If you’re planning to commit the perfect crime and kill your fussy, noisy neighbor with some arsenic you ordered on Amazon, you may be interested to know that it is easier than previously thought. Indeed, the most effective way to poison someone with arsenic is to serve the unfortunate soul a generous portion of your best risotto recipe!
Ok, I’m not really suggesting you try to kill your neighbor, with or without risotto. Nevertheless, the reason why I’m joking about this famous Italian recipe is because of a comment I recently received from a good friend of mine, who told me I should stop eating rice because of its high arsenic content.
Risotto happens to be one of my favorite dishes, and I took this comment very seriously! I turned myself into the most grotesque version of Sherlock Holmes and, armed with a newly bought tweed suit and cloth cap (and obviously a fuming pipe), I immediately started my search for the truth.
Arsenic, as we all know, is a very toxic trace mineral and is a human group I carcinogen causing skin, kidney, bladder, and lung tumors (IARC). Swallow slightly less than 2 grams before watching a movie, and you won’t see the end of it! Trust me, you don’t want to mess with it!
Chronic exposure to arsenic has also been associated with cardiovascular disease and diabetes, while exposure in utero and during early childhood negatively impacts cognitive development and increases death risk in young adults.
Judging by my low mental acuity, it might be that I was exposed to some of it in the past …. But let’s continue with this intriguing investigation.
Our murderous friend could also sneak into several common house products, such as fertilizers, wood preservatives, insecticides, and herbicides. Luckily for us, the EU has strict regulations to protect its citizens from these products.
Over 150 million people worldwide, nearly half the population of the US, are currently threatened by arsenic contamination in drinking water. More than 70% of them live in 10 countries in South and South-East Asia: Bangladesh, Cambodia, China, India, Laos, Myanmar, Nepal, Pakistan, Taiwan, and Vietnam[1].
This capricious, noiseless killer appears to contaminate the water used for drinking and preparing food and the water used to irrigate food crops. Food analysis often provides total arsenic levels, which comprise both inorganic and organic arsenicals, with the former exhibiting a far higher degree of toxicity compared to naturally occurring organic arsenic forms. Fish, shellfish, meat, poultry, dairy products, and cereals can all be dietary sources of arsenic, although exposure from these foods is generally much lower compared to exposure through contaminated groundwater. In seafood, particularly, arsenic is found in its less toxic form (i.e. the organic one). And finally, some bad news for smokers! Tobacco can also be contaminated and therefore cigarette smoke is another potential source of arsenic exposure. Just in case you needed another good reason to cut down on your smoky treat!
Smoke kills you. Elementary, Watson!
Exposure in Europe is much lower than in the countries with the highest contamination levels (e.g. Bangladesh), however, according to EFSA, the average dietary arsenic intake in infants, toddlers, and older children up to adolescence were at levels considered high enough to increase cancer risk by a very low margin (i.e. approximately 1% higher risk)[2]. EFSA’s exposure estimations in infants and toddlers showed young people to be mostly exposed through dairy products, whereas adults are mostly exposed to arsenic by eating grains. Notably, dietary supplements based on algae were found to contain 6134 μg/kg inorganic arsenic, but this is maybe a good topic for another blog post.
By going through the data collected by EFSA, it appears that exposure is mainly driven by consumption levels and not by high concentrations in the foods mentioned above. In practice, this means that adults are mostly exposed through grains because of the amount of grains they consume, whereas younger individuals get more exposure via dairy products, which constitute an important component of their diets.
But rice seems to be different….
Rice contains high arsenic levels, particularly brown rice, due to the relatively high concentration in rice husks. Apparently, its roots are particularly good at taking up the poisonous compound from soil, which has, in turn, been contaminated via both irrigation and contaminated pesticide formula[3]. Modified rice plants with a lower propensity to take up arsenic are under study[4], and therefore it seems that a potential solution is around the corner, although not yet available.
Meanwhile, what should we all do? Stop eating rice? I’m not really sure I can stay away from my beloved risotto for that much time….
Luckily enough, despite rice containing a good deal of arsenic, a limited consumption of it and its products is considered safe by health authorities. Therefore, consuming rice and rice-based products ‘in moderation and varying these products with products based on other cereals’[5] is a valid recommendation. By following this rule, only a moderate influence on total arsenic exposure is expected for the average consumer for whom rice contributes to a relatively low part of the overall diet. Obviously, people who usually have high rice intake should consider reducing their consumption levels. Indeed, in China (where rice contributes more to total diet), the government has introduced a threshold value of 150 μg arsenic/kg rice to protect its Citizens.
It’s time now to put my tweed suit and cloth cap back in the closet. Although from now on, my delicious treat will never taste the same….
For those of you who want more science…
In both drinking water and food, inorganic arsenic occurs as arsenate (iAsV) or as arsenite (iAsIII). Living organisms are able to convert the majority of arsenate into arsenite6; therefore, both forms tend to be combined during risk evaluation. Fish and seafood contain instead high amounts of arsenobetaine and arsenocholine, two of arsenic’s organic forms[6]. Among the latter, arsenobetaine is the most abundant, although different types of arsenosugars and arsenolipids exist as well[7]. Since arsenobetaine cannot be metabolized by the human body, its importance from a toxicological point of view is considered minor. On the other hand, it is not clear what potential health risk is associated with exposure to either arsenosugars or arsenolipids from seafood, since they can be metabolized to the major metabolite generated from inorganic arsenic, i.e. dimethylarsinate. It is indeed not known if any toxic intermediaries appear at some point during the metabolism of these compounds. However, limited data on arsenosugars point to an apparently low toxicity.
[1] Arsenic contamination, consequences and remediation techniques: a review. https://www.ncbi.nlm.nih.gov/pubmed/25463877.
[2] According to the EFSA Contam Panel, a dose comprised between 0.3 and 8 μg/kg body weight/day results in a 1 % increased risk of lung, skin and bladder tumors in humans. On the other hand, the Joint FAO/ WHO Expert Committee on Food Additives in 2011 calculated that the lower benchmark dose that resulted in a 0.5 % increased risk of lung cancer was 3.0 μg/kg body weight/day (range 2–7 μg/kg body weight/day). EFSA estimated that the mean dietary exposure to arsenic in infants, toddlers and ‘other children’ (aged up to adolescence) ranged from 0.2 to 1.37 μg/kg bw/day. The 95th percentiles were between 0.36 and 2.09 μg/kg bw/day (EFSA (2014) Dietary exposure to inorganic arsenic in the European population. EFSA J 12(3):3597).
[3] Abedin MJ, Cresser MS, Meharg AA, Feldmann J, Cotter-Howells J (2002a) Arsenic accumulation and metabolism in rice (Oryza sativa L.). Environ Sci Technol 36(5):962–968.
[4] Wang X, Peng B, Tan C, Ma L, Rathinasabapathi B (2015) Recent advances in arsenic bioavailability, transport, and speciation in rice. Environ Sci Pollut Res Int 22(8):5742–5750.
[5] BfR (2015) Rice and rice products contain high levels of inorganic arsenic. 14/2015, 11.06.2015.
[6] Watanabe T, Hirano S (2013) Metabolism of arsenic and its toxico- logical relevance. Arch Toxicol 87(6):969–979.
[7] Francesconi KA (2010) Arsenic species in seafood: origin and human health implications. Pure Appl Chem 82(2):373–381.
