Provisional Tolerable Daily Intakes PTDIs

The risk to health from chemicals in food can be assessed by comparing estimates of dietary exposure with recommended safe levels of exposure. For most metals and other elements, these are the Provisional Tolerable Weekly Intakes (PTWIs) and the Provisional Tolerable Daily Intakes (PTDIs) recommended by the Joint Expert Committee on Food Additives of the Food and Agricultural Organisation of the United Nations and the World Health Organisation International Programme on Chemical Safety (JECFA). The European Commission s Scientific Committee on Food has established other relevant safe levels. These are Acceptable Daily Intakes (ADIs) for chemicals added to food, and Tolerable Daily Intakes (TDIs) for chemical contaminants. The use of the term tolerable implies permissibility rather than acceptability. All the above recommendations are estimates of the amount of substance that can be ingested over a lifetime without appreciable risk, expressed on a daily or weekly basis as appropriate. 

It can be seen from Table 7.4 that the population dietary exposure to total arsenic for UK consumers has remained fairly constant. The dietary exposures for mean and 97.5th percentile adult UK consumers in 1997 were 0.12 mg/day and 0.42 mg/day respectively. Although these exposures are similar or greater than the JECFA Provisional Tolerable Daily Intake (PTDI) for inorganic arsenic of 0.002 mg/kg bodyweight, which is equivalent to 0.12 mg/day for a 60 kg person, these are estimated for total arsenic. As has been stated before, most of the arsenic in the diet is from fish and most of the arsenic in fish is in the less toxic organic forms. 

Abbreviations EPA, Environmental Protection Agency ATSDR, Agency for Toxic Substances and Disease Registry FDA Food and Drug Administration NOAEL no-observed-adverse-effect level LOAEL, lowest-observed-adverse-effect level UF, uncertainty factor SF, safety factor RfD, reference dose (an amount of a substance that is anticipated to be without adverse health effects in humans, including sensitive populations, when ingested daily over a lifetime MRL, minimal risk level (an estimate of daily human exposure to a hazardous substance that is likely to be without an appreciable risk of adverse noncancer health effects over a specified route and duration of exposure) pTDI, provisional tolerable daily intake (maximum daily exposure level to a contaminant provisional meaning that it is considered temporary until more data are available, especially the completed Seychelles study) JECFA, Joint FAO/WHO Expert Conunittee on Food Additives pTWl, provisional tolerable weekly intake. 

Toxic and essential trace elements intakes were computed from food consumption data of the population in northern Italy and element concentration measurements. The results (Table 10.6) were compared with the Italian Recommended Dietary Allowance (RDA) for essential trace elements and with the Provisional Tolerable Daily/Weekly Intake (PTDI/PTWI) for toxic elements. Finally, an assessment was made of the extent to which each food contributes to the total intake of trace elements by the population under study and the most contaminated foods were also detected. On the whole, mean intake values satisfied the Italian RDA for all the essential trace elements [31], while the potentially toxic trace elements were below the relevant threshold limits. 

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