Biomonitoring of trace elements in urine samples of

Chemosphere 197 (2018) 622e626

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Biomonitoring of trace elements in urine samples of children from a coal-mining region Marina dos Santos a, b, Maria Cristina Flores Soares a, b, Paulo Roberto Martins Baisch a, c, Ana Luíza Muccillo Baisch a, b, Flavio Manoel Rodrigues da Silva Júnior a, b, * ~o em Ci^ , 102 96203-900 Rio Grande, RS, Brazil s-Graduça Programa de Po encias Da Saúde, Faculdade de Medicina e FAMED, Rua Visconde de Paranagua rio de Ensaios Farmacolo gicos e Toxicolo gicos, Instituto de Ci^ gicas e ICB, Universidade Federal Do Rio Grande, FURG, Rio Grande, Rio Laborato encias Biolo Grande do Sul, Brazil c rio de Geoquímica Ambiental, Universidade Federal Do Rio Grande, FURG, Brazil Laborato a

b

h i g h l i g h t s The study was conducted in an area with the largest coal mining area of Brazil. Urine levels of Pb, Cd, Mn, Cu, Zn and Se were determined in school children. The urine concentration of Se and Zn were above the reference values. The exposed to environment pollution can increase the vulnerably to health problems.

a r t i c l e i n f o

a b s t r a c t

Article history: Received 3 October 2017 Received in revised form 13 December 2017 Accepted 16 January 2018 Available online 19 January 2018

Biomonitoring through urine samples is important for evaluating environmental exposure, since urine is the main form of excretion for most chemical elements. Children are considered more vulnerable to adverse environmental conditions, especially children in developing countries. This study aimed to biomonitor trace elements in urine samples in children from a coal-mining region in the extreme south of Brazil. A cross-sectional study was conducted on 96 children between 6 and 11 years of age. Socioeconomic data and urine samples were collected to estimate the concentration of iron, zinc, selenium, lead, and cadmium. The prevalence of metals above the reference values was 52.0% for Se, followed by 15.6% for Zn. The data point toward a vulnerability to adverse environmental conditions in these children. Although the concentrations of the elements did not reveal intoxication cases, biomonitoring should be carried out continuously in order to assess exposure to metals and ensure the health of the population. This article provides data that help determine natural levels of metallic elements in children, specifically in South America, which have not yet been established. © 2018 Elsevier Ltd. All rights reserved.

Handling Editor: Jian-Ying Hu Keywords: Human biomonitoring Urinary levels Schoolchildren Environmental pollutants

1. Introduction Humans are exposed to a wide variety of chemicals, especially metals and metalloids, that are naturally found in the environment. Pollution and anthropogenic activities, such as mining, combustion of fossil fuels, and industrial application of metals, can increase their release into the environment. In addition, metals are water-

s-Graduç~ ^ncias Da Saúde, Fac* Corresponding author. Programa de Po ao em Cie , 102 96203-900 Rio uldade de Medicina e FAMED, Rua Visconde de Paranagua Grande, RS, Brazil. E-mail address: [email protected] (F.M. Rodrigues da Silva Júnior). https://doi.org/10.1016/j.chemosphere.2018.01.082 0045-6535/© 2018 Elsevier Ltd. All rights reserved.

soluble, and therefore are easily absorbed by vegetation and consumed by animals and humans (Nunez et al., 1999). Some metals, such as Cadmium (Cd) and Lead (Pb), are often associated with biological toxicity, primarily causing damage to the nervous system. Meanwhile, other metals are essential for normal development through life, such as Selenium (Se), Copper (Cu), Manganese (Mn), and Zinc (Zn). Inappropriate exposure to these elements may result in deficiency or toxicity, causing a number of health consequences, particularly in the vulnerable populations, such as children (CDC, 2009; ATSDR, 2017). Biomonitoring of elements reflects the relationship between the environment, the body load of elements, and the possible effects on human health (Cerna et al., 2012), and is defined as the evaluation

M. Santos et al. / Chemosphere 197 (2018) 622e626

of human exposure to an environmental chemical element through the analysis of metabolites in blood, urine, milk, saliva, and other tissues. In this way, biomonitoring has become an important tool for assessing environmental exposure, since the results obtained provide information on the dose and route of exposure (Yusa and Pardo, 2015; Roca et al., 2016). Urine samples are often used in clinical chemistry and environmental, occupational, and toxicological studies, because urine is easy to collect, representing a non-invasive and economically viable biomonitoring method (Zhang et al., 2016). Furthermore, urine is the main form of excretion for most chemical elements (Zeiner et al., 2004; Heitland and Koster, 2006). Urine element concentrations are influenced by innumerable environmental and physiological factors (Nunes et al., 2010). Thus, there are considerable variations in the concentration of each element among different populations and subgroups (Bernard, 2008; McElroy et al., 2007; Ranft et al., 2008; Nunes et al., 2010). Several studies have performed biomonitoring of elements in urine samples, but some elements still do not have a reference value description (RV) for both adults and children. In general, for children, these data are especially limited (Heitland and Koster, 2006). There are few studies in Brazil evaluating the levels of elements in children's urine and no studies have been performed in populations exposed to adverse environmental conditions, such as in coal mining areas. In addition, children are considered as a category of individuals with greater vulnerability, especially in developing and emerging countries, that are more susceptible to the effects of environmental pollution (Sughis et al., 2014). The region examined in this study is an important coal mineral area, currently produces approximately one billion tons of coal per year. Coal is one of the most damaging energy sources to the environment, causing socio-environmental and health impacts. During the coal-mining process, significant amounts of solid residues and atmospheric particulate material containing potentially toxic chemical elements are generated (Gomes et al., 1998). Therefore, the present study aimed to conduct the biomonitoring of metals Pb, Cd, Mn, Cu, Zn, and Se in urine samples from children in a region under the influence of the largest thermoelectric coal complex in Brazil. 2. Materials and methods 2.1. Sample and place of study This was a cross-sectional study, covering seven municipalities in a region of coal mineral, located in the extreme south of Brazil. , Bage , Herval, The following municipalities were included: Acegua Hulha Negra, Pedras Altas, Pinheiro Machado, and Candiota, the latter being the seat of activities for the use of coal (Fig. 1) (Pinto et al., 2017). The study sample consisted of 96 children, aged between 6 years and 11 years and eight months. To define the number of schoolchildren evaluated by municipality, the number of students enrolled in primary level schools and the number and location of public schools in each municipality were taken into account, as reported by the education departments. Sampling was performed by randomly selecting schoolchildren for examination. 2.2. Data collection 2.2.1. Socioeconomic data collection A questionnaire was used to collect family socioeconomic information: family income per capita with was mensural trough the minimum wage (MW) of R $ 724.00 per month in 2014 ( 720 MW); socioeconomic classification (according

623

Fig. 1. Coal mining area in the extreme south of Brazil (Pinto et al., 2017).

to criteria established by the Brazilian Association of Research Companies (ABEP, 2013); housing conditions: type of housing (masonry, others), type of toilet (with, without discharge), and running water (yes or no); municipality of residence of the child; and if the child always resided in the same municipality. This questionnaire was given to parents or guardians of children from July to December 2013. 2.3. Urine testing The urine samples were collected in the school itself, individually by each of the children, in a sterilized plastic bottle provided by the laboratory where the analyses were performed. Samples were adequately identified, packed in a Styrofoam box at 4 C, and sent for laboratory analysis. The analysis was performed in a certified laboratory (Toxilab, Porto Alegre, RS), using the methodology of atomic absorption in a graphite furnace. The limits of detection (LD) and quantification (LQ) were, respectively: Cd (LD: 0.01 mg.L1, LQ: 0.1 mg.L1), Pb (LD: 0.05 mg.L1), Cu (LD: 0.2 mg.L1; LQ: 2 mg.L1), Mn (LD: 0.01 mg.L1), Cu (LD: 0.1 mg.L1; LQ: 1 mg.L1), and Zn (LD: 10 mg.L1; LQ: 50 mg.L1). The concentrations of Pb and Cd in the urine were normalized to the creatinine concentration. Creatinine level was determined by spectrophotometry using the method described by Martensson et al. (2004). The reference values (RVs) for cadmium (up to 2.0 mg g1 creatinine) and for lead (up to 50 mg g1 creatinine) used by the laboratory were those indicated in Regulatory Norm NR-7 - Control Program Occupational Health Physician Ministry of Labor (Brasil, 1978). For the other elements, the laboratory considered the following RVs: selenium (4.5e11 mg L1); copper (5e30 mg L1); manganese (up to 3 mg L1); zinc (400e1000 mg L1). However, the RVs used by the laboratory are for adults. In cases where the reference values are represented by an interval between two concentrations, the minimum and maximum values were observed in order to better characterize the affected populations. 2.4. Statistical analysis The STATA 10.0 program was used to analyze the data.

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Frequency distribution was performed for the variables investigated. In addition, urine element concentrations were expressed as mgL1 for Mn, Cu, Zn, and Se, and in mgg1 creatinine for Pb and Cd to account for the effects of urine dilution. The mean ± standard error of the mean and the geometric mean of the concentrations were calculated, and the concentration variation (minimum and maximum values) was identified. 2.5. Ethical aspects All the ethical precepts recommended by Resolution 466/12 of the National Health Council of the Ministry of Health, which regulates research involving human beings, were respected. The study was approved by the Research Ethics Committee in the Health Area of the Federal University of Rio Grande (CEPAS - FURG) under No. 36/2013. 3. Results The sample consisted of 96 children, composed of an equal number of boys and girls, there were some loss of information in all socioeconomics and demographics variables, but the greatest loss was in the variable economy class (10 missing information). The majority of which were self-declared caucasian (58.3%). Regarding socioeconomic characteristics, 58.3% of families reported a per capita income less than half of minimum wage, with most of the sample belonging to economy class C (59.4%). Regarding demographic conditions, more than half of the participants lived in masonry (79.1%) containing sanitary with discharge (95.8%) and running water (92.7%). The majority of the children resided in the municipality from birth (74.0%) (Table 1). The mean concentrations of the trate elements Mn, Cu, Zn and Se was 1.0 ± 0.1 mg.L1, 8.7 ± 0.7 mg.L1, 653.4 ± 43.6 mg.L1, and 14.9 ± 1.3 mg.L1, respectably. The mean concentration for Pb was 6.0 ± 0.5 mg g1 creatinine, whereas Cd was the only element for which no traces were detected in the urine (Table 2). Zn and Se presented greater amplitude in their concentrations, exhibiting maximum values well above the RV. The prevalence of the elements in the urine above the RV determined for populations not exposed to the pollutant was observed for Se and Zn, in 52.0% and 15.6% of the children, respectively. Lead was the only element with urinary contents below the RV (Table 3). In relation to the spatial distribution of these cases, 62.5% of the children studied in Hulha Negra have a urinary level above the reference value, followed by Pinheiro (59.4%), Acegua (50%), Machado (60%), Pedras Altas (60%), Bage Candiota (42.9%) and Herval (25%). Zn, second metal found in higher concentration in urine, presented an excess in 30% of schoolchildren in the municipality of Pinheiro Machado, followed (16.6%), Bage (15.6%), Candiota (14.3%), %), Herval (12.5%) by Acegua (Table 3). 4. Discussion Most of the families included in this study lived with a per capita income less than half a minimum wage. According to the literature, the socioeconomic level and the development index of the region can influence the concentrations of elements in the urine, making the population more or less susceptible to adverse environmental conditions (Inoue et al., 2014; Sughis et al., 2014). Developing and emerging countries tend to have a greater risk for health problems related to environmental conditions. In addition, the majority of the children studied had a long period of exposure to the regional conditions, since most of them had always lived in the same place and contact with environmental components begins during

Table 1 Descriptive analysis of socioeconomics and demographics characteristics of children of a coal mining area, Brazil (n ¼ 96).

Sex Male Female Skin color White Nonwhite Family income per capita 720 MW per capita Economic Classa A B C D Type of housing Masonry Others Toilet type With flush Without flush Company water No Yes Residence in the municipality since birth No Yes

n

%

48 48

50.0 50.0

56 37

58.3 38.5

56 24 14

58.3 25.0 14.6

1 19 57 9

1.0 19.8 59.4 9.4

76 19

79.1 19.9

92 03

95.8 3.1

5 89

5.2 92.7

23 71

23.9 74.0

a The variable with the greatest loss of information was economy class (10 missing information). MW: Minimum wage.

gestation. In Brazil, there have been only a few studies on biomonitoring, mainly evaluating urinary levels of elements in children. Meanwhile, some developed countries such as the USA (CDC, 2009), Italy (Minoia et al., 1990), Canada, Germany (Becker et al., 2006; Schultz et al., 2011), and Spain (Roca et al., 2016) have established biomonitoring programs to evaluate levels of contaminants in the general population. Recently, there has emerged a concern that children may be more vulnerable to toxic substances than adults (Au, 2002), because they are still developing (Tuakuila et al., 2015). There is still much controversy regarding the definition of RVs, the procedures used to obtain them, and the applications of biomonitoring (Feliu et al., 2005), since the analyzed elements present great degrees of variation depending on the region studied (Inoue et al., Heitland and Koster, 2006; Kuiper et al., 2014). However, Molina-Villalba et al. (2015) and Aguilera et al. (2010) observed no significant difference between the concentrations of metals in urine samples of individuals living in zones with different levels of exposure, except for mercury. The region examined in this study conducts extensive coal exploration, which can influence the levels of elements in the environment. According to Pinto et al. (2017), there are differences in the DNA damage of volunteers from different cities of the carboniferous region. Some studies in these Brazil coal mining area have shown emissions of particles with character acid and with elevated concentration of heavy metals and fluorides (Pires et al., 2001). The elements associated an organic fractions and sulfate volatilize during the coal combustion (Sanchez et al., 1994). In addition, the number solubilizing elements and their concentration tends to increase with pH decreasing (Pires et al., 2001). In the study area the pH was considerate acid and these can interfere in the mobility of the metallic elements in the ashes (Sanchez et al., 1994). Furthermore, the concentration of metals in these region are within the range found in studies around the world, except for Mn, where the coal of the study region presents high levels (Pires et al., 2001).


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Table 2 Concentration of trace elements in urine samples of children of a coal mining area, Brazil (n ¼ 96). Elements

n

Mean

Geometric mean

Range

Reference Value

Coal levels in study areaa

Coal levels worldwidea

Mn Cu Zn Se Pb Cd

92 96 96 94 72 96

1.0 ± 0.1 8.7 ± 0.7 653.2 ± 43.6 14.9 ± 1.3 6.0 ± 0.5 n/d

0.8 6.9 509.4 10.0 4.8 e

n/d e 5.40 n/d e 31.6 140e1988 n/d e 76.2 n/d - 21.6 e

3.0 5.0e30.0 400.0e1000.0 4.5e11.0 50.0 2.0

534 20 85,1 1,5 20,5 0,1

5e300 0.5e50 5e300 0.2e10 2e80 0.1e3

Concentration of Mn, Cu, Zn, and Se in mgL1; Pd and Cd in mgg1 creatinine. n/d: Not detected. a Data extracted from Pires et al. (2001) mean in mg.kg1.

Table 3 Prevalence of trace element above of reference value in children residence different cities in a coal mining area, Brazil (n ¼ 96). City

Acegu a Bage Candiota Herval Hulha Negra Pedras Altas Pinheiro Machado Total

Pb

Cu

Mg

Se

Zn

n

%

n

%

n

%

n

%

n

%

0 0 0 0 0 0 0 0

0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

0 0 0 1 0 0 0 1

0.0 0.0 0.0 12.5 0.0 0.0 0.0 1.0

0 1 0 1 0 0 1 1

0.0 3.12 0.0 12.5 0.0 0.0 10.0 3.1

6 19 9 2 5 3 6 50

50.0 59.4 42.9 25.0 62.5 60.0 60.0 52.0

2 5 3 1 1 0 3 15

16.6 15.6 14.3 12.5 12.5 0.0 30.0 15.6

However, this high concentration of Mn is not reflected in the urinary levels of this element, since only 3% of the samples are above the reference values. Among the analyzed elements, Pb is widely resistant to the environment, can be an environmental pollutant and is associated with several health problems, especially neurological problems, due to its toxicity. In addition, Pb exposure may disturb the growth and development of children (Tuakuila et al., 2015). According to the ATSDR (2017), regardless of the mode of contact to Pb, excretion occurs mainly through urine and feces. The Pb mean concentrations previously found in children was 3.36 mg/L (Blaurock-Busch et al., 2011; 5.56 mg/L (Tuakuila et al., 2012), 1.3 mg/L (Heitland and Koster, 2006), were very different from those observed in this study. Afridi et al. (2011) reported the highest (40.85e55.3 mg/L) concentration of Pb in urine samples of children between 8 a 12 years of both sexes, which may be associated with petroleum exploration in the region. Cd, considered a toxic non-essential metal, is distributed throughout the environment at low levels. Bao et al. (2009) reported levels up to 7.33 mg g1 in Chinese children. However, in this study, Cd was not detected in the analyzed samples. The essential elements Zn, Cu, and Mn participate in different physiological functions, such as in the oxidation of distinct enzymes, energy metabolism, and translation and transcription of genes, among others. These elements may interact with toxic metals, especially with Cd (Cerna et al., 2012). The urine concentrations of these elements are associated with exposure and consumption. According to the literature, high levels of Zn, Cu, and Mn can also produce adverse effects on the health of children (ATSDR, 2017). Zn levels found in urine by this study presented a great amplitude, ranging from concentrations considered deficient to toxic. However, the Cu and Mn levels remained within the RV. Se presented the highest prevalence above the RV; according to the literature, increased excretion rate occurs when ingested at high concentrations (Suzuki et al., 2006). Studies report that the half-life for excretion of the element after high exposure is around 24e48 h, while small amounts may remain in the body for months

(Inoue et al., 2014; Yoneyama et al., 2008; Lemire et al., 2009; Combs, 2015). Excess Se can be derived from natural or anthropomorphic accumulation, since it is a geochemically mobile element and recognized for its accumulation capacity in some foods (Rayman, 2008). The excess of Se in the urine of the children studied may be due to high values of the element in the environment, since the region contains the most coal exploration endeavors in the country. However, there is still disagreement about the association of coal with this element. Heitland and Koster (2006) found levels of Se in urine samples from children in areas close to industrial areas (automobile, steel, food) and coal mining areas, similar to the results of this study. Another study of children residing in areas with Keshan-Back disease and control regions showed no significant difference in the concentration of Se in the urine (Lei et al., 2016). According to Yoneyama et al. (2008), urine excretion of Se is the best indicator of acute exposure to the element. Biomonitoring through urine samples needs to be better studied; there are several interactions between human beings and the environment that still do not present satisfactory data. For example, Yoneyama et al. (2008) reported that individuals in South Dakota (USA) have a higher consumption of Se compared to individuals in Japan, but consumption and excretion per kg of weight s et al. of Se is higher in Japan than in Dakota. According to Corte (2016), the population remains exposed to metals in matrices such as soil, food, and dust in suspension for a long period. Areas such as coal mines, even when inactive, expose the populations to contact with various elements. In this way, biomonitoring is required continuously. One of the limitations of this study is that the RVs used for the elements were for adults, but for children, these values should be smaller. Zhang et al. (2016) reported that urine creatinine concentrations in children from 2 to 6 years of age were significantly lower than concentrations in children 7e12 years. Likewise, Tuakuila et al. (2012) reported that levels of Cd, Cu, and Se in urine are more important in adults than in children. As a result, we compared these results with populations of the same age group, to minimize error. 5. Conclusion The examined region presented low socioeconomic status, and children were exposed to local environmental conditions throughout their life, revealing the vulnerability of this population. Although the concentrations of the elements found do not suggest intoxication, biomonitoring should be carried out continuously in this region to evaluate the exposure to metals and try to estimate their health damages, thus ensuring the health of the population. Appendix A. Supplementary data Supplementary data related to this article can be found at

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https://doi.org/10.1016/j.chemosphere.2018.01.082. References ABEP 2014-Associaç~ ao Brasileira de Empresas de Pesquisa, 2013. Dados Com Base cio Econo ^mico 2013. IBOPE. No Levantamento So Afridi, H.I., Kazi, T.G., Kazi, N., Kandhro, G.A., Baig, J.A., Shah, A.Q., Wadhwa, S.K., Khan, S., Kolachi, N.F., Shah, F., Jamali, M.K., Arain, M.B., Sirajuddin, 2011. Evaluation of essential trace and toxic elements in biological samples of normal and night blindness children of age groups 3e7 and 8e12 years. Biol. Trace Elem. Res. 143, 20e40. ndez, A.F., Godoy, P., Pla, A., Ramos, J.L., 2010. Aguilera, I., Daponte, A., Gil, F., Herna Urinary levels of arsenic and heavy metals in children and adolescents living in the industrialised area of Ria of Huelva (SW Spain). Environ. Int. 36, 563e569. ATSDR (Agency for Toxic Substances and Disease Registry), 2017. Toxicological Profile for Lead. U.S. Department of Health and Human Services, Atlanta, GA. www.atsdr.cdc.gov/toxprofiles/tp13.html. (Accessed 20 March 2017). Au, W.W., 2002. Susceptibility of children to environmental toxic substances. Int. J. Hyg Environ. Health 205, 501e503. Bao, Q.S., Lu, C.Y., Song, H., Wang, M., Ling, W., Chen, W.-Q., Deng, X.-Q., Hao, Y.-T., Raoet, S., 2009. Behavioural development of school-aged children who live around a multi-metal sulphide mine in Guangdong province, China: a crosssectional study. BMC Publ. Health 9, 217. Becker, K., Seiwert, M., Angerer, J., Kolossa-Gehring, M., Hoppe, H.W., Ball, M., et al., 2006. GerES IV pilot study: assessment of the exposure of German children to organophosphorus and pyrethoid pesticides. Int. J. Hyg Environ. Health 209 (3), 221e233. Bernard, A., 2008. Biomarkers of metal toxicity in population studies: research potential and interpretation issues. J. Toxicol. Environ. Health 71, 1259e1265. Blaurock-Busch, E., Amin, O.R., Rabah, T., 2011. Heavy metals and trace elements in hair and urine of a sample of Arab children with Autistic spectrum disorder. Mædica 6 (4), 247e257. Center for Disease Control and Prevention (CDC), 2009. National Health and Nutrition Examination Survey Data. U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, Hyattsville, MD. Available: http://www.cdc.gov/nchs/about/major/nhanes/datalink.htm. Cerna, M., Krskova, A., Cejchanova, M., Spevackova, V., 2012. Human biomonitoring in the Czech Republic: an overview. Int. J. Hyg Environ. Health 215, 109e119. Combs Jr., G.F., 2015. Biomarkers of selenium status. Nutrients 7, 2209e2236. s, S., Lagos, L.C.M., Burgos, S., Adaros, H., Ferreccio, C., 2016. Urinary metal Corte levels in a Chilean community 31 Years after the dumping of mine tailings. J. Health Psychol. 6 (10). ~ eiro, A., Lo pez, C., Slobodianik, N.H., 2005. Valores de referencia de Feliu, M.S., Pin ~ os. Acta Bioquim. Clin. Latinoam. 39 (4), 459e462. cobre, zinc y selenio en nin ssil. Estud. Gomes, P.A., Ferreira, J.A.F., Albuquerque, L.F., Telmo, S., 1998. Carv~ ao fo Av. 12 (33). Heitland, P., Koster, H.D., 2006. Biomonitoring of 30 trace elements in urine of children and adults by ICP-MS. Clin. Chim. Acta 365, 310e318. Inoue, Y., Umezaki, M., Jiang, H., Li, D., Du, J., Jin, Y., Yang, B., Li, B., Li, Y., Watanabe, C., 2014. Urinary concentrations of toxic and essential trace elements among rural residents in Hainan Island, China. Int. J. Environ. Res. Publ. Health 11, 13047e13064. Kuiper, N., Rowell, C., Nriagu, J., Shomar, B., 2014. What do the trace metal contentes of urine and toenail samples from Qatar's farm workers bioindicate? Environ. Res. 131, 86e94. Lei, R., Jiang, N., Zhang, Q., Hu, S., Dennis, B.S., He, S., Guo, X., 2016. Prevalence of selenium, T-2 toxin, and deoxynivalenol in Kashinebeck disease areas in Qinghai province. Northwest China. Biol. Trace Elem. Res. 171, 34e40. Lemire, M., Mergler, D., Huel, G., Passos, C.J.S., Fillion, M., Philibet, A., Guimaras, J.R.D., Rheault, I., Borduas, J., Normand, G., 2009. Biomarkers of selenium status in the amazonian context: blood, urine and sequential hair segments. J. Expo. Sci. Environ. Epidemiol. 19, 213e222. Mårtensson, A., Rustad, P., Lund, H., Ossowicki, H., 2004. Creatininium reference intervals for corrected methods. Scand. J. Clin. Lab. Invest. 64 (4), 439e441. McElroy, J.A., Shafer, M.M., Trentham-Dietz, A., Hampton, J.M., Newcomb, P.A., 2007.

Urinary cadmium levels and tobacco smoke exposure in women age 20e69 years in the United States. J. Toxicol. Environ. Health 70, 1779e1782. Minoia, C., Sabbioni, E., Apostolli, P., Pietra, R., Pozzoli, L., Gallorini, M., Nicolaou, G., Alessio, L., Capodaglio, E., 1990. Trace element reference values in tissues from inhabitants of the european community I. A study of 46 elements in urine, blood and serum of Italian subjects. Sci. Total Environ. 95, 89e105. ~ a, M., Rodríguez-Barranco, M., Hern Molina-Villalba, I., Lacasan andez, A.F., Gonzalez~ o, C., Gil, F., 2015. Biomonitoring of arsenic, cadmium, Alzaga, B., Aguilar-Gardun lead, manganese and mercury in urine and hair of children living near mining and industrial areas. Chemosphere 124, 83e91. dico de saúde BRASIL Norma Regulamentadora e NR-7 e Programa de controle me rio do Trabalho, 1978. 16p. ocupacional. Ministe Nunes, J.A., Batista, B.L., Rodrigues, J.L., Caldas, N.M., Neto, J.A.G., Barbosa Jr., F., 2010. A simple method based on ICP-MS for estimation of background levels of arsenic, cadmium, copper, manganese, nickel, lead, and selenium in blood of the brazilian population. J. Toxicol. Environ. Health 73, 878e887. Nunez, J.E.V., Amaral Sobrinho, N.M.B., Palmeiri, F., Mesqueita, A.A., 1999. Con~o do sequencias de difenretes sistemas de preparo do solo sobre a contaminaça gua por metais pesados. Rev. Bras Ci Solo 981e990. solo, sedimentos e a Pinto, E.A.S., Garcia, E.M., De Almeida, K.A., Fernandes, C.F.L., Tavella, R.A., Soares, M.C.F., Baisch, P.R.M., Muccillo-Baisch, A.L., Da Silva Júnior, F.M.R., 2017. Genotoxicity in adult residents in mineral coal region-a cross-sectional study. Environ. Sci. Pollut. Res. Int. 24 (20), 16806e16814. ~o do carva ~o de Candiota e de Pires, U., Querol, X., Teixeira, E.C., 2001. Caracterizaça suas cinzas. Geochim. Bras. 15 (1/2), 113e130. Ranft, U., Delschen, T., Machtolf, M., Sugiri, D., Wilhelm, M., 2008. Lead concentration in the blood of children and its association with lead in soil and ambient air-trends between 1983 and 2000 in Duisburg. J. Toxicol. Environ. Health 71, 710e715. Rayman, M.P., 2008. Food chain Se and human health: emphasis on intake. Br. J. Nutr. 100, 254e268. Roca, M., Sanchez, A., Perez, R., Pardo, O., Yusa, V., 2016. Biomonitoring of 20 elements in urine of children. Levels and predictors of exposure. Chemosphere 144, 1698e1705. Sanchez, J.C.D., Teixeira, E.C., Fernandes, I.D.M., Pestana, M.H.D., Machado, R.P., 1994. ~o e da mobilidade dos elementos met Estudos da concentraça alicos nas cinzas trica de Candiota. Geochim. Bras. 8 (1), 41e50. da usina termoele Schulz, C., Wilhelm, M., Heudorf, U., Kolossa-Gehring, M., German Fed Environm, A., 2011. Update of the reference and HBM values derived by the German Human Biomonitoring Commission. Int. J. Hyg Environ. Health 215, 26e35. Sughis, M., Nawrot, T.S., Riaz, A., Ikram-Dar, U., Mahmood, A., Haufroid, V., et al., 2014. Metal exposure in schoolchildren and working children. A urinary biomonitoring study from Lahore, Pakistan. Int. J. Hyg Environ. Health 217 (6), 669e677. Suzuki, K.T., Doi, C., Suzuki, N., 2006. Metabolism of 76Se-methylselenocysteine compared with that of 77Se-selenomethionine and 82Se-selenite. Toxicol. Appl. Pharmacol. 217, 185e195. Tuakuila, J., Lison, D., Lantin, A.C., Mbuyi, F., Deumer, G., Haufroid, V., et al., 2012. Worrying exposure to trace elements in the population of Kinshasa, Democratic Republic of Congo (DRC). Int. Arch. Occup. Environ. Health 85, 927e939. Tuakuila, J., Kabamba, M., Mata, H., Mbuyi, F., 2015. Tentative reference values for environmental pollutants in blood or urine from the children of Kinshasa. Chemosphere 139, 326e333. Yoneyama, S., Miura, K., Itai, K., Yoshita, K., Nakagawa, H., Shimmura, T., Okayama, A., Sakata, K., Saitoh, S., Ueshima, H., Elliott, P., Stamler, J., 2008. Dietary intake and urinary excretion of selenium in the Japanese adult population: the INTERMAP study Japan. Eur. J. Clin. Nutr. 62, 1187e1193. Yusa, V., Pardo, O., 2015. Chapter four: human risk assessment and regulatory framework for minerals in food. Handbook of mineral elements in food. In: Miguel de la Guardia and Salvador Garrigues. Whiley-Blackwell, Oxford, UK. Zeiner, M., Ovari, M., Zaray, G., Stefan, I., 2004. Reference concentrations of trace elements in urine of the budapestian population. Biol. Trace Elem. Res. 101 (2), 107e115. Zhang, X., Cui, X., Lin, C., Ma, J., Liu, X., Zhu, Y., 2016. Reference levels and relationships of nine elements in first-spotmorning urine and 24-h urine from 210 Chinese children Xuan. Int. J. Hyg Environ. Health 220, 227e234.