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Part A - 20th ATDS

20th Australian Total Diet Survey

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Pesticides have been used in world agriculture for many years and provide important benefits in agriculture, resulting in a number of benefits to society. Their use provides the community with year-round availability of, and improved quality and variety in, our food supply, and leads to the production of food at a cost to the consumer that would otherwise not be possible.

Although pesticides present the community with significant benefits, there are risks associated with their use. In order to ensure safe pesticide use, a number of Australian government agencies assess the various safety aspects of pesticides before the pesticide is approved for use in Australia. It is FSANZ’s responsibility to assess the safety of pesticide residues in food. Other Australian government agencies assist in this assessment via the provision of information such as Acceptable Daily Intakes (ADIs) and Maximum Residue Limits (MRLs). An ADI is an estimate of the amount of a chemical that can be ingested daily over a lifetime without appreciable risk to health. An MRL is the highest concentration of a chemical residue that is legally permitted or accepted in a food or animal feed and is an indicator of the highest residue that could result from the registered conditions of use. All agencies must be satisfied that the use of the pesticide will result in no appreciable risk of adverse health effects.

Between 1998 and 2000, ANZFA conducted a review of the Australian Food Standards Code (referred to as Volume 1 of the Food Standards Code). In November 2000, the Australia New Zealand Food Standards Code(referred to as Volume 2 of the Food Standards Code) came into effect. Until 20 December 2002 when Volume 2 becomes the sole Food Standards Code, foods must comply with either Volume 1 or Volume 2 of the Food Standards Code, but not a combination of both.

During the review of Volume 1 of the Food Standards Code, the following substances in foods were examined: antimony, arsenic, cadmium, copper, lead, mercury, selenium, tin and zinc (ANZFA 1999). In Volume 2 of the Food Standards Code,maximum levels (MLs) were set only for those contaminants that presented a significant risk to public health and safety and for those foods that significantly contributed to the dietary exposure of the contaminant. The ML is the limit placed on the level of a contaminant, such as a heavy metal, in food. The 20th ATDS examined the metals that were examined during the review of Volume 1 of the Food Standards Code.

Aflatoxins and ochratoxins were included in the 20th ATDS due to the high toxicity of these substances. Additionally, there were detections of aflatoxins in peanuts in the 19th ATDS. Due to recent interest in the presence of antibiotic residues in foods, inhibitory substances were also included in the 20th ATDS.

Origin of the survey

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The NHMRC conducted the first total diet survey in 1970. Another 15 surveys were conducted by the NHMRC before responsibility passed to the predecessor of the Australia New Zealand Food Authority (ANZFA), the National Food Authority. The 20th ATDS is the fifth survey to be conducted by ANZFA or its predecessor.

The ATDS is conducted approximately every two years. The sampling and analysis of foods usually take place over 12 months, and the report writing and planning for the next survey take place in the following 12 months. Publication of the report follows peer review of the survey.

Pesticide, contaminant and other substance surveillance in Australia

The Commonwealth Government, through the Department of Agriculture, Fisheries and Forestry - Australia, conducts two further programs that collect information on the levels of pesticide residues, contaminants and other substances in foods:
  • the National Residue Survey; and
  • the Imported Food Program, conducted by the Australian Quarantine and Inspection Service (AQIS), which undertakes the surveillance of imported foods to ensure that they comply with the Imported Food Control Act 1992 and the Food Standards Code.

The main aim of these programs is to monitor pesticide residues, contaminants and other substances in food commodities in export and import trade respectively. In contrast, the ATDS aims to estimate the level of dietary exposure to pesticide residues, contaminants and other substances in the overall Australian diet, including both locally produced and imported foods which are prepared to ‘table ready’ form.

In addition to these programs, State and Territory health and agriculture authorities carry out surveys of specific contaminants, pesticide residues or other substances. These surveys usually investigate specific concerns and determine whether primary producers are complying with the law. They are a valuable source of supplementary information on the contaminant, pesticide residue and other substance status of foods.

Comparison with other surveys

The ATDS differs from other surveys of pesticide residue, contaminant and other substance levels in the following ways:
  • ATDS monitors the level of certain substances in the total diet to determine whether they pose an unacceptable risk to human health. Other surveys examine the level of residues, contaminants and other substances in individual raw agricultural commodities or foods to determine compliance with the law but do not carry out a comprehensive examination of their significance in the diet; and
  • The ATDS contrasts with other national surveys in that all ATDS food samples are prepared to a ‘table-ready’ state before they are analysed, that is, they are subjected to prescribed preparation or processing steps. Food preparation varies with the type of food. For example, fruits may be peeled if they are usually eaten without their skins, while beef is dry fried because this food is nearly always consumed after cooking. As food preparation is known to affect the concentration of pesticide residues, contaminants or other substances in the food, an analysis of prepared foods more accurately reflects the levels of residues, contaminants or other substances that are likely to be consumed.

Using information from the survey

Data from the ATDS provide information for developing food regulatory measures. During the review of the Food Standards Code, data from previous Australian Market Basket Surveys were used to supplement dietary modelling information in the risk assessments for metal contaminants (ANZFA 1999). The ATDS data on the dietary exposure to agricultural and veterinary chemicals can be used as a check on exposure assessments undertaken during the registration process at the National Registration Authority for Agricultural and Veterinary Chemicals (NRA).

Caution should be exercised in the direct comparison of the levels of residues, contaminants and other substances found in this total diet survey with food standards since samples are analysed ‘table-ready’ and the sampling protocols used differ from those employed for compliance with food standards.

In addition, the results of the survey are a source of information for Australia’s contribution to the World Health Organization/Food and Agriculture Organization (FAO/WHO) Global Environmental Monitoring System (GEMS), which monitors food contamination internationally, the Codex Committee on Pesticide Residues, the Codex Committee on Food Additives and Contaminants, and independent researchers both inside and outside government agencies.

Conducting the survey

This survey was coordinated by ANZFA and undertaken in cooperation with each of the States’ and the Northern Territory’s departments of health or equivalent. A working group, including liaison officers nominated by each State and the Northern Territory, was formed to advise ANZFA on the food and contaminants to be examined in the survey. Other participants in the working group were representatives of the Australian Government Analytical Laboratories (AGAL) and the National Residue Survey as well as ANZFA staff.

State and Territory officers were responsible for arranging the purchase and preparation of food samples. Food was sampled in each State capital city and Darwin - seven jurisdictions in all. Food was sampled over an entire year in four batches in July and November 2000, and in February and April 2001. This accommodates seasonal variation in foods and allows for the sampling of foods that are available only in certain seasons.

The food was prepared according to strict instructions, frozen and dispatched for analysis. Analytical chemists in the laboratories undertook the chemical analyses of the foods in accordance with quality assurance procedures. Following analysis, the results were sent to ANZFA where the total dietary exposures were estimated and a report prepared. States and Territories were informed of any results that indicated a breach of the Food Standards Code.

Foods included in the survey

The ATDS Working Group chose foods according to the following criteria:

  • Representative foods from each major food group [1] and therefore the total foods surveyed must be consistent with a nutritionally acceptable diet;
  • The most commonly consumed food in each food group, as shown by the National Nutrition Survey 1995 (NNS). If the food was examined in a recent survey then another representative food from the group may be chosen;
  • Foods that may be of particular interest from a pesticide, contaminant or other substance viewpoint may be included in the survey, although their intake may be low. For example, offal and offal products are not a significant component in the Australian diet. However, these products are recognised as typically high in accumulated metal contaminants and pesticide residues and therefore were sampled in the 20th ATDS;
  • Foods may be included if they form a significant part of the diet of a subpopulation of Australians.

The 65 foods surveyed in the 20th ATDS were chosen according to the above criteria and are shown in Part 1 (Table 1) of the Supplementary Information (FSANZ 2002). All the foods examined in the survey were prepared to a ‘table ready’ state before analysis (refer to Part 5 of the Supplementary Information (FSANZ 2002) for details on food preparation instructions). For example, meats and eggs were cooked, while fruits that are normally consumed without peel were peeled. In preparing food as ‘table ready’, local tap water is used rather than distilled water to ensure that pesticide residues, contaminants and other substances that may be present in tap water are taken into account in the overall estimate of dietary exposure.

Foods were sampled according to a schedule that categorises them into core, national or regional foods. This allows a good overview of the Australian diet.

Core foods were defined as foods central to the Australian diet. In the 20th ATDS, these foods were bread, beef, eggs, milk, orange juice, margarine, potatoes and tomatoes.

Composite samples of core foods, consisting of four purchases each, were collected in each of Australia’s six States and the Northern Territory in each of the four seasons. This results in 28 composite samples of each core food.

Regional foods were defined as those foods that might be expected to show regional variation of residue, contaminant or other substance levels. Regional foods include fruits, vegetables and meats. Three composite samples of these foods, consisting of three purchases each, were collected in each of Australia’s six State capital cities and Darwin, making 21 composite samples for each regional food.

National foods were defined as those foods that are available nationwide and are not expected to show regional variation. They are foods, such as sweet biscuits, canned tuna and infant cereal, that are distributed nationwide from a small number of outlets. Three composite samples, of three purchases each, were collected in three capital cities, making nine composite samples for each national food.

Pesticide residues, contaminants and other substances examined

All foods were tested for pesticides residues including residues of chlorinated organic pesticides, organophosphorus pesticides, carbamates, synthetic pyrethroids and fungicides (see Part 1 (Table 5) of the Supplementary Information (FSANZ 2002) for a complete list). All foods were tested for antimony, arsenic, cadmium, copper, lead, mercury, selenium and zinc. A selected range of foods was tested for tin. Breads, biscuits, rice, oats, processed wheat bran, breakfast cereals (including infant cereal), instant coffee, peanut butter, almonds and milk chocolate were tested for aflatoxins (B1, B2, G1 and G2) and ochratoxin A. Inhibitory substances (penicillin G, streptomycin and oxytetracycline) were tested for in meats, liver pate, dairy products and eggs.

Estimating dietary intake of chemical contaminants

Dietary modelling was used to estimate the exposure to chemical contaminants through the diet for a number of age-gender groups of the Australian population. These age-gender groups were infants (9 months), toddlers (2 years), girls (12 years), boys (12 years), adult females (25-34 years), and adult males (25-34 years).

What is dietary modelling?

Dietary modelling is a scientific method for estimating the levels of pesticide residues, contaminants, or other substances a person or population may be eating. Dietary modelling techniques have been used by food regulators internationally for a number of years to determine if dietary exposure to pesticide residues, contaminants and other substances represents an unacceptable risk to public health and safety.

Dietary modelling is an important part of the ATDS as it translates analytical results for individual foods into dietary exposure data for the total diet that can be compared to established reference health standards. The comparison of dietary exposure data to health standards is crucial in identifying whether the estimated dietary exposure to pesticide residues, contaminants or other substances from foods poses an unacceptable health risk to any population group.

A glossary of terms used in determining safe exposures and regulatory limits for pesticide residues, contaminants and other substances is included in Appendix 5.

How is dietary modelling conducted?

DIAMOND (Dietary Modelling of Nutritional Data) is a computer program developed by ANZFA to computerise dietary modelling calculations. The amount of chemical in each food is multiplied by the amount of food consumed and summed over all foods to determine the exposure to the chemical from the whole diet.

Once dietary exposure to the chemical from the total diet has been estimated, this is compared to reference health standards to assess the potential risk to human health. Reference health standards are Acceptable Daily Intakes (ADIs) for pesticide residues and Tolerable Limits for contaminants and other substances. These are the amounts of substances that can be consumed on a daily or weekly basis without appreciable risk.

The chemical levels used in dietary modelling for the ATDS are representative levels taken from the analytical tests on each surveyed food conducted by the AGAL. The data on the amount of foods consumed are taken from the Australian National Nutrition Survey (NNS) that was conducted in 1995 and released in 1998.

A major step in dietary modelling is matching (or mapping) the 65 ATDS foods to the 4053 foods reported as consumed in the food consumption data (the NNS foods). This process assigns the levels of substances detected in the ATDS survey foods to the appropriate food consumption data to estimate dietary exposure to the substance. Given that the ATDS cannot survey all foods in the food supply, a single ATDS food (for example milk) may be assumed to represent a whole group of foods (for example milk, yoghurt and dairy fats) with appropriate adjustment factors for concentration (e.g. the proportion of milk fat in these foods). Recipes are used for mixed foods to assign ingredients to the appropriate ATDS food (e.g. the proportion of milk in vegetables in white sauce). Food mapping is based on traditional nutritional groupings as well as potential or possible pesticide use.

It is recognised that registered pesticide uses may apply only to specific crops (often major crops) in a crop group rather than to the whole group. Therefore, the assumption of a certain residue level, normally measured in the major crop, to the whole group is generally conservative in those cases and may overestimate the amount of potential pesticide exposure.

Use of DIAMOND for dietary modelling brings many benefits. DIAMOND enables the dietary exposure assessments to be conducted more efficiently and accurately. Records from the NNS of actual diets for approximately 13,800 people of all ages ( greater than or equal to 2 years of age) are used in place of ‘average’ diets that were used in surveys prior to the 19th ATDS. This means that dietary exposure is calculated for each individual in the survey before deriving mean dietary exposure results for the age-gender group. Use of this more up-to-date food consumption data greatly improves the reliability and accuracy of the dietary exposure estimates, and takes account of the different eating patterns of consumers.

Construction of the infant diet

As there are no data available from the NNS on children under two years, a diet was constructed to estimate dietary exposure to the food chemicals of interest for infants at 9 months of age. Recommended energy intake for a nine-month-old boy at the 50th percentile weight was used as the basis for the model diet (WHO 1983). Boys’ weights were used because boys tend to be heavier than girls at the same age and therefore have higher energy and food requirements. It was assumed that 50 per cent of the energy intake was derived from milk and 50 per cent from solids (Hitchcock et al. 1986). The patterns of consumption of a two-year-old child from the NNS were scaled down and used to determine the solid portion of the nine-month-old’s diet. Certain foods such as nuts, coffee and alcohol were removed from the infant diet since nuts can be a choking risk (NHMRC 2001a) and coffee and alcohol are unsuitable foods for infants (ACT Community Care 2000). Consumption of breakfast cereals was assumed to be in the form of either infant cereal or single grain breakfast cereals, excluding bran-based cereals. All milk consumption was assumed to be in the form of infant formula.

Limitations and assumptionsin dietary modelling

Although improvements have been made to the methods of estimating dietary exposure, limitations do exist in the methods as well as in the data itself. For example, we draw conclusions about lifetime eating patterns from food consumption data derived from a single 24-hour diet, leading to conservative dietary exposure estimates. More comprehensive data on multiple-day intakes may provide better estimates of long-term dietary exposure and food consumption.

Assumptions were also made about the value of analytical results below the limit of reporting (LOR). The LOR is the lowest concentration of a chemical that can be detected and quantified, with an acceptable degree of certainty, using a specified laboratory method and/or item of laboratory equipment. In the case of pesticide residues, some results were reported between the limit of detection (LOD) and the LOR. The LOD is the lowest concentration of a chemical that can be qualitatively detected using a specified laboratory method and/or item of laboratory equipment (i.e. its presence can be detected but not accurately quantified). There is a lower degree of certainty associated with results reported between the LOD and LOR. In the 20th ATDS, reported results below the LOR were used in calculating the mean concentrations of pesticide residues in foods.

In the 20th ATDS, pesticide residue results that were reported as less than LOD were assumed to be zero when calculating the mean concentrations of pesticide residues in foods. Given that pesticides are selectively applied to food crops, it has been assumed that pesticide residues are not present when pesticide residues are less than LOD.

In the case of metal contaminants that occur naturally in the environment, it may not be reasonable to assume that the metal is not present in the food when the analytical results are less than the LOR. For this reason, results below the LOR could be anywhere between zero and the LOR. To allow for this uncertainty, the results for dietary exposure to metals are presented as a range. The lower end of the range was calculated using a median metal concentration, based on the assumption that results below the LOR are equal to zero. The upper end of the range, representing a very conservative ‘worst-case’ estimate, was calculated using a median metal concentration, based on the assumption that results below the LOR are all equal to the LOR.

The DIAMOND program multiplied the mean concentration of each pesticide residue or metal by the amount of food that an individual consumed from that group in order to estimate the intake of a specific pesticide residue/metal from each food. Once this had been completed for all of the foods found to contain a particular chemical, the total amount of the chemical consumed from all foods was summed for each individual. Population statistics (mean intakes) for each age-gender group were then derived from the individuals’ ranked intakes.

Use of mean concentration levels for pesticide residues

In choosing a pesticide residue concentration level for use in dietary modelling, FSANZ chose the mean level. Where a high number of results are below the LOD, the mean level is a more conservative indicator of the detected levels of pesticide residues than the median level. This method is also consistent with the approach used in previous surveys.

Use of median concentration levels for substances other than pesticide residues

In choosing a concentration level for substances other than pesticide residues for use in dietary modelling, FSANZ used the statistical middle value (median), rather than the mean level (as in surveys prior to the 19th survey), to represent the most likely level in any given commodity. The median level is a more stable central statistic and is not sensitive to skewing by chemical detections above the normally expected range. The median simplifies calculations for surveys containing analytical results below the limit of reporting (LOR) because the position of the median, unlike the mean, is not dependent on the treatment of results below the LOR. Median values were used in the review of metal contaminants in food (ANZFA 1999). Means and medians are generally well correlated where there are few results reported below the LOR. This is demonstrated by the results for copper and zinc, where the means and medians are very similar.

Previous recommendations

In the 19th ATDS, it was recommended that the age groups used in calculating dietary exposures be reviewed to ensure that they are in line with changing demographics. The need to consider the age groups was reviewed for this survey. However, changing the age groups would make it difficult to compare the 20th ATDS with previous surveys. For this reason, it was considered appropriate to continue with the existing age groups, particularly since modelling was already being conducted for the group with the highest expected exposure per kilogram of body weight.

The age-gender groups included in this survey were:

  • Infants (9 months)
  • Toddlers (2 years)
  • Girls (12 years)
  • Boys (12 years)
  • Adult Females (25-34 years)
  • Adult Males (25-34 years)

[1]The major food groups considered are Breads and Cereals, Fruits and Vegetables, Milk and Dairy Products, Meat and Meat Alternatives, and Fats and Oils.

20th ATDS | Part B | Part C | Supplementary Information


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