Exposure to a given amount of a given contaminant may not present an issue for one individual, but may be a serious issue for another. Thus the questions, which must be considered in any exposure assessment, include the sensitivity of the individual, in the sense that an infant has a much lower body weight than the conventional assumption used in the EU that a person weighs 60 kg. Also a child, whilst having a lower body weight, consumes a relatively higher proportion of foodstuffs/kg of body weight, which results in a higher exposure in terms of mg or mg/kg body weight (Castle 2004). Edler et al. (2002) address the consumption of infants and children with reference to their relative immaturity compared to adults, particularly with respect to their immune systems and potential inability to eliminate compounds from their system (toxicokinetics) or the response of target organs (toxicodynamics).
Regulatory limits based upon toxicological data have a safety factor, typically 100-fold to allow for differences between species (10-fold factor), as most testing is on rats rather than mankind, and variability between humans (another 10-fold factor) (Renwick et al. 2000). Additionally, in order to address potential areas of concern, it may be desirable to distinguish between different consumers and their habits. Certain groups may be more vunerable due to age, dietary habits, ethnicity, gender, genetic make up, any medical conditions, etc. As an example, consider a teratogen and its potential to be effective. A pregnant woman consuming a teratogen may result in damage to the foetus, whilst it could be argued that an infant consuming a teratogen will not affect the development of the foetus, because the infant cannot become pregnant. Consult Edler et al. for further details on the treatment of sensitive groups.
The protection of the high consumer from contamination by migrants from the packaging of the food they are consuming is important not only for governments and their advisory bodies, such as EFSA, but also for industry. Obtaining a realistic estimate of exposure to a particular migrant(s) for the high consumer is always an issue with the current lack of data. However per-capita estimates normally include non-consumers, which reduce the exposure to the consumer population. They cannot be used to express exposure for non-average consumers, particularly the high consumer. However, it is accepted by some (Rees and Tennant 1994) that multiplying the per-capita estimate by three gives an estimated exposure for the high consumer (97.5th percentile), but whilst this may be valid for individual foodstuffs it is less likely to hold when a chemical can be present in several foodstuffs, or by two for the 90th percentile (Rees N., private communication 1998). A pragmatic approach to estimating exposure for the high consumer is to derive the per capita estimate and multiply by a factor of three. Moy (2005) considers that the high consumer of a single food consumes three times the per capita consumption, whilst for the whole diet a factor of two is more appropriate. Thus estimates of exposure for the population to a migrant from a food packaging material are needed and they will have varying degrees of refinement.
Another factor which could result in non-average exposure is loyalty, either to a brand or to a type of packaging which could impact any estimate of exposure. Packaging loyalty is when a consumer will always drink a can (or glass bottle or PET bottle) of beverage irrespective of brand, as distinct to a brand loyal consumer who will always drink the same brand of beverage irrespective of its packaging. Packaging loyalty or brand loyalty will skew any exposure estimate. Packaging loyal, high consumers are subjected to a higher exposure (if the migrant originates from that packaging) than a non-packaging loyal consumer, if there is more than one form of packaging for that foodstuff.
Brand loyalty is the preference of a consumer for a particular brand of the same foodstuff, but this has implications as described in SCOOP (Report EUR 17528EN). The exposure for a brand loyal and non-loyal consumer could vary significantly if there were, for example, a different food additive present in one brand compared to another, for example, present in biscuit X but not Y or Z. Do brand loyal biscuit X consumers eat biscuit X at the same level as brand loyal biscuit Y consumers eat biscuit Y and do the aggregated (non-brand loyal and brand loyal) biscuit consumers (biscuits X, Y and z) eat biscuits at the same levels as the brand loyal consumers of biscuits X and Y? If the additive is only present in say biscuit X, then the aggregated biscuit consumption would under-estimate the exposure to the additive for the brand loyal consumer who only ate biscuit X, but would over-estimate the exposure for the consumer who only ate biscuit Y, but would be most representative for the non-loyal biscuit consumer. However, until more information is available from dietary surveys about brand loyalty, it must not be assumed that if only a single brand of the products in a particular food item contain the migrant then there is less concern, even if the brand has a small market share, partly because brand loyal consumers may belong to a vulnerable group for whatever reason. Today dietary intake studies generally contain inadequate data to accurately determine the exposure of brand loyal consumers.
Another factor, which may influence the realistic concentration data, is store loyalty, which is in reality a sub-set of brand loyalty. This applies in those situations where for whatever reasons, such as lack of mobility, the consumer is effectively forced to purchase from a local store. If they purchase 'own brand' foodstuffs and if these foodstuffs have a different concentration of the migrant data set compared to the overall concentration data compiled during a survey, such as the FSA BADGE survey (2000), then it is necessary to ensure that if the concentration data are higher the consumers who purchase only 'own brands' are protected. It could be argued that if the concentration data are lower, then these data should also be used.
One of the simplest approaches for packaging loyalty is to assume that if a consumer initially consumes a foodstuff in a particular type of packaging then they will always consume that item in the same packaging (100% loyalty), whereas the non-packaging loyal consumer will consume that foodstuff item with its packaging randomly selected in proportion to the market share of the packaging for that type of foodstuff. If a food item is packaged in more than one material, then there will always be a proportion of the population who consume the food item, but due to packaging loyalty they will never be exposed to that migrant from that source.
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