We have written about the toxicity of arsenic in food twice before. The first time was in 2012 covering a 2009 opinion from the European Food Safety Authority (EFSA) and a 2012 report from the US Food and Drug Administration. The second time was in 2020 based on research from the University of Washington covering the impact of climate change on further accumulation of arsenic in rice due to a warmer climate.
Previous problems in determining the chemical form of arsenic (arsenic speciation)
Arsenic exists in several different forms in nature bound to a number of other compounds resulting in varying toxicity. It is the inorganic arsenic (compounds that do not contain carbon) commonly found in water and rice that is particularly toxic. Soluble inorganic arsenic is rapidly and nearly completely absorbed after ingestion and widely distributed to almost all organs. Organic arsenic commonly found in fish and other seafood is far less toxic.
And here we have a real problem in that arsenic analysis at speciation level has been very difficult. Unfortunately, the EFSA risk assessment in 2009 had to make assumptions about the proportion of inorganic arsenic in different food commodities based on the total arsenic levels reported to allow calculation of specific exposure to the toxic species. With an improved focus on arsenic speciation, the European Commission asked EFSA to first update the exposure assessment based only on inorganic arsenic results and secondly to update its risk assessment of inorganic arsenic to consider new studies on its toxic effects.
The new exposure results
In 2021, EFSA published an updated exposure assessment. It was based on a total of 13,608 analytical results on inorganic arsenic of which 7,623 covered drinking water and 5,985 covered different types of food, in particular rice and rice-based products. Samples were collected across Europe between 2013 and 2018. Consumption data from 23 different European countries and a total of 44 different dietary surveys (87,945 subjects) were used to better estimate the chronic dietary exposure of inorganic arsenic.
The highest dietary exposure to inorganic arsenic was seen in the young population (infant, toddlers and other children) with mean values in the different surveys ranging between 0.07-0.61 μg/kg bodyweight per day, and high exposure consumers (the 95th percentile estimates) between 0.17-1.20 μg/kg bodyweight per day. In the adult population (adults, elderly and very elderly), mean dietary exposure estimates ranged between 0.03-0.15 μg/kg bodyweight per day, and between 0.06-0.33 μg/kg bodyweight for high intake consumers (the 95th percentile estimates).
These dietary exposure estimates of inorganic arsenic were noticeably lower than previously reported, with the new estimates being around 1.5–3 times lower across the different age classes. This difference can be explained by the use of measured rather than previously calculated inorganic arsenic and more accurate consumption data. The higher dietary exposure seen in the young population is to a large extent due to consumption of rice-based foods for infants as well as biscuits, rusks and cookies for children.
And the new risk assessment results
In 2024, EFSA published a new risk assessment of inorganic arsenic in food based on the new exposure assessment and updated toxicity results. The latter used findings from existing human epidemiological studies not normally available, and not animal studies as proxies for human effects. The epidemiological studies showed that chronic intake of inorganic arsenic via diet and/or drinking water was associated with increased risk of several adverse outcomes including cancers of the skin, bladder and lung.
For its risk assessment, EFSA considered the increased incidence of skin cancers associated with inorganic arsenic exposure as the most relevant harmful effect. The experts concluded that ensuring protection against skin cancer would also be protective against other potentially harmful effects.
When assessing genotoxic and carcinogenic substances that are unintentionally present in the food chain, EFSA calculates a margin of exposure (MOE) for consumers. The MOE is a ratio of two factors: the dose at which a small but measurable adverse effect is observed called the reference point, and the level of exposure to a substance for a given population.
In its 2009 opinion, EFSA calculated the reference point as a range of values between 0.3 and 8 µg/kg bodyweight per day of inorganic arsenic associated with cancers of the lung, skin and bladder, as well as skin lesions. In the new opinion of 2024, the reference point was lowered to a single value of 0.06 μg/kg bodyweight per day using a case–control study of skin cancer (squamous cell carcinoma) carried out in the US. This is in the range of the new mean dietary exposure estimates for inorganic arsenic in adults (0.03–0.15 μg/kg bodyweight per day), and below any of the high exposure estimates in adults ( 0.07–0.33 μg/kg bodyweight per day). In adults, the calculated MOEs ranged between 2 and 0.4 for mean consumers and between 0.9 and 0.2 for high consumers, respectively. An MOE calculated from human data of 1 or less would correspond to an exposure level to inorganic arsenic that might be associated with an increased risk of skin cancer and thus raises a health concern.
The same conclusion applies to the younger age groups despite their higher exposure to inorganic arsenic as the harmful effect seen in adults are due to chronic exposure and the epidemiological studies would have captured their dietary exposure during early life.
So what can be done to limit the risk?
As has been indicated above, rice is a major contributor to inorganic arsenic exposure as it is a dietary staple for millions of people around the world. So what can be done to limit the risk?
Authorities could introduce maximum levels for arsenic in rice, consumers could look at rice types and try to buy rice from regions with less natural levels of arsenic, rice preparation in kitchens could be changed or rice consumption could be reduced if there are alternatives available.
Regulating inorganic arsenic levels
Unfortunately, regulating a naturally occurring element in such a widely eaten food as rice is no easy task. Arsenic levels can vary widely in rice from different countries and states, and among different rice cultivars. This raises difficult questions about how a regulated standard could be monitored and enforced.
Codex Alimentarius has adopted a recommended limit for inorganic arsenic of 200 μg/kg for polished rice, and 350 μg/kg for husked rice. In the European Union maximum levels for inorganic arsenic in rice was introduced in 2016 varying from 100-300 μg/kg depending on the specific product. The Australian guidelines are for total arsenic (organic and inorganic) in rice and set a maximum level of 1000 μg/kg.
However, looking at the reported inorganic arsenic levels in rice reported to EFSA only 15 samples exceeded European Union maximum levels and still a health concern was identified.
Buying rice with proven lower levels
The amount of arsenic in rice depends on the variety of rice and where it was grown. Brown rice has more arsenic than white rice since arsenic is accumulated in the outer layers of the grain, while basmati rice regularly has the lowest levels. Globally, inorganic arsenic in polished rice varied from < 2 to 399 μg/kg in a recent study. The lowest levels were found in East Africa followed by Indonesia and California, while West African rice had an order of magnitude higher inorganic arsenic followed by South America and Southern American states like Texas and Luisiana.
Although it can be quite difficult to know where the rice is grown, it is clear that basmati rice is a preferred choice and brown rice should be avoided despite its better nutritious profile.
Changing rice preparation
Rinsing rice before cooking has a minimal effect on the arsenic content of the cooked grain, but washes enriched iron, folate, thiamin and niacin from polished and parboiled rice. However, cooking rice in excess water efficiently reduces the amount of arsenic in the cooked grain by 40% to 60%. It is recommended to use six cups of water to one cup of rice. After boiling the rice, pour off the remaining water, then rinse the cooked rice again.
Unfortunately, this cooking method common in Asia will also reduce some of the nutrients but is recommended on balance to minimise arsenic toxicity.
Limit rice consumption
It is not necessary to eliminate rice completely from your diet, but If you eat a lot of rice eat it less often substituting rice with other whole grains, such as quinoa, barley, ferro, amaranth, bulgur and millet. They’ll be just as nutritious and don’t have arsenic in them because they don’t take up arsenic from the ground as they grow.
Arsenic in rice is a real concern. Be more choosey with the type and origin of your rice, always cook it with excess water, and be aware of how much you’re consuming. Try looking at other whole grain alternatives to keep your arsenic consumption to a minimum.
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