Risc of arsenic in food examined
In the classic film "Arsenic and Old Lace", the two nice, elderly ladies have many a skeleton in the closet: their victims are lonely men, whom they poison with arsenic in their wine. Today, arsenic is less interesting as an "assassin's poison", but it is still a problem in food.
Arsenic enters the environment and thus the food chain from volcanic eruptions, combustion of fossil fuels and also through groundwater. But actually how big is the risk from arsenic in food? Are arsenic-containing compounds absorbed by the human body and possibly converted into more toxic forms? So far, very little is known about this. To address these issues, chemists of the BAM Federal Institute for Materials Research and Testing have investigated herring fillets for arsenic and various arsenic compounds in cooperation with the Helmholtz Centre for Environmental Research (UFZ) in Leipzig.
So far interest has mainly been directed towards the total arsenic content. "The total arsenic content in food, however, does not say anything about the effect arsenic may have on the human body. For each arsenic-containing compound has a different toxicological significance", says BAM's Christian Piechotta. Therefore, extensive analyses have been performed to identify arsenic-containing compounds in herring.
Food is routinely analysed quantitatively for certain, and therefore known, ingredients within food control. However standardised methods for the analysis of individual arsenic compounds in food are not yet available. "The difficult thing about our study is that we do not know exactly what compounds to look for, accordingly the analysis method must be comprehensive", says Susanne Lischka, who, together with Christian Piechotta, has conducted and reported the tests in the journal "Talanta"*. Frozen herring fillets from the supermarket were peeled, chopped and freeze-dried to remove the high water content in the fish - then ground, homogenised and dried again.
"This extent of sample preparation is necessary to ensure that we have a homogeneous material", says Piechotta. The scientists believe that this is not a conventional food analysis, rather a comprehensive speciation analysis, which needs to detect all chemical compounds of an element which occur in the sample. Thus 18 arsenic compounds have been clearly characterised and amongst them, seven new arsenolipids are described for the first time. Arsenolipids are fat-soluble arsenic compounds. They are produced naturally by fish, but their effect on the human body has so far been unexplored.
"Our results are the fundamentals for toxicologists. They can only assess their health risks when the various arsenic compounds have been clearly identified in the herring and the human body", says Lischka. It is known that the human body can metabolise arsenolipids. Back in 2006, Austrian scientists in Prof. Ernst Schmeisser's working group found that panellists who had been given arsenic-containing cod liver to eat, later had specific arsenolipids in their urine that had not previously been detected in the cod liver. Over the long term, BAM scientists want to synthesise individual arsenic compounds in the laboratory in order to provide reference materials which can then be used in food analysis laboratories to search for these arsenic compounds - for prophylaxis to keep fish as a healthy food.
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