In dietary exposure assessments, FSANZ may estimate the potential dietary exposure of different population groups to a range of food chemicals. These chemicals include food additives, contaminants, novel foods and food ingredients, pesticide and veterinary drug residues and nutrients. Read more about dietary exposure and intake assessments
A population sub-group of potential concern is one we call 'high consumers'. High consumers can be people who consume:
- a lot of one food that contains a chemical of interest
- smaller amounts of a number of different foods that all contain the same chemical
- small amounts of a food which contains a high concentration of a chemical.
Where relevant, FSANZ reports dietary exposure for high consumers when assessing dietary exposure to food chemicals, as well as population average exposure, so that we know we are considering the potential risks across the population.
How do we identify the high consumers?
We use Australian and New Zealand national nutrition survey (NNS) data to estimate dietary exposure to food chemicals. The 1995 Australian NNS and the 1997 New Zealand adult and 2002 New Zealand children's NNS only captured a single 24-hour time period for all participants, although a subset (10-15% of participants in each NNS) were studied for an additional separate 24 hour period. The 2007 Australian Children's NNS captured two non-consecutive 24-hour time periods for all participants. Across the thousands of people who participated in these surveys, we will typically find a wide range of eating patterns and therefore a wide distribution of dietary exposure to food chemicals.
Part of the survey population may have no exposure to the chemical in question, because they didn't report eating food/s containing that chemical on the day of the survey. These are the 'non-consumers'. The sub-group who are exposed, the 'consumers' are often the focus of a dietary exposure assessment. Each consumer's exposure will be estimated from their individual consumption records and then ranked from lowest to highest. Average consumer exposure will be reported, as will that of the high consumer.
There are international conventions regarding dietary exposure assessment reports in regulatory risk assessment. Where possible, FSANZ adopts principles and procedures from international best practice. When assessing dietary exposure for high consumers, countries with one or two days of food consumption data from NNSs tend to report high consumer dietary exposures at a lower percentile than those with surveys of a longer duration, for example the 90th percentile of exposure is commonly reported for countries with NNSs of 1 or 2 days duration.
Following an International peer review of our dietary modelling program and procedures in 2006, FSANZ reports the following values to represent dietary exposure for high consumers:
Assessments for agricultural and veterinary chemical residues and contaminants
Chronic dietary exposure assessments
We estimate chronic dietary exposure for agricultural and veterinary chemical residues using an specific internationally accepted methodology where only the mean (average) dietary exposure for the whole population is reported (consumers and non-consumers).
For contaminants, chronic dietary exposures are estimated using the mean and 90th percentile exposures for consumers of the chemical of interest only.
Acute dietary exposure assessment
An acute exposure assessment examines dietary exposure over a short time period, for example a single meal or 24 hour period only. Acute, or short term, dietary exposure estimates for agricultural and veterinary chemical residues are based on food consumption data at the 97.5th percentile for consumers of the food, which is also an internationally accepted methodology. When the survey has two days of records for each respondent, these data are pooled (as individual eating days, not averaged across two days) before deriving the 97.5th percentile food consumption.
A similar approach is taken for acute dietary exposure assessments for contaminants.
Additives
We estimate chronic dietary exposure to additives using the mean (average) and 90th percentile of exposure for consumers of the chemical only.
Nutrients
For nutrients, we use an established statistical adjustment method to estimate 'usual' nutrient intake in all NNS respondents, where the intakes are normally distributed. The adjustment takes into account the differences in intake for an individual over different days (within person variation) and requires a sub-set of the NNS respondents to have a second day record. A 10% (1995 Australian NNS) or 15% (1997 and 2002 New Zealand NNSs) sub-sample for which two 24-hour recalls are available is generally sufficient to allow estimation of the within-person standard deviation for nutrient intakes. The adjustment may also be used for the 2007 Australian NNS that has 100% respondents with a second day record.
This adjustment can be used for most nutrients, as opposed to other types of food chemicals, because nutrients are widely dispersed in foods and therefore all respondents will have a nutrient intake on both days on which they were surveyed.
Exceptions are nutrients such as folic acid and omega-3, where only some respondents will have consumed foods containing these nutrients and the distribution of intakes is not normally distributed. In these cases where two days of records are available for all or most respondents (2007 ANCNPAS) a two day average is used to estimate usual intake. FSANZ uses the 95th percentile to report high percentile nutrient intakes after an adjustment has been made for the second day of intake. Figure 1 illustrates the effect of using this statistical adjustment on the predicted distribution of nutrient intakes and the potential this can have to alter the interpretation of a population's nutritional status, that is, the proportion of a population estimated to be above or below a health based guidance value (A or B).
Figure 1: Comparison of the predicted distribution of nutrient intakes estimated using one day of food consumption data or data adjusted to reflect longer term intakes. Points A and B represent lower and upper reference health standards, respectively
Risk management implications
Employment of international best practice and sound science when estimating and reporting dietary exposure for high consumers as part of our risk assessments ensures that any risk management strategy proposed will protect high consumers.
More information
Principles and Practices of Dietary Exposure Assessment for Food Regulatory Purposes(pdf 582 kb)
Principles and methods for the risk assessment of chemicals in food (Food and Agricultural Organization/World Health Organization)