Original research articleExposure assessment of arsenic speciation in different rice types depending on the cooking mode
Introduction
Arsenic (As) is an ubiquitous metalloid that is widely dispersed at trace levels in the environment, particularly in air, water, and the Earth’s crust; it enters the food chain mainly from contaminated drinking water (European Food Safety Authority, 2009) and several widely consumed foodstuffs, such as fish and rice, the latter being an important contributor to As intake in countries with traditionally rice-based diets (Feldmann and Krupp, 2011, Jiang et al., 2015). Arsenic levels in rice depend on the geographical location, growing/soil conditions and also on the level of contamination of the irrigation water (Batista et al., 2011, Ma et al., 2014, Das et al., 2016, Signes-Pastor et al., 2016a, Signes-Pastor et al., 2016b). Despite the relatively large variety of As species present in food, rice accumulates mostly monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenite (As(III)) and arsenate (As(V)), the latter two inorganic species being the most widespread (Feldmann and Krupp, 2011, Signes-Pastor et al., 2016a, Signes-Pastor et al., 2016b). Given their similar toxicological properties, the sum of As(III) and As(V) is in most cases referred to as inorganic arsenic (Asi). Asi is carcinogenic for humans (European Food Safety Authority, 2009) and acute exposure to high Asi levels can also cause vomiting, abdominal pain and diarrhea (FAO/WHO, 2010). Chronic exposure to Asi can cause skin lesions, diabetes, hypertension and cardiovascular diseases. MMA and DMA (the methylated metabolites of inorganic arsenic) are excreted in urine and are considered less toxic than Asi; nevertheless, MMA and DMA have also been identified as possible cancer promoters and further studies are underway regarding their actual toxicity (Batista et al., 2011). Several other arsenic species commonly present in rice, such as arsenobetaine (AsB), arsenocholine (AsC), trimethylarsine oxide (TMAO) and arseno-sugars are currently considered non-toxic (Feldmann and Krupp, 2011).
Taking into account the high health risk associated to arsenic poisoning, the European Food Safety Authority (EFSA) stated that an intake ranging from 0.3 to 8 μg kg−1 body weight (b.w.) per day should be used as a reference for characterizing Asi risk (European Food Safety Authority, 2014a, European Food Safety Authority, 2014b). Similarly, the Agency for Toxic Substances and Disease Registry (ATSDR) provided a Minimal Risk Level (MRL) of daily intake between 0.3 and 20 μg kg−1 b.w. for individual As species (Asi, MMA and DMA), which is defined as the dose that is likely to lead to no appreciable risk of adverse non-cancer health effects over a specific duration of exposure (U.S. Department of health and human services, 2007). In 2014, the Joint Expert Committee on Food Additives (JECFA) (FAO/WHO, 2014) recommended a maximum level for Asi in milled and parboiled rice of 0.2 mg kg−1 (no such limit is yet regulated for husked brown rice). Very recently, the European Commission regulated the maximum levels of Asi in different types of rice, with maximum levels (ML) ranging from 0.10 mg kg−1 for rice destined for infant foods up to 0.30 mg kg−1 for rice waffles, wafers, crackers and cakes (Official Journal of the European Union, 2015). Apart from the EU regulations, at an international level, the only existing regulatory limit for As in rice is applied in China (0.15 mg Asi kg−1) (FAO/WHO, 2014).
The lack of international regulations in terms of health risk related to As exposure via food relates also to the difficulty of its accurate determination in biological matrices, especially at trace and ultra-trace levels. The most common analytical approach for As speciation analysis relies on the coupling of (anion exchange) high performance liquid chromatography (AE-HPLC) with inductively coupled plasma-quadrupole mass spectrometry (ICP-QMS) (Welna et al., 2015, Ma et al., 2016). Despite the well-recognized advantages of ICP-QMS as a detection technique for trace and ultra-trace elemental analysis, its application to As determination is still difficult because of several severe spectral interferences such as 40Ar35Cl and 40Ca35Cl (Wang and Forsyth, 2012, Nardi et al., 2009). In addition, since As is mono-isotopic, the use of a primary method for its quantification such as isotope dilution-ICP-MS is not possible. In such circumstances, one of the main approaches of method validation for As determination (including speciation analysis) is based on assessment of the accuracy profile (Comité Français d’Accréditation, 2016, Agence Francaise de Normalisation, 2010).
The aim of this study was to determine the concentration and toxicological relevance of Ast, Asi and organic As species in a variety of rice (types of grain, industrial processing and geographical origin) commonly consumed in France. The influence of four different cooking approaches was assessed regarding exposure to children (3–10 years old) and adults. For this task, fully validated methods based on the accuracy profile were employed (Leufroy et al., 2011). These results can be useful to understand as well as to mitigate arsenic exposure related to consumption of specific types of rice depending on the consumer profile.
Section snippets
Reagents
Ultrapure water (18 MΩ cm) obtained by purifying distilled water using a Milli-Q™ PLUS system combined with an Elix 5 pre-purification system (Millipore SA, Saint-Quentin-en-Yvelines, France) was used throughout the study. The As concentration (Ast) of this ultra-pure water was ≤0.012 μg L−1, which was considerably lower that the method limit of detection (MDL), hence it was considered As-free water.
Methanol (HPLC gradient grade), nitric acid (Suprapur, 67%) and hydrogen peroxide (Normapur, 30%
Total arsenic
Ast concentrations in the samples analyzed in this study showed a large variation, spanning between 0.041 mg kg−1 for long-grain white organic Basmati rice from India up to 0.535 mg kg−1 for a duo of long-grain organic rice from France (Table 4). The lowest levels were found in Basmati rice, ranging from 0.041 to 0.129 mg kg−1. Lower but still consistent levels were found in a three-rice mix (unknown origin) (0.301 mg kg−1), a short-grain rice for risotto from France (0.280 mg kg−1), a whole-grain rice
Conclusions
Assessment of total, inorganic and organic arsenic levels in different varieties of raw and boiled rice commercialized in France is proposed in this study. For all samples investigated here, the most abundant species was the inorganic arsenic, which is the species of major concern in terms of toxicity. It is worthy to underline that the results reported here may be specific to each rice sample type studied, as the level of arsenic in rice depends on soil properties, harvesting time, groundwater
Acknowledgements
The French Ministry of Food, Agriculture and Fisheries is acknowledged for financial support. We thank Paul Vallelonga for editing assistance.
References (44)
- et al.
Speciation of arsenic in rice and estimation of daily intake of different arsenic species by Brazilians through rice consumption
J. Hazard. Mater.
(2011) - et al.
Simultaneous determination of 31 elements in foodstuffs by ICP-MS after closed-vessel microwave digestion: method validation based on the accuracy profile
J. Food Compos. Anal.
(2015) - et al.
Water management impacts on arsenic behavior and rhizosphere bacterial communities and activities in a rice agro-ecosystem
Sci. Total Environ.
(2016) - et al.
Levels of arsenic pollution in daily foodstuffs and soils and its associated human health risk in a town in Jiangsu Province, China
Ecotoxicol. Environ. Saf.
(2015) - et al.
Determination of seven arsenic species in seafood by ion exchange chromatography coupled to inductively coupled plasma-mass spectrometry following microwave assisted extraction: method validation and occurrence data
Talanta
(2011) - et al.
Impact of agronomic practices on arsenic accumulation and speciation in rice grain
Environ. Pollut.
(2014) - et al.
Simultaneous analysis of 21 elements in foodstuffs by ICP-MS after closed-vessel microwave digestion: method validation
J. Food Compos. Anal.
(2011) - et al.
The use of inductively coupled plasma mass spectrometry (ICP-MS) for the determination of toxic and essential elements in different types of food samples
Food Chem.
(2009) - et al.
Determination of total arsenic: total inorganic arsenic and inorganic arsenic species in rice and rice flour by electrothermal atomic absorption spectrometry
Microchem. J.
(2013) - et al.
Arsenic burden of cooked rice: traditional and modern methods
Food Chem. Toxicol.
(2006)
Geographical variation in inorganic arsenic in paddy field samples and commercial rice from the Iberian Peninsula
Food Chem.
Inorganic arsenic in rice-based products for infants and young children
Food Chem.
Comparison of strategies for sample preparation prior to spectrometric measurements for determination and speciation of arsenic in rice
Trends Anal. Chem.
FD EN V03-115 Standard
Arsenic speciation in rice and risk assessment of inorganic arsenic in Taiwan population
Environ. Sci. Pollut. Res. Int.
Trends in food and nutritional intakes of French adults from 1999 to 2007: results from the INCA surveys
Brit. J. Nutr.
Toxicity and Assessment of Chemical Mixtures
Scientific opinion on arsenic in food. EFSA panel on contaminants in the food chain (CONTAM)
EFSA J.
Cited by (25)
Arsenic contamination, impact and mitigation strategies in rice agro-environment: An inclusive insight
2021, Science of the Total EnvironmentCitation Excerpt :Such differences in the extent of arsenic decrease may be due to the washing procedure followed and the arsenic in washing water (Bhowmick et al., 2018). However, irrespective of the washing procedure, sequential washing with deionized water have shown to reduce the arsenic content in the washed rice grains (Jitaru et al., 2016; Liu et al., 2018). Therefore, washing of rice with low arsenic water may be beneficial and can be a modification at kitchen level to reduce arsenic in cooked rice, although maybe at the expenses of some loss of essential nutrients (Gray et al., 2016).
Dietary exposure to potentially toxic elements through sushi consumption in Catalonia, Spain
2021, Food and Chemical ToxicologyDietary exposure to total and inorganic arsenic via rice and rice-based products consumption
2020, Food and Chemical Toxicology
- 1
Present address: ECSIN-European Center for the Sustainable Impact of Nanotechnology, ECAMRICERT SRL, Viale Porta Adige 45, I-45100 Rovigo, Italy.
- 2
Present address: The French Directorate General for food, Ministry of Agriculture, Agro-Food and Forestry, 75732 Paris Cedex 15, France.