Is arsenic in rice cakes a health risk?
WWarnings about arsenic in rice or rice cakes have been circulating for a long time. Since 2016 the EU Limits specified for this. These relate to inorganic arsenic (iAs), which can be reliably analyzed and can be toxic in sufficient doses: it is held responsible for an increase in the risk of cancer, for example. Researchers at the University of Bayreuth have now also discovered the organic arsenic compound dimethyl monothioarsenate (DMMTA) in a global screening of rice and rice cakes.
The results were published last year in “Journal of Agricultural and Food Chemistry” and in “Environmental Science & Technology”. DMMTA belongs to the group of sulphur-containing arsenic compounds, the so-called thioarsenates, and has been shown in studies on various cell lines to be more toxic than the inorganic arsenic compounds. In order to be able to assess the risk potential of DMMTA, the authors call for further toxicological investigations and, as a precaution, advocate regulation of the total arsenic content.
Arsenic is a natural component of the earth’s crust and thus appears in rocks and through leaching in the soil and in groundwater. Arsenic can be taken up by crops such as rice. The European Commission announced in early March as part of the “European plan to fight cancer” a further tightening of the permissible iAs concentration in food. For example, the limit for iAs in white, polished rice is to be reduced from 0.20 to 0.15 milligrams per kilogram.
However, organic arsenic species, especially DMMTA, are still not tested, as the authors of the DMMTA studies Britta Planer-Friedrich and Stephan Clemens emphasize. According to Planer-Friedrich, the relevance of organic arsenic had been misunderstood for a long time, because up to now mainly dimethyl arsenate (DMA) has been found in nature. However, this was only classified as “potentially carcinogenic” and was therefore not regulated.
Higher levels of arsenic than rice itself
For a long time it was ignored that DMMTA can form from DMA in the presence of reduced sulfur in rice soil, since standard measurement methods incorrectly determine DMMTA as DMA. Only after the development of suitable stabilization and analysis methods Planer-Friedrich succeeded in detecting thioarsenates in 2007 in high sulfur geothermal waters of Yellowstone National Park. In 2020 the realization camethat even low concentrations of sulfur are sufficient to form thioarsenates in bogs, groundwater and rice soils. Two years later, the scientists succeeded in detecting the substance in rice grains and rice products.
Using a method that simulates the digestion of rice in the gastrointestinal tract, the Bayreuth researchers have now demonstrated that DMMTA can be released from rice after consumption and thus poses a potential health hazard. In addition, they observed initially on a small number of samplesthat rice cakes have higher DMMTA concentrations than rice itself.
“In rice cakes, there seem to be conditions during production that lead to low levels of DMMTA in the rice accumulating more in the cake or even more DMMTA being formed from DMA,” Planer-Friedrich suspects. This seems to apply to a wide range of rice cakes, says Stephan Clemens: “Since the first findings, we have examined more than 70 commercially available rice cake products and found DMMTA concentrations that alone exceed the valid iAs limit of 0.30 milligrams per exceed kilos.”
The author also has on the subject a film report created.
