ALAD genotypes and blood lead levels of neonates and children from e-waste exposure in Guiyu, China

摘要

Extensive e-waste recycling activity in Guiyu, China, has been conducted using primitive techniques for the last 20 years, resulting in serious heavy metal environmental contamination. A polymorphic variant of the 6-aminolevulinic acid dehydratase (ALAD) gene has been found to influence lead uptake and, thus, may influence an individual's susceptibility to lead toxicity. We therefore explored whether the ALAD gene polymorphism affects blood lead levels of newborns and children in Guiyu. A total of 273 newborns and 504 children, and a combination of 2004/2005 and 2006 independent recruitments were used for this study. Umbilical cord blood from newboms (Guiyu/exposed group 189 vs. Chaonan/reference group 84) and venous blood from children (exposed group, 319 vs. Chendian/reference group 185) were collected. Blood lead levels (BLLs) were measured via graphite furnace atomic absorption spectrometry (GFAAS) for all samples, while ALAD genotyping was performed using PCR-RFLP for 273 neonate cord blood and 246 children's blood. The median BBLs of neonates in exposed group vs. the reference group were 10.50 (2.36-40.78) vs. 7.79 (0.8-19.51) for 2004/2005 and 9.41 (9.28-47.60) vs. 5.49 (0.35-18.68) for 2006, while child mean BLLs were 15.31 ±5.79 vs. 9.94±4.05 for 2004/2005 and 13.17±5.98 vs. 10.04±4.85 for 2006. The genotype frequencies in newborns were 98.90 % for the ALAD-1/ALAD-1 homozy-gote and 1.10 % for the ALAD-1/ALAD-2 heterozygotes, while the values were 95.93 and 4.07 %, respectively, in children. The allele frequencies of the ALAD-1 and ALAD-2 were 99.45 and 0.55 % for newborns, but 97.97 and 2.03 % for children, respectively. No significant differences in blood lead levels were found between ALAD-1/ALAD-1 and ALAD-l/ALAD-2 either in newborns or in children. The frequency distribution of the ALAD-2 allele in newboms from the exposed group was lower than that of the reference group. There were no significant differences, between the two different ALAD genotypes in the lead load of newborns and children. The frequency distribution of ALAD gene does not influence the blood lead levels of newborns and children in this case, which means that the higher lead burden in the exposed children was possibly influenced by e-waste recycling, but not ALAD genotypes.