ZHOU Shan-shan, LIU Ying*

1.College of Life and Environmental Sciences, Minzu University of China, Beijing 100081, China 2.Beijing Engineering Research Center of Food Environment and Public Health, Minzu University of China, Beijing 100081, China

The Levels of 21 Elements and Inter-element Interactions in Scalp Hairof Women at Childbearing Age in A Rural Area, Inner Mongolia

ZHOU Shan-shan1,2, LIU Ying1,2*

1.College of Life and Environmental Sciences, Minzu University of China, Beijing 100081, China 2.Beijing Engineering Research Center of Food Environment and Public Health, Minzu University of China, Beijing 100081, China

Women of reproductive age are at an increased risk of minerals deficiencies, especially for women in recent years.The objective of this study was to investigate the concentrations of 21 elements (Ca, Mg, Cu, Zn, Fe, Mn, Cr, Ti, B, Co, Mo, Si, V, Ni, Cd, Al, Pb, Ba, Sr, Sn and Se) in scalp hair of apparently healthy women at childbearing age of Xinghe County, Ulanqab city of Inner Mongolia.The hair samples were determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES) and atomic fluorescence spectrometry (AFS), respectively.The results revealed that the concentration levels of 21 elements were clearly differed from the mean levels reported in the literatures.Micronutrient deficiencies and apparent excess of toxic elements are present in female of childbearing age in studied area.The higher Mg and Al levels may be due to the largest bentonite deposit in North China lay in the study area.The soils in the studied areas had been detected to have low total Se concentration which may account for that 98% participants had Se concent below 0.2 μg·g-1.Inter-element interactions were studied by evaluation of correlation coefficients between two elements, as well as by multiple regression analysis.These elements form divalent ions and their sources are similar were significantly inter-correlated.The strongest relations found between the elements in the hair were as follows: Mg and Ca, Cr and B, Si and Pb, Mn and Pb, Fe and Mn.No correlation was found between Cd and Pb, which is different with other reports.This could be explained by the rarely industrial exposure to these elements.And kinds of geographical environment, dietary habits and other factors in different regions impact human trace element metabolism.Multiple regression analysis presented the results: Ca=f(Mg, Se) (Se are negatively correlated,β<0), Fe=f(Cu, Mn, Ti), Zn=f(Ca, Se, Fe, Ni) (Fe, Ni are negatively correlated,β<0), Cu=f(Pb, Fe, Cd), Al=f(Mg, Pb), Se=f(Zn, Cr, Ca) (Ca are negatively correlated,β<0).These relations can be useful to study the relationships among different elements inside an organism of women.Cluster analysis (CA) was used for further classifying the different sources of elements on the basis of the similarities of their chemical properties.The significantly correlated subcluster of Mn-Pb-Si-Al proved that Pb exposure came from a nature source.The results will provide a reliable basis for improving macro- and microelements status of women in childbearing age in rural area.Meanwhile，this study may help to make more effective strategies to improve the reproductive-aged women’s health and the pregnancy outcome.

Trace elements; Scalp hair; Childbearing-aged women; Inter-element interactions

Introduction

Elements are naturally occurring and widely distributed in the environment, they enter the organism via multipath ways, such as inhalation, ingestion and dermal absorption[1].They are removed from the organism through the following excretory pathways: sweat, hair, urine and feces.Due to the presence of cystine, hair has high affinity to metals.Their contents in hair can reflect the body status for a long period, including exposure in time[2], recording the history of personal metals exposure in time.The analysis of trace elements in human hair has been used in health assessment, as well as in forensic science to demonstrate poisoning states[2].The investigation of trace elements in human hair is used for estimation of the nutritional status of individuals[3].According to the Environmental Protection Agency (EPA), human hair is one of the most important biological materials for worldwide environmental toxic chemicals monitoring.

Hair, unlike blood or organs, can be collected painlessly and is easy to transport and store[2].The interior of hair tissues ensures the chemical stability of elements and their higher concentrations (i.e.than in blood and urine).Same as serum analysis, assessment of the statuses of elements in an individual also relies on normal range or reference ranges for the specific elements in human hair.To date, many papers[4]have elaborated reference values for the content of particular elements in human hair.But ethnic and geographic origin, age, gender, sample location, dietary and living habits, health conditions and environment exposure can affect the hair content[5-6].

Inter-element interactions study is useful to the discussion of the function and metabolism of the elements in the body, such as synergistic interactions between Hf-Zr, Pb-K, Cs-Rb, Sr-Mg, Nb-Th, K-Na and Tl-Fe from non occupational exposure urban population group living in the north-east of Sweden[7], significant correlations between Cd-Pb, Cd-As, Pb-As, and Se-Hg were found in hair of residents living in villages around Fenghuang mine[8], Mg-Ca, Mn-Ca, Sr-Ca, Sr-Mg, Ni-Zn, Mn-Sr, Cd-Ni in inhabitants of urbanized and industrialized region of south-west Poland[2], the results turned out that industrially related elements have stronger inter-relations.They also found different inter-element interactions between women and men[9], but these researches are scarce.

Women at reproductive age are at an increased risk of minerals deficiencies, particularly due to higher requirements in the periconceptional period and during pregnancy.The necessity for improved diets habits, health and living environment are consistently recommended.Multinutrient interactions may affect supplementation absorption for reproductive women.After summary the Fe-Zn-Cu interactions, Lonnerdal[10]noted that a high concentration of Fe can interfere with Zn uptake and Cu absorption when the elements are given as a supplements.Ca also interacts with Zn and Mg, but little evidence suggests that high intakes of Ca can cause the depletion of any of these 3 minerals or iron[10].

Base on above research background, the present study aims to (1) investigate the concentration levels of 21 elements, which contain 8 essential elements (Mg, Ni, Se, Zn, Ca, Fe, Cu, Mn) related to women reproduction and fetal growth, 13 non-essential elements and toxic elements (Sr, Cr, Mo, Co, V, Ti, Ba, B, Sn, Pb, Cd, Al, Si) in healthy reproductive-aged women in unpolluted rural area; (2) study inter-element interactions in hair and the influence of several elements using multiple stepwise regression analysis to determine whether the concentration of a given metal was correlated with the concentration of another metal; (3) examine the linkage and interplay between multiple elements using multivariate cluster analysis to find out the main source of elements in studied women.

1 Materials and methods

1.1 Hair samples

The hair samples were sampled from195 subjects living in 7 towns of Xinghe county, Ulanqab city of Inner Mongolia.All participants gave their written informed consent after receiving detailed explanations of the study and potential consequences prior to enrollment.Hair was sampled from nape of the neck.

Samples were washed using shampoo, then distilled water (Millipore, Massachusetts, USA) and drying.Hair (ca.0.1～0.2 g) was mineralized with concentrated nitric acid (3 mL, GR) on graphite heating block.

1.2 Instrument and Reagents

Multielemental analysis was performed with inductively coupled plasma atomic emission spectroscopy (ICP-AES) (CirosCCD, Spectro, German) for the elements, except Se that were analyzed with an atomic fluorescence spectrometer (AF640, Beijing Rayleigh Analytical Instrument Corporation, China).

All single element calibration standard solution containing the elements of interest at concentrations of 1 000 mg·L-1were purchased from CRM/RM Iformation center of China.

1.3 Statistical analysis

Inter-element correlation coefficients, multiple stepwise regression analysis and Cluster analysis (CA) were used for the multivariate apportionment of the elemental data.All statistical analyses were performed with software of Statistical Packages for Social Sciences (SPSS 19.0).APvalue of <0.05 was considered statistically significant.

2 Results and discussions

2.1 The levels of 21 elements and comparison with other studies

The average concentrations of elements along with relevant standard deviation (SD) values are determined in Table 1.The macronutrient Ca recorded the highest average concentration in the hair of the participants, followed by Mg and Zn (close to Mg).It indicated that Ca, Mg and Zn constituted a major quantitative proportion of metals in the hair.

The decreasing order of hair contents of trace metals were following as : Ca>Mg>Zn>Si>Fe>Al>Cu>Pb>Ba>Sn>B>Ni>Sr>Cr>Mn>Ti>V>Mo>Co>Se>Cd.It differed from the order of the Poland and Tonglu city (Ca>Zn>Mg>Cu>Fe>Si>Al>Sr>Sn>Pb>Ba>Ti>Cr>Ni>B>V>Co>Mn>Mo>Cd and Ca>Zn>Mg>Fe>Cu>Al>B>Mn>Pb>Se>Sr>Cr>Ti>Ba>Ni>Mo>Cd>V>Co, respectively), in those literatures, the concentration of Zn is higher than Mg, it is obviously different from our study and Russia (Ca>Mg>Zn>Fe>Sr>Ba>Cr>Mn>Se>Co>Cd), whose order of Mg concentration is also differenced heavily from Poland and Tonglu city.

Table 1 Descriptive statistics for element concentrations in hair of this study, Poland, Russia and Tonlu city of China (Mean±S.D., μg·g-1)

Compared with the average levels of elements of Russia, Polish and Tonglu (a village in central China), we found that the mean concentrations for all elements were obviously different from the mean levels reported in the literature, such as Mg (2.4-fold higher than in Poland, 1.5-fold higher level in Russia, 8.5-fold higher than in Tonglu city), Ca (1.3-fold lower than in Poland, 1.5-fold higher than in Russia, 5.3-fold higher than in Tonglu city), Fe (3.4-fold lower than in Russia, 2.3-fold higher than in Tonglu city), Cu (2.6-fold lower than in Poland), Mn (1.5-fold higher than in Poland and Tonglu city, 1.2-fold lower than in Russia), Cr (1.4-fold higher than in Poland, 1.8-fold lower than in Russia, 4-fold higher than in Tonglu city), Co (1.7-fold lower than in Poland, 7.1-fold higher than in Russia, 54.9-fold higher than in Tonglu city) and Ni (2.2-fold higher than in Poland, 9.6-fold higher than Tonglu city).Pb (1.8-fold higher than in Poland, 8.3-fold higher than in Tonglu city), Cd (1.8-fold higher than in Poland, 6.8-fold higher than in Tonglu city), Al (2.85-fold higher than in Poland, 11.1-fold higher than in Tonglu city).The levels of Zn obtained in this study were 1.3-fold lower than in Poland while the level of Se is 2.27-fold lower than in Tonglu city.

Metal elements are considered to play consistent and vital metabolic roles in human body.In comparison with the work reported of Poland and Tonglu, the Mg and Al levels were higher, this may be due to the largest bentonite deposit in North China lay in the study area.The Se level was comparatively lower in this study.Some study considered hair Se<0.2 μg·g-1was defined deficiency[11].Overt Se deficiency is associated with Keshan disease, a cardiomyopathy affecting mainly women of childbearing age, frequently fatal[11].Literatures[10]have reported significant associations between clinical pregnancy loss and Se deficiencies.In our study, the Se content of 98% participants were below 0.2 μg·g-1.This may be due to the studied areas had soils containing drab soil, dark brown soil and chestnut soil which have been detected to have low total Se concentration[12]and a high proportion of subsistence farmers who were very dependent on their local food supply.

2.2 Inter-element interactions

Correlation is defined as the relationship between two elements and does not consider the presence of other elements.In some paper, correlations between elements were determined in the whole population, but Chojnacka et al.[9]found some essential correlations differed according to the gender.The correlations of Mg-Ca, Sr-Ca, Sr-Mg, Co-Cr, Fe-Ti, Ba-Ca, Ba-Mn, Ba-Sr, B-Mo, Al-Ca, Al-Fe and Al-Cu in this paper were consistented with the literature[9]for the female, while opposite correlation were found between Ti-Ca, Ti-Mg and Pb-Cr.

Table 2 listed element-to-element correlation coefficient matrix for the studied population.The first group concerned the following elements: (essential metals-Ca, Mg, Cu, Zn, Se, Fe, Mn, toxic elements-Pb, Cd, Ni, Al, and other elements-Ti, Sr, Cr, Mo, Co, V, Ba, Si, Sn, B).The correlation coefficients show that there is significantly positive correlation between Mg-Ca, Fe-Cu, Fe-Mn, Zn-Mg, Cu-Ca，F(xiàn)e-Mg, Fe-Mn, Mn-Cu.Essential elements belonging to this group (Ca, Mg) were antagonistic to Se.Ni inter-correlated with all elements except Ca, Cu, Pb, Al, Si and Se.However, not all the elements were inter-correlated within this group.In the group (Pb, Cd, Ni, Al), Pb and Cd were not inter-correlated with each other, they all together with Cu and Sn.Pb were inter-correlated with Fe, Cu and Mn, while Cd inter-correlated with Cu and Ni.The last group is also identified: (Co, Mo, Ti, V, Ba, Si, B, Cr, Sr)—this is the group, which composed of microelements in common origin, Cr were inter-correlated with all elements.

Table 2 Statistically significant correlations (p<0.05) between elements in the hair of reproductive-aged women in Xinghe County of China

*: correlations found in the literature; bold: correlations confirmed in the present study and in the literature

In the correlation matrix, the two elements with the highest number of significant correlations with each other were Ca and Mg (R0.839), which is similar to Chojnacka et al.[9].The process of Ca absorption in the gastrointestinal tract is an Mg-dependent process.Alkaline earth elements (Ca, Mg, Sr, Ba) were significantly inter-correlated, which is confirmed in literatures[2, 9].These elements form divalent ions and their sources are similar.Sr acts similarly to Ca, the proper dose of Sr in biological microenvironment play essential roles in bone formation.Due to the synergistic effect of Sr and the surrounding Ca, the bone formation can be enhanced.The excess of Al in the body causes the disturbance of metabolic processes, which are related with enzymes depending on Ca, Mg and Fe[9].In this paper, the interaction between Al and Se was observed (R-0.215).Excessive Al exposure can induce inflammatory process in the kidney of pregnant rats while selenium minimized these harmful effects[2].

Table 3 The relationships among elements, determined from stepwise multiple regression analysis

DependentvariableIndependentvariablesβ>0aβ<0bCaMgSeMgCa,Sr,Pb,SiTi,NiZnCa,SeFe,NiFeCu,Mn,TiZnMnPb,Fe,BaCuPb,Fe,CdSrMg,B,NiSiCrB,Ni,Mg,VMoCo,CrBaCoB,Mo,Cd,NiSeZn,CrCaNiV,Ti,Co,Pb,CrZnVNi,TiTiV,Fe,Mg,Ni,SrBaB,Mn,Ca,CrMoBCr,Ba,Co,Mo,CdPbSnCd,Cr,PbPbMn,Si,Cu,SnBCdSn,Cu,CoAlMg,PbSiPb

a: The element is positively correlated;

b: The element is negatively correlated

Toxic elements (Cd, Pb and Ni) may deplete glutathione and protein-bound sulfhydryl groups, resulting in the production of reactive oxygen species, such as superoxide anion, hydrogen peroxide and hydroxyl radical[13].Human is exposed to them from contaminated foods as well as by inhalation of polluted air.Some studies reported that positive correlation between Cd and Pb may be a result of similar environmental exposure to heavy metals or smoking.No correlation was found between Cd and Pb, which is different with other reports (R0.33)[8-9, 13].Vishwanathan et al.[14]reported statistically significant correlations between Ni-Pb and Ni-Cd in hair of drivers occupationally exposed to vehicular and industrial pollution.Ni has weak correlation with Cd, but no correlation with Pb in this study.This could be explained by the rarely industrial exposure to these elements.It was reported that increasing Se intake might reduce the Cd exposure[15], but no correlation was found in this study.The interactions inside an organism of human are of more complex nature.The level of a given element in hair should be influenced by the exposure to several elements[2].

The relationships among different elements are better presented by multiple stepwise regression analysis (Table 3).The following dependences were observed: Ca=f(Mg, Se) (Se are negatively correlated,β<0), Mg=f(Ca, Sr, Pb, Si, Ti, Ni)(Ti, Ni are negatively correlated,β<0), Fe=f(Cu, Mn, Ti), Zn=f(Ca, Se, Fe, Ni) (Fe, Ni are negatively correlated,β<0), Cu=f(Pb, Fe, Cd), Al=f(Mg, Pb), Se=f(Zn, Cr, Ca) (Ca are negatively correlated,β<0).The results are different with other reports[2].These may be due to kinds of geographical environment, dietary habits and other factors in different regions impact human trace element metabolism.

2.3 Cluster analysis

CA was performed to further classify elements of different sources on the basis of the similarities of their chemical properties, which is shown as a dendrogram in Fig.1, the results showed that six major clusters of the selected metals were identified in turn.

Fig.1 Dendrogram of the metals showing the clustering behaviour of metals in the scalp hair of reproductive women in Xinghe County of China

The Ca-Mg-Sr cluster (called as Ⅰ cluster) is mainly due to their similar properties and metabolism in human body.As discussed above, toxic elements Pb and Cd have no correlation, which indicated their different sources.In the second cluster (Fe-Cu-Mn-Pb-Si-Al, Ⅱ cluster), the subcluster of Mn-Pb-Si-Al are significantly correlated, as can be shown from their correlation coefficient, and have a nature source, while Al and Si are originate mainly from local mineral resources.The results are in line with other findings[13]where the concentrations of non-essential metals of Cd and Pb in the hair of were largely related to environmental metal concentrations, such as soil metal concentrations.The strongest cluster Ni-V-Ti (Ⅲ cluster) may result from the exposure to the Ni-V-Ti-Fe alloys which are used in diesel engine, automotive and tractor.The last three clusters containing Mo-Co-Cr-B-Ba (Ⅳ cluster), Cd-Sn (Ⅴ cluster) and Zn-Se (Ⅵ), respectively.To our knowledge, there is insufficient information on the accumulation of Sn in human scaple hair related to environmental and occupational exposures.Cd-Sn cluster may indicate the same smoking exposure while the forth cluster shows the common exposure to man.The soil in the area is lack in Se, Zn-Se cluster may derived from meat source foods.

3 Conclusions

In the present work, hair from the population (195 subjects) living in rural area of China (Xinghe County, Inner Mongolia) was studied.The results displayed that the level of the majority toxicants was elevated, when comparing with the population from Russia, Wrocaw city of Poland and Tonglu of China.Inter elements interactions with statistically significant (p<0.05) dependences were found between the elements of common origin (geological and environmental source).Also, a group of elements, mutually positively correlated was distinguished (Ca, Mg, Sr and Ba).This was probably due to similar chemical nature of these elements (Ca, Mg, Sr and Ba).The results of multiple stepwise regression analysis showed that the level of a given element might be influenced not simply by the level of another element, but most probably by the level of group of elements.CA provided evidence to the different sources of elements: geological and living environment, dietary habits or food.

However, it is necessary to perform further studies on inter-element interactions on another unenvironmentally exposed population, in order to confirm universal character of dependencies found in this study.The study will contribute to the understanding the concentration status and the main sources of metal elements of local women, give a guide for women of childbearing age a trace elements supplement program.Also, base on the literature data, it is necessary to take into consideration that differences between element levels are indicative of individual variability, individual metabolic activity, occupational exposure, geological location and food habits of the donors.

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*通訊聯(lián)系人

O657.3

A

內(nèi)蒙古農(nóng)村地區(qū)育齡婦女頭發(fā)中21種元素含量水平及相互作用

周珊珊1,2，劉 穎1,2*

1.中央民族大學(xué)生命與環(huán)境科學(xué)學(xué)院，北京 100081 2.中央民族大學(xué)北京市食品環(huán)境與健康工程技術(shù)研究中心，北京 100081

近年來育齡婦女礦物質(zhì)缺乏的風(fēng)險(xiǎn)增加，特別是農(nóng)村地區(qū)婦女。研究使用電感耦合等離子體原子發(fā)射光譜法(ICP-AES)和原子熒光光譜法(AFS)測(cè)定內(nèi)蒙古烏蘭察布市興和縣健康育齡婦女頭發(fā)中21種元素含量(Ca，Mg，Cu，Zn，F(xiàn)e，Mn，Cr，Ti，B，Co，Mo，Si，V，Ni，Cd，Al，Pb，Ba，Sr，Sn和Se)。結(jié)果顯示，21個(gè)元素的濃度水平明顯地不同于文獻(xiàn)報(bào)道的平均水平。育齡女性存在微量營(yíng)養(yǎng)素缺乏和有毒元素明顯過剩的現(xiàn)象。當(dāng)?shù)氐V產(chǎn)及土壤種類導(dǎo)致鎂和鋁的含量較高而硒含量較低。通過相關(guān)分析和逐步多元回歸分析研究了元素間的相互作用，性質(zhì)相似的金屬元素具有顯著的相互作用，且最強(qiáng)的是鎂與鈣、鉻與硼、硅與鉛、錳與鉛、鐵與錳。研究地區(qū)鎘、鉛沒有顯著的相關(guān)作用，這可能與工業(yè)暴露少有關(guān)。同時(shí)其他因素也影響元素在人體內(nèi)的代謝水平。多元回歸分析發(fā)現(xiàn)：Ca=f(Mg，Se)(Se為負(fù)相關(guān)，β<0)，F(xiàn)e=f(Cu，Mn，Ti)，Zn=f(Ca，Se，F(xiàn)e，Ni)(Fe，Ni為負(fù)相關(guān)，β<0)，Cu=f(Pb，F(xiàn)e，Cd)，Al=f(Mg，Pb)，Se=f(Zn，Cr，Ca)(Ca為負(fù)相關(guān)，β<0)。這些參數(shù)可以用于研究生物體內(nèi)不同元素之間的關(guān)系。聚類分析法進(jìn)一步對(duì)不同元素的來源進(jìn)行分類，結(jié)果表明該地鉛暴露主要來源于自然環(huán)境。研究結(jié)果將為改善農(nóng)村地區(qū)育齡婦女宏觀和微量元素水平提供可靠的依據(jù)，同時(shí)，也有助于制定更有效的提高婦女生殖健康和妊娠結(jié)局的策略。

微量元素；頭發(fā)；育齡婦女；元素相互作用

2015-08-04，

2015-12-22)

Foundation item：The National Natural Science Foundation of China (21177163), 111 Project B08044, First-class University First Class Academic Program of Minzu University of China (YLDX01013), Coordinate Development of First-Class and First-Class University Discipline Construction Funds(10301-0150200604), The Academic Team Construction Project of Minzu University of China (2015MDTD25C&13C)

10.3964/j.issn.1000-0593(2016)09-3068-07

Received：2015-08-04; accepted：2015-12-22

Biography：ZHOU Shan-shan, (1981—), doctor of College of Life and Environmental Sciences, Minzu University of China e-mail: deleteshan@126.com *Corresponding author e-mail: liuying4300@163.com