Contamination of groundwater and risk assessment for arsenic exposure in Ha Nam province, Vietnam Van Anh Nguyena, Sunbaek Bangb,⁎ , Pham Hung Vietc, Kyoung-Woong Kima,b,⁎ a Department o
Trang 1Contamination of groundwater and risk assessment for arsenic exposure in Ha Nam province, Vietnam
Van Anh Nguyena, Sunbaek Bangb,⁎ , Pham Hung Vietc, Kyoung-Woong Kima,b,⁎
a
Department of Environmental Science and Engineering, Gwangju Institute of Science and Technology (GIST), Republic of Korea
bInternational Environment Research Center (IERC), Gwangju Institute of Science and Technology (GIST), Republic of Korea
c
Center of Environmental Technology and Sustainable Development (CETASD), Hanoi University of Science, Vietnam
a b s t r a c t
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
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
325μg/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 sandfiltration 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
1 Introduction
Arsenic is known as a human carcinogen and assigned to a Group A
classi fication 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
monomethylarsi-nous 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.
(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 signi ficant 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) Signi ficant contamination of arsenic was reported in Ha Nam province (Red river delta, northern part of Vietnam) and Dong Thap province
Environment International 35 (2009) 466–472
⁎ 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
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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
Trang 2(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
water is available in several recent publications Typical
ground-water 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
path-ways were estimated.
2 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 ha Groundwater samples were collected from private tube-wells 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 thefirst 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 thefirst batch except for 1 site in VT, 1 site in BD and 2 sites in HH because the tube-wells were ruined In total, 40 groundwater samples were collected from the tube-wells for thefirst batch and 26 tube-wells were sampled for the second batch Sampling locations are presented
inFig 1.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 sandfiltration 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 byBerg 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 min before sample collection, in order toflush out all retained water in the pipes Samples were filtered through disposable syringe membranes (0.45μm), then transferred into 60 mL plastic bottles, and kept in the dark at 4 °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
467 V.A Nguyen et al / Environment International 35 (2009) 466–472
Trang 3deviations were less than 5% Arsenic speciation of groundwater was directly conducted
in thefield using disposable arsenic speciation cartridges designed byMeng 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 2 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 wereb10 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 byflame 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 0.1μg/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 ofN90%
was achieved The amount of 0.3 g human hair was placed into a Teflon vessel containing
3 mL of concentrated HNO3and 1 mL of H2O2 The digestion program utilized in this
study was modified based on the program described byVi 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 wereb10%
Arsenic concentrations in human hair samples were analyzed by ICP-MS
3 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 byBerg et al (2007) The
River where eutrophic lakes are very abundant The average total arsenic concentra-tions in the groundwater of VT, BD, and HH were 348, 211, and 325μg/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 5 out of 10 samples in ND were detected at levels that exceeded the Vietnamese standard for arsenic in drinking water (10μg/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 pb0.05) 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 NH4 In all samples, the concentration of NH4normally exceeded the Vietnamese standard of 4 mg/L for NH4in drinking water (Ministry of Science, Technology and Environment, 2002) by 3 to 10 times (except some of the BD samples which contained more than 150 mg/L of NH4) Because both NO3 −and NO2 −were at low levels, remarkable NH4concentrations suggested the reduction of NO3 −and NO2 −(probably by the occurrence of organic mater) Two major groundwater anions (HCO3 −and PO4 −) in contaminated areas were at higher ranges as compared to the concentrations in the Mekong River delta reported byBerg et al (2007) andBuschmann et al (2007) The silicate concentration varied in a wide range fromb1.0
to 69.7 mg/L On the other hand, sulfate (SO4 −) was not detected in most samples This could be due to the initial low SO4 −content of the groundwater or the reduction of SO4 −
to S2−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 (b0.1 μg/L) The chemical compositions of the groundwater in target areas are summarized inTable 1
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 (pN0.05) No significant seasonalfluctuation of total arsenic concentration was observed in the contaminated villages (p-valueN0.05) 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
Sandfiltration 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 fromBerg
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 sandfiltration, as the result of the coprecipitation mechanism In spite of high arsenic
Table 1 Chemical compositions of groundwater Parametersa
a
Fig 2 Relationship between the arsenic concentration in groundwater and Eh Vinh Tru
village: (□); Nhan Dao village: (■); Bo De village: (○); Hoa Hau village: (●)
Trang 4removal, the sandfilter 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 50μg/L (Bangladesh drinking water
standard) According to the effects of anions on arsenic removal reported byMeng 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 sandfiltration 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
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–
439μg/L
In addition, after the use of groundwater during a 9 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 fromDang 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 arsenic-contaminated 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 byArnold 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 isN1.00 mg/kg.Table 4shows 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 10μg/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 byMasud Karim (2000)andAnawar et al (2002) The possible reasons for this could be the difference of the arsenic exposure time and the amount of
Table 2
Arsenic concentrations in raw and treated groundwater; Arsenic speciation of the groundwater
Vinh Tru
Bo De
Hoa Hau
Nhan Dao
Fig 3 Removal of arsenic by sandfiltration systems in four villages Vinh Tru village:
(□); Nhan Dao village: (■); Bo De village: (○); Hoa Hau village: (●); Vietnamese
μg/L): (- - -)
Table 3 Skin lesions in contaminated villages (Dang et al., 2004)
469 V.A Nguyen et al / Environment International 35 (2009) 466–472
Trang 5water 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–
5 L/day (Masud Karim, 2000; Anawar et al., 2002), contaminated groundwater in the
target areas has only been used for more than 8 years with a lower rate (approximately
2 L/day)
A significant Pearson correlation of 0.82 with a p-valueb0.05 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)
ADD¼f½C⁎IR⁎EF⁎EDg
AT⁎BW
where
ADD average daily dose from ingestion (mg/kg day)
C Arsenic concentration in water (mg/L)
IR Water infestation rate (L/day) (assumed value)
EF exposure frequency (day/year) (assumed value)
ED exposure duration (year) (assumed value)
AT averaging time (day)−Life time (assumed value)
BW 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 sandfilter system) and
untreated water (for families using raw groundwater directly) The range of arsenic levels
in treated water wasb5–82 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 2 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 8 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 8 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 inTable 5
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 fromb0.1–1.1 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 arsenic-contaminated 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)
HQ¼ ADD=RfD Risk is considered occurring when HQsN1
Meanwhile, carcinogenic risk can be calculated as:
R¼ 1− exp − SF⁎ADDðð ÞÞ where SF is the slop factor
Table 4
Classification of arsenic levels in human hair samples
(mg/kg) (%)
0.08–0.25 (mg/kg)a(%)
0.25–1.00 (mg/kg) (%)
N1.00 (mg/kg)b(%)
a
Normal level of arsenic in human hair (Arnold et al., 1990)
b
Indication of toxicity (Arnold et al., 1990)
Fig 4 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: (★)
Fig 5 Correlation between arsenic concentrations in groundwater and human hair
Table 5 Parameters used for calculation of the ADD values
Table 6 Calculated ADD values for people using treated and raw groundwater
Trang 6Toxicity 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
7440-38-2, 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 byNguyen 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 1 in 1,000,000 is considered to
be significant by the USEPA, the potential carcinogenic rate was found to be 4 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 5 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 sandfilter 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
4 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 con firm 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
con-taminated target areas was signi ficantly affected Higher potential
risks were indicated for the group of people using untreated
groundwater The calculated potential carcinogenic rate of 5 in 1000
people is signi ficant for the people using untreated groundwater A
higher removal ef ficiency 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
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