NZTDS

Fig. 10.3 Estimated daily dietary exposure to total DDT for a young male (YM) in the 1997/98 New Zealand Total Diet Survey (NZTDS) compared to previous NZTDSs (adapted from Cressey et al., 2000).

A distinguishing characteristic of Total Diet Surveys like the NZTDS (Cressey et al., 2000) is that foods are analysed as normally consumed (e.g. bananas peeled, meat cooked etc.). They therefore frequently provide the most relevant means of assessing the consumer s exposure. A Total Diet Survey is essentially a public health risk assessment tool, and not a compliance monitoring tool. 

In New Zealand, the 1997/98 NZTDS food list consisted of 114 different commodities, representing about 70% of those most commonly consumed by New Zealanders. 

The NZTDS thus provides a reliable snapshot of the overall quality and safety of the NZ food supply, and is a means (albeit not ideal) of checking the effectiveness of regulatory systems established to control pesticide residues in food. Total Diet Studies are also valuable in determining whether particular pesticide residues occur across the diet as a whole, or are restricted to certain food groups or even individual foods. The NZTDS provides readily understandable information on the dietary exposures of pesticide residues for the use of regulatory agencies, lawmakers and the public. 

In the 1997/98 NZTDS, some 2,440 food samples were collected. After compositing some samples of the same food type, 460 samples were actually screened, with 272 samples (59%) being found to contain detectable residues. 

First, with constraints on resources always an issue, there is usually a need to balance effectively the range of pesticide residues screened for and the number of samples analysed. The sampling plan for the NZTDS was devised to look closely at foods that were more likely to contain pesticide residues. For example, previous NZTDSs had indicated that carbonated cola beverage was unlikely to contain pesticide residues and so only two composite samples were analysed. By contrast, bread often contains residues of organophosphorus pesticides and so eight samples of each of three different types of bread were analysed. 

Only 20 different pesticide residues were detected in the 1997/98 NZTDS out of a screen of 90. Of these, none of the pesticide residue levels detected exceeded the New Zealand Food Regulations 1984 MRL, where one was listed for the specific food item. Of approximately 29,000 individual analytical pesticide residue results in the 1997/98 NZTDS, only 397 (1.4%) were detectable residues. Many of these detectable residues might not have been detected in a compliance monitoring programme, with the often higher limits of reporting. 

It is interesting that a comparison of concentrations analyzed 80 years later for the 2003—2004 New Zealand Total Diet Survey (NZTDS) (Vannoort and Thomson, 2005) indicates that the iodine content of cereals, fruits, vegetables and meat is similar to the previous values (Table 129.1). 

NZTDS From typical diets and 180-300 Vannoort and Thomson... 

Notes-. NZTDS, New Zealand Total Diet Survey. Iodine Intakes (rrg/day) In New Zealand from the 1920s to 2000s estimated from typical diets and concentrations In foods, or from dally urinary excretion assuming that approximately 90% of Intake Is excreted In urine. 

Despite the reduction in iodine content of dairy products, the contribution of these foods to the total iodine intake in the 2003-2004 NZTDS was still high, with 34% of the intake of a young male and 67% of that of a 1—3-year-old child (Vannoort and Thomson, 2005). A comparison of concentrations in corresponding foods analyzed for the 2003—2004 NZTDS (Vannoort and Thomson, 2005) with early values produced by Hercus and Roberts (1927), indicates that the only foods that show higher concentrations are cheese and milk as a result of iodophor contamination, and eggs as a result of trace mineral supplementation of poultry feed (Table 129.1). 

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