Chapter III. Distribution characteristics of arsenic speciation and health risk
3.4. Results and discussion
3.4.4. Contamination by habitat and feeding
are freshwater fishes among the seven omnivorous ones. This result suggests that marine carnivorous fishes can be more contaminated by arsenicals.
Figure 3.9.Comparison of levels of arsenicals in fish according to (a) habitat and (b) feeding.
AsC AsB As (III) DMA MMA As (V)
Omnivorous Carnivorous
AsC AsB As (III) DMA MMA As (V)
Concentration (ng As/g ww)
1 10 100 1000 10000
Freshwater Marine
(a) (b)
3.4. Conclusion
Koreans are mainly exposed to arsenic via ingestion of seafood with a world-top level of exposure rate.
Therefore, arsenic speciation is a critical issue of food safety in Korea. However, there are only limited data on arsenic speciation in fish. In this study, we provided arsenic speciation data for various fish species in Korea. The levels of total arsenic in the 36 fish species varied substantially, being log- normally distributed at a 5% significance level. Four species (i.e., Far eastern catfish, Japanese anchovy, Pacific cod, and Chub mackerel) exceeded the guideline of China (0.1 μg As/g dw), and Japanese anchovy exceeded the guideline of the Australia New Zealand Food Standard of 2 μg As/g dw.
For all the fish samples, fractions of AsB were dominant among the six arsenicals, followed by DMA, AsC, AsV, AsIII, and MMA, consistent with those in previous studies, and the levels of arsenicals are also comparable with those in previous studies in Korea. AsIIIis statistically significantly correlated with AsB and AsC, indirectly suggesting bio-transformation of inorganic arsenicals into organic arsenicals. Water content is also positively correlated with AsIII. The average total arsenic concentration in the freshwater fishes is 20 times higher than that in the marine fishes, suggesting that arsenicals in fish feed living in waters with higher salinity were accumulated in fishes. Consequently, marine carnivorous fishes with high water content could be more contaminated by arsenic in terms of toxicity.
For the seaweeds, AsVhad the highest concentration and AsB and DMA were detected. The contribution of As species in the seaweed samples was 73.2% for AsB, 26.5% for As V and 0.3% for DMA.
As the results of this study are based on monitoring of relatively small numbers (n=3) of each species, further monitoring studies are required to more exactly evaluate human health risk by arsenicals. For this reason, the data and discussions in this study can be a basis for a more comprehensive and large- scale monitoring study.
Acknowledgements
This work was supported by the Ministry of Food and Drug Safety (MFDS, No.12162KFDA015) and the National Institute of Fisheries Science (NIFS, R2015066).
Chapter IV
Dietary exposure to arsenic species in agricultural products from South Korea
4.1. Abstract
Arsenic (As) contamination in agricultural products is derived from both natural processes and anthropogenic activities, such as mining, smelting, coal combustion, and arsenic-based pesticides. It also exists in agricultural systems in various inorganic and organic structures. Inorganic arsenicals (arsenite [AsIII] and arsenate [AsV]) are known to be more toxic than organic arsenicals. Therefore, the concentration of total As cannot accurately describe the toxicity of As in the environment. In this study, six arsenicals were analyzed in major agricultural products (crops, fruits, and vegetables), which are a major part of the Korean diet. A total of 150 individual samples representing 37 different agricultural products were purchased from local markets in three cities (Seoul, Gwangju, and Gangneung) in South Korea. The samples using a collection blender was immediately frozen at −20°C until preparation and pretreatment by grinding the edible part. Then, inductively coupled plasma mass spectrometry (ICP- MS) was used to determine the total As quantity, and high performance liquid chromatography (HPLC) coupled with ICP-MS was used for As speciation. Since the toxicity of organic arsenicals is much lower than that of inorganic arsenicals, the daily intake of inorganic arsenicals (AsIIIand AsV) from agricultural product consumption was calculated for the human health risk assessment.
4.2. Introduction
Arsenic (As) is originally a harmful element and an essential element of the human body (ATSDR, 2007). As is a metal that exists in various forms, is known as one of the highly toxic heavy metals, and is abundant enough to have 1.5 to 2 mg/kg on the earth's surface and 2 μg/L on the sea surface (Watt and Le, 2002). As is a major environmental pollutant with strong toxicity. It has different physical and chemical properties depending on the type of elements it combines or the state of oxidation (Mandal and Suzuki, 2002). The risk to the human body of As is that the arsenite (AsIII) compounds are more toxic than the arsenate (AsV) compounds, and the inorganic compounds are more toxic to the human body than the organic compounds. Most arsenic exists in the form of As2O3and As2O5and the majority of arsenic found in organisms is organic form, with organic arsenic having biochemical significance, containing methylators (Mandal and Suzuki, 2002).
For humans, the main pathways to As are respiratory (nose) and digestive systems (mouth), and skin exposure is very minimal. The arsenic absorbed after excessive consumption of fish, shellfish, lobsters and other seafood is known to be free from the risk of addiction, even if it is larger than usual (Moon and Choi, 2009). The body's risk from arsenic may vary depending on the source of arsenic exposure, exposure path, etc. According to the Korean Food and Drug Administration (KFDA), the Codex Alimentarius Commission (CAC) provision may temporarily apply to the determination of the appropriateness of hazardous substances, such as heavy metals, which are not supported by the standards and specifications in the field, and if there is no regulation by the International Food Standards Commission, the Director of the Food and Drug Administration may apply foreign standards and daily capacity for such substances (KFDA, 2007). Currently, there is no domestic arsenic intake or maximum allowable. According to Codex Annexes V of the CAC, there is no clear data on organic arsenic content in food and no regulations related to As content and intake. However, the Provisional Tolerable Weekly Intake (PTWI) of As prescribed by the FAO/WHO Joint Expert Committee on Food Additives, a world- renowned organization that evaluates daily intake capacity and safety, is 350 μg/kg of As. The Food and Aggregate Organization of the United Nations/World Health Organization (FAO/WHO) Joint Conference in 1974 emphasized the need and importance of continuous monitoring of heavy metals, residual pesticides, and organic chlorine compounds remaining in food, followed by FAO and UNEP (United Nations Environment Programme) in GEMS/Food, founded in 1976 (WHO, 2010).
In Korea, however, the general standard of food for heavy metals, which are currently marked in terms of food process, the criteria for residual acceptance of mercury and lead in case of fish, shellfish and freshwater fish and cadmium in case of shellfish and rice are prescribed. Standards for heavy metals in food standards and standards are specified in tofu, powdered drinks, and capsellates, but there is no regulation on individual items. Among fish and shellfish, Australia, New Zealand, China, Thailand, Finland, Canada, and the European Union regulate only toxic inorganic As. In addition, from European
Food Safety Authority (EFSA) has been published the standard at 6 mg/kg for organic As and 2 mg/kg for inorganic As. FAO/WHO had been established the safety assessment for As intake through food at 15 μg/kg bw/week for highly toxic inorganic As, and recently in developed countries, arsenic is a highly hazardous chemical for the human body due to its carcinogenic and general toxicity.
In the United States, the priority list of hazardous chemicals is set and managed, and As has been ranked No. 1 in the management list for many years. In 2001, the Environmental Protection Agency (EPA) strengthened the permissible level of arsenic in drinking water from 50 ppb to 10 ppb in consideration of the high risk of As cancer, focusing on improving existing As treatment techniques and developing innovative treatment technologies. However, since accurate standards for inorganic and organic As have not yet been established in Korea. In this study, the proposed method was also successfully applied to agricultural product samples, including tomato, glutinous rice, white rice, oyster mushroom, Chinese cabbage, oriental melon, sweet potato, shiitake mushroom, soybean, garlic, onion, banana, cucumber, wheat flour, green pumpkin, strawberry, daikon radish, bean sprouts, corn samples. Different levels and patterns of arsenicals for individual rice species and grain product samples were clearly identified. This method can thus be useful for the comprehensive monitoring of arsenic contamination in agricultural products.
4.3. Materials and methods
4.3.1. Collection of agricultural samples
For the agricultural food sample collection, the 37 most-consumed agricultural products (Chinese- radish dried, brown rice, adzuki beans, tomato, glutinous rice, white rice, oyster mushroom, Chinese cabbage, oriental melon, sweet potato, shiitake mushroom, soybean, garlic, onion, banana, cucumber, wheat flour, green pumpkin, strawberry, daikon radish, bean sprouts, corn, barley, apple, pleurotus eryngii, mandarin, carrot, green chilli, welsh onion, orange, peanut, grape, potato, cabbage, pear, and ginger) were bought from traditional markets and national chain supermarkets from March–April 2016 in three South Korean cities (Gangneung, Gwangju, and Seoul). For each fresh food, four or five samples were collected from the markets and supermarket to create a composite sample, with a total of 150 samples.
After the sampling, the water samples were tightly sealed to avoid air exposure for further analysis, then for water content, dried in an oven at 110 °C for 2 h, cooled in a desiccator and weighted. The food samples were stored at −4 °C prior to analysis.
Figure 4.1. Sampling sites: traditional markets and supermarkets in three cities (Gangneung, Gwangju, and Seoul) in South Korea.
4.3.2. Sample digestion and analysis
For As analysis, each sample (5 g) was digested with 9 mL of HCl and 3 mL HNO3 in Teflon vessels were digested using a graphite digestion system (Odlab, OD-98-002P, Korea) at 200°C for 2 h using USEPA Method 3050B. The extracts were analyzed for As using an inductively coupled plasma-optical emission spectrometer (ICP-OES, Varian 720 ES, USA). RF power, nebulizer gas and auxiliary gas flow rates were 1,200 W, 0.7 L/min, and 1.5 L/min, respectively.
For the arsenic species analysis, 170 µL of HNO3 was added into 10 mL of each water sample (1%
HNO3) in a 15-mL polyethylene tube (Falcon, USA). The tube was vortexed for 30 s and then analyzed by HPLC (PerkinElmer Series 200, USA) coupled to an ICP-MS. The operating parameters for HPLC and ICP-MS are listed in Table 2.1. The concentration of As was quantified using a method described in a previous study (Park et al., 2019). Six forms of As including arsenite (AsIII), arsenate (AsV), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), arsenobetaine (AsB), and arsenocholine (AsC) were separated on an anion exchange column (Hamilton PRP X-100, 250 mm × 4.1 mm, 10 μm particle, USA). A dynamic reaction cell (DRC) was used to minimize the polyatomic interference of chloride (i.e., 40Ar35Cl+) on m/z 75 (Choi et al., 2015; Park et al., 2019). Detailed information on the reagents and solutions used for HPLC/ICP-MS are provided in Section 2.3.1 in Chapter II.
4.3.3. Health risk assessment of food consumption
Considering lower toxicity or harmlessness of organic As, only inorganic forms (AsIIIand AsV) were devoted to health risk assessment. Estimated daily intake of inorganic As (iAs) from fishery product consumption was calculated according to the equation:
EDIiAs=CiAs× IR BW
where EDIiAs(mg/BWkg/day) is the estimated daily intake of iAs, CiAs (mg/kg) is iAs concentration of seaweeds (wet weight), IR (kg/day) is the daily ingestion rate of seaweeds, and BW (kg) is the body weight of consumer. The hazard quotient (HQ) was introduced to evaluate the potential non- carcinogenic risk of As exposure from seaweed ingestion. The HQ value was calculated by the following equation:
HQ=EDIiAs RfDiAs
where RfD (mg/BWkg/day) is the oral reference dose for As. The probability of excess lifetime cancer risk (CR) of As exposure for vegetable consumer was calculated according to the equation as follow:
CRiAs=EDIiAs × SFiAs
where CRiAs is the probability of excess lifetime cancer risk, and SFiAs(mg/BWkg/day−1) is the slope factor of As. In this work, BW and IR for Korean are 62.3 ± 12.0 kg and 0.060 ± 0.046 kg/day, respectively. The values of RfDiAs and SFiAs regulated by USEPA (2015) are 3.0×10−4 and 1.5, respectively.
4.3.4. Quality control and data analysis
An external calibration (1, 5, 10, 20, and 50 μg/L) was conducted to quantify the six As species, and high correlation coefficient values (R2 > 0.999) were obtained. The MDLs were 0.133, 0.216, 0.126, 0.200, 0.154, and 0.158 μg/L for AsIII, AsV, DMA, MMA, AsB, and AsC, respectively. Since there was no freshwater or seawater CRM for As, the recovery rate was confirmed using the standard addition method (Park et al., 2019; Wahlen et al., 2004). The accuracy and precision were evaluated using the 1 μg/L standard solution of the target As species in 10 mL of 1% HNO3. The mean recoveries of As species (n = 3) with RSD were 92 ± 3.3, 113 ± 5.6, 104 ± 2.7, 102 ± 1.6, 87 ± 2.1, and 92 ± 2.9% for AsIII, AsV, DMA, MMA, AsB, and AsC, respectively.
For data comparison, t-test and rank-sum test were performed using SigmaPlot 14.0 (Systat Software Inc., USA). For Spearman correlation analyses, a statistical package for the social sciences (SPSS 22, IBM Corp., USA) was used. SPSS 22 was also used for cluster analysis (CA) and principal component
analysis (PCA). The heavy metal data were normalized by the total concentration of individual samples for CA. As a cluster method, the between-groups linkage was used, and squared Euclidean distance was selected as a measure interval.
4.4. Results and discussion
In this study, concentrations of As were determined in the 37 most-consumed agricultural products in Korea. All agricultural products contained detectable metal concentrations, including arsenic (Figs. 4.1 and 4.2). The maximum acceptable metal concentrations in agricultural products were expressed based on fresh weight. However, different countries have different regulations, with Korea lagging behind in this area. For example, the As standard is 200 μg/kg for fresh vegetables in Poland, 500 μg/kg for rice, beans, and vegetables in China (NHFPC, 2012), and 1000 μg/kg for spinach (Spinacia oleracea), tomato, and cucumbers (Cucumis sativus) in Japan. The Cd standard for the European Union is 100 μg/kg for root vegetables, 200 μg/kg for leafy vegetables, and 50 μg/kg for others (JECFA, 2016).
4.4.1. Comparing arsenical levels among different agricultural products
The concentrations of As in the top 10% agricultural products in the collected samples (Chinese-radish dried, shiitake mushroom, brown rice, sesame seed, and Chinese cabbage) were 223±58, 150±112, 146±76, 133±5, and 117±14 μg/kg, respectively. Based on their characteristics, the 37 most-consumed agricultural products can be categorized as a grain, leafy green, fruit, or root vegetable. Grains had the highest As concentrations, followed by leafy greens, vegetables, and fruits (Fig. 4.1). Based on the average values, As levels varied greatly among the agricultural products. While ginger had the lowest As (9.07 μg/kg) level, dried Chinese radish had the highest As level (223.2 μg/kg) (Fig. 4.2).
Table 4.1. Concentration of total arsenic and arsenic species in agricultural products (μg/kg)
No. Food items AsIII AsV DMA MMA sum As Total As
1 Sesame seed 9.04 28.16 37.19 132.93
2 Chinese-radish dried 10.53 23.92 34.45 223.20
3 Brown rice 17.08 10.23 4.00 2.62 33.93 146.10
4 Adzuki beans 8.12 10.80 5.02 5.66 29.60 33.62
5 Tomato 19.04 9.98 29.02 65.32
6 Glutinous rice 10.39 10.24 7.02 27.65 114.82
7 White rice 15.44 7.84 3.83 27.10 114.36
8 Oyster mushroom 17.86 7.71 25.56 92.58
9 Chinese cabbage 16.80 8.21 25.01 116.92
10 Oriental melon 10.38 7.51 1.82 3.95 23.66 59.76
11 Sweet potato 15.84 6.24 22.09 28.33
12 Shiitake mushroom 10.00 9.93 1.94 21.87 149.59
13 Soybean 7.12 9.66 4.81 21.59 63.26
14 Garlic 5.65 8.33 7.15 21.12 35.66
15 Onion 12.06 7.30 19.35 73.51
16 Banana 5.80 8.10 4.95 18.85 18.25
17 Cucumber 8.89 9.29 18.19 114.15
18 Wheat flour 7.16 8.77 15.93 19.96
19 Green pumpkin 8.80 6.19 14.99 49.65
20 Strawberry 5.84 8.42 14.26 78.17
21 Daikon radish 7.50 6.75 14.25 48.87
22 Bean sprouts 5.63 7.73 13.35 63.31
23 Corn 4.81 7.68 12.48 20.76
24 Barley 5.03 7.26 12.29 17.85
25 Apple 5.70 6.16 11.86 16.18
26 Pleurotus eryngii 3.88 7.91 11.78 28.49
27 Mandarin 3.66 6.98 10.64 31.43
28 Carrot 3.16 6.15 9.31 44.95
29 Green chilli 2.44 6.52 8.95 44.21
30 Welsh onion 2.53 5.92 8.45 56.39
31 Orange 2.20 6.13 8.33 44.21
32 Peanut 2.03 5.57 7.59 9.97
33 Grape 2.19 5.18 7.37 11.13
34 Potato 5.63 5.63 17.07
35 Cabbage 5.61 5.61 43.61
36 Pear 5.48 5.48 20.08
37 Ginger 5.25 5.25 9.07
Figure 4.2. Average level of arsenic in agricultural products. Error bars are standard deviations for three replicate analyses.
Figure 4.3. Average level of arsenic species in agricultural products.
4.4.2. Arsenic species in agricultural products
Among the As species, the concentrations of inorganic As (AsIII and AsV) were relatively high and dominated in the agricultural products. In contrast, organic As species (AsC and AsB) were not detected, except for DMA and MMA. The concentration of As species in each sample was observed in the descending order of AsV > AsIII > DMA > MMA (Fig. 4.3). MMA was only detected in brown rice, adzuki beans, and Oriental melon, while AsIIIwas detected in most samples except for potato, cabbage, pear, and ginger. The proportions of As species ranged from 12.8%–99.9% of the total As. The unknown As species may be arsenosugars (e.g., glycerol sugar, phosphate sugar, sulfonate sugar, and sulfate sugar) released from aquatic organisms. The concentrations of the sum of As species and AsVincreased linearly as the total As concentration increased (Fig. 4.4).
Inorganic arsenic among rice was mainly in the form of AsIII, with a content of less than 0.5 mg/kg, while in seaweed, AsVwas the main arsenic and seaweed, seaweed, and kelp were low in content, but in the case of seaweed fusiforme, it was the level of mg/kg. In the case of long-range white rice belonging to the Indica subspecies, the inorganic arsenic content was 21 to 280 μg/kg, which was 11 to 100 percent of the total arsenic, while the mono-inorganic white rice belonging to the Zaponica subspecies was 41 to 120 μg/kg, which was 56 to 120 percent of the total arsenic. The inorganic arsenic content of white rice and brown rice, whose varieties are not identified, was 28 to 510 μg/kg and 40 to 567 μg/kg, respectively. The inorganic arsenic content of short-lived brown rice was 86 to 412 μg/kg, equivalent to 71 to 113 percent of the total arsenic, which was higher than that of white rice. In short, the inorganic arsenic content of rice was not significantly different depending on the cultivation country, region, variety, harvest time, etc., but the inorganic arsenic content of rice was higher than that of white rice, because the inorganic arsenic was distributed a lot towards the rice paddies. The inorganic arsenic content of rice produced and distributed in Korea was around AsIII71 μg/kg (38−112 μg/kg) and AsV6 μg/kg (2−18 μg/kg) and the total arsenic content of rice grown in areas near the abandoned mine area was 90 μg/kg (20−6,580 μg/kg) (Fig. 4.5).
Figure 4.4. Correlation between total arsenic and As species in agricultural products
Figure 4.5. Concentration by rice species (Brown rice, Glutinous rice, and White rice) and MFDS standards.
y = 0.0777x + 3.7998 R² = 0.4093
0 10 20 30 40 50 60
0 100 200 300
y = 0.0465x + 5.3784 R² = 0.287
0 100 200 300
y = 0.1264x + 7.2946 R² = 0.5012
0 100 200 300
Concentration (µg/kg)
Concentration of total As (µg/kg)
AsIII AsV Inorganic As
4.4.3. Chronic daily intake (CDI) and hazard quotient
The CDI of agricultural products was calculated for age based on the equations in Section 4.3.3. The age range was divided into 8 sections from 1−2 years old to over the 65 years old. The CDI values were compared to the oral reference dose (RfD) to assess their potential health risks. Conventional rice species had a slightly higher contribution to As intake. However, the daily intake was lower than the TDI for As (JECFA, 2016). The CDI of As through vegetable consumption was < 0.3 μg/kg bw/day (Table 4.1), which is much lower than the recommended oral RfD (USEPA, 1989).
The hazard quotient (HQ) was developed by USEPA in 1989 as a quantitative way to evaluate potential health risks associated with long-term exposure to pollutants in foodstuffs. It is calculated as the ratio of the measured dose to the RfD. When HQ ≤ 1.0, the risk of metals from agricultural products is lower than the RfD, indicating little health risk. In this study, the HQ for As ranged from 0.0001–0.185, showing a low health risk from vegetable consumption. Although metal exposure through agricultural product consumption was limited, it is also important to consider exposure from other sources.
Arsenic concentrations in all agricultural products were low and within the maximum allowable limits established by the FAO/WHO (JECFA, 2016). According to the results in this study, based on both CDI and HQ, the risk of metal exposure through consumption of the 5 most-consumed agricultural products is likely of limited concern. The HQs calculated were the following: white rice: 0.0554, onion: 0.0098, apple: 0.0052, daikon radish: 0.0052, tomato: 0.0041 μg/kg bw/day.