Concentrations of Inorganic Arsenic in Milled Rice from China and

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Concentrations of inorganic arsenic in milled rice from China and associated dietary exposure assessment Yatao Huang, Xuefei Mao, Min Wang, Yongzhong Qian, Tianjin Chen, and Ying Zhang J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.5b04164 • Publication Date (Web): 07 Dec 2015 Downloaded from http://pubs.acs.org on December 12, 2015

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Journal of Agricultural and Food Chemistry

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Concentrations of inorganic arsenic in milled rice from China and associated dietary exposure

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assessment

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Yatao Huang,†‡ Xuefei Mao,*,† Min Wang,*,† Yongzhong Qian,† Tianjin Chen,† Ying Zhang†

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†

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Agricultural Sciences, and Key Laboratory of Agro-food Safety and Quality, Ministry of Agriculture,

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Beijing 100081, China

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‡

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Sciences, and Laboratory of Risk Assessment for Processed Agro-food Quality and Safety, Ministry of

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Agriculture (Beijing), Beijing 100193, China

Institute of Quality Standard and Testing Technology for Agro-products, Chinese Academy of

Institute of Agro-Products Processing Science and Technology, Chinese Academy of Agricultural

ACS Paragon Plus Environment


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ABSTRACT: Total arsenic (As) and inorganic As (Asi) in milled rice (n = 1,653) collected from China

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were studied to evaluate the contamination level, distribution and health risks. The mean concentrations

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of the total As and Asi were 116.5 µg/kg and 90.9 µg/kg, respectively. There were significant

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differences (P < 0.01) between the 11 provinces, and 1.1% of samples exceeded the maximum

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contaminant level established by Chinese legislation. According to the exposure assessment method of

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probabilistic simulation, all values of the target hazard quotients (THQs) for chronic non-carcinogenic

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risks (skin lesions as the point of departure) were below one, suggesting that the Chinese population

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will not encounter a significant non-carcinogenic risk. However, the mean values of margin of

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exposure (MOE) for lung cancer risks ranging from 3.86 to 8.54 were under 100 for all age groups and

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genders of Chinese, moreover MOE values for some major rice producing and consuming countries,

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such as Japan, Thailand, Bangladesh, USA, were all also below 100. It should be paid more attentions

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to carcinogenic risks from rice Asi intake, and some control measurements of reducing rice Asi intake

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should be taken.

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KEYWORDS: rice, arsenic contamination, inorganic arsenic, dietary exposure assessment


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INTRODUCTION

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Arsenic (As) is one of the most hazardous chemical elements. It is found in the environment as well as

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in some foods and is present in various compounds with varied toxicities1,2 recently proved trivalent

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methylated species to be more genotoxic than arsenite; however, the order of As compounds in terms of

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general toxicity (lethal dose 50%) is usually As III (arsenite) > As V (arsenate) >> MMA

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(monomethylarsonic acid) > DMA (dimethylarsinic acid) >> arsenosugars > AsC (arsenocholine) >

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AsB (arsenobetaine), of which inorganic As (Asi) including As III and As V is the most toxic species.

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For chronic toxicity, Asi is likely to cause bladder, lung and skin cancers, skin lesions, cardiovascular

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disease, neurotoxicity, and diabetes given long term exposure3. Asi is also classified as a class IA

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human carcinogen by the International Agency for Research on Cancer (IARC). Contaminated drinking

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water has been considered one of the primary sources for human exposure to Asi4. For example, the

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total daily intake of Asi in rural Bengal posed a significant health threat to the local population5.

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However, recent studies showed that rice and its products were also identified as significant dietary

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sources of Asi in areas where rice is a staple food6~9. This is partly because rice and its kernels are more

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efficient in arsenic uptake and accumulation from soil and water than other agricultural plants9.

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According to the data from the Food and Agriculture Organization (FAO) in 2011, China was the

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highest rice producing and consuming country in the world, accounting for more than one third of the

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global supply10. It is thus essential to investigate the concentrations of Asi in rice and assess its health

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risks nationwide. However, up to now, with the exception of studies on total As8, most reports on Asi in

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rice in China were confined to the point of pollution such as metal mining11, sewage irrigation12, metal

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factories, waste disposal13 areas, among others, or other local areas with a small sample size10,14. This

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was due to the absence of government and financial supports. Hence, little is known of the current

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status of rice contamination by Asi throughout the country. Due to this reason, the associated dietary

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exposure to Asi in rice for the entire Chinese population could not be assessed.

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Non-carcinogenic risk assessments were frequently performed to estimate the potential health risks

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of contaminations using the target hazard quotient (THQ), a ratio of the estimated dose of one

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contaminant to the dose level without any appreciable risk such as provisional tolerance week intake

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(PTWI) or acceptable daily intake (ADI). If the estimated value of THQ is below one, it is believed to

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be safe for non-carcinogenic effects; if it exceeds one, there is a risk of non-carcinogenic effects, and

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the risk probability is positively correlated with the value of THQ8,15. On the other hand, the margin of



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exposure (MOE) was recommended for estimating the carcinogenic risks of certain contaminant by

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JECFA3, which was determined by the ratio of BMDL0.5 to the Asi dietary exposure. If the estimated

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value of MOE exceeds 100, it is believed to be safe for carcinogenic effects; if it is below 100, there is

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a significant risk of carcinogenic effects, and the risk probability is negatively correlated with the value

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of MOE. In 2010, the Joint FAO/ World Health Organization (WHO) Expert Committee on Food

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Additives (JECFA) withdrew the previous PWTI of 15 µg/kg bw (equivalent to 2.1 µg/kg bw per day)

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for Asi because the Asi lower limit for the benchmark dose for a 0.5% increased incidence of lung

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cancer (BMDL0.5) was determined to be 3.0 µg/kg bw per day (in range of 2 - 7 µg/kg bw per day) by

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JECFA. Meanwhile, in the process of BMDL0.5 estimation for Asi, lung cancer, bladder cancer and skin

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lesions were all taken into consideration as points of departure (POD). The estimated BMDL0.5 (3.0

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µg/kg bw per day) for lung cancer was smaller than those for bladder cancer (5.2 µg/kg bw per day)

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and skin lesions (5.4 µg/kg bw per day), thus 3.0 µg/kg bw per day was chosen as the recommended

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BMDL0.5 value by JECFA. To perform dietary exposure assessment, the probability functions were

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introduced to evaluate the occurrence, variability and uncertainty of risks, such as the Monte Carlo

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simulation, which was a probabilistic risk assessment approach that was popularly used in previous

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reports8,16. However, the probabilistic approaches often rely on a large sample size. Song et al.17

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estimated that the appropriate sample size for risk assessment of mercury exposure of milled rice in

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China should be a minimum 1,500 samples for 99th percentile (P99) accuracy and precision and 99.9th

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percentile (P99.9) estimates using the Weibull distribution simulation.

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In this work, 1,653 samples were collected from the 11 provinces in which rice production accounted

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for 80.7% of the total output in China during 2012. For all samples, concentrations of the total As and

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Asi were determined using inductively coupled plasma mass spectrometry (ICP-MS) and

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high-performance liquid chromatography coupled with hydride generation atomic fluorescence

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spectrometry (HPLC-HG-AFS), respectively. The variation of total As and Asi levels in milled rice

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classified were calculated according to region, and all of the data were processed to determine its

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dietary exposure in the target population.

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MATERIALS AND METHODS

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Sample collection and preparation. A total of 1,653 paddy rice samples were obtained from the top

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11 producing provinces of China in 2012 with sample quotas depending on the rice output proportion

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of each province. Detailed information of the sample sources is as follows: Hunan (250 from 26 major


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rice-producing counties), Jiangxi (200 from 20 counties), Hubei (150 from 15 counties), Jiangsu (143

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from 29 counties), Heilongjiang (95 from 10 counties), Sichuan (150 from 15 counties), Anhui (145

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from 16 counties), Guangxi (200 from 39 counties), Guangdong (200 from 22 counties), Zhejiang (60

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from 7 counties) and Yunnan (60 from 6 counties), and sampling sizes of every county ranged from 3

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to 20 according to the rice output where every sampling site covering approximately 15,000 square

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hectometer paddy fields on average were distributed as evenly as possible in all counties. The

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geographical locations of sampling counties from 11 producing provinces were shown in Fig. 1. Each

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rice sample (with hulls) was collected from five random and well-distributed points of one paddy field

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(more than 100 m2) and quartered after blending manually on site during the harvest seasons. Then, one

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quarter of each rice sample (each ≥ 2 kg) was randomly chosen and transported to the laboratory as

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soon as possible to air dry and to obtain a constant weight. After removing the outer hull and bran

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layers, the rice samples were ground and homogenized with a mortar grinder (RM 200, Retsch,

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Germany), sieved with 0.45 mm mesh, and then stored at 4°C for further analysis.

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Analytical procedure. Total As analysis: According to SN/T 0448-201118, approximately 0.5 g of the

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rice sample (accurate to 1 mg) was loaded into a digestion vessel with 8 mL 16 mol/L HNO3 and 2 mL

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30 % H2O2. The vessel was placed on the hot block and heated to 130°C for 2 hours and then heated to

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145°C until approximately 1 mL volume remained. Next, the digest was transferred and quantitatively

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diluted to 50 mL after cooling. The solution was sufficiently homogenized and then subjected to

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measurement using ICP-MS (X Series 2, Thermo Scientific, Germany). The ICP-MS normal operating

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parameters were as follows: incident RF power 1,300 W, cooling Ar gas flow rate 13 L/min, nebulizer

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Ar gas flow rate 0.9 L/min and auxiliary Ar gas flow rate 1 mL/min. The ICP-MS was used in a

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collision-reaction cell with kinetic energy discrimination (CCT-KED) mode using H2 - He (v:v = 7:93)

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as the collision cell gas (5 mL/min) to reduce 40Ar35Cl+ interference with 75As, and Ge was used as an

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internal standard. The sampling tube was 152 mm long and 0.02 mm I.D., and the peristaltic pump rate

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was 30 rpm. The ion count was monitored at m/z = 75. The method detection limit (LOD) of the total

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As was 0.5 µg/kg.

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Speciated As analysis: Approximately 1 g of rice powder was weighed into a 50 mL polypropylene

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tube with a 10 mL 0.02 and 0.1 mol/L TFA, 0.02 and 0.1 mol/L HNO3, methanol/water (v:v =1:1), and

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methanol/water (v:v =1:1) with 0.02 mol/L HNO3. After thorough mixing using a vortex mixer, the

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tube was stored in a water bath at 90°C for 60 min and then centrifuged at 5,000 rpm for 10 min. The



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supernatant (4 mL) was transferred to a 5-mL graduated centrifuge tube and blown to less than 1.5 mL

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via gentle nitrogen flow at 50°C to remove methanol. Then H2O2 (120 µL) was added to oxidize

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arsenite to arsenate at 70°C for 30 min, and then the solution was quantitatively diluted to 2.0 mL and

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filtered with a 0.22-µm microporous membrane prior to analysis via HPLC-HG-AFS (AFS 8220,

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Beijing Titan Instruments Co., Ltd., China).

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An anion exchange column (PRP-X 100, Hamilton, USA) was employed to separate As species with

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a 1 mL/min flow rate of 15 mmol/L (NH4)2HPO4 at pH 6.0 during the mobile phase (Dai, Wang, Qiu,

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Yang, & Wang, 2011). The HG-AFS operating and instrumental parameters were as follows: the flow

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rates of the carrier gas and shield gas were 0.4 and 0.6 mL/min, respectively; the column effluent was

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first mixed at a T-joint with a 7 % HCl solution and next met with 20 % KBH4 dissolved in 5 % KOH

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solution as the reducing reagent in another T-joint. The mixture was then delivered with two peristaltic

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pumps at flow rates of 6.0 and 3.4 mL/min, respectively; the AFS was equipped with an As-boosted

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hollow cathode lamp (HCL; 193.7 nm, Beijing Research Institute of Nonferrous Metals, Beijing, China)

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as the light source, and the HCL was operated at 100 mA with a working voltage for the

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photomultiplier ranging from -270 to -360 V. The LODs for Asi, DMA and MMA were 6.0, 6.0 and 8.0

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µg/kg, respectively.

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Quality assurance. The certified reference material (CRM) of GBW 10043 rice flour (114±18 µg/kg

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for total As) (Chinese Academy of Geographical Sciences, Beijing, China) was used to verify the

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measurement of total As and Asi in rice for quality assurance. Moreover, the rates of extracting As from

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rice samples were also verified using one CRM per 20 samples by comparing the sum of Asi, DMA and

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MMA with the total As.

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Risk assessment of Asi through rice consumption. The estimated daily intake (EDI) of Asi depended

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on both the concentrations of Asi in milled rice and the associated amount of rice consumption. The

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EDI was determined using the following equation:

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EDI = (EF × ED × FIR × C) / (WAB × TA)

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EF is the exposure frequency (365 days/year), ED is the exposure duration (70 years), FIR is the rice

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ingestion rate (g/person/day), C is the Asi concentration of rice (mg/kg), WAB is the average body

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weight and TA is the average exposure time (EF×ED). FIR and WAB (shown in Table 1) were obtained

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from the report on nutrition and health status of Chinese residents (2002).

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Target hazard quotient. Non-carcinogenic risks for residents (the point of departure is skin lesion)


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through consuming contaminated rice were estimated according to THQ (USEPA, 2000), where the

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skin lesion was chosen as POD for the non-carcinogenic risk assessment. And the equation was as

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follows:

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THQ = EDI / BMDL0.5 (skin lesions)

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The PTWI of 15 µg/kg bw per week for Asi has been withdrawn by JECFA in 2010, so the BMDL0.5

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(skin lesions) of 5.4 µg/kg bw per day3 is adopted to replace the previous PTWI here. However, the

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health risks should be considered separately because the contact pathway with each exposure medium

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changes with age19.

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Carcinogenic risks were estimated according MOE, which was determined by the ratio of BMDL0.5 to the Asi dietary exposure:

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MOE = BMDL0.5 (lung cancer) / EDI

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Here the lung cancer was chosen as POD for the carcinogenic risk assessment of Asi, because the

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BMDL0.5 (lung cancer) of 3 µg/kg bw per day was lower than the BMDL0.5 (bladder cancer) of 5.2

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µg/kg bw per day according to JECFA3. When a MOE value ≥ 100, it means no significant

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carcinogenic risk for human; otherwise, it shows an unacceptable risk.

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Exposure assessment model. The dietary exposure to Asi was calculated depending on model

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construction theories and the Monte Carlo method and bootstrap values. To estimate the variability and

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uncertainty of the exposure, the simulation procedures were divided into U-step (for uncertainty) and

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V-step (for variability). Firstly, at U-step, bootstrap samples with the same sample size were drawn

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from an empirical distribution of 1,653 rice samples; Secondly, at V-step, Monte Carlo sampling was

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operated n times from the bootstrap samples above. The statistics of individual samples such as the

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mean values and percentiles (P50, P90, P97.5 and P99.9 in this work) were obtained; after repeating

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the U and V steps B times, the confidence intervals of all statistics were attained and the variability of

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EDI across the entire sample could be characterized. Additionally, n and B in the simulation procedures

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were set to 100,000 and 2,000, respectively, which resulted in 100,000 × 2,000 = 2 × 108 simulations to

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guarantee the reliability of the results.

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Statistical analysis. Results from the experiments were calculated using the statistical software SAS

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9.2. The statistical significance of the difference was assessed using Duncan’s multiple range test. A

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probability of 0.01 was considered significant.

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RESULT AND DISCUSSION



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Extraction method of As speciation from rice samples. The extraction of As speciation from rice

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samples should be a gentle procedure with moderate temperature and acidity to avoid the

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transformation from organic As to Asi and for attaining good extraction rates (ratio of all species to

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total As). Many types of extracts for As speciation extraction have been reported, such as trifluoroacetic

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acid (TFA), nitric acid 20 and methanol/water solution21. To select the optimal extractant, the extraction

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rates of various extracts were calculated by comparing the sum of Asi, DMA and MMA using

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HPLC-HG-AFS to the total As via ICP-MS. The results in Table 2 showed that the extraction rates of

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TFA, HNO3 and methanol/water with 0.02 mol/L HNO3 all exceeded 90%, whereas that of the

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methanol/water treatment was only 65.4%. We also found that the extracted solutions treated using

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methanol/water (v:v = 1:1) with 0.02 mol/L HNO3 were relatively clear and could be concentrated via

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nitrogen flow to reduce the method’s LOD. Therefore, methanol/water (1:1, V/V) with 0.02 mol/L

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HNO3 was selected as the optimal extractant. The particle size of the powdered rice sample was also an

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important factor for As extraction, and we chose 0.45 mm mesh to sieve rice powder according to our

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previous study22. Using the above method, the extraction rates for As speciation in GBW 10043 were

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86.7% - 104.9% for our experiment’s quality control. The method detection limits (LODs) for Asi,

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DMA and MMA were 6.0, 6.0 and 8.0 µg/kg, respectively, and the LOD of the total As was 0.5 µg/kg.

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Three duplicates were analyzed as individual samples and the RSDs between the duplicates were lower

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than 10%.

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Concentrations of speciated As of rice samples in China. Asi, DMA and MMA concentrations of

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1,653 rice samples were determined using HPLC-HG-AFS. The detectable rates of the total As, Asi,

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DMA and MMA were 99.7%, 99.6%, 87.0% and 1.5%, respectively. The mean ratios of Asi and DMA

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concentrations to the total As were 78.3% and 18.9%, respectively, whereas MMA was only 0.8%.

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Judging from the detectable rates and the concentration distributions of speciated As, Asi was the most

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dominant As speciation in rice produced from China, and DMA was the second most dominant, as

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previously reported10,14 . In contrast, Meharg et al.23 reported that DMA was the dominant speciation in

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rice from the US. The difference between China and US in this case may be caused by different rice

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varieties, agricultural environments, cultural practices, etc. Notably, a higher Asi percentage in the total

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As in rice potentially poses higher risks to human health than a lower Asi percentage because of the

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highest toxicity of Asi among all As speciations.

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However, the mean concentration of Asi in all rice samples was 90.9 µg/kg, which was nearly


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consistent with other previous reports of rice Asi monitoring in China (Table 3), such as Li et al. (108

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µg/kg)24 and Liang et al. (82 µg/kg) for milled rice. However, the rice sample size in this work was

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much bigger than others. Meanwhile, from the Table 3, the rice Asi in China reported and in this work

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were almost at the same level with that in USA (100 µg/kg or 91.2 µg/kg), Thailand (100 µg/kg) and

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Italy (110 µg/kg), and higher than that in Bangladesh (80 µg/kg) and India (30 µg/kg). The rice Asi

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level of 90.9 µg/kg was substantially less than the maximum contaminant level (MCL, 200 µg/kg for

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Asi) of China from GB 2762-201229, and the violation rate of all of the samples was only 1.1 %. Thus,

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Asi contamination in rice produced from China was not a threat without taking into consideration of the

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residents’ age, genders or regional differences. However, Chinese consume more rice than many other

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countries, such as US, Japan, India, Africa.30 In another word, the further risk assessment for Asi in rice

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was necessary.

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Regional distributions of Asi concentrations in rice. The concentrations of Asi in rice samples

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collected from the top 11 rice producing provinces in China were detected (Table 4). The mean Asi

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concentration of 11 individual provinces ranged from 48.4 µg/kg (Jiangsu) to 116.1 µg/kg (Jiangxi),

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and there were significant differences (P < 0.01) between them according to Duncan’s multiple-range

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test at a 95% confidence level due to variables in their agricultural environments such as those related

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to soil, irrigation water13,31 and rice varieties. The Asi concentration in the rice of Jiangxi, Hunan,

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Sichuan and Guangxi were higher than 100 µg/kg. These four provinces are all located in central and

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south China and are the primary rice-producing and -consuming regions. Regarding the violation rate

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of Asi in rice, Hunan had the highest (5.2%) with the second highest mean value of Asi at 114.5 µg/kg.

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Asi rice contamination in Hunan was particularly serious compared with other provinces in China,

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which was in accordance with previous reports32. Hunan is well-known for its nonferrous metal ore,

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which presents two problems to food safety. Firstly, the environmental background value for As is

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relatively higher than that for other regions due to the release of heavy metals from rocks and stratum

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through weathering and leaching processes; additionally, its extensive nonferrous metal exploitation

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and smelting industries (with nearly 7,000 mines in the province) inevitably lead to environmental

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contamination, especially to the soil and water system in adjacent areas. As in the environment is

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transferred into rice grains by uptaking, transferring and accumulating within the rice plant. Rice is also

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a plant with a relatively high As enrichment factor 9. Moreover, the Asi contents of rice in Jiangxi,

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Guangxi, Guangdong, and Hubei provinces, which are adjacent to Hunan, were relatively higher than



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those in other areas. Thus, government organizations at all levels should enhance their monitoring

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efforts on As and especially rice species in the above-mentioned areas.

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Dietary exposure assessment of Asi. The THQ and MOE have been recognized as the major

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parameters for assessing the non-carcinogenic and carcinogenic risks associated with the consumption

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of contaminated food by toxic elements, respectively, and the results of THQs and MOEs of Asi in rice

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for the Chinese population at a 95% confidence interval are listed in Table 5 and 6 (with various age

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groups and genders). For THQ, the PTWI was always employed as a denominator of the equation.

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However, the PTWI of 15 µg/kg bw per week for Asi has been withdrawn by JECFA in 2010 according

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to the latest epidemiological survey and toxicological study. In the evaluation of BMDL0.5, cancer

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effects of urinary bladder and lung and non-cancer effect of skin lesions including hyperkeratosis,

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hyperpigmentation and hypopigmentation were all taken into consideration. With regardless of cancer

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end-point, the BMDL0.5 of skin lesion was 5.4 µg/kg bw per day, which was the typical chronic toxicity

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of Asi. Because BMDL0.5 of skin lesion was newer than Asi RfD (0.3 µg/kg bw per day) from USEPA

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in 1991, 5.4 µg/kg bw per day was adopted to evaluate the non-carcinogenic risk of rice Asi in this

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work. On the other hand, for carcinogenic effects, although the lung and bladder cancers were both

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taken into account, the calculated BMDL0.5 of lung cancer was smaller than that of bladder cancer.

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Thus, BMDL0.5 (lung cancer) of 3.0 µg/kg bw per day was employed to evaluate the carcinogenic risk

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of rice Asi in this work.

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For non-carcinogenic risk assessment in Table 5, the values at P50 exhibited the median exposed

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consumers of the distribution, whereas those at P97.5 and P99.9 exhibited high exposure. When

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observing THQs for all age and gender groups, there were no mean or median values (0.060 - 0.144)

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exceeding one, suggesting that the Chinese population will not encounter a significant

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non-carcinogenic risk (skin lesions) through the intake of Asi due to rice consumption. The THQs

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gradually increased with rising exposure levels, of which no value for P97.5 and P99.9 exceeded one in

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any group too. However, in fact, the BMDL0.5 of lung cancer was smaller than that of skin lesions,

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therefore the carcinogenic risks from rice Asi intake should be paid more attentions compared with the

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non-carcinogenic risks.

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MOE was always utilized for the dietary exposure assessment of Asi in milled rice to establish its

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MCL by FAO and WHO33. In Table 6, the MOE values for all age groups and genders of Chinese were

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under 100, ranging from 3.86 to 8.54 at mean value and from 4.15 to 9.21 at P50. In the previous study,


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Li et al.24 attained the similar MOE values using BMDL0.5 of lung cancer for Asi in milled rice in China,

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where mean and median MOE values were 7.3 and 7.4 for Chinese adult. It is obvious that the

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carcinogenic risks from rice Asi exposure for Chinese are relatively high, which demonstrated a

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different result in contrast with the THQs in Table 5. To compare the carcinogenic risks of rice Asi

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intake among different countries, the MOE values in milled rice for adults were estimated using rice

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consumption per capita, according to the rice Asi levels from Bangladesh, China, India, Italy, Japan,

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Thailand, Turkey and US reported previously. The results were also listed in Table 3. In spite of the

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same Asi level in rice of China with US, China consumers might encounter a significantly higher risk

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of carcinogenic effects (MOE: 9.3 for China < 54.6 or 59.8 for US) due to the higher daily rice

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consumption. On the contrary, the residents in southeast Asia, such as Bangladesh (daily rice

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consumption is 441 g) and Thailand (285 g), might encounter a higher health risk than Chinese due to

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the higher rice consumption (MOE: 9.3 for China > 5.1 for Bangladesh or 6.3 for Thailand). For

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another specific example, although rice from Japan was popular and expensive in China recently, the

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rice Asi of Japan (120 µg/kg) was higher than that of China in this work, which leaded to the same

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MOE value for Japanese consumers (Japanese rice consumption is only approximately three quarters of

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Chinese) with China’s in this work. Unfortunately, in Table 3 and Table 6, no MOE value exceeded 100,

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which indicated a worldwide health risk for Asi intake of rice consumption including China. Hence,

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risk managers of food safety in major rice consuming countries should pay more attentions for

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carcinogenic risks from rice Asi intake.

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To lessen the health risks from rice Asi for residents in China and other major rice consuming

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countries, some measures should be taken to control Asi intake from rice consumption, especially in the

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more extensively arsenic contaminated regions. These measures could include changing to other grains,

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removing the outer layer of the rice grain34 and washing rice properly before cooking35. Besides,

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reducing the industrial and mineral arsenic emission to planting environment and controlling arsenic

288

level in drinking water should not be ignored.

289

AUTHOR INFORMATION

290

Corresponding Authors

291

*(M.W) Phone: +86 10 82106546. Fax: +86 10 82106566. E-mail: [email protected].

292

*(X.M.) Phone & Fax: +86 10 82106566. E-mail: [email protected], [email protected].

293

Funding



294

This work was financially supported by the Special Fund for Special Project for National Key

295

Scientific Instruments and Equipment Development of China (Grant No. 2011YQ14014904) and

296

Agro-scientific Research in the Public Interest of China (Grant No. 201303088-01).

297

Acknowledgments

298

The authors also delighted to express their gratefulness and sincerest thanks to Professor Zhiwei Zhu,

299

China National Rice Research Institute, China, for his sampling assistance.

300

Notes

301

The authors declare no competing financial interest.

302

REFERENCES

303

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Statistics (database). CHAPTER 4. CEREALS. (DOI: http://dx.doi.org/10.1787/data-00659-en).


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Total Environ. 2011, 412, 324-335.

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Rice (Raw and Polished Rice). Codex Committee on Contaminants in Foods, 8th Session.

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CX/CF/14/8/6, 2014.

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(34) Sun, G. X.; Williams, P. N.; Carey, A. M.; Zhu, Y. G.; Deacon, C.; Raab, A.; Feldmann, J.; Islam, R.

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M.; Meharg, A. A. Inorganic arsenic in rice bran and its products are an order of magnitude higher

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than in bulk grain. Environ. Sci. & Technol. 2008, 42, 7542-7546.

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(35) Sun, G. X.; Van de Wiele, T.; Alava, P.; Tack, F.; Du Laing, G. Arsenic in cooked rice: Effect of

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398



399

FIGURE CAPTIONS

400

Figure 1. The geographical locations of the sampling sites of rice samples in China. Percentage %,

401

the rice output proportion of each province to the entire China.


Page 16 of 23

Page 17 of 23


402

TABLES

403

Table 1. Body weights and daily intake of rice for Chinese residents Rice daily intakes of body weight Body weight (kg)

Rice daily intakes (g/d) (g/kg/d)

Age Male

Female

Male

Female

Male

Female

2–4

14.06

13.48

116.8

115.3

8.3

8.6

4–7

18.20

17.61

154.9

137.5

8.5

7.8

7–11

25.98

25.12

199.0

182.8

7.7

7.3

11–14

36.22

36.39

229.5

205.5

6.3

5.6

14–18

50.58

47.81

266.1

207.5

5.3

4.3

18–30

62.52

52.85

266.9

224.9

4.3

4.3

30–45

64.42

55.73

272.6

240.2

4.2

4.3

45–60

62.71

56.59

271.5

235.2

4.3

4.2

60–70

60.48

53.51

236.2

209.4

3.9

3.9

70–80

57.33

49.80

222.7

192.7

3.9

3.9

404 405

Table 2. Extraction rates of different extracts for As speciation from rice samples (n = 3) Total As a

DMA

Asi

Sum of species

Extraction rates

(µg/kg)

(µg/kg)

(µg/kg)

(µg/kg)

(%)

0.02mol/L TFA

79.4±6.3

182.5±12.4

261.9±18.7

90.3±6.4

0.1mol/L TFA

68.3±8.5

195.0±8.8

263.4±17.3

90.8±6.0

0.02mol/LHNO3

90.6±4.7

189.4±10.8

280.0±15.5

96.5±5.3

81.5±5.8

189.3±13.8

270.8±19.6

93.4±6.7

54.5±8.9

135.1±16.0

189.6±24.9

65.4±8.6

82.7±5.0

190.0±9.6

272.7±14.6

94.0±5.0

Extracts

0.1mol/LHNO3 methanol/water (1:1, V/V)

290±15

methanol/water (1:1, V/V) with 0.02mol/L HNO3

406

a

The rice sample was selected randomly from 1653 samples.

407 408



409

Page 18 of 23

Table 3. Arsenic levels (µg/kg) in milled rice from different countries

Country

Total As

Asi

mean (range)

mean (range)

Rice

% of Asi

N

mean

Bangladesh

-

80 (10 - 210)

China

143 (33 - 437)

108 (28 - 217)

114.4 (65.3 -

82.0 (48.5 -

274.2)

216.6)

116.5 (NDc -

90.9 (ND -

665.2)

303.2)

India

-

30 (20 - 70)

-

Italy

-

110 (70 - 160)

Japan

139 (29 - 430)

consumption a

Estimated

(g/capita per

MOE b

References

day) 15

441

5.1

23

75.5

446

214

7.8

24

71.7

21

-

10.3

14

78.0

165

-

9.3

This study

12

194

30.9

23

-

5

-

-

23

120 (28 - 261)

86.3

600d

162

9.3

25

190 (70 - 420)

-

-

26

-

-

23

Thailand

-

100 (50 - 150)

-

10

285

6.3

23

Turkey

202

160

79.2

50

-

-

26

USA

-

100 (50 - 150)

-

10

33

54.6

23

210 (26 - 1000)

91.2 (25 - 157)

43

60

-

59.8

27

3

410

a

Rice consumption is calculated from the data of OECD-FAO Agricultural Outlook 2015 - 2024 29.

411

b

Assuming that mean body weight is 60 kg per capita for adults of every country.

412

c

ND means not detectable.

413

d

The samples were brown rice, so the concentrations of total As (82.3%) and Asi (79.7%) in milled rice

414

were both converted from 170 µg/kg and 150 µg/kg in brown rice, respectively, in consideration of the

415

degree of polishing 95%28.

416 417

Table 4. Regional distributions of Asi concentrations in rice from 11 provinces Mean

Mean

(Asi)

(As)

(µg/kg)

(µg/kg)

Sample Provinces size

Medium

Max.

Violation

Duncan

(µg/kg)

(µg/kg)

rate (%)

grouping

STD


Page 19 of 23


Jiangxi

200

116.1

155.0

44.2

116.0

221.1

1.5

A

Hunan

250

114.5

148.0

46.6

113.0

303.2

5.2

A

Sichuan

150

110.9

148.6

30.3

112.5

192.1

0

AB

Guangxi

200

103.8

122.1

31.6

104.8

220.9

0.5

B

Guangdong

200

90.1

105.3

39.7

88.2

233.8

0.5

C

Hubei

150

86.0

113.5

40.7

82.5

208.4

0.7

C

Yunnan

60

69.8

112.2

26.8

68.6

139.0

0

D

Heilongjiang

95

66.8

113.4

25.2

65.6

187.6

0

D

Zhejiang

60

62.6

71.0

20.4

59.2

119.6

0

D

Anhui

145

61.3

85.2

24.7

60.2

129.5

0

D

Jiangsu

143

48.4

62.8

15.1

47.4

99.0

0

E

Total

1653

90.9

116.5

42.0

84.0

303.2

1.15

-

418



419

Page 20 of 23

Table 5. Dietary exposures of Asi in rice for different age and gender groups (THQ for non-carcinogenic effects) Dietary exposures of Asi in rice for different age and gender groups (THQ) Age

Male

Female

Mean

P50

P90

P97.5

P99.9

Mean

P50

2–4

0.140 (0.137–0.143)

0.130 (0.125–0.135)

0.228 (0.222–0.235)

0.276 (0.268–0.290)

0.393 (0.340–465)

0.144 (0.141–0.147)

0.134 (0.129–0.139)

4–7

0.143 (0.140–0.146)

0.133 (0.120–0.138)

0.234 (0.228–0.241)

0.283 (0.275–0.297)

0.402 (0.348–0.476)

0.131 (0.129–0.135)

7–11

0.129 (0.126–0.132)

0.120 (0.115–0.125)

0.211 (0.205–0.217)

0.254 (0.247–0.267)

0.362 (0.321–0.429)

11–14

0.107 (0.104–0.109)

0.099 (0.096–0.103)

0.174 (0.169–0.179)

0.211 (0.204–0.221)

14–18

0.088 (0.087–0.090)

0.082 (0.079–0.086)

0.144 (0.141–0.149)

18–30

0.072 (0.070–0.073)

0.067 (0.064–0.069)

30–45

0.071 (0.069–0.073)

45–60

P97.5

P99.9

0.235 (0.229–0.242)

0.284 (0.276–0.298)

0.404 (0.350–0.479)

0.122 (0.118–0.127)

0.215 (0.209–0.221)

0.260 (0.252–0.273)

0.369 (0.320–0.437)

0.122 (0.120–0.125)

0.114 (0.110–0.118)

0.200 (0.194–0.206)

0.242 (0.235–0.254)

0.344 (0.298–0.408)

0.300 (0.260–0.355)

0.095 (0.093–0.097)

0.088 (0.085–0.092)

0.155 (0.151–0.160)

0.188 (0.182–0.197)

0.267 (0.231–0.316)

0.175 (0.170–0.184)

0.249 (0.215–0.294)

0.073 (0.071–0.075)

0.068 (0.065–0.071)

0.119 (0.116–0.123)

0.114 (0.140–0.152)

0.205 (0.178–0.243)

0.117 (0.114–0.121)

0.142 (0.138–0.149)

0.202 (0.175–0.239)

0.071 (0.070–0.073)

0.067 (0.064–0.071)

0.117 (0.114–0.120)

0.141 (0.137–0.148)

0.201 (0.174–0.238)

0.066 (0.064–0.069)

0.116 (0.113–0.120)

0.140 (0.137–0.148)

0.200 (0.173–0.237)

0.073 (0.071–0.074)

0.067 (0.065–0.070)

0.118 (0.115–0.122)

0.143 (0.139–0.150)

0.204 (0.177–0.241)

0.073 (0.071–0.075)

0.067 (0.065–0.071)

0.119 (0.116–0.123)

0.144 (0.140–0.151)

0.205 (0.177–0.242)

0.070 (0.068–0.071)

0.065 (0.063–0.067)

0.114 (0.111–0.117)

0.138 (0.134–0.145)

0.196 (0.170–0.233)

60–70

0.066 (0.064–0.067)

0.061 (0.059–0.063)

0.107 (0.104–0.110)

0.130 (0.126–0.136)

0.185 (0.160–0.219)

0.066 (0.064–0.067)

0.061 (0.059–0.063)

0.108 (0.105–0.111)

0.130 (0.126–0.137)

0.185 (0.160–0.219)

70–80

0.065 (0.064–0.067)

0.061 (0.059–0.063)

0.107 (0.104–0.110)

0.129 (0.125–0.136)

0.184 (0.159–0.217)

0.065 (0.063–0.067)

0.060 (0.058–0.063)

0.106 (0.104–0.110)

0.129 (0.125–0.135)

0.183 (0.158–0.217)


P90

Page 21 of 23


420 421

Table 6. Dietary exposures of Asi in rice for different age groups and genders of Chinese (MOE for lung cancer) Dietary exposures of Asi in rice for different age groups and genders (MOE) Age Mean 2–4 4–7 7–11 11–14 14–18 18–30 30–45 45–60 60–70 70–80

Female

Male P50

Mean

P50

3.98

4.28

3.86

4.15

(4.07–3.89)

(4.43–4.11)

(8.81–3.77)

(4.31–3.99)

3.88

4.18

4.23

4.55

(3.97–3.79)

(4.32–4.01)

(4.32–4.13)

(4.71–4.38)

4.31

4.64

4.55

4.88

(4.40–4.22)

(4.81–4.46)

(4.64–4.43)

(5.05–4.70)

5.20

5.60

5.83

6.31

(5.32–5.09)

(5.81–5.38)

(5.98–5.71)

(6.51–6.03)

6.28

6.76

7.61

8.19

(6.42–6.14)

(7.00–6.48)

(7.78–7.45)

(8.48–7.87)

7.73

8.33

7.78

8.33

(7.91–7.57)

(8.64–8.00)

(7.95–7.61)

(8.64–8.00)

7.78

8.38

7.65

8.24

(8.00–7.61)

(8.70–8.05)

(7.82–7.49)

(8.54–7.91)

7.61

8.24

7.95

8.54

(7.82–7.45)

(8.48–7.87)

(8.14–7.78)

(8.86–8.24)

8.43

9.15

8.43

9.09

(8.64–8.28)

(9.46–8.75)

(8.64–8.24)

(9.40–8.75)

8.48

9.15

8.54

9.21

(8.70–8.33)

(9.46–8.81)

(8.75–8.33)

(9.52–8.81)

422 423

TOC Graphic

424

For Table of Contents Only



Figure 1. The geographical locations of the sampling sites of rice samples in China. Percentage%, the rice output proportion of each province to the entire China. 230x164mm (300 x 300 DPI)


Page 22 of 23

Page 23 of 23


TOC 68x47mm (300 x 300 DPI)


Concentrations of Inorganic Arsenic in Milled Rice from China and

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