Mapping is the process of matching the foods analysed in the Plasticisers survey to the foods consumed in the national nutrition survey. Given that the Plasticisers survey could not survey all foods consumed in the national nutrition survey, mapping is a major step in the dietary exposure assessment process. In the 2011-12 NNPAS, foods were typically not reported with details of their packaging type, with the exception of some canned food. Therefore, in the Plasticisers survey, it was not possible to directly map analysed foods to similar foods that also had the same type of packaging. For this survey, the mapping was based on the food additive classification system used in Standard 1.3.1 in the Code. This classification system is used by FSANZ for other food additive dietary exposure assessments as food additives are specifically added to foods during processing and are therefore usually in a restricted range of processed foods and beverages. As the foods analysed for plasticisers matched closely with the food groups in this classification system, using the food additive classifications was deemed the most appropriate for estimating plasticiser dietary exposures. Due to the lack of data on packaging type in the 2011-12 NNPAS, Plasticiser survey foods which were sampled in two different packing types, (i.e. instant noodles and hamburgers), were unable to be differentiated in the mapping process so were included in the same food group for the dietary exposure assessment.
There were three types of mapping used for plasticiser dietary exposure estimates:
Direct mapping – where the Plasticiser survey foods were directly matched to a corresponding Food Additive Classification which contained the analysed food and comparable foods with similar packaging type, from the 2011-12 NNPAS (e.g. the Plasticiser survey food ‘Bacon, middle cut, rind on’, was mapped to ‘Cured meat’ and ‘Fermented, uncooked, processed comminute meat products’ using the assumption that any migrating chemicals from packaging present in bacon are the same in all cured and fermented meats with similar packaging).
Mapping using custom classifications – where a Plasticiser survey food could not be directly mapped to a suitable Food Additive Classification, a customised classification group was developed and the appropriate 2011-12 NNPAS foods assigned to the classification (e.g. the classification ‘Canned legumes’ was created and all the 2011-12 NNPAS canned legumes such as ‘Bean, cannellini, canned, drained’ and ‘Chickpea, canned, drained’ were allocated to this new classification group).
Recipes – used where a food consumed in the 2011-12 NNPAS was composed of more than one analysed survey food (e.g. the 2011-12 NNPAS food ‘Curry, commercial, beef, tomato based sauce’ is made up of the survey foods ‘Beef, steak, untrimmed’, ‘tomatoes, canned’ and ‘Oil, Canola oil or sunflower oil’). These mixed foods were not mapped directly but a recipe is used to disaggregate the consumption to the relevant components.
Details of the Plasticiser survey foods and the 2011-12 NNPAS foods that they represent, and the group name used for reporting purposes are provided in Appendix 6.
To obtain an indication of the contribution each food group made to total estimated exposures, the sum of all individuals’ two day average exposures from one food group was divided by the sum of all individuals’ two day average exposures from all foods containing the plasticisers assessed, and multiplied by 100. All contributors are calculated using the lower bound ND=0 scenario. In this scenario, for individual foods where more than 50% results were non-detects, a median concentration of zero was assigned so the food would not be listed as a contributor to estimated total dietary exposure.
There is no direct association between the analytical concentration of a phthalate, adipate or citrate in an analysed food and its identification as a major contributor to dietary exposure. Even if a food contains a relatively high concentration of a particular plasticiser, the amount of the food consumed, the mapping process and the number of individuals that were exposed to the plasticiser, will determine its level of contribution.
Assumptions and limitations in dietary modelling
The aim of dietary exposure assessments is to make as realistic an estimate of dietary exposure to the food chemicals of interest as possible.
Dietary exposure assessments based on the 2011-12 NNPAS provide the best available estimates of actual consumption of foods in Australia and the resulting estimated dietary exposure to a food chemical for the population. Nevertheless, limitations still exist in dietary exposure assessment methods as well as in the data. Limitations relating to the food consumption and chemical concentration data include:
Diets derived from one or two 24-hour food recall surveys are used as the basis for drawing conclusions on lifetime eating patterns. This normally leads to conservative dietary exposure assessments, particularly where exposure arises from the consumption of non-habitually eaten foods.
Participants in 24-hour food recalls may over- or under- report food consumption, particularly for certain types of foods.
The model diet used for 9 month old infants is not as specific as the data derived for other population groups from the 2011-12 NNPAS that use reports of food consumption data of individuals because the model diet includes only mean consumption amounts for the population group as a whole.
The list of analysed foods is only a sample of the foods consumed by the population and may not accurately represent the whole diet.
Only a small number of samples of each food was collected and analysed. These samples were then used to represent the whole range of that food or similar foods, therefore limiting the potential range of variability in concentrations captured.
Assumptions made in the dietary exposure assessment for the Targeted Survey of Plasticisers in Australian Foods include:
The food chemical concentration in the analysed food was representative of the concentration of that chemical in all of the other foods to which it was mapped.
No contribution to dietary exposures was included for medicines or vitamin and mineral supplements.
Appendix 3: Median plasticiser concentrations (mg/kg) in foods for dietary exposure assessment
Table A3.1: Median plasticiser concentrations in analysed survey foods expressed in mg/kg