Exposure assessment of arsenic speciation in different rice types depending on the cooking mode

doi:10.1016/j.jfca.2016.09.007

Journal of Food Composition and Analysis

Volume 54, December 2016, Pages 37-47

https://doi.org/10.1016/j.jfca.2016.09.007 Get rights and content

Highlights

•
Risk assessment of rice consumption by different French populations groups.
•
Rice cooking mode has a different toxicological implication for children and adults.
•
Mitigate inorganic arsenic exposure related to consumption of contaminated rice.

Abstract

Total (As_t), inorganic arsenic (As_i = As(III) + As(V)) and dimethylarsonic acid (DMA) were determined in 37 commercial rice samples collected in France. As_t was measured by inductively coupled plasma-mass spectrometry (ICP-MS) whereas anion-exchange chromatography – ICP-MS was used for As_i and DMA determination. As_t in raw rice varied from 0.041 to 0.535 mg kg⁻¹ whereas As_i varied from 0.025 mg kg⁻¹ (polished Basmati rice) up to 0.471 mg kg⁻¹ (organic rice duo). The daily intake and associated health risk for different population groups as a function of age and gender was also assessed. The intake varied between 0.002 and 0.184 μg kg⁻¹ body weight for As_t and 0.002 and 0.153 μg kg⁻¹ body weight for As_i, which do not pose a chronic toxicity risk. Organic wholegrain rice may entail a risk for children in the case of sole consumption at the expense of polished rice. The impact of rice cooking/boiling in terms of the overall toxicological risk related to As species was also investigated. Pre-rinsing and boiling the raw rice by using an excess of water is the most efficient mode to obtain a significant As_i removal and further reduction of the toxicological risk for children, particularly for white rice varieties.

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 (As_i). As_i is carcinogenic for humans (European Food Safety Authority, 2009) and acute exposure to high As_i levels can also cause vomiting, abdominal pain and diarrhea (FAO/WHO, 2010). Chronic exposure to As_i 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 As_i; 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 As_i 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 (As_i, 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 As_i 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 As_i 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 As_i 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 As_t, As_i 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 (As_t) 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

As_t 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.

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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.

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Original research articleExposure assessment of arsenic speciation in different rice types depending on the cooking mode

Highlights

Abstract

Introduction

Section snippets

Reagents

Total arsenic

Conclusions

Acknowledgements

J. Hazard. Mater.

J. Food Compos. Anal.

Sci. Total Environ.

Ecotoxicol. Environ. Saf.

Talanta

Environ. Pollut.

J. Food Compos. Anal.

Food Chem.

Microchem. J.

Food Chem. Toxicol.

Food Chem.

Food Chem.

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.

Original research article
Exposure assessment of arsenic speciation in different rice types depending on the cooking mode