Tolerances foodstuffs

A varied diet containing a wide range of foodstuffs provides adequate intake of vitamins for most people, and supplementing these amounts will have no beneficial effect and may result in the toxicity associated with hypervitaminosis. The DRI also includes the tolerable... 

Table 11.3 Tolerances for Veterinary Medicinal Products in Foodstuffs of Animal Origin According to the US Code of g Federal Regulations... 

The setting of MRLs for residues of veterinary drugs has been simplified somewhat since 1999, when the evaluation of old substances was completed and all MRLs are now developed and adopted by a unified central procedure. Much work has still to be done on the preparation and adoption of maximum levels for mycotoxins, heavy metals and other contaminants, such as PCBs and dioxins. Here one of the main factors delaying progress is the lack of data for toxicological evaluations and setting tolerable daily or weekly intakes. Furthermore, there is a lack of reliable data on levels of contaminants in individual foodstuffs and on dietary intakes of such substances. 

If there is no choice in using pesticides in agriculture, there is also no choice about adequate monitoring of all of our foodstuffs or about setting valid tolerances for pesticides on foods. We cannot afford even one mistake which involves all or most of the population. 

Contaminants also have to be evaluated for safety. As we saw earlier, there are many substances in food that occur naturally or as a result of contamination from human activities. Thus shellfish may be contaminated with heavy metals and oily fish with substances such as dioxin. The levels of these contaminants in our food have to be regularly monitored and if the level rises above that permitted, known as the tolerable daily intake (TDI), the sale of that foodstuff is restricted. 

M. Takano, H. Takemura, and T. Tsuchido. Freeze-drying tolerance of Escherichia coli rec A mutants caused by growth temperature shift, in Fundamentals and Applications of Freeze-Drying to Biological Materials, Drugs, and Foodstuffs, International Institute of Refrigeration, Commission, Cl, Tokyo, 1985, pp. 279-284. 

A well-known phenomenon in inorganic salts is the salting-out effect. Adding sodium sulphate, ammonium sulphate or sodium chloride (common salt), for example, in portions to aqueous systems has the effect of driving out some of the volatile compounds into the gaseous phase, or into a solvent which is immiscible with water. Of the salts mentioned above, only common salt has any relevance to food. Additions of 5 to 15% to aqueous systems result in increases of head space concentration of ethyl acetate, isoamyl acetate and menthone up to 25% [10,32], This common salt concentration, however, is way above what is tolerated normally in foodstuffs. In foods with a normal salt content, the salt has virtually no effect on the vapour pressure of volatile compounds [9,10,32], The same is true for calcium chloride [8[, The possibility, that the salt content of the saliva has some effect on the vapour pressure cannot be ruled out however [32],... 

As discussed, aflatoxins are genotoxic and carcinogenic, and for substances of this type, there is no threshold below which no harmful effect is observed. Subsequently, no tolerable daily intake has been set by the JECFA or any other international or national authority. Limits for foods are set as low as reasonably achievable. The current legislation in the European Union includes a maximum level of 2 pg/kg for aflatoxin B, and 4 pg/kg aflatoxin B1 B2, Gi, and G2 for dried fruits and products processed thereof, intended for direct human consumption or as an ingredient in foodstuffs. 

The European Union has implemented Regnlation 466/2001 of the Commission, according to which the maximum permitted tolerance valnes in total mercury in foodstuffs amounts to 0.5 mg/ kg fresh weight product in fishery products, except for certain fishes where the maximum level is 1 mg/kg fresh weight product. 

In contrast, fish and fish products can be highly burdened with mercury, especially methylmercury. The highest concentrations are found both in marine and freshwater fish at the highest trophic levels of the aquatic food chain, caused by bioaccumulation [4-6] (see Sec. 2.1). The mean mercury concentration in the edible parts of these problem fishes is approximately 1 mg/kg, but peak values even of 10 mg/kg have been reported [16,17]. Shellfish also accumulate methylmercury to a high extent. For instance, the weekly consumption of 200 g of fish containing only 0.5 mg mercury/kg results in the intake of 100 p,g mercury per week [2]. This amounts to one-half of the PTWI (provisional tolerable weekly intake), as recommended by the World Health Organization (WHO) [4,18]. The feeding of animals like chickens with fish meal may raise the mercury burden of terrestrial animal foodstuffs too. 

After these introductory remarks, I shall attempt to give you an account of the current recommendations of the World Health Organization in this field. In particular, I will stress the "safe" levels of intake based on concepts such as Acceptable and Admissible Daily Intake (ADI), respectively, for intentional food additives and pesticide residues in food Provisional Tolerable Weekly Intake (PTWI) for cumulative toxic metals figures for body burdens and the corresponding "safe" limits recommended for foodstuffs, including the relatively recent definition of irreducible limits to deal with the problem of trace contaminants in food. 

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