Arsenic mainly finds its way into soils and accumulates in rice cultivation through polluted irrigation water, and through historic contamination with Arsenic-based insecticides, herbicides, fungicides, desiccants and wood preservatives; however, studies show that not all rice are affected the same and some rice varieties, through each mature rice plant mechanism (via absorption and chemical processes within the plant), may be more contaminated than others (~0.05—1 mg per kg): arsenic absorbed by the roots, travelling to the straw, husk, and finally to the grain, depending on the level of arsenic in the soil, the pH, clay content, and other ions present in the soil, but also the size of the grain. The longer the grain the higher the concentration.
Rice accumulates the highest amount of Arsenic of all grain crops, because rice is largely grown in depleted soils, and the absent ions can no longer interfere with Arsenic absorption.
Arsenic-contaminated rice does not depend on a brand either but on its origin.
Nearly half-a-century of studies also show that there are four main molecules of Arsenic present in the soil, two of which are actually toxic to the plant, demonstrating that arsenic reduces overall productivity of the soil and can also prevent plant development.
Furthermore, arsenic is considered one of the most important toxic elements found in the environment (and drinking water system) because of its potential risk to ecosystems and to human health. The International Agency for Research on Cancer (IARC) places Arsenic in the highest health hazard category (Class-1 carcinogen), and there is substantial evidence that it increases risk of cancer of the bladder, lung, skin, and prostate. Rice is one of the major staple food in the world, with a daily intake, in most Asian countries, of up to 0.5 kg (dry weight).
A recent study showed that rice grown in the US (Texas, the most), Italy and Spain contained the highest levels of arsenic, and in Pakistan and India the least.
Polishing rice to generate white rice also contributes to a reduction of arsenic in the grain.
Washing rice may be effective in removing some arsenic (~10%) from basmati rice only. To effectively remove 1/3 to nearly half of the arsenic in the grain, rice must be cooked in high volume of water (1:6 ratio of rice:water); however, studies show that, when coupled with overnight soaking, this may reduce arsenic content even further.
If you consume very little rice, and mainly white basmati rice, there may be little reason for concern, as you may be exposed to less arsenic than others; however, if you consume rice very regularly, it makes sense to reduce the exposure as much as possible, by soaking rice overnight, boiling it in high volume of water and rinsing the rice well at every step. Checking the origin of the rice on the label may also help you avoid buying grains with higher concentration of arsenic.
The food Standard Association (FAS) recommends that toddlers and children under 4 1/2 year old SHOULD NOT BE GIVEN RICE MILK "as a substitute for: breast milk, infant formula., cows’ milk. This is because, compared to other consumers, they tend to drink more milk and have a lower bodyweight." Adding: "There are a number of alternatives to suit young children with an allergy or intolerance to cows’ milk or soya. Talk to a health professional such as a doctor or dietician to find a suitable milk alternative."1
1 Food Standard Agency. (2018). Available at: www.food.gov.uk/print/pdf/node/282. Last accessed: 20 July 2018
Liu, WJ. Zhu, YG. Hu, Y. et al. (2006). Arsenic Sequestration in Iron Plaque, Its Accumulation and Speciation in Mature Rice Plants (Oryza Sativa L.). Environmental Science and Technology. 40 (18), pp. 5730–5736
Marin, AR. Masscheleyn, PH. Patrick Jr, WH. (1992). The influence of chemical form and concentration of arsenic on rice growth and tissue arsenic concentration. Plant and Soil. 13(2). pp 175–183
Meharg, AA. (2004). Arsenic in rice – understanding a new disaster for South-East Asia. Trends in Plant Science. 9 (9), pp. 415–417
Raab, A. Baskaran, C. Feldmann, J. et al. (2009). Cooking rice in a high water to rice ratio reduces inorganic arsenic content. Journal of Environmental Monitoring. 11, pp. 41–44
Zavala, YJ. Duxbery, JM. (2008). Arsenic in Rice: I. Estimating Normal Levels of Total Arsenic in Rice Grain. Environmental Science and Technology. 42, pp. 3856–3860
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