Environment International 35 (2009) 466–472 Contents lists available at ScienceDirect Environment International j o u r n a l h o m e p a g e : w w w e l s e v i e r c o m / l o c a t e / e n v i n t Contamination of groundwater and risk assessment for arsenic exposure in Ha Nam province, Vietnam Van Anh Nguyen a, Sunbaek Bang b,⁎, Pham Hung Viet c, Kyoung-Woong Kim a,b,⁎ a b c Department of Environmental Science and Engineering, Gwangju Institute of Science and Technology (GIST), Republic of Korea International Environment Research Center (IERC), Gwangju Institute of Science and Technology (GIST), Republic of Korea Center of Environmental Technology and Sustainable Development (CETASD), Hanoi University of Science, Vietnam a r t i c l e i n f o Available online 21 September 2008 Keywords: Arsenic Risk assessment Groundwater Ha Nam province Vietnam a b s t r a c t The characteristics of arsenic-contaminated groundwater and the potential risks from the groundwater were investigated Arsenic contamination in groundwater was found in four villages (Vinh Tru, Bo De, Hoa Hau, Nhan Dao) in Ha Nam province in northern Vietnam Since the groundwater had been used as one of the main drinking water sources in these regions, groundwater and hair samples were collected in the villages The concentrations of arsenic in the three villages (Vinh Tru, Bo De, Hoa Hau) significantly exceeded the Vietnamese drinking water standard for arsenic (10 µg/L) with average concentrations of 348, 211, and 325 μg/L, respectively According to the results of the arsenic speciation testing, the predominant arsenic species in the groundwater existed as arsenite [As(III)] Elevated concentrations of iron, manganese, and ammonium were also found in the groundwater Although more than 90% of the arsenic was removed by sand filtration systems used in this region, arsenic concentrations of most treated groundwater were still higher than the drinking water standard A significant positive correlation was found between the arsenic concentrations in the treated groundwater and in female human hair The risk assessment for arsenic through drinking water pathways shows both potential chronic and carcinogenic risks to the local community More than 40% of the people consuming treated groundwater are at chronic risk for arsenic exposure © 2008 Elsevier Ltd All rights reserved Introduction Arsenic is known as a human carcinogen and assigned to a Group A classification by the United States Environmental Protection Agency (USEPA) Arsenic exists in four oxidation states (+5, +3, 0, −3) in nature The most common inorganic arsenic species in aqueous environments are arsenate [As(V)] and arsenite [As(III)] (Bissen and Frimmel, 2003) Studies on long-term exposure for arsenic showed that arsenic in drinking water could be associated with liver, lung, kidney and bladder cancers, as well as skin cancer Most organic arsenic species are less toxic than inorganic arsenic (ATSDR, 2000; Bissen and Frimmel, 2003) However, the toxicity of monomethylarsinous acid [MMA(III)] is higher than As(III) in an vitro study with the microorganism Candida humicola and also in an vivo study (Cullen et al., 1989; Petrick et al., 2000) The toxicity of arsenic in terms of cell survival (genotoxicity) strongly depends on its oxidation states According to studies by Fischer et al (1985) and Bertolero et al ⁎ Corresponding authors Bang is to contacted at International Environment Research Center (IERC), Gwangju Institute of Science and Technology (GIST), Republic of Korea Kim, Department of Environmental Science and Engineering, Gwangju Institute of Science and Technology (GIST), Republic of Korea E-mail addresses: sbang@gist.ac.kr (S Bang), kwkim@gist.ac.kr (K.-W Kim) 0160-4120/$ – see front matter © 2008 Elsevier Ltd All rights reserved doi:10.1016/j.envint.2008.07.014 (1987), As(V) was at least 10-fold less toxic than As(III) As(III) was about 40-fold more toxic to KB oral epidermoid carcinoma cells (Huang and Lee, 1996) As the results of arsenic biotransformation show, As(V) is rapidly reduced to As (III) in the human body (Bertolero et al., 1987; Vahter, 2002) Due to this reason, total arsenic is usually counted in human health risk assessments of arsenic through oral pathways Arsenic groundwater contamination resulted in significant human health effects in many countries such as Taiwan, Bangladesh, Vietnam, India, Chile, etc In Vietnam, groundwater is used as the main water source for local communities Approximately 13 million people (16.5% population) are using water from tube-wells (NEA, 2002) Elevated arsenic concentrations were found in numerous regions in Vietnam Berg et al (2001) published the first publication on arsenic contamination of groundwater in the city and rural districts of Hanoi Arsenic levels of raw groundwater used in three water treatment plants ranged from 240–320 μg/L and concentrations in five other plants ranged from 37–82 μg/L Arsenic concentrations in 50% of the tap water samples exceeded 50 μg/L The average arsenic concentration in groundwater samples from private tube-wells in suburban areas was 159 μg/L (Berg et al., 2001) Significant contamination of arsenic was reported in Ha Nam province (Red river delta, northern part of Vietnam) and Dong Thap province V.A Nguyen et al / Environment International 35 (2009) 466–472 (Mekong river delta, southern part of Vietnam) (Chander et al., 2004) Severe arsenic poisoning symptoms were found in 2004 by the Vietnam National Institute of Occupational and Environmental Health (Dang et al., 2004) Approximately 0.5–1 million people in this area were estimated to be at chronic risk for arsenic exposure (Berg et al., 2007) Appropriate treatment methods are needed to remove arsenic from the groundwater in these contaminated areas Sand filtration systems with coprecipitation are considered as one of the most effective treatment systems (Berg et al., 2006) Detailed information on the composition of Vietnamese groundwater is available in several recent publications Typical groundwater is the CaHCO3–MgHCO3 type in anoxic conditions and contains high iron and manganese concentrations (Postma et al., 2007; Berg et al., 2007, 2008; Buschmann et al., 2008) Noticeable levels of ammonium, phosphate, and DOC were found in the areas of abundant peat and high groundwater abstraction in the Red river delta (Northern Vietnam) and in the Mekong river delta (Southern Vietnam) (Berg et al., 2008; Buschmann et al., 2008) On the other hand, data about arsenic speciation is quite limited Only one study of groundwater in a shallow Holocene aquifer on the Red river flood plain near Hanoi reported that As(III) is the predominant species (Postma et al., 2007) The arsenic concentration in groundwater and its adverse human health risks were investigated in this study Analyses for the composition and arsenic speciation in groundwater were conducted Since arsenic mainly accumulates in keratin-containing tissues (such as skin, hair and nails) as potentially excretory routes, human hair was selected as the biomarker to evaluate the arsenic accumulation in the human body Both chronic and carcinogenic risks to human health, caused by arsenic exposure, through drinking water pathways were estimated 467 Materials and methods 2.1 Sampling 2.1.1 Target areas The Ha Nam province was selected for sampling due to the fact that both arsenic contamination and the adverse effects of arsenic exposure to human health were found in the area by previous publications (Chander et al., 2004; Dang et al., 2004) The Ha Nam province with the population of 820,100 is located in the North Vietnam Plains and Midlands, and in the right bank of the Red River, which is about 38.6 km long in the province The Red River plays an important role in irrigation and forms fertile land with an area of nearly 10,000 Groundwater samples were collected from private tubewells in four villages (Vinh Tru — VT, Nhan Dao — ND, Bo De — BD, and Hoa Hau — HH) from two riverside districts (Ly Nhan and Binh Luc) of the Red River and Chau Giang River (the unconfined sub-brand of the Red River) The total population was more than 30,000 in selected target areas 2.1.2 Sampling procedure Groundwater samples were collected two times over a year (excepted ND) in the dry season (February, 2006) and rainy season (September, 2006) For the first sampling batch, 10 families were randomly selected for sampling in each village For the second sampling batch, samples were collected from the same families as the first batch except for site in VT, site in BD and sites in HH because the tube-wells were ruined In total, 40 groundwater samples were collected from the tube-wells for the first batch and 26 tube-wells were sampled for the second batch Sampling locations are presented in Fig Since the depths of the tube-wells mostly ranged from 16–40 m, the groundwater was considered to be from the shallow Holocene aquifer Approximately 87% of households used groundwater treated by sand filtration systems Originally, sand filters were installed for iron removal since iron concentrations are commonly high in the groundwater Typical construction of the system was described by Berg et al (2006) However, a few families were directly using raw groundwater pumped from tube-wells In this study, both raw and treated groundwater samples were collected, if available Raw groundwater was pumped from wells for 10 to 15 before sample collection, in order to flush out all retained water in the pipes Samples were filtered through disposable syringe membranes (0.45 μm), then transferred into 60 mL plastic bottles, and kept in the dark at °C Groundwater samples were acidified in the field and the laboratory with nitric acid There was no significant difference in analytical results between samples acidified in the field and in the laboratory because standard Fig Map of the sampling site, Ha Nam porvince 468 V.A Nguyen et al / Environment International 35 (2009) 466–472 Fig Relationship between the arsenic concentration in groundwater and Eh Vinh Tru village: (□); Nhan Dao village: (■); Bo De village: (○); Hoa Hau village: (●) deviations were less than 5% Arsenic speciation of groundwater was directly conducted in the field using disposable arsenic speciation cartridges designed by Meng and Wang (1998) Treated groundwater was also collected by the same method, however, no arsenic speciation was conducted Human hair samples from both male (n = 16) and female (n = 27) at the average age of 26 were collected together with groundwater samples At least g of human hair samples were kept in sealed plastic bags at ambient temperature for arsenic analysis In addition, three tap water samples from three main water treatment plants (with the arsenic concentrations were b10 μg/L) were collected with 13 hair samples as control samples 2.2 Analysis Arsenic in groundwater was analyzed by graphite furnace atomic absorption spectrometry (GFAAS, Perkin Elmer 5100) and inductively coupled plasma mass spectrometry (ICP-MS, Agilent 7500) Total iron and manganese concentrations were measured by flame atomic absorption spectrometry (Flame-AAS, Perkin Elmer 5100) ICP-MS was used to measure other trace elements such as Ba, Ni, Zn, etc (detection limit of 0.1 μg/L) Standard reference material (SRM) for natural water (National Institute of Standards & Technology — NIST 1640) was used to assure the precision of the measurement After every 10 samples during analysis, the SRM sample was analyzed to check the accuracy of analysis All samples were measured at least two times in order to assess the repeatability of the measurement Samples were reanalyzed if the error of the SRM sample exceeded 10% or the relative standard deviation of the measurement exceeded 5% Dilution was made with 2% nitric acid, when the concentration of the sample was over the upper limitation of the standard range Total organic carbon (TOC) and total carbon (TC) were analyzed by the PPM LABTOC analyzer Other parameters such as pH, Eh, and conductivities were measured on-site by potable meters (HORIBA pH meter D55 and the ORION conductivity meter model 125) Concentrations of nitrate, nitrite, ammonium, phosphate, silicate, NO3, NO2, NH4, silica, phosphate, and sulfate were measured on site by the Spectrophotometer (Hach DR2400) SRM certified human hair (GW 07601 GSH1) was used to check the accuracy of the analytical process Human hair samples were washed with MilliQ water and acetone as recommended by the International Atomic Energy Agency procedure (IAEA, 1976) Washed samples were dried overnight at 60 °C in a drying oven The microwave digestion system (Ehos EZ, Milestone, America) with a rotor for 10 Teflon vessels was used for total digestion of arsenic in hair samples In the analysis, a recovery rate of N90% was achieved The amount of 0.3 g human hair was placed into a Teflon vessel containing mL of concentrated HNO3 and mL of H2O2 The digestion program utilized in this study was modified based on the program described by Vi et al (2004) All vessels were cleaned by the microwave digestion system with the same digestion program described before For each digestion batch, SRM, a reagent blank, and a duplicated sample were digested in order to check the consistency of the recovery rate and the accuracy of the digestion procedure The standard deviation of the SRM and duplicates were b10% Arsenic concentrations in human hair samples were analyzed by ICP-MS Results and discussion 3.1 Arsenic contamination in target areas 3.1.1 Groundwater composition Groundwater in the three studied areas (VT, BD, and HH) was seriously contaminated by iron, manganese, ammonium, and arsenic Arsenic concentration ranges were similar to other regions in the Red River delta but significantly higher than in the Mekong River delta (southern Vietnam) as reported by Berg et al (2007) The three contaminated villages are located on the right and left side of the Chau Giang River where eutrophic lakes are very abundant The average total arsenic concentrations in the groundwater of VT, BD, and HH were 348, 211, and 325 μg/L, respectively during the whole year The arsenic level in the groundwater of ND (located on the bank of the Red River) was much lower than other villages Only out of 10 samples in ND were detected at levels that exceeded the Vietnamese standard for arsenic in drinking water (10 μg/L) (Ministry of Science, Technology and Environment, 2002) The groundwater was found in strongly reducing conditions (−188–43 mV) at a neutral pH (6.57–7.29) A noticeable negative correlation between arsenic concentration in the groundwater to the Eh value (correlation R = −0.7 and p b 0.05) indicated that the arsenic was released by the reduction process (Fig 2) Approximately 90% of the arsenic existed in As(III) form Reduced species of Fe, Mn, and N were also the predominant species as compared to the oxidized species as commonly found in the reduced groundwater in Bangladesh and other regions in Vietnam More than 70% of the samples exceeded the Vietnamese aqueous manganese standard of 0.5 mg/L for raw groundwater (Ministry of Science, Technology and Environment, 2002) The manganese concentration ranged from 0.1– 1.7 mg/L in VT; 0.3–1.3 mg/L in BD; 0.1–1.8 mg/L in HH; and 0.1–1.2 mg/L in ND The average total concentration of iron was 18.1 mg/L in VT, 23.9 mg/L in BD, 23.1 mg/L in HH, and 40.8 in ND The most abundant nitrogenous species is NH+4 In all samples, the concentration of NH+4 normally exceeded the Vietnamese standard of mg/L for NH+4 in drinking water (Ministry of Science, Technology and Environment, 2002) by to 10 times (except some of the BD samples which contained more than 150 mg/L of NH+4) Because both NO−3 and NO−2 were at low levels, remarkable NH+4 concentrations suggested the reduction of NO3− and NO2− (probably by the occurrence of organic mater) Two major groundwater anions (HCO−3 and PO3− ) in contaminated areas were at higher ranges as compared to the concentrations in the Mekong River delta reported by Berg et al (2007) and Buschmann et al (2007) The silicate concentration varied in a wide range from b 1.0 to 69.7 mg/L On the other hand, sulfate (SO2− ) was not detected in most samples This 2− could be due to the initial low SO2− content of the groundwater or the reduction of SO4 2− to S which precipitates with the metal ions (Zheng et al., 2004; O'Day et al., 2004) Trace heavy metals such as Cd, Cr, Cu, and Pb were not detected (b 0.1 μg/L) The chemical compositions of the groundwater in target areas are summarized in Table In order to assess the impact of seasonal variation for the arsenic concentration of the groundwater, the t-test was used to compare the arsenic levels in groundwater samples taken between two sampling times The normality of the data sets was confirmed by the Shapiro–Wilk test with the SPSS program (p N 0.05) No significant seasonal fluctuation of total arsenic concentration was observed in the contaminated villages (p-value N 0.05) In contrast, the highest concentration of arsenic at the transition of the rainy season to the dry season was reported (Berg et al., 2001; Stanger et al., 2005) 3.1.2 Arsenic in treated groundwater Sand filtration systems are widely used in the studied areas Treated groundwater is considered as one of the main water sources consumed directly by the local communities The arsenic removal efficiency for the existing sand filtration system was investigated because many people were using the treated groundwater for washing and cleaning More than 90% of the total arsenic was removed from the groundwater treated during February (Table 2) This result agreed with the recent study from Berg et al (2006) conducted in other regions of Red River delta High iron concentrations in the groundwater played important roles in improving the efficiency of arsenic removal by sand filtration, as the result of the coprecipitation mechanism In spite of high arsenic Table Chemical compositions of groundwater Parametersa Vinh Tru Bo De Hoa Hau Nhan Dao TDS (mg/L) As-III (µg/L) Total As (µg/L) Total Fe (mg/L) Mn (mg/L) Ba (µg/L) Ni (µg/L) Se (µg/L) Zn (µg/L) Ca (mg/L) Na (mg/) Mg (mg/L) Cd (µg/L) Cr (µg/L) Cu (µg/L) Pb (µg/L) SiO2 (mg/L) SO4 (mg/L) NO2(mg/L) NO3 (mg/L) NH4 (mg/L) PO4 (mg/L) HCO3 (mg/L) 881.9 292 348 18.1 0.7 789 131.8 12.2 70.9 b 0.1 b 0.1 b 0.1 b 0.1 28.2 b2 0.01 3.7 21.7 9.8 658.1 1836.5 198 211 23.9 0.5 1338 149.3 33.2 74.1 b 0.1 b 0.1 b 0.1 b 0.1 46.3 b2 0.02 8.6 94.6 6.3 575.0 973.2 302 325 23.1 0.7 824 145.4 19.7 45.3 b0.1 b0.1 b0.1 b0.1 22.9 b2 0.01 4.1 38.4 5.7 677.6 856.9 50 51 40.8 0.8 553 86.8 26.0 58.7 b 0.1 b 0.1 b 0.1 b 0.1 37.3 b2 0.01 0.9 (aAverage value for the whole year; n = 10 for each village) 4.2 172.8 V.A Nguyen et al / Environment International 35 (2009) 466–472 469 Table Arsenic concentrations in raw and treated groundwater; Arsenic speciation of the groundwater Raw groundwater Treated groundwater As — III (µg/L) As — total (µg/L) As — total (µg/L) % Removal February September February September February September February September Vinh Tru Mean Range Medium n 334 10–489 338 10 251 93–361 302 366 13–582 364 10 331 84–479 377 33 nd–82 13 10 40 3–192 17 92 71–100 84 10 85 18–97 96 Bo De Mean Range Medium n 211 107–334 181 10 186 85–297 179 219 112–350 198 10 203 94–288 208 14 3–48 40 7–156 11 96 76–99 97 84 45–97 93 Hoa Hau Mean Range Medium n 306 224–390 283 10 299 202–376 317 322 238–439 285 10 327 248–377 361 26 14–48 21 36 6–95 32 92 86–94 92 90 74–98 92 Nhan Dao Mean Range Medium n 50 b5–123 37 10 51 b5–127 44 10 removal, the sand filter system is not enough to reduce arsenic concentrations to safe levels (Fig 3) The percentage of treated groundwater containing arsenic concentrations higher than the Vietnamese standard was still extremely high (70% in VT, 40% in BD and even 100% in HH) except for the ND village This is attributed to the Fe/As ratio (mg/mg) and the high levels of anions such as bicarbonate, silicate, and phosphate in the groundwater Meng et al (2001) reported that Fe/As ratios of greater than 40 (mg/mg) were required to decrease arsenic to less than 50 μg/L (Bangladesh drinking water standard) According to the effects of anions on arsenic removal reported by Meng et al (2002), the presence of three anions significantly decreased arsenic removal The average Fe/As ratio in the ND village was more than 800, while the average Fe/As ratios in other villages ranged from 52–113 Higher levels of these anions were observed in the groundwater in Ha Nam province Especially, high bicarbonate concentrations were found in the VT, BD, and HH villages These results suggest that the improvement of the current sand filtration operation is needed to reduce arsenic below the arsenic drinking water standard 3.2 Arsenic risk assessment through the drinking water pathway 3.2.1 Hazard identification According to the information from our interviews and the literature (Chander et al., 2004), people in these areas have used groundwater since 1995 The percentage of the b5 b5 b5 100 100 100 population using the groundwater in VT, BD, HH and ND are 47%, 8%, 45%, and 100%, respectively Groundwater was widely used as drinking water until 2003 However, the residents of these areas have been trying to replace groundwater as their drinking water source with other sources (rainwater, and surface water), after the release of the arsenic contamination information Moreover, due to the lack of a clean water source, especially in dry season, they could not completely stop using groundwater Nguyen et al (2004) reported that groundwater is still mainly used for cleaning, bathing and washing food The rate of households using groundwater as drinking water and for cooking is 27%, and about half of these households are using groundwater all year round Approximately 13% of the investigated families have directly used raw contaminated groundwater with an arsenic concentration in the range of 161– 439 μg/L In addition, after the use of groundwater during a year period (1995–2004), early symptoms of arsenic poisoning such as hyperkeratosis and hyper-pigmentation diseases were found in local residents of the three villages (Table 3) Data for the health status of the people in VT, BD, and HH from Dang et al (2004) showed that the general cancer rate (0.15% in VT, 0.1% in BD, and 0.05% in HH) was higher than in other rural areas throughout the whole country This suggests that the use of arseniccontaminated groundwater results in potential health problems to local communities 3.2.1.1 Arsenic in human hair Human hair samples were used as a biomarker for arsenic accumulation and toxicity in humans As suggested by Arnold et al (1990), the normal level of the arsenic concentration in human hair ranges from 0.08–0.25 mg/kg and the concentration which is an indication of toxic effects is N1.00 mg/kg Table shows that most of the samples from the contaminated villages are higher than the normal range (79% in VT, 59% in BD and 75% in HH) Three out of thirty four samples collected in the contaminated villages exceeded 1.00 mg/kg, indicating the occurrence of toxic effects The arsenic concentrations in all of the samples from the ND village were under or in normal range for arsenic concentrations found in human hair In addition, arsenic concentrations detected in the human hair samples collected in the contaminated areas were much higher than that of the control samples collected from people using tap water containing less than 10 μg/L of arsenic in Hanoi (Fig 4) While the arsenic concentrations of the control samples ranged from less than 0.01–0.09 mg/kg, the concentrations of the samples in the contaminated areas ranged from 0.12–1.09 mg/kg However, these levels were much lower as compared to the Bangladesh cases (1.1– 19.84 mg/kg) reported by Masud Karim (2000) and Anawar et al (2002) The possible reasons for this could be the difference of the arsenic exposure time and the amount of Table Skin lesions in contaminated villages (Dang et al., 2004) Fig Removal of arsenic by sand filtration systems in four villages Vinh Tru village: (□); Nhan Dao village: (■); Bo De village: (○); Hoa Hau village: (●); Vietnamese standard for arsenic in drinking water (10 μg/L): (- - -) Hyperpigmentation (%) Hyperkeratosis (%) n Vinh Tru Bo De Hoa Hau 12 10.6 132 11.3 29.0 62 7.3 14.3 456 470 V.A Nguyen et al / Environment International 35 (2009) 466–472 Table Classification of arsenic levels in human hair samples Village b0.08 (mg/kg) (%) 0.08–0.25 (mg/kg)a (%) 0.25–1.00 (mg/kg) (%) N1.00 (mg/kg)b (%) Vinh Tru Bo De Hoa Hau Nhan Dao Control 11 85 21 33 25 89 15 65 59 62 0 14 13 0 a b Normal level of arsenic in human hair (Arnold et al., 1990) Indication of toxicity (Arnold et al., 1990) water consumed between two regions While the arsenic-contaminated groundwater in Bangladesh has been used for more than 10 years with a high consumption rate of 4– L/day (Masud Karim, 2000; Anawar et al., 2002), contaminated groundwater in the target areas has only been used for more than years with a lower rate (approximately L/day) A significant Pearson correlation of 0.82 with a p-value b 0.05 was determined between the arsenic concentration in groundwater and the arsenic accumulation in female human hair (Fig 5) This data indicated that the intake of arsenic-contaminated groundwater resulted in highly accumulated arsenic in the female human body No correlation was found for the males (R-Pearson = 0.34 p-value = 0.28) because the local male population normally has a haircut every month The arsenic concentration in human male hair may not be well represented for long-term exposure as compared to females having long hair In addition, the local male population spends most of their time out of the village working Therefore, they are not directly exposed to contaminated groundwater as long as the women These results suggest that the exposure time is one of the key factors for arsenic accumulation and the adverse health effects in the local communities associated with the use of arsenic-contaminated groundwater 3.2.2 Exposure assessment Although arsenic can enter the human body through several pathways, all other intakes of arsenic (inhalation and dermal) are usually negligible in comparison to the oral route (ATSDR, 2000) The average arsenic daily dose (ADD) through the drinking water pathway was, therefore, calculated with the formula given by the USEPA as follows (Integrated Risk Information System (IRIS): Arsenic, inorganic; CASRN 7440-38-2, 1998) ADD ẳ fẵCIREFEDg ẵATBW where ADD C IR EF ED AT BW average daily dose from ingestion (mg/kg day) Arsenic concentration in water (mg/L) Water infestation rate (L/day) (assumed value) exposure frequency (day/year) (assumed value) exposure duration (year) (assumed value) averaging time (day) − Life time (assumed value) body weight (kg) (assumed value) Values of C were taken from the available data of directly used water which was divided into two groups: treated water (used in families having a sand filter system) and Fig Correlation between arsenic concentrations in groundwater and human hair untreated water (for families using raw groundwater directly) The range of arsenic levels in treated water was b 5–82 μg/L while the arsenic concentration in untreated water ranged from 161–439 μg/L According to the biological factor of the Vietnamese people, an adult at the age of 26 years old has a weight of 55 kg (BW) and an average lifetime of 50 years (18,250 days) The daily water consumption rate is L/day (Nguyen et al., 2004) Due to the information given by the communities in the target areas, groundwater has been used as drinking water for a total of years (from 1995 to 2003) and as washing water (food, cloth, and body washing) from 2003 to the present The ED and IR in this study were, therefore, assumed to be years for IR=2 L/day and 27 years for IR= 0.5 L/day, corresponding to the two periods The other parameters are listed in Table The obtained results suggest that the people consuming raw groundwater intake arsenic at a higher amount than 1.1–4.3 μg/kg day The level of ADD for a group of people using treated groundwater ranged from b0.1–1.1 μg/kg day Approximately 34% of the people in this group could consume safe groundwater (Table 6) In comparison with the situations in Bangladesh and India where groundwater generally contained 50–500 μg/L arsenic (sometimes more elevated) and the daily-ingested water was 4–6 L/day (Mazumder et al., 1998; Masud Karim 2000; Smith et al., 2000; Anawar et al., 2002), the magnitude of ADD in Vietnam was supposed to be lower However, the development of adverse health effects for the Vietnamese seemed to be quicker than for the Bangladeshi or Indian Arsenic poisoning in Bangladesh and India occurred after the use of arseniccontaminated groundwater for more than 10 years This may be attributed to the difference in dietary and genetic characteristics (Anawar et al., 2002) 3.2.3 Human health risk assessment Regarding previous evaluations, both chronic and carcinogenic risks were assessed further in this study Generally, chronic risks can be evaluated by the ratio between the estimated exposure and the reference dose (RfD) called the “Hazard Quotient” (HQ) HQ ¼ ADD=RfD Risk is considered occurring when HQs N Meanwhile, carcinogenic risk can be calculated as: R ẳ expSFADDịị where SF is the slop factor Table Parameters used for calculation of the ADD values Period IR (L/day) ED (years) EF (days/year) AT (days) BW (kg) 1995–2003 From 2003 0.5 27 365 365 18250 18250 55 55 Table Calculated ADD values for people using treated and raw groundwater Group Arsenic concentration ADD (mg/kg day) % Treated (n = 26) b 10 10–50 50–100 100–200 200–300 300–400 N 400 b 0.0001 0.0001–0.0005 0.0005–0.0011 0.0011–0.0021 0.0021–0.0032 0.0032–0.0043 N 0.0043 34 58 25 25 25 25 Untreated (n = 4) Fig Arsenic concentrations in human hair samples Female: Vinh tru village: (●); Nhan Dao village (▲); Bo De village: (■); Hoa Hau village: ( ); Male: Vinh tru village: (○); Nhan Dao village: (△); Bo De village: (□); Hoa Hau village: ( ); Control sample: (★) ◆ ◇ V.A Nguyen et al / Environment International 35 (2009) 466–472 Ministry of Science and Technology through the International Environmental Research Center (UNU and GIST Joint Program) Table Results for the chronic risk assessment Group HQ % Category Treated (n = 26) b1 1–10 1–10 N10 58 42 100 Non effect Effect Effect Significant effect Untreated (n = 4) 471 Toxicity data for threshold and non-threshold effects from arsenic exposure are available in the USEPA database — Integrated Risk Information System (IRIS) Oral toxicity reference values (RfD) and oral slope factor (SF) for arsenic are 3.0E− 04 and 1.5 mg/kg day, respectively (IRIS: Arsenic, inorganic; CASRN 744038-2, 1998) As the results of high arsenic consumption through the drinking water pathway, both potential chronic and carcinogenic risks of the two groups were calculated Approximately, 42% of the families which use treated groundwater could be affected by arsenic The situation was much more serious in the case of residents directly using untreated groundwater (Table 7) All of them were considered to be at a significant chronic risk These results corresponded to the fact that the first victims of arsenic poisoning in the three villages were reported by Nguyen et al (2004) The manifestation of carcinogenic effects in the contaminated areas was not clearly demonstrated since the exposure duration was not long enough to develop cancer (it normally takes decades to develop cancer) However, elevated potential carcinogenic risks were present While the ratio of in 1,000,000 is considered to be significant by the USEPA, the potential carcinogenic rate was found to be in 10,000 for people using treated groundwater in the target areas The value of the carcinogenic risk index was much higher in the case of residents using untreated groundwater It was determined that about in 1000 people could possibly suffer from cancer Obviously, arsenic contamination in groundwater presents significant threats to human health in the local communities examined in this study Nevertheless, groundwater has been widely used due to the lack of clean water resources, since other water sources were inadequate for the water demands of these communities Even though the current sand filter system was demonstrated to have a high arsenic removal efficiency, it was not enough to completely mitigate the problem This fact leads to the urgent need for the development of more effective arsenic removal methods Conclusion Severe arsenic contamination in groundwater was found in three out of four studied villages The predominant arsenic species in the groundwater was As(III), since the groundwater was in a strong reduced condition Elevated concentrations of iron and manganese were also found in the groundwater of all studied areas In addition, ammonium also occurred at elevated levels that requires further studies to confirm whether it could cause effects to the residents that consume the groundwater A survey of groundwater usage in the target areas showed that the sand filtration systems were effective for arsenic removal from groundwater with the presence of high soluble iron concentrations However, in many cases, arsenic concentrations in the groundwater treated by sand filtration were not enough to reach safe levels Arsenic accumulation in female hair samples was proved to be closely related to the arsenic concentration in treated water The results for both the chronic and carcinogenic risk assessments indicated that the health of the people in the contaminated target areas was significantly affected Higher potential risks were indicated for the group of people using untreated groundwater The calculated potential carcinogenic rate of in 1000 people is significant for the people using untreated groundwater A higher removal efficiency for arsenic treatment technology is needed to minimize the human health risk Acknowledgements This work was supported by the Korea Science and Engineering Foundation (KOSEF) through the National Research Laboratory Program funded by the Ministry of Science and Technology (No M10300000298-06J0000-29810) and by the research project from the References Anawar HM, Akai J, Mostofa KMG, Safiullah S, Tareq SM Arsenic poisoning in groundwater: health risk and geochemical sources in Bangladesh Env Int 2002;27:597–604 Arnold HL, Odam RB, James WD Disease of the skin clinical dermatology 8th ed Philadelphia: WB Sauders 1990:p.21 ATSDR Toxicological profile for arsenic Atlanta, Georgia, Agency for Toxic Substances and Disease Registry, U.S Department of Health & Human Services TP-92/02; 2000 Berg M, Tran HC, Nguyen TC, Pham HV, 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Environ Int 2008;34(6):756–64 Chander B, Nguyen TPT, Nguyen QH Random survey of arsenic contamination in tubewell water of 12 provinces in Vietnam and initially human health arsenic risk assessment. .. the drinking water pathway 3.2.1 Hazard identification According to the information from our interviews and the literature (Chander et al., 2004), people in these areas have used groundwater since