Lead exposure in children: Levels in blood, prevalence of intoxication and related factors

Lead is a highly toxic metal, the main source of which is contamination from combustion of unleaded petrol. The aims of this work were to detect the degree of lead exposure in a large sample of children; determine the relationship between blood lead levels (BPb) and age, sex, habitat and season of the year; and correlate BPb with zinc protoporphyrin (ZPP) values. A cross-sectional study was carried out. Blood from routine extractions drawn at our centre was used. BPb and ZPP were measured by atomic absorption spectrophotometry and haematofluorimetry, respectively. We analysed 1158 blood samples from children. BPb (mean ± SEM): 0.22 ± 0.04 μmol l-1. Correlation BPb-age: BPb = 0.19 + 0.086 x age (months), r = 0.129, P < 0.0001. BPb was greater in boys (0.23 ± 0.007 versus 0.20 ± 0.006 μmol l-1, P < 0.0002). No differences were observed between habitats (urban versus rural), BPb were higher in the warm months (0.24 ± 0.013 versus 0.21 ± 0.007 μmol l-1, P < 0.0001). Prevalence of lead intoxication (BPb > 0.48 μmol l-1) was 4.2%. No differences in prevalence were found among the different groups. The correlation between BPb and ZPP showed r = 0.0969, P = 0.0024. Utility for screening: sensitivity of 53.7% and specificity of 59.3% (cut-off point of 60 μmol ZPP mol-1 haem). We can conclude that lead exposure in children in our sample was in the range reported in similar studies in other areas and countries, and below the toxic limit. None of the factors analysed significantly influenced lead intoxication prevalence. There was no good correlation between ZPP and BPb in our sample and the ZPP cut-off point used did not present good specificity and sensitivity values.