Assessing the risks on human health associated with inorganic
arsenic intake from groundwater-cultured milkfish
in southwestern Taiwan
M.C. Lin
a,*, C.M. Liao
b aGeneral Education Center/Graduate Institute of Environmental Management, Nanhua University, Dalin, Chiayi 622, Taiwan
b
Department of Bioenvironmental Systems Engineering, National Taiwan University, Taipei 106, Taiwan Received 15 August 2006; accepted 17 September 2007
Abstract
The risk of consuming groundwater-cultured milkfish (Chanos chanos) was assessed. Samples of water and milkfish from
groundwa-ter-cultured ponds in southwestern Taiwan were analyzed. One third of the 12 sampled ponds had arsenic concentrations in the water
higher than 50 lg/L, which is the maximum allowed concentration for arsenic in aquacultural water in Taiwan. Of the total amount of
arsenic in water, the percentage of inorganic arsenic was 67.5 ± 8.8%. The inorganic arsenic level in milkfish was 44.1 ± 10.2%. The
bio-concentration factors (BCFs) of milkfish for total arsenic and inorganic arsenic were 11.55 ± 4.42 and 6.8 ± 2.64, respectively. The target
cancer risk (TR) for intake of the milkfish from those ponds was higher than the safe standard 1
· 10
6, while in 8 of the ponds the TR
values were higher than 1
· 10
4. Among the 12 ponds, 7 of those had the target hazard quotient (THQ) for intake of the milkfish higher
than the safe standard 1. The actual consumption (IRF) of milkfish from most of those ponds were higher than the calculated acceptable
consumption (RBIRF), based on TR = 1
· 10
6–1
· 10
4. Only three sampled ponds (Putai 2, Peimen 2 and Peimen 3) did not show
differences between the IRF and the RBIRF. Based on the standard TR = 1
· 10
6, both the risk-based concentration for inorganic
arsenic in milkfish (RBC
f) and the risk-based concentration for inorganic arsenic in pond water (RBC
w) were lower than the levels of
inorganic arsenic in reared milkfish (C
b) and the concentration of inorganic arsenic in pond water (C
w), respectively. When the
calcu-lation was based on TR = 1
· 10
4, only one sampled pond (Putai 3) had a RBC
f
value higher than C
b. The inhabitants might be exposed
to arsenic pollution with carcinogenic and non-carcinogenic risks.
2007 Elsevier Ltd. All rights reserved.
Keywords: Bioconcentration; Cultured milkfish; Groundwater; Inorganic arsenic; Risk assessment
1. Introduction
As a notorious element, arsenic remains a significant
human health concern (
Tsai et al., 2003
). Of the various
sources of arsenic in the environment, waterborne arsenic
probably poses the greatest threat to human health.
Air-borne arsenic, particularly through burning
arsenic-con-taining coal and occupational exposure, can also cause
problems for human health. Among the natural sources
of arsenic contamination, high concentrations are mainly
found in groundwater (
Smedley and Kinniburgh, 2002
).
It is toxic for the general population, mainly caused by
exposure from drinking water (
Liu et al., 2004
) and
seafood (
Donohue and Abernathy, 1999
). It has been well
recognized that consumption of arsenic, even at low levels,
increases the risk of producing or inciting cancer (
Buchet
et al., 1996; Abernathy et al., 2003; Yu et al., 2003; Chen
et al., 2004
).
Arsenic has been classified as a carcinogen, based on
human epidemiological data (
Chiou et al., 1995
); arsenic
is associated with different kinds of cancers (
IPCS, 2001;
Ng et al., 2003
). Many reports showed that the population
exposed to arsenic-contaminated water in Taiwan, Japan,
0278-6915/$ - see front matter 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.fct.2007.09.098
*
Corresponding author. Tel./fax: +886 5 272 2295. E-mail address:[email protected](M.C. Lin).
www.elsevier.com/locate/foodchemtox
Available online at www.sciencedirect.com
Bangladesh, West Bengal-India, Chile and Argentina have
higher cancer risks at skin and various viscera, including
lung, bladder, kidney and liver (
Mandal and Suzuki,
2002
). A significant exposure-response between arsenic
concentration and the mortality from cancers has been
reported (
Chiou et al., 1995; Chen et al., 2004
).
Arsenic has been well documented as one of the major
risk factors for blackfoot disease (BFD). This disease is
considered to be correlated with the consumption of
arsenic-contaminated groundwater by local inhabitants
liv-ing in the four towns, Putai, Yichu, Peimen and Hsuehchia,
known as the BFD area, in southwestern Taiwan (
Chiou
et al., 1995; Lin et al., 2004
). An increase in internal organ
and skin cancers as well as BFD disease was significantly
associated with the use of groundwater (
Chen et al.,
1999
). Today groundwater in this area is no longer used
for drinking or cooking, after tap water has been made
available in 1970s; however, the groundwater is still used
for aquaculture (
Lin et al., 2001,2004
). Since arsenic can
be accumulated in aquatic organisms (
Phillips, 1990; Ling
et al., 2005
), use of high arsenic content groundwater for
aquaculture has resulted in an accumulation of arsenic in
cultured animals, such as fish. Based on studies carried
out so far, it is significant to note that high concentrations
of total arsenic were found in cultured fish from the
arsenic-contaminated area (
Lin et al., 2001,2004; Huang
et al., 2003; Liao and Ling, 2003; Liao et al., 2003
).
After tilapia (Oreochromis mossambicus), milkfish
(Cha-nos cha(Cha-nos) is the most consumed fish in Taiwan. With high
market values, milkfish farming is an important
commer-cial practice. Most of the milkfish aquaculture is located
in the coastal region of southwestern Taiwan. Part of that
region is situated in and around the four towns in the BFD
area mentioned above. A high amount (38,000–49,000 ton/
ha) of freshwater is needed for milkfish culture.
Groundwa-ter is used for aquaculture because the waGroundwa-ter from rivers in
this area is too polluted. Several studies have been
con-ducted to demonstrate that to use arsenic-contaminated
groundwater for aquaculture may cause an overexposure
of arsenic in fish (
Lin et al., 2001, 2004; Liao and Ling,
2003; Ling et al., 2005; Ling and Liao, 2007
). Ingestion
of arsenic-contaminated fish could result in arsenic
accu-mulation in inhabitants and lead to adverse health effects
(
Falco et al., 2006
).
Lin et al. (2005)
have estimated the risk of the intake of
aquacultural milkfish from the ponds using
arsenic-con-taminated groundwater. In this study however, the risks
were calculated based on the total arsenic level in fish.
Phil-lips (1990)
noted that arsenic is more toxic in its inorganic
form. Organic arsenic species, such as the methylated
arsenic, are less toxic than the inorganic species (
Chiou
et al., 1995
). It has been well known that fish can covert
the toxic inorganic arsenicals in their bodies into non-toxic
methylated forms.
Borum and Abernathy (1994)
revealed
that the inorganic arsenic in fish is much more toxic than
the organic forms. Assessing the risks on human health
associated with inorganic arsenic intake from fish is more
important than the total arsenic intake. Therefore, target
cancer risk (TR) and target hazard quotient (THQ) values
should be calculated based on the inorganic arsenic level in
fish. In this study, we measured the inorganic arsenic levels
and conducted a risk assessment of inorganic arsenic
expo-sure from consuming the arsenic-contaminated milkfish
harvested from the groundwater ponds in southwestern
region of Taiwan.
2. Materials and methods
2.1. Sampling and preparation
Scheme of the research procedure is shown inFig. 1. Samples of water and adult milkfish (body length 35–40 cm, age 1 yr) from 12 ponds in the four towns, Putai, Yichu, Peimen and Hsuehchia (Fig. 2), in the arsenic-contaminated area were analyzed to determine the arsenic level. Only the milkfish in the monoculture ponds reared with groundwater and fed with artificial feed were selected. The groundwater used for culture in these ponds had a salinity of 0. With three replications for each sample, three 500 ml water samples, three fish and three feedstuffs per pond were col-lected. The water samples were fixed by adding 5 ml 1 N HNO3. After
measuring the weight and total length, the milkfish samples were placed on ice immediately and kept at 4C during transfer to the laboratory. The dorsal flesh of the fish was dissected and stored at20 C. The frozen flesh was dehydrated in a dryer (40C) for 96 h, and then ground into powder. All water and flesh samples were sent to the Super Micro Mass Research
Questionnaire Interview Sampling
Fish Water
Risk Assessment
Fish Ingetion Rate Asenic in Fish
Arsenic Analysis TR THQ RBIRF RBCf Asenic in Water RBCw BCF
Fig. 1. Scheme of the research procedure (TR: target cancer risk; THQ: target hazard quotient; RBIRF: risk-based fish ingestion rate, or accept-able consumption of fish; RBCf: risk-based inorganic arsenic
and Technology Center, Cheng Shiu University for analysis of total and inorganic arsenic using Inductively Coupled Plasma Mass Spectrometry (ICP-MS, Agilent 7500a).
The internal standard (Sc, Y, Tb and Ho) and the external standard for arsenic were added to correct for variations in ICP-MS and to verify the sensitivity and stability of the instrument. These standards were used to generate the calibration curves from which the composition of the arsenic samples was inferred. Blank, fortified control and test samples were ana-lyzed to obtain the concentrations of arsenic.
2.2. Analysis of total arsenic
Aliquots of dry flesh powder weighing 0.50 ± 0.01 g were placed into a 250 ml beaker. Nitric acid (65%, 10 ml) was added for an overnight (12– 15 h) digestion. The beaker with flesh solution, after the digestion, was heated with a water bath (Firstek, B206-T2) at 70–80C for 2–4 h until the total volume reduced to 1–2 ml. The solution was transferred to a volu-metric flask (50 ml), and then filled with 0.01 N of HNO3to make a 50 ml
of final solution. After filtration, this 50 ml solution was transferred to test tubes for arsenic analysis using ICP-MS. Analytical quality control was achieved by digesting and analyzing identical amounts of rehydrated (90% H2O) standard reference materials (DORM-2, Dogfish Liver-2-organic
matrix, NRC-CNRC, Canada). Recovery rates ranged from 95% to 97%. The limit of detection (LOD) for arsenic was 0.0052 mg/kg.
2.3. Analysis of inorganic arsenic
The methods employed for determination of inorganic arsenic have been described in Munoz et al. (2000) and Hung et al. (2003). The
lyophilized flesh powder with a weight of 0.50 ± 0.01 g was placed into a 50 ml screw-top centrifuge tube. An amount of 4.1 ml deionized water was added into the tube and then agitated until the sample was completely moistened. After adding 18.4 ml of concentrated HCl, the sample was agitated again for 1 h, and then left to stand for 12–15 h (overnight). The reducing agent (1 ml of 1.5% w/v hydrazine sulfate solution and 2 ml of HBr) was added and allowed for a 30-s agitation. An amount of 10 ml CHCl3 was added to the sample for a further agitation of 3 min. The
phases were separated by centrifuging at 2000 rpm for 5 min. The chlo-roform phase was separated by aspiration and poured into another tube. The extraction process was repeated two more times. The chloroform phases were combined and centrifuged again. The remnants of the acid phase were eliminated by aspiration (acid phase remnants in the chloro-form phase cause substantial overestimates of inorganic arsenic). Possible remnants of organic material in the chloroform phase were eliminated by passing it through Whatman GD/X syringe filters with a 25 mm PTFE membrane.
The inorganic arsenic in the chloroform phase was backextracted by agitating for 3 min with 10 ml of 1 mol/L HCl. The phases were separated by centrifuging at 2000 rpm, and the aqueous phase was then aspirated and poured into a beaker. This stage was repeated once again and the backextraction phases obtained were combined. When the backextraction phase generated emulsions that could not be broken by centrifuging at over 2000 rpm, the emulsion was transferred to the beaker. Ashing aid suspension and HNO3were added and the result was heated gently in the
sand bath for not more than 30 s. The emulsion was then broken and the chloroform phase formed was removed by aspiration.
The determination of inorganic arsenic in the back-extraction phase was performed by means of the following procedure: 2.5 ml of ashing aid suspension and 10 ml of concentrated HNO3were added to the combined
back-extraction phases. The result was evaporated on a sand bath until total dryness, and then dissolved in 3 ml of water. Inorganic arsenic was determined in the water extract using ICP-MS.
2.4. Questionnaire interview
A questionnaire interview was conducted to analyze the consumption habits on milkfish of the residents in the four towns mentioned above. We interviewed 141 residents, including the owners of the 12 milkfish ponds from March 2002 to January 2003. A brief questionnaire was filled in with demographic information and data on nutritional habits. The interview questionnaire included detailed questions about milkfish consumption to determine the amount and frequency of consumption. The personal, die-tary, and residential information was also obtained.
2.5. Calculation of bioconcentration factor (BCF)
The bioconcentration factor (BCF), relating the concentration of arsenic in water to its level in fish (Lin et al., 2004), was used to estimate the propensity of arsenic accumulation in milkfish:
BCF¼Cb Cw
ð1Þ
where Cb(mg/kg) is the arsenic level in fish; Cw(mg/L) is the arsenic
con-centration in water.
2.6. Estimation of potential health risks
The risk of arsenic accumulation from the ambient water to humans via the milkfish was assessed. All information from the residents, who consume the local cultured milkfish, was classified to evaluate the car-cinogenic risks of arsenic exposure. Target cancer risk (TR) and target hazard quotients (THQ) were used to indicate carcinogenic and non-car-cinogenic risks. The method to estimate TR and THQ was provided in USEPA Region III Risk-Based Concentration Table (USEPA, 2006). The models for estimating TR and THQ are shown as follows:
Fig. 2. Map showing locations of sampling sites (j) in the southwestern region of Taiwan.
TR¼ ðCb IRF 103 CPSo EFr EDtotÞ=ðBWa ATcÞ ð2Þ
THQ¼ ðCb IRF 103 EFr EDtotÞ=ðRfD BWa ATnÞ ð3Þ
where TR is the target cancer risk; Cbis the arsenic level in fish (mg/kg);
IRF is the fish ingestion rate (g/d); CPSo is the carcinogenic potency slope, oral (kg d/mg); EFr is the exposure frequency (350 d/yr); EDtot is the exposure duration, total (30 yr); BWa is the body weight, adult (70 kg); ATc is the averaging time, carcinogens (25,550 d); THQ is the target haz-ard quotient; RfD is the reference dose (mg/kg/d); ATn is the averaging time, non-carcinogens (EDtot· 365 d/yr). The health protection standard of lifetime risk for TR is 1· 106, and the standard for THQ is 1 (USEPA,
2006). Since the range for assumable risk is 104106, the maximum
amount of milkfish consumption based on acceptable risks of 104and
106were both calculated.
The only values of CPSo and RfD for arsenic that we could find were from theUSEPA (2006). However, it is not clarified whether those two values refer only to the inorganic arsenic or the total arsenic. The methods employed to determine the risks, associated with inorganic arsenic intake, were described inHan et al. (1998) and Lin et al. (2005). We followed their methods to evaluate potential human health risks (TR and THQ), based on the values of CPSo and RfD for arsenic (1.5 kgd/mg and 3 · 104mg/ kg/d, respectively), provided by USEPA (USEPA, 2006).
The acceptable consumption of milkfish, or the risk-based fish inges-tion rate (RBIRF, g/d), was calculated, based on the arsenic level in fish and the acceptable values for TR, using Eq.(2),
RBIRF¼ TR BWa ATc=ðCb 103 CPSo EFr EDtotÞ ð4Þ
The actual milkfish consumption and the upper limit for TR were inserted to Eq.(2)to calculate the risk-based concentration of arsenic in milkfish (RBCf). Furthermore, BCF and RBCfvalues were used to calculate the
risk-based concentration of arsenic in water (RBCw) (Lin et al., 2005):
RBCf¼ TR BWa ATc=ðIRF 103 CPSo EFr EDtotÞ ð5Þ
RBCw¼ RBCf=BCF ð6Þ
where RBCfis the risk-based concentration of arsenic in milkfish (mg/kg);
RBCwis the risk-based concentration of arsenic in water (mg/L).
3. Results
No arsenic was detected from the feedstuffs. The mean
length of sampled milkfish was 37.38 ± 1.32 cm and the
mean weight was 522.67 ± 76.25 g.
Fig. 3
shows
least-squares linear regressions plotted for the total arsenic level
in fish and the total arsenic concentration in water (C
b=
0.0092 C
w, R
2= 0.96), the inorganic arsenic level in fish
and the total arsenic concentration in water (C
b=
0.0042 C
w, R
2= 0.92), the total arsenic level in fish and
the inorganic arsenic concentration in water (C
b=
0.0115 C
w, R
2= 0.95), and the inorganic arsenic level in
fish and the inorganic arsenic concentration in water
(C
b= 0.0054 C
w, R
2= 0.96). C
bis the arsenic level in fish
(mg/kg) and C
wis the arsenic concentration in water (lg/
L). The arsenic level in milkfish showed a significant
posi-tively correlating with the arsenic level in pond water
(R
2> 0.9) (
Fig. 3
). Among the sampled ponds, Putai 3,
Yichu2, Yichu 3 and Hsuehchia 1 had arsenic
concentra-tions higher than the maximum allowed concentration of
50 lg/L for arsenic in aquacultural water in Taiwan,
whereas, the other ponds had arsenic concentrations in
water higher than 10 lg/L (
Fig. 4
). The total arsenic levels
in milkfish ranged from 0.21 ± 0.02 mg/kg to 3.35 ±
0.32 mg/kg, whereas the inorganic arsenic levels ranged
from 0.11 ± 0.03 mg/kg to 1.69 ± 0.74 mg/kg (
Fig. 5
).
Among the 12 ponds, Hsuehchia 1 had the highest arsenic
levels in water and fish.
The percentage of inorganic arsenic in total arsenic in
pond water was 67.5 ± 8.8%, and the percentage of
inor-ganic arsenic in total arsenic in fish was 44.1 ± 10.2%
(
Table 1
). The mean BCFs for total and inorganic arsenic
accumulated in milkfish were 11.55 ± 4.42 and 6.8 ± 2.64,
respectively. The nutritional habits of the 141 residents
from the arsenic-contaminated area showed that the actual
consumption on milkfish (IRF) from the 12 ponds, ranging
from 103.22 ± 43.69 g/d to 374.07 ± 134.22 g/d, were all
higher than the acceptable consumption (RBIRF) based
on TR = 1
· 10
6, ranging from 0.08 ± 0.03 g/d to 1.36 ±
0.21 g/d (
Fig. 6
). While the BRIRF was calculated based
on TR = 1
· 10
4, the IRFs from most of those ponds were
higher than their RBIRFs. Only Putai 2, Peimen 2 and
Pei-men 3 showed no significant difference between the IRF
and the RBIRF (
Fig. 6
).
The values of TR and THQ were calculated based on
the median values of consumption rates. The values of
TR for consuming milkfish from varied ponds, ranging
from 4.77
· 10
5± 6.92
· 10
6to 7.26
· 10
4± 3.19
·
10
4, were all higher than the acceptable risk 1
· 10
6(
Table 2
). It shows that the inhabitants from the
arsenic-Cb = 0.0115Cw R2 = 0.95 Cb = 0.0054Cw R2 = 0.96 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 0 50 100 150 200 250 300
Inorganic As Concentration in Water (μg/L)
A s l evel i n F is h ( m g/ kg) Cb= 0.0092Cw R2 = 0.96 Cb = 0.0042Cw R2 = 0.92 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 0 50 100 150 200 250 300 350
Total As Concentration in Water (μg/L)
A s L evel i n F is h ( m g /k g) Inorganic As in Fish Total As in Fish Inorganic As in Fish Total As in Fish
Fig. 3. Plots of the correlation between the arsenic (As) level in milkfish and the arsenic concentration in pond water from the arsenic-contami-nated area.
contaminated area were exposed to arsenic pollution with a
carcinogenic risk based on the standard 1
· 10
6, while in 8
of the ponds the risk was higher than 1
· 10
4. The values
of THQ for intake of the milkfish ranged from 0.25 ± 0.04
to 3.76 ± 1.65 (
Table 2
). Among the 12 ponds, 7 of them
had THQ values higher than the safe value 1, which
dem-onstrates a non-carcinogenic risk for humans. The
resi-dents consuming the milkfish from the pond Hsuehchia 1
had the highest carcinogenic and non-carcinogenic risks.
The risk-based concentrations (RBC
f) for inorganic
arsenic level in milkfish (ranging from 8.70
· 10
4±
4.59
· 10
4mg/kg to 1.14
· 10
2± 7.09
· 10
4mg/kg for
TR = 1
· 10
6and ranging from 8.70
· 10
2± 4.59
·
10
2mg/kg to 1.14 ± 7.09
· 10
2mg/kg for TR = 1
·
10
4) were mostly lower than the amounts we obtained
from the fish samples (ranging from 0.08 ± 0.01 mg/kg
to 1.69 ± 0.74 mg/kg). Only in Putai 3 the RBC
fwas higher
than the value we obtained from the field data (
Tables 1
0 50 100 150 200 250 300 350 400 Puta i 1 Putai 2 Putai 3 Yich u 1 Yich u 2 Yich u3 Hsueh chia 1 Hsu ehchi a 2 Hsuehc hia 3 Pei men 1 Peim en 2 Pei men 3 Location As Concentration in Water ( μ g/L) Total As Inorganic AsFig. 4. Total and inorganic arsenic (As) concentrations in pond water from the arsenic-contaminated area.
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
Putai 1 Putai 2 Putai 3 Yic hu 1 Yic hu 2 Yic hu 3 Hsueh chia 1 Hsueh chia 2 Hsueh chia 3 Peime n 1 Peimen 2 Peime n 3 Location As level in Fish (mg/kg) Total As Inorganic As
and 2
). The risk-based concentrations (RBC
w) for
inor-ganic arsenic concentration in pond water, ranging from
0.06 ± 0.04 lg/L to 0.45 ± 0.13 lg/L, were lower than the
pond water in situ, ranging from 13.34 ± 7.17 lg/L to
296.96 ± 32.73 lg/L (
Tables 1 and 2
). When it was
calcu-lated based on the standard 1
· 10
4, only one pond (Putai
3) was higher than the risk-based concentration for
inor-ganic arsenic level in milkfish.
4. Discussion
Most of the arsenic in the water of culture ponds from
the arsenic-contaminated area in southwestern Taiwan is
inorganic.
Huang et al. (2003)
reported a similar
phenom-enon for the water from the cultured ponds of tilapia
(Ore-ochromis mossambicus) in the same arsenic-contaminated
area.
Edmonds and Francesconi (1993), Macintosh et al.
(1996) and Han et al. (1998)
have evaluated potential
human health risks associated with inorganic arsenic
uptake from various kinds of seafood. In their studies,
inorganic arsenic in seafood was assumed to be 10% of
total arsenic.
Huang et al. (2003)
conducted a study
mea-suring the arsenic species in cultured tilapia, demonstrating
that the amount of inorganic arsenic is 7.4% of the total
arsenic
in
this
fish.
The
inorganic
arsenic
level
(44.1 ± 10.2%) we found in milkfish is much higher than
the levels in the seafood and tilapia mentioned above. It
demonstrates that milkfish might have a lower ability to
covert the inorganic arsenic into organic forms, whereas,
arsenic in ambient water is often in inorganic form.
Table 1
Percentage of inorganic arsenic in total arsenic (As) and the BCF values of pond water and milkfish from the arsenic-contaminated area (mean ± standard error)
Location Percentage of inorganic As in total As in water (%) Percentage of inorganic As in total As in fish (%) BCF of total As BCF of inorganic As Putai 1 63.4 47.7 14.09 ± 7.71 11.05 ± 7.44 Putai 2 68.8 36.0 10.51 ± 1.04 5.82 ± 2.02 Putai 3 60.9 26.3 10.05 ± 1.71 4.84 ± 2.37 Yichu 1 63.3 49.7 9.50 ± 3.70 9.32 ± 7.18 Yichu 2 75.8 39.4 4.25 ± 1.29 2.25 ± 0.78 Yichu 3 68.2 48.5 7.28 ± 3.20 5.25 ± 0.62 Hsuehchia 1 86.0 50.4 9.69 ± 0.60 5.56 ± 1.83 Hsuehchia 2 56.5 38.2 13.32 ± 2.06 9.33 ± 1.93 Hsuehchia 3 63.9 66.5 8.55 ± 3.19 10.08 ± 6.39 Peimen 1 71.7 40.3 12.44 ± 6.15 6.75 ± 4.23 Peimen 2 75.5 37.0 9.26 ± 1.27 4.55 ± 0.91 Peimen 3 55.8 49.7 7.68 ± 0.60 7.47 ± 2.23 Average 67.5 ± 8.8 44.1 ± 10.2 11.55 ± 4.42 6.80 ± 2.64 0.01 0.10 1.00 10.00 100.00 1000.00 Puta i 1 Putai 2 Puta i 3 Yichu 1 Yichu 2 Yich u 3 Hsuehchia 1 Hsuehchia 2 Hsuehchia 3 Peim en 1 Peimen 2 Peimen 3 Location Consumption (g/d) Actual Consumption Acceptable Consumption I Acceptable Consumption II
Fig. 6. The actual consumption (g/d) and the acceptable consumption (g/d) of cultured milkfish from the arsenic-contaminated area (Acceptable consumption I: TR = 1· 104; Acceptable consumption II: TR = 1· 106).
The inorganic arsenic level in milkfish increases with the
inorganic arsenic concentration in pond water. The values
of TR and THQ show that consumption of
arsenic-polluted milkfish might cause an overexposure of inorganic
arsenic and pose cancer and non-cancer risks to human
health. The RBC
fand RBC
wvalues indicate that the
arsenic levels in groundwater-cultured milkfish and pond
water are relatively high. It is recommended that legislation
should be established limiting the arsenic levels in pond
water and cultured fish.
In a 15-year study of a cohort of 789 patients, an
increased mortality from cancers of the liver, lung, bladder
and kidney was seen among the patients from the
arsenic-contaminated area, compared with the general population
in the endemic area or compared with the general
popula-tion of Taiwan (
Chen et al., 1980
). Several follow-up
studies of the Taiwanese population exposed to inorganic
arsenic showed an increase in fatal internal organ cancers
as well as an increase in skin cancer (
Chen et al.,
1995,1999,2004
). In these studies, the age-adjusted and
sex-adjusted mortality for cancers of skin, lung, liver,
kid-ney, bladder and prostate among the residents in the
arsenic-contaminated area were found significantly higher
than that of the general population of Taiwan. These
can-cers as well as BFD were documented associating with high
levels of arsenic in drinking water. Although a large
num-ber of studies have been conducted on dose–response
rela-tionship between the arsenic level in drinking water and
mortality because of cancers (
Wu et al., 1989; Yu et al.,
2003
), most of these studies involve the connections
between arsenic in water and human health, and not so
much an appraisal from a food safety perspective.
Some recently published reports on farmed fish have
involved analyses of total arsenic accumulation in cultured
fish (e.g.
Liao et al., 2003; Lin et al., 2005; Jang et al., 2006;
Ling and Liao, 2007
), but few of them have examined the
risk based on the exposure of inorganic arsenic.
Liao and
Ling (2003)
carried out a risk analysis to quantify the
inorganic arsenic bioaccumulation in cultured tilapia and
large-scale mullet (Liza macrolepis) from the
arsenic-con-taminated area in Taiwan, as well as the risk caused by
consumption of these fish.
Lin et al. (2005)
demonstrated
that the arsenic exposure because of milkfish consumption
would pose health risks to residents via the food chain.
Chou et al. (2006)
have presented a
toxicokinetic/toxicody-namic analysis to appraise the risks. In these three studies
however, the risk was calculated based on the assumption
that inorganic arsenic constitutes 10% of total arsenic in
fish. Our study calculated the risk directly from the
mea-sured data and showed that the inorganic arsenic level is
44.1 ± 10.2% of total arsenic in milkfish. It demonstrates
that the values of TR and THQ for milkfish consumption
were underestimated and the RBC
fand RBC
wvalues were
overestimated in
Lin et al. (2005)
.
Table 2
Target cancer risk (TR), target hazard quotient (THQ), risk-based inorganic arsenic concentration in fish (RBCf, mg/kg) and risk-based inorganic arsenic
concentration in water (RBCw, lg/L) for consuming cultured milkfish from the arsenic-contaminated area (mean ± standard error)
Location TR THQ RBCf RBCw Putai 1 3.00· 104± 1.53· 104** 1.55 ± 0.79*** 4.43· 104± 1.81· 104a 0.06 ± 0.04a 4.43· 102± 1.81· 102b 5.64 ± 3.96b Putai 2 4.77· 105± 6.92· 106* 0.25 ± 0.04 1.78 · 103± 8.48· 104a 0.33 ± 0.12a 1.78· 101± 8.48· 102b 33.32 ± 11.94b Putai 3 3.58· 104± 5.43· 105** 1.86 ± 0.28*** 1.14 · 102± 7.09· 104a 0.27 ± 0.11a 1.14 ± 7.09· 102b 27.12 ± 11.27b Yichu 1 2.09· 104± 5.78· 105** 1.09 ± 0.30*** 8.70 · 104± 4.59· 104a 0.13 ± 0.07a 8.70· 102± 4.59· 102b 13.00 ± 7.34b Yichu 2 2.10· 104± 6.50· 105** 1.09 ± 0.34*** 7.66 · 104± 6.64· 104a 0.37 ± 0.12a 7.66· 102± 6.64· 102b 36.82 ± 12.07b Yichu 3 5.36· 104± 8.52· 105** 2.78 ± 0.44*** 1.10 · 103± 2.30· 104a 0.21 ± 0.03a 1.10· 101± 2.30· 102b 21.22 ± 2.52b Hsuehchia 1 7.26· 104± 3.19· 104** 3.76 ± 1.65*** 2.32· 103± 9.63· 104a 0.45 ± 0.13a 2.32· 101± 9.63· 102b 44.57 ± 12.54b Hsuehchia 2 6.62· 105± 2.86· 105* 0.34 ± 0.15 1.80· 103± 9.06· 104a 0.20 ± 0.04a 1.80· 101± 9.06· 102b 19.83 ± 3.67b Hsuehchia 3 2.55· 104± 1.31· 104** 1.32 ± 0.68*** 8.30· 104± 3.83·104a 0.11 ± 0.08a 8.30· 102± 3.83· 102b 11.27 ± 7.73b Peimen 1 1.19· 104± 8.14· 105** 0.62 ± 0.42 1.58· 103± 5.51· 104a 0.29 ± 0.13a 1.58· 101± 5.51· 102b 29.05 ± 13.45b Peimen 2 6.37· 105± 1.61· 105* 0.33 ± 0.08 1.66 · 103± 7.19· 104a 0.38 ± 0.08a 1.66· 101± 7.19· 102b 37.62 ± 8.26b Peimen 3 7.09· 105± 2.03· 105* 0.37 ± 0.11 1.50 · 103± 3.51· 104a 0.22 ± 0.08a 1.50· 101± 3.51· 102b 21.61 ± 7.59b * > 1
· 106, higher than the safe standard for cancer risk 1· 106.
** > 1
· 104, higher than the safe standard for cancer risk 1· 104.
***> 1, higher than the safe standard for non-cancer risk 1. a Calculated based on TR = 1
· 106.
b Calculated based on TR = 1
The inhabitants in the arsenic-contaminated area, who
consume the arsenic-contaminated milkfish, might be
exposed chronically to arsenic pollution with carcinogenic
and non-carcinogenic risks. Public health experts are
concerned since it has been known for years that using
groundwater for aquaculture is a common situation in
the arsenic-contaminated area in Taiwan (
Chou et al.,
2006
). Many cultured stocks, such as eel, carp and shrimp,
from this area may also be contaminated by arsenic, but
only few quantitative risk estimates have been done. A
greater understanding of the arsenic accumulation in
human bodies by consuming the arsenic-contaminated
sea-food and the subsequent health effects is needed. The dose–
response relationships are also necessary to be analyzed in
further studies.
Acknowledgment
We thank Dr. G.P. Chang-Chien and Mr. C.H. Hung
for deploying experimental equipment and providing
tech-nical assistance and Dr. Y.M. Yeh for her help with
statis-tical analysis. The earlier draft of this manuscript benefited
from the comments of Mr. R. Regout. This study was
supported by the National Science Council of Republic
of China under Grant NSC 94-2313-B-343-001.
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