Correlation of blood lead level with iron, zinc and calcium as well as neonatal neurobehavioral development

摘要

BACKGROUND: Endothelial cell in brain of undeveloped fetus cannot inhibit entrance of lead so as to cause toxic effect. Over-accumulation of lead can cause toxic effect on children's growth and development, especially on development of nervous system. Lead in fetus body is mainly derived from its mother's; therefore, blood lead reflects the level of mother's lead.OBJECTIVE: To analyze the correlations among blood lead level, trace elements, mental development index (MDI) and psychomotor development index (PDI) of 3-month-old children. DESIGN: Contrast observation. SETTING: Maternity and Child Care Hospital, Shanxi Provincial Children Hospital. PARTICIPANTS: A total of 128 neonates with spontaneous delivery were provided by Shanxi Maternity and Child Care Hospital and Jiexiu Municipal Maternity and Child Care Hospital from September 2004 to January 2005. There were 76 boys and 52 girls. All subjects did not have history of ischemia and hypoxia during perinatal period and umbilical blood was accepted to be used in experiments. METHODS: ① Levels of iron, calcium and zinc in umbilical blood: 0.5 mL umbilical blood and 2 mL blood samples were selected from neonates to measure lead content with graphite-oven atom absorption spectrum and contents of iron, calcium and zinc in umbilical blood with atom absorption spectrum. ② Grouping: According to level of blood lead, neonates were divided into high-dosage lead group (blood lead ≥ 0.24 μmol/L) and low-dosage lead group (blood lead ＜ 0.24 μmol/L). ③ Evaluation of neurobehavioral development: Neurobehavioral development of 3-month-old neonates was evaluated with Bayley scale, which was consisted of intelligence scale, motor scale and behavioral scale. Intelligence scale, which was expressed as intelligence development index, contained 163 items, such as adaptability, behavior, language, pilot activities, etc. Motor scale, which was expressed as mental motor development index, contained 81 items, such as vulgar motor, refined motor, etc. The total score was 100 and the standard deviation was 16 points. If MDI and PDI were less than 70 points, neonates were determined as mental retardation. ④ Correlation of blood lead with calcium, iron and zinc in umbilical blood was analyzed with partial correlation coefficient and relation of blood lead with MDI and PDI was detected with linear correlation analysis. MAIN OUTCOME MEASURES: ① Comparisons of iron, calcium and zinc in umbilical blood of neonates in the two groups; ② neurobehavioral scores; ③ correlations among level of blood lead, contents of calcium, iron and zinc in umbilical blood and MDI and PDI. RESULTS: Among all subjects, 28 were lost because of blood coagulation and uncompleted data, and other 100 were involved in the final analysis with 50 in each group. ① Comparisons of iron, calcium and zinc in umbilical blood: Contents of iron and calcium was (2.17±0.51) and (73.6±21.7) mg/L in high-dosage lead group, which was lower than those in low-dosage group [(2.66±0.58), (83.8±24.9) mg/L; t=3.01, 2.72; P＜ 0.01]. ② Comparisons of MDI and PDI in the two groups: MDI in high-dosage lead group was obviously lower than that in low-dosage group [(103.50± 10.36), ( 109.44±9.71 ) points; t =2.19, P ＜ 0.01 ]. ③ Correlation of blood lead with calcium, iron and zinc in umbilical blood: Blood lead was negative correlation with blood iron (partial correlation coefficient = -0.47, P＜ 0.05). 4 Correlation of blood lead with MDI and PDI: MDI and PDI were negative correlation with blood lead (r= -0.417, -0.327, P＜ 0.05).CONCLUSION: ① Blood lead is correlated with contents of iron, calcium and zinc. ② Blood lead (≥ 0.24 μmol/L) can cause side effects on neurobehavioral development of infants.