| Lead is a kind of widespread metal element,rarely existing in as the free state in nature,but often coexisting with zinc,copper and other heavy metal elements.With the rapid development of industrialization and urbanization in China,The problem lead pollution caused by excessive emissions is becoming increasingly serious.Because children have more hand-mouth behavior,more sensitive to lead,higher absorption rate,and lower excretion rate.Besides,children’s blood-brain barrier and intestinal mucosal barrier development is immature.The effect of lead on children’s nervous system development is irreversible.Children become the biggest victims of lead.Therefore,more people can be protected from lead hazards if children are treated as research objects.Although there are related research report that the contribution of lead content in the environment of children’s blood lead,there are still two major problems in the previous studies on the interpretation of the contribution rate of blood lead to multiple environmental exposures in our children.One is the lack of a large-scale survey of the whole country,the second is the calculation of children’s lead intake in China is used in Europe and the United States the behavior of children exposed to the relevant parameters.Therefore,carrying out environmental investigation of lead concentration in the whole country for the calculation of our children’s blood lead multi-way environmental exposure contribution rate based on our children’s behavior exposure parameters,so it can be targeted to control the source of lead exposure in children and reduce the level of lead load in children.Under the finance support of environmental public welfare project "the research on the method of establishing the limit value of environmental air lead quality standard based on health risk assessment",I conducted a survey of the environmental lead concentrations in seven provinces of China(the survey of blood lead baseline levels in children was performed by Xinhua Hospital Affiliated to Shanghai Jiao Tong University),and calculated the contribution rate of multi-pathway environmental exposure to children’s blood lead in China.In addition,we can’t ignore the children at early life especially the exposure of the fetal period and its impact on children’s health.Since lead can easily penetrate the placental barrier,the risk of lead exposure for intrauterine fetus is high.Therefore,the discussion of the relationship between lead exposure and adverse birth outcomes in the fetus will help to focus on and protect children from the early stages of life.Part 1:The Environmental Lead Concentration Baseline Levels in Seven Provinces of ChinaObjective:To study the current lead concentration in seven provinces in China.Methods:The survey was made in the representative areas using the multi-stage stratified sampling method.In this study,seven provinces(autonomous regions and municipalities)were selected as the Level I survey spots of lead exposure in environmental medium and children’s blood lead level.Three survey areas in each province were selected as the Level II survey spots of lead exposure in environmental medium,which represented the large city,small and medium-sized city and rural area.The areas were mainly concentrated in children’s activities or life.The types of samples included the air,water,soil,dust and food samples.Results:In China,the annual average lead content in the air was 0.08μg/m3;the average lead content in drinking water was 0.28μg/L,which was lower than that in flushing water(0.94μg/L),but higher than that in flowing water(0.18μg/L),which reach the drinking water health standards(≤ 0.01mg/L);the average lead content in soil was 52.39mg/kg,which reach the secondary soil environmental quality standard(≤ 250 mg/kg);and the average lead contents in the indoor and outdoor dust samples were 150.25mg/kg and 134.70mg/kg,respectively.No food lead content exceeding the concentration limit prescribed by national standard was found in the overall average content of children’s food lead in China.Conclusion:The lead content in the air in China is still higher than that in developed countries,so the air lead emissions should be further controlled.The lead content in drinking water is likely to be affected by drinking water network or drinking vessels.The distribution of the lead concentration in the soil within the range of children’s activity shows a descending trend in large city,rural areas and middle-sized and small cities;the lead content in the dust has a significant indoor and outdoor difference.Part 2:Research on the contribution rate of multi-pathway environmental exposure to children’s blood lead in ChinaObjective:To study the contribution rate of multi-pathway environmental exposure to children’s blood lead in ChinaMethods:In this part,the data were selected from the survey of the environmental lead concentrations in seven provinces of China and the survey of blood lead levels in children performed by the Xinhua Hospital Affiliated to Shanghai Jiao Tong University.The exposure module of IEUBK model was used first to calculate the daily lead intake of children,the BP neural network model was established by Matlab software and the path analysis model was established by Stata software,so as to conduct the research on contribution rate of multi-pathway environmental exposure to children’s blood leadResults:China’s urban children daily through the dust and diet intake of lead were 1.65 μg/d、8.40 μg/d respectively,rural children daily through the dust and diet intake of lead were 1.61 pg/d、8.67 μg/d respectively.The results of BP neural network model showed that the lead intake rates via the diet,dust/soil,air and drinking water in urban areas were 52.87%,38.67%,5.31%and 3.15%,respectively.The contribution rate to lead intake via the drinking water in rural areas(5.61%)was slightly higher than that in urban areas.The results of path analysis model showed that the lead intake rates via the diet,dust/soil,air and drinking water in urban areas were 38.89%,44.65%,1 1.41%and 5.04%,respectively.The contribution rate to lead intake via the drinking water in rural areas(8.52%)was slightly higher than that in urban areas.The main sources of children’s blood lead are still the diet and dust/soil.Conclusion:It was found in both models that the diet and dust/soil had the highest contribution rates to children’s blood lead in urban and rural areas in China.The analysis results of both models showed that the contribution rate of air lead to blood lead was higher in urban areas than that in rural areas;in other words,the proportion of children’s blood lead generated by air lead exposure in urban areas is higher than that in rural areas.Part 3:Fetal exposure to lead during pregnancy and the risk of preterm and early-term deliveriesObjective:This research evaluated whether maternal urinary lead levels are associated with the risks for preterm and early-term births in a prospective birth cohort in Wuhan,China.Methods:This part of the study based on prospective birth cohort,aiming at that recruited 7299 mothers and their single births during 2012-2014 years in Wuhan City.Inductively coupled plasma mass spectrometry was employed in order to analyze concentrations of lead in maternal urine samples.The associations between tertiles of urinary lead levels and the risks for preterm and early-term deliveries were assessed with multiple logistic regression models.Results:The geometric mean of creatinine-adjusted urinary lead concentrations among the total,preterm birth and early-term birth were 3.18 μg/g cr,3.68 μg/g cr,and 3.17μg/g cr,respectively.Compared with the lowest tertile,exposure to the highest tertile of lead resulted in a significant increase in preterm birth risk(adjusted odds ratio(OR)(95%CI):1.96(1.31,2.44)),and the association was more pronounced among 25-36 years old mothers(adjusted OR(95%CI):2.03(1.97,3.42)).Similar but non-significant associations were found among mothers with early-term birth.Conclusions:Our findings indicate that the risk for preterm birth may be increased with higher fetal lead exposure and this relationship is more evident among women of 25-36 years of age. |
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