DSpace at VNU: Contamination by arsenic and other trace elements in tube-well water and its risk assessment to humans in Hanoi, Vietnam

Environmental Pollution 139 (2006) 95e106 www.elsevier.com/locate/envpol Contamination by arsenic and other trace elements in tube-well water and its risk assessment to humans in Hanoi, Vietnam Tetsuro Agusa a, Takashi Kunito b, Junko Fujihara a,1, Reiji Kubota a, Tu Binh Minh a, Pham Thi Kim Trang c, Hisato Iwata a, Annamalai Subramanian a, Pham Hung Viet c, Shinsuke Tanabe a,* a Center for Marine Environmental Studies (CMES), Ehime University, Bunkyo-cho 2-5, Matsuyama 790-8577, Japan b Department of Environmental Sciences, Faculty of Science, Shinshu University, 3-1-1 Asahi, Matsumoto, Nagano 390-8621, Japan c Research Center for Environmental Technology and Sustainable Development, Hanoi University of Science, VNU Hanoi, 334 Nguyen Trai, Thanh Xuan, Hanoi, Vietnam Received November 2004; accepted 23 April 2005 High concentrations of arsenic, manganese and barium were found in tube-well water and human hair in suburban areas of Hanoi, Vietnam Abstract Concentrations of As and other trace elements and their association were examined in groundwater (nZ25) and human hair (nZ59) collected at Gia Lam District and Thanh Tri District, suburban areas of Hanoi, Vietnam, in September 2001 Concentrations of As in the groundwater ranged from !0.10 to 330 mg/l, with about 40% of these exceeding WHO drinking water guideline of 10 mg/l Also, 76% and 12% of groundwater samples had higher concentrations of Mn and Ba than WHO drinking water guidelines, respectively Arsenic concentrations in hair of residents in Gia Lam and Thanh Tri Districts (range 0.088e2.77 mg/g dry wt.) were lower than those in other As-contaminated areas of the world, but were higher than those of people in noncontaminated areas Concentrations of As and Mn in hair of some individuals from the Gia Lam and Thanh Tri Districts exceeded the level associated with their toxicity and, therefore, a potential health risk of As and Mn is a concern for the people consuming the contaminated water in this area Cumulative As exposure was estimated to be lower than the threshold levels at the present, which might explain the absence of manifestations of chronic As poisoning and arsenicosis in the residents of Gia Lam and Thanh Tri Districts To our knowledge, this study revealed for the first time that the residents are exposed not only to As but also Mn and Ba from groundwater in the Red River Delta, Vietnam Ó 2005 Elsevier Ltd All rights reserved Keywords: Arsenic; Manganese; Barium; Groundwater; Human hair; Hanoi; Vietnam Introduction * Corresponding author Tel./fax: C81 89 927 8171 E-mail address: shinsuke@agr.ehime-u.ac.jp (S Tanabe) Present address: Department of Legal Medicine, Shimane University School of Medicine, 89-1 Enya, Izumo, Shimane 693-8501, Japan 0269-7491/$ - see front matter Ó 2005 Elsevier Ltd All rights reserved doi:10.1016/j.envpol.2005.04.033 Arsenic is not contained so much in the Earth’s crust but greatly concentrated in pyrite, hydrous Fe oxides and sulfur compounds (Smedley and Kinniburgh, 96 T Agusa et al / Environmental Pollution 139 (2006) 95e106 2002) It is known that As would be easily solubilized in water from these minerals depending on pH, redox conditions and temperature (Smedley and Kinniburgh, 2002) Nickson et al (1998) suggested that As may be released from As-rich Fe oxyhydroxides into groundwater under reductive conditions in alluvial sediments in Bangladesh and West Bengal Increased usage of groundwater for drinking in these areas has caused serious health problems (Bagla and Kaiser, 1996; Nickson et al., 1998), because inorganic As is carcinogenic and causes skin and various internal cancers (IARC, 1980; WHO, 2001) It is reported that about 36 million of the population in the Bengal Delta is at risk from drinking As-contaminated groundwater (Smith et al., 2000) Tondel et al (1999) reported a relationship between As concentration in drinking water and prevalence of skin lesions in Bangladesh A significant doseeresponse relationship was also observed between As level in well water and mortality from cancers of bladder, kidney, skin, and lung in residents of the southwestern coast of Taiwan (Wu et al., 1989) Furthermore, recent studies suggest that As acts as an endocrine disruptor at very low concentrations Stoica et al (2000) reported that As activates estrogen receptor-a through an interaction with the hormonebinding domain at concentrations as low as nM (0.075 mg/l) Kaltreider et al (2001) demonstrated that As blocked glucocorticoid receptor-dependent induction of gene expression when administered at 0.3 mM (22.5 mg/L) Around the Red River Delta in Vietnam, Berg et al (2001) found elevated As concentrations (up to 3050 mg/l) in the groundwater, which is over the WHO drinking water guideline (10 mg/l) and the levels are comparable to those in Bangladesh and West Bengal, India The area of the Red River Delta is much smaller than that of the Bengal Delta, but there are 11 million people Although the health risk to the population consuming As-contaminated groundwater is of great concern, there is no information on As contamination in residents around the Red River Delta, Vietnam In the present study, the contamination status of As was evaluated in groundwater pumped from the tube wells in the households at the suburban areas of Hanoi Also, As level in human hair from the corresponding household with the tube well was determined Recently, Frisbie et al (2002) revealed that concentrations of Mn, Pb, Ni, and Cr as well as As were above the WHO drinking water guidelines in some groundwater of Bangladesh, suggesting the need for research on contamination of multiple elements in groundwater and their mixture toxicity Hence, concentrations of other trace elements in groundwater and human hair were also determined to assess the health effect of multielements in the present study Materials and methods 2.1 Samples Groundwater samples were randomly collected from 25 tube wells in Gia Lam District and Thanh Tri District in the suburban area of Hanoi, Vietnam (Fig 1), during September (dry season) 2001 These sampling locations correspond to the As-contaminated area reported by Berg et al (2001) Pond water (nZ1) and rainwater stored for drinking (nZ2) in Thanh Tri District were also sampled Polypropylene bottles (100 ml), which were soaked in a nitric acid bath and then washed with Milli-Q water, were used for water sampling Collected groundwater, pond water, and rainwater samples were stored at ÿ20  C as immediately as possible Human hair samples (nZ59; 24 families) were also collected from each house equipped with a tube well at Gia Lam District (nZ20; families) and Thanh Tri District (nZ39; 13 families) We obtained the informed consent from all the donors in an ethical manner Hair samples were taken into the polyethylene bags and were kept at ÿ20  C until chemical analysis The details of the hair samples are shown in Table 2.2 Water analysis After transporting to the laboratory, the water samples were acidified with H2SO4 for As and HNO3 for other elements Milli-Q water acidified with H2SO4 or HNO3 was used as control Arsenic concentration of water was measured by hydride generation atomic absorption spectrometry (AAS) using a Shimadzu HVG-1 hydride system coupled to a Shimadzu-AA680 AAS (Kubota et al., 2001; Agusa et al., 2002) Concentrations of V, Cr, Mn, Co, Cu, Zn, Ga, Rb, Sr, Mo, Ag, Cd, In, Sn, Sb, Cs, Ba, Tl, Pb and Bi were determined by inductively coupled plasma mass spectrometry (ICP-MS; Hewlett-Packard, HP-4500) (Anan et al., 2001; Agusa et al., 2003) Yttrium was used as an internal standard for ICP-MS measurements Concentration of Hg was determined with a cold vapor AAS (CV-AAS) (Sanso, Model HG-3000) Iron was measured by AAS Water pH was measured by a glass electrode pH meter (Asahi Techno Glass) 2.3 Hair analysis Human hair samples were washed by sonication with 0.3% polyoxyethylene lauryl ether (Okamoto et al., 1985), and subsequently dried for 12 h at 80  C For As analysis, dried hair sample was accurately weighted directly into a Kjeldahl flask and ml of purified HNO3 was added After pre-digestion at room temperature overnight, the sample was treated with 16 ml of acid mixture (HNO3:HClO4:H2SO4Z1:2:1) and digested by 97 T Agusa et al / Environmental Pollution 139 (2006) 95e106 China Laos Thailand Gia Lam Cambodia Vietnam Thanh Tri Fig Map showing sampling location Groundwater, rainwater, pond water, and human hair were collected from Gia Lam District and Thanh Tri District in the suburban areas of Hanoi during September 2001 heating to over 300  C until the perchloric acid was removed (Kubota et al., 2001) Arsenic concentration was measured by HG-AAS For analysis of other trace elements, about 0.1 g of hair sample was digested in 1.5 ml of concentrated HNO3 in a Teflon PTFE tube in a microwave oven (Agusa et al., 2003; Ikemoto et al., 2004) Concentrations of 20 elements (V, Cr, Mn, Co, Cu, Zn, Ga, Rb, Sr, Mo, Ag, Cd, In, Sn, Sb, Cs, Ba, Tl, Pb and Bi) and Hg were determined by ICP-MS and CV-AAS, respectively The accuracy of the method was assessed using a certified reference material NIES No.5 Human Hair (Okamoto et al., 1985) provided by the National Institute for Environmental Studies (NIES), Japan Recoveries of the elements ranged from 79.2 to 108% distribution with KolmogoroveSmirnov’s one sample test Because some variables were not normally distributed, nonparametric tests were used to compare different groups and correlation for analysis The ManneWhitney U-test was employed to detect gender and regional (Gia Lam and Thanh Tri) differences in trace element concentrations KruskaleWallis test was also used for comparison of more than two groups Spearman’s rank correlation coefficient was used to measure the strength of the associations between As concentration and other variables A p value of less than 0.05 was considered to indicate statistical significance All statistical analyses were performed with StatView (version 5.0, SASÒ Institute, Cary, NC, USA) and SYSTAT (version 9, SPSS, Chicago, IL, USA) 2.4 Statistical analysis One half of the value of the respective limit of detection was substituted for those values below the limit of detection and used in statistical analysis All data were tested for goodness of fit to a normal Table Details of human hair samples from suburban areas of Hanoi Area N Agea Gia Lam Total Female Male 20 12 29 (2e71) 26 (4e38) 31 (2e71) Thanh Tri Total Female Male 39 20 19 25 (4e50) 27 (4e50) 22 (5e41) a Mean and range Results and discussion 3.1 Contamination status of As in groundwater Concentrations of As in the groundwater ranged from !0.1 to 330 mg/l (Table 2) Median As concentration in groundwater in Gia Lam (5.0 mg/l) was comparable to that in Thanh Tri (1.5 mg/l) ( pO0.05; Table 2) About 40% of these samples contained As concentrations exceeding WHO drinking water guideline of 10 mg/l (WHO, 1996) (Fig 2), which confirmed the findings of Berg et al (2001) in which an elevated level of As was observed in the groundwater of the Red River Delta In contrast, As concentrations were low in pond water and rainwater (Table and Fig 2) To understand the magnitude of As contamination, concentrations of As in groundwater in the present study were compared with those in other As-contaminated 98 Table Concentrations of arsenic and other trace elements (mg/l) in groundwater, rainwater, and pond water in suburban areas of Hanoi Sample Cr Mn Fe Co Cu Zn Ga As Rb Sr Mo Mean SD Min Max Median Na 0.14 0.13 0.04 0.48 0.07 11/11 2.1 0.37 1.6 3.0 2.1 11/11 1520 1530 2.67 5530 1040 11/11 5100 5100 290 13000 1700 11/11 1.1 1.2 0.09 3.9 0.82 11/11 3.85 1.82 0.894 6.81 3.74 11/11 6.42 5.54 0.24 17.6 4.59 11/11 22.0 12.7 7.77 44.0 17.6 11/11 10.8 14.2 !0.1 38.2 5.04 7/11 3.32 3.41 0.24 10.9 1.76 11/11 370 92.7 249 552 348 11/11 1.18 1.86 0.16 6.69 0.73 11/11 Mean SD Min Max Median N 0.90 0.91 0.05 2.7 0.67 14/14 2.2 0.45 1.3 3.0 2.2 14/14 1260 1130 25.2 4190 1100 14/14 4400 6000 220 16000 1000 14/14 1.6 1.5 0.26 5.8 1.2 14/14 2.63 2.28 0.88 8.22 1.65 14/14 18.3 28.2 2.03 95.1 4.89 14/14 15.5 10.8 6.43 49.9 12.0 14/14 44.0 88.2 !0.1 330 1.5 10/14 2.01 2.40 0.06 7.38 1.00 14/14 582 151 358 909 585 14/14 1.58 1.50 0.23 5.25 1.26 14/14 Rainwater Mean (median) Min Max N 1.9 1.3 2.5 2/2 0.30 0.19 0.41 2/2 1.61 1.34 1.88 2/2 48 38 58 2/2 0.03 0.03 0.04 2/2 0.76 0.32 1.2 2/2 1.06 0.35 1.77 2/2 0.91 0.57 1.26 2/2 0.58 0.56 0.59 2/2 6.01 4.26 7.75 2/2 46.2 14.6 77.7 2/2 0.10 0.07 0.14 2/2 Pond water Concentration N 1.7 1/1 0.34 1/1 105 1/1 220 1/1 0.27 1/1 1.52 1/1 1.99 1/1 1.57 1/1 4.45 1/1 4.36 1/1 54.6 1/1 0.85 1/1 50 500 Ag Cd In Sn Sb Cs Ba Hg Tl Pb Bi !0.01 0.03 0.04 !0.01 0.13 !0.01 3/11 0.01 0.00 !0.01 0.01 !0.01 1/11 !0.1 !0.1 !0.5 !0.1 0.2 !0.1 1/11 0.01 0.02 !0.01 0.06 !0.01 2/11 0.08 0.09 !0.01 0.22 0.02 7/11 !0.01 !0.1 !0.1 !0.1 0/11 410 240 160 820 360 11/11 !0.01 0.01 !0.01 1/11 0.27 0.29 !0.01 0.93 0.13 13/14 0.01 0.02 !0.01 0.06 !0.01 2/14 Gia Lam Groundwater Thanh Tri Groundwater Drinking water guideline (WHO, 1996) Gia Lam Groundwater 2000 10 70 Mean SD Min Max Median N !0.01 0.02 !0.01 1/11 0.04 0.05 !0.01 0.16 0.02 7/11 Mean SD Min Max Median N 0.06 0.20 !0.01 0.75 !0.01 3/14 0.12 0.21 0.01 0.81 0.06 14/14 0.07 0.05 !0.01 0.23 0.06 13/14 0.01 0.02 !0.01 0.07 !0.01 2/14 0.1 0.1 !0.1 0.3 !0.1 6/14 0.1 0.0 !0.1 0.2 !0.1 2/14 250 170 95 770 210 14/14 !0.5 !0.5 !0.5 0/14 0.01 0.02 !0.01 0.07 !0.01 3/14 Rainwater Mean (median) Min Max N !0.01 !0.01 !0.01 0/2 !0.01 !0.01 !0.01 0/2 !0.01 !0.01 !0.01 0/2 !0.01 !0.01 !0.01 0/2 0.4 0.3 0.4 2/2 !0.1 !0.1 0.1 1/2 13 8.0 18 2/2 !0.5 !0.5 !0.5 0/2 0.01 !0.01 0.02 1/2 0.05 0.03 0.08 2/2 !0.01 !0.01 !0.01 0/2 Pond water Concentration N !0.01 0/1 0.02 1/1 !0.01 0/1 !0.01 0/1 0.5 1/1 !0.1 0/1 26 1/1 !0.5 0/1 !0.01 0/1 0.51 1/1 0.02 1/1 700 Thanh Tri Groundwater Drinking water guideline (WHO, 1996) a N, number of samples with detectable concentration !0.5 !0.5 !0.5 0/11 !0.5 10 T Agusa et al / Environmental Pollution 139 (2006) 95e106 V 99 T Agusa et al / Environmental Pollution 139 (2006) 95e106 Gia Lam district Groundwater Thanh Tri district Groundwater F21 F22 F23 F24 F25 F26 F27 F28 F29 F30 F31 F01 F02 F03 F04 F05 F06 F07 F08 F09 F10 F11 F12 F13 F14 Rainwater F07 F09 Pond water F12 ND ND ND ND ND ND ND ND ND ND WHO guideline (10 µg/l) 50 100 150 200 250 300 350 As concentration (µg/l) Fig Arsenic concentrations in groundwater, rainwater and pond water in the suburban areas of Hanoi Sample number of groundwater (F01-14, F21-31) indicates well in each home areas (Fig 3a) Median values in groundwater in Gia Lam and Thanh Tri were lower than those in other Ascontaminated areas However, the maximum value (330 mg/l) was comparable to the levels in other Ascontaminated areas In a previous report, high concentrations of As were observed in groundwater of Gia Lam (2e3050 mg/l) and Thanh Tri (9e3010 mg/l) (Berg et al., 2001) In the present study, however, a lower concentration (!0.1e330 mg/l) of As was observed in groundwater though these samples were collected from the same area (Fig 3a) Because the As level in groundwater varied considerably between tube wells (2e3050 mg/l) (Berg et al., 2001), the difference in As concentration between the present and previous studies might be related to the sampling points even within the same area Also, annual and seasonal variation of the As level might be partly responsible for the inconsistency between the studies 3.2 Contamination status of other trace elements in groundwater Various trace elements in the groundwater, pond water and rainwater were also measured in the present study (Table 2) Concentrations of Fe and Mn in groundwater were higher than those of other elements, followed by alkaline earth metals such as Sr and Ba On the other hand, concentrations of Ag, In, Sn, Sb, Cs, Hg, Tl and Bi were very low Concentrations in pond water and rainwater were lower than those in groundwater for most of the elements Concentrations over the WHO drinking water guideline were also found for Mn (500 mg/l) and Ba (700 mg/l) (WHO, 1996) in some groundwater samples from Gia Lam and Thanh Tri (Fig 4a,b) Particularly, the median value of Mn concentration in groundwater in both Gia Lam and Thanh Tri was higher than 1000 mg/l and about 76% of the samples exceeded the WHO guideline of 500 mg/l (Fig 4a) Our study also indicates that Ba concentrations in three samples of groundwater were higher than WHO drinking water guidelines (700 mg/l) (Fig 4b) These findings indicate that people in the Red River Delta may be exposed not only to As but also to Mn and Ba from groundwater, and the possible adverse effects are of concern as described later 3.3 Influence of various factors on As concentration in groundwater A significant positive correlation was found between As and Fe concentrations in the groundwater ( p!0.001; Fig 5) Hence, the As level in groundwater may be the result of reductive dissolution of Fe oxyhydroxides adsorbed with As in the Red River alluvial tract as suggested by Berg et al (2001) Significant positive correlations were also found between As, and Mo, Ga and Ba in groundwater ( p!0.01), while the As concentration was negatively correlated with Pb and V ( p!0.01) The reasons for these relationships are not known, but these might be related to geological and geochemical properties in the subsurface of Red River alluvial tract Concentrations of 100 T Agusa et al / Environmental Pollution 139 (2006) 95e106 (a) Gia Lam, Vietnam (This study) Thanh Tri, Vietnam (This study) Bangladesh-1 (Karim, 2000) West-Bengal, India-1 (Das et al., 1995) Vietnam (Berg et al., 2001) Thailand (Foy et al., 1992) Inner Mongol, China (Yoshida and Yamauchi, 2000) Taiwan (Wu et al., 1989) Bangladesh-2 (Chowdhury et al., 2000) West-Bengal, India-2 (Chowdhury et al., 2000) Finland-1 (Kurttio et al., 1998) Kratie, Cambodia (Agusa et al., 2002) Kandal, Cambodia (Agusa et al., 2002) Mexico (Cebrian et al., 1983) Utah, USA-1 (Lewis et al., 1999) Finland-2 (Kurttio et al., 1999) 10-1 100 101 102 103 104 105 As concentration (µg/l) (b) Gia Lam, Vietnam (This study) Thanh Tri, Vietnam (This study) Chile (Das et al., 1995) West-Bengal-1 (Das et al., 1995) Bangladesh-2 (Chowdhury et al., 2000) West-Bengal-2 (Chowdhury et al., 2000) Bangladesh-1 (Karim et al., 2000) Finland-1 (Kurttio et al., 1998) Kratie, Cambodia (Agusa et al., 2002) Utah, USA-2 (Das et al., 1995) Kandal, Cambodia (Agusa et al., 2002) Alaska, USA (Das et al., 1995) Normal people (Arnold et al., 1990) 10-2 10-1 100 101 102 As concentration (µg/g dry wt.) Fig Arsenic concentrations in groundwater (a) and hair (b) in arsenic-contaminated areas Bar and circle indicate range and median (or arithmetic mean), respectively As and Mn were not significantly correlated in groundwater ( p>0.05), suggesting that the contamination source of As and Mn was different in the wells Depth of well (12e45 m) and pH in groundwater (7.6e9.0) were not related to the As concentration in the groundwater (data not shown) 3.4 Contamination status of As in human hair Arsenic concentrations in hair of residents from Gia Lam and Thanh Tri ranged from 0.088 to 2.77 mg/g dry wt (Table 3) Arsenic levels in hair of residents at both sites were comparable, which was consistent with the results of groundwater (Table 2) Variation in As levels in hair resembled the geographical pattern of As level in groundwater, showing higher concentrations of As both in hair and water of households F05, F07, F08 and F11 (Figs and 6a) Also, a significant positive correlation between As concentrations in groundwater and human hair was observed (rZ0.57, p!0.001; Fig 7a) A similar doseeresponse relationship between As concentrations in groundwater and human hair was reported in southwest Finland (Kurttio et al., 1998) This result suggests that groundwater is probably the main source of As exposure for these people Arsenic levels in human hair in the present study were lower than those from other contaminated areas such as Bangladesh and West Bengal, India (Das et al., 1995; Chowdhury et al., 2000; Karim, 2000), but higher than those of people in non-contaminated areas (Arnold et al., 1990) (Fig 3b) Also, As levels in hair of some individuals exceeded the level that may be related to skin pathology (Arnold et al., 1990) (Fig 6a), suggesting the potential health effects for populations in the area investigated 101 T Agusa et al / Environmental Pollution 139 (2006) 95e106 (a) Gia Lam district Groundwater Thanh Tri district Groundwater F21 F22 F23 F24 F25 F26 F27 F28 F29 F30 F31 F01 F02 F03 F04 F05 F06 F07 F08 F09 F10 F11 F12 F13 F14 Rainwater F07 F09 Pond water F12 WHO guideline (500 µg/l) 1000 2000 3000 4000 5000 6000 Mn concentration (µg/l) (b) Gia Lam district Groundwater F21 F22 F23 F24 F25 F26 F27 F28 F29 F30 F31 Thanh Tri district Groundwater F01 F02 F03 F04 F05 F06 F07 F08 F09 F10 F11 F12 F13 F14 Rainwater F07 F09 Pond water F12 WHO guideline (700 µg/l) 200 400 600 800 1000 Ba concentration (µg/l) Fig Concentrations of manganese (a) and barium (b) in groundwater, rainwater and pond water in the suburban areas of Hanoi Sample number of groundwater (F01-14, F21-31) indicates well in each home 3.5 Contamination status of other trace elements in human hair Concentrations of trace elements other than As were also determined in human hair from Gia Lam and Thanh Tri (Table 3) To understand the accumulation status of trace elements in this population, trace element levels of hair were compared with those in other studies (Chittleborough, 1980; Takeuchi et al., 1982) Concentrations of ‘‘Rb, Cd and Hg’’ in hair of the residents from Gia Lam and Thanh Tri (Rb: !0.001e0.124 mg/g dry wt., Cd: !0.001e0.965 mg/g dry wt., Hg: 0.09e0.98 mg/g dry wt.; Table 3) were lower than those reported by Chittleborough (1980) (Rb: 0.2e0.23 mg/g dry wt.; Cd: 0.34e 1.6 mg/g dry wt.; Hg: 1.08e1.55 mg/g dry wt.) and Takeuchi et al (1982) (Cd: 1.18 mg/g dry wt.; Hg: 3.9 mg/g dry wt.) In contrast, concentrations of V (median, 0.119 mg/g dry wt.) and Mn (median, 16.7 mg/ g dry wt.) in residents of Gia Lam and Thanh Tri (Table 3) were high, compared to the median values of V (0.029 mg/g dry wt.) and Mn (0.42 mg/g dry wt.) for Japanese (Takeuchi et al., 1982) Also, the hair concentrations of Ga and Ba in residents of Gia Lam and Thanh Tri (Ga: 0.019e3.02 mg/g dry wt., Ba: 0.3e34 mg/ g dry wt.; Table 3) were higher than the levels in the population in non-contaminated areas (Ga: 0.02e 0.14 mg/g dry wt., Ba: 0.6e5.6 mg/g dry wt.; Chittleborough, 1980) The high hair concentrations of Mn and Ba in the residents were consistent with the results obtained for the drinking water (Fig 4) Also, concentrations of Mn ( p!0.001), Co ( p!0.001), Ga ( p!0.01), Ba ( p!0.05), Mo ( p!0.05) and Sr ( p!0.05) in human 102 T Agusa et al / Environmental Pollution 139 (2006) 95e106 103 p