Reassessment of critical lead effects by the German Human Biomonitoring Commission results in suspension of the human biomonitoring values (HBM I and HBM II) for lead in blood of children and adults.

In Germany, the Human Biomonitoring Commission of the Federal Environment Agency continuously assesses environmental pollutants to derive human biomonitoring (HBM) and reference values. HBM values are derived on the basis of toxicological, epidemiological studies or toxicokinetic extrapolation which provides a concentration of a substance or its metabolites corresponding to tolerable intake doses. Two levels are defined: HBM I and HBM II. In 1996, the Commission set a HBM I of 100 microg/l for lead in blood of children < or =12 years and females of a reproductive age and a HBM I of 150 microg/l for the other persons. In the light of findings from epidemiological studies on effects below 100 microg/l, the Commission reevaluated and confirmed the assessment from 1996 in 2002. Meanwhile the general decline in lead pollution has allowed recent studies to include more cohorts with blood lead levels predominantly below 100 microg/l. These data confirm that lead's critical effect, particularly on the developing organism and during early childhood, concerns the nervous system and that negative correlations between blood lead levels and relevant variables (cognitive function, behaviour) occur at blood lead levels below 100 microg/l. The new data also support the possible persistence of lead-induced effects into adulthood. It is not possible to indicate thresholds. Concerning the estimation of the size of the effects, recent studies suggest that lead's influence on development is comparable with other factors influencing development. Furthermore inorganic lead and compounds were classified by IARC in group 2A (probably carcinogenic to humans) and by the German Research Foundation (MAK Commission) in category 2 (to be regarded as human carcinogen). We conclude that any setting of an "effect threshold" for blood lead levels would be arbitrary and therefore unjustified. As a consequence the Commission suspends the HBM values for lead in blood of children and adults.