D IETARY I NTAKE E STIMATION

11.3.1 D IETARY I NTAKE E STIMATION

To perform a dietary intake estimation is basically easy. The consumption is multiplied with the content:

Intake The question is, however, what consumption and which content should be used.

Should it be mean values? Should it be high values, a kind of worst-case situation? And how is the consumption respectively the content estimated? There is not one way of performing dietary intake estimations and in the literature different ways of performing the estimations have been used and in addition the data collection has been very diverse. Therefore, it is also often very difficult to compare the dietary estimations directly.

Dietary surveys can be performed in many ways. In some surveys, participants are asked to fill out a diary about what they have been eating and the amounts; in others, people are interviewed about what they have been eating, for example,

Levels of Pesticides in Food and Food Safety Aspects 307 yesterday. In some surveys, the food bought in the household is used for the

estimation of the consumption. Here, the total amount of, for example, potatoes is divided by the number of people in the household and number of meals, where the potatoes are eaten. Both number of participants, number of days, and the details concerning the food eaten differ between dietary surveys. In many circumstances, the food as eaten are calculated back by using recipes to ingredients or RAC; for example, an apple pie is divided into flour (grain), apple, and other ingredients.

For total diet studies and duplicate diet studies, however, the content is directly determined in the food eaten. In total diet studies, a certain number of raw and prepared foods are chosen to represent the total diet of the population. The foods are then bought and prepared according to recipes and the content of the pesticides or other substances are directly determined in the foods. In the duplicate diet studies, the participants collect exactly the same amount of food as they eat and the pesticides are then determined in the collected foods.

Data concerning the content of the pesticides often comes from monitoring or surveillance. These studies differ widely in regard to which pesticides that are included, the number of pesticides included, and the number of commodities included.

In the calculation of the dietary exposure, other factors such as correction for undetectable residues or processing also influence the result. Although a pesticide is not detected in a commodity, this does not necessarily mean that it is not present; just that the level could be lower than the analytical LOD. In some calculations, the

undetectable residues are set at, for example, 1 2 LOD or another factor. It is known that for examples peeling or boiling can reduce the amount of pesticides, whereas drying (e.g., grapes to raisins) can increase the content of the pesticides. To perform the most reliable estimation of the dietary exposure, processing factors should be included if available.

Dietary exposure calculations can be performed with different approaches, deterministic or probabilistic, and for both chronic and acute intake. The chronic intake or the long-term intake is the possible intake over a long time, for example, a whole life and in the risk assessment this intake is compared with the ADI. The acute intake or the short-term intake, on the other hand, is the intake within 24 h or less, for example, a meal. The acute intake is compared with the ARfD in the risk assessment.

11.3.1.1 Deterministic Approach (Chronic and Acute Intake)

A calculation of the chronic intake by the deterministic approach yields only a single value for the intake and is also called a point estimate. In this approach,

a single value of the consumption of a commodity is multiplied with a single value of the concentrations of residues. Often consumption and concentrations are average values, but they can also be high percentiles if a worst-case calculation is performed. If the chronic intake for a certain pesticide from all commodities is calculated, the single intakes for each possible commodity are summed.

The acute intake in the deterministic approach is always calculated for a single commodity. Depending on the commodity, different equations defined by JMPR 82

are used for calculation of the acute intake. In the two most often used equations,

308 Analysis of Pesticides in Food and Environmental Samples the so-called variability factor is included. This factor is based on the variation of the

residues in a composite sample. In monitoring, usually analyzed samples are com- posite samples, while all the content of a pesticide found can be from just one sample. In an estimation of the acute intake, the intake from this one sample is of interest and the variability factor is an expression used to estimate the content in a single sample from the content in a composite sample.

The deterministic approach is the absolute most often used method for the calculations of pesticide intakes. The advantages of the approach are that the approach is easy and simple to perform and the results are easy to interpret. The drawback of the approach is that the exposure is expressed as single values because single values are used for both consumption and content regardless of the variability in both variables. Thus, intakes determined by the deterministic approach are generally highly overestimated.

11.3.1.2 Probabilistic Approach Probabilistic modeling is called so because this approach yields the probability for an

intake. In this approach, the whole distribution of consumption data and concentra- tions are used in the calculations, resulting in a new distribution for the intake; a consumption of a commodity is chosen; and a residue in this commodity is chosen; and the two values are multiplied to yield an intake. Then a new consumption value and a new residue value are chosen. This is done several times, for example 100,000

times, resulting in a distribution of intakes 83 (Figure 11.3). In this way, percentiles of the intake can be determined. The probabilistic modeling determines the acute or

short-term intake, if it is the consumption for a meal or a day that is used in the calculation. Algorithms to calculate the chronic intake have become a part of some programs and the chronic intake can be compared with the ADI. The advantage of this approach is that all data of both consumptions and concentrations are used, the whole distribution of the intake is shown, and the uncertainties in the calculation can

be estimated. Probabilistic modeling is, at the moment, not widely used. In connection with authorization of pesticides, EPA in the United States use probabilistic modeling as

FIGURE 11.3 How a distribution of intake is performed from a distribution of consump- tion and of contents. (From Pieters, M.N. et al., Probabilistic Modelling of Dietary Intake of Substances, The Risk Management Question Governs the Method, RIVM, Report 3200110012005, 2005. With permission.)

Levels of Pesticides in Food and Food Safety Aspects 309 part of their evaluations of the pesticides and have published guidelines for the

work. 84 Both in Codex and in the EU, the use of probabilistic modeling is discussed and projects concerning the subject have been initiated. 85 –87

11.3.1.3 Cumulative Exposure The term ‘‘cumulative exposure’’ can be used in different ways. Some use it as the total

intake of a single pesticide from all commodities. The most often applied definition of the term, and the definition used in this book, is that the cumulative exposure is the total intake of all pesticides or a group of pesticides from all commodities. Several

approaches can be used 88 but at the moment there is no common agreement on which approach to use to calculate the cumulative exposure for pesticides in our food. Examples using two different approaches are summarized here, namely the so-called TEF approach for the Danish and Brazilian population and the margin of exposure (MOE) for the U.S. population. In both examples, the cumulative dietary exposure is calculated for choline esterase inhibiting substances (organophosphates and carbamates).

Using the TEF approach, exposures of a group of common mechanism chem- icals with different potencies are normalized to yield a total equivalent exposure to one of the chemicals, the so-called index compound (IC). TEFs are obtained as the ratio of the toxic potency at the chosen toxicological end point of the IC to that of each of the other members in the group. This means that a substance with a toxic potency 10 times the IC is assigned a TEF value of 10. The exposure to each chemical is then multiplied by the appropriate TEF for example, 10 to express all exposures in terms of the IC. Summation of these values provides a total combined exposure to all chemicals in terms of the IC.

To assess the cumulative risk of the exposure in the United States, the total MOE 75 is used. MOE for a single chemical is the ratio of the effect dose level (ED) at the chosen toxicological end point to the level of dietary exposure.

The combined MOE is

Combined MOE ¼ , etc: 1=MOE1 þ 1MOE2 þ 1=MOE3

The greater the MOE, the lesser is the risk. In the assessments, a target value of 100 is acceptable. MOEs <100 are undesirable.