Health effects of environmental lead exposure in children

Abstract

Children comprise the most susceptible part of the population with regard to lead exposure. The lowest level of lead exposure considered to cause adverse health effects has fallen with time, as the research techniques have improved. The aim of the present work was to assess the exposure to lead as well as some other toxic metals in children from Katowice in Poland, and to evaluate the association with health effects, in particular hearing and kidney function. The Katowice area is a heavily polluted industrial zone with lead mining and processing.

An initial biological monitoring survey in 1992 revealed blood lead concentrations (B Pb) exceeding 0.5 µmol/L (100 µg/L), previously reported to cause cognitive deficits, in 20% of the investigated children (median, 0.38 µmol Pb/L). In 1995, the corresponding figure was 7% (median, 0.27 µmol Pb/L), indicating a decrease in the lead exposure. B-Pb was found to be influenced by several socio-economic factors, e.g., number of siblings, maternal smoking, and playing outdoors. A study group of children was selected based on previous biological monitoring data, for studies of the effects of lead on hearing and kidney function. The hearing thresholds increased significantly with increasing B-Pb (range 0.09 to 1.36 µmo/L) at all investigated frequencies.

The results indicated a more pronounced impact of lead, within a wider frequency range, than had been reported previously. The brainstem auditory evoked potential (BAEP) latency of wave one (I) was significantly increased, also after adjustment for age, in the group of children with the highest B-Pb, compared to the group with the lowest ones. The audiometric results indicated that auditory function in children is impaired even at B-Pb below 0.5 µmol/L. There was an association between the urinary concentration of protein HC and B-Pb, indicating an effects of lead on tubular function, also at lower B-Pb than had been reported previously. The glomerular filtration rate (GFR), based on serum creatinine in relation to body height, decreased with increasing B-Pb. Further, serum cystatin C, an alternative marker of GFR, increased with B-Pb.

The results indicated that lead also has an effect on glomerular function. In the same study group, selenium and iron status were associated with the concentrations of toxic metals in blood. The children with low serum ferritin levels (reduced iron stores) had higher blood concentrations of cadmium and a tendency for higher concentrations of lead, indicating increased gastrointestinal absorption. B-Pb was inversely associated with selenium in whole blood and serum, as well as selenoprotein P and glutathione peroxidase in serum. There was a positive association between blood mercury and the markers of selenium status.