ and, consequently, influence of the low-level exposure to lead (< 100 μg/l) on the health and socioeconomic status of the exposed population.